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All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? ? 73 – Steve, KW4H ?
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Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901
(505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ?
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From: [email protected] <[email protected]> On Behalf Of KW4H via groups.io
Sent: Thursday, October 27, 2022 2:17 PM
To: [email protected]
Subject: [HallicraftersRadios] SX-110 2nd IF Circuit Design? All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? ? 73 – Steve, KW4H ?
|
Thanks, Mike!? In contrast, National often used all 6SG7’s in their IF design (such as in my HRO-60).? The difference is an interesting point. ? 73 – Steve, KW4H ? Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901 (505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of KW4H via groups.io
Sent: Thursday, October 27, 2022 2:17 PM
To: [email protected]
Subject: [HallicraftersRadios] SX-110 2nd IF Circuit Design? All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? ? 73 – Steve, KW4H ?
|
Just thinking.. if the intent of the receiver was to function only with weak signals? present, the extra gain of the 6SG7 would be preferable, but if? there were strong in-band signals, the 6SK7 might be preferred. Seems to me ?there must be trade-offs depending on the rf gain[s], the AVC and any bypassing of an Rf amp ?for lower frequencies.. so 6SK7 or 6SG7 isnt a one size fits all. Intermod {IMD} must be in the designer’s mind. ? Reminds me; at about grade 10 in school, and in the pursuit of getting more weak signals from Heathkit AR-3, ?I somehow connected an If output from the AR-3 into the early IF stage of an old console with a good AF amp and speaker; and man oh man; did I get stations… all over the dial from 540 kilocycles to 3o MCees. ?I had not yet discovered resonance, let alone intermod! Don VA3DRL ?
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From: [email protected] [mailto:[email protected]] On Behalf Of KW4H via groups.io
Sent: Thursday, October 27, 2022 5:22 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design? Thanks, Mike!? In contrast, National often used all 6SG7’s in their IF design (such as in my HRO-60).? The difference is an interesting point. ? 73 – Steve, KW4H ? Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901 (505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ? ? All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? ? 73 – Steve, KW4H ?
|
It isn't the gain but the Internal noise.? ?One can have too much gain.? The internal noise of a tube is roughly proportional to its Gm.? A 6SG7 has about four times the Gm of a 6SK7.? One problem with just plugging a "better" tube in is that the load resistances and other characteristics will be different.? For the better tube to be optimum the associated RF coils will have to be designed to match.?? While the higher Gm tube will be quieter it may not make s lot of difference at communications frequencies where atmospheric noise often exceeds receiver noise by many times.? ? Another factor at least for these two tubes is the range of control grid voltages.? A 6SK7 requires about 40 volts to be cut off,? 20V will cut off a 6SG7.? A 6BA6,? which is si.ilar to the 6SG7, also takes about 40 to 50V to cut off.? So the AVC and gain budget must be designed for the particular tube.? Minimising IMD also requires the correct voltages and transformer design. It's not a trivial problem.
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-------- Original message -------- From: don Root <drootofallevil@...> Date: 10/27/22 3:59 PM (GMT-08:00) Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design
Just thinking.. if the intent of the receiver was to function only with weak signals? present, the extra gain of the 6SG7 would be preferable, but if? there were strong in-band signals, the 6SK7 might be preferred. Seems to me ?there must be trade-offs depending on the rf gain[s], the AVC and any bypassing of an Rf amp ?for lower frequencies.. so 6SK7 or 6SG7 isnt a one size fits all. Intermod {IMD} must be in the designer’s mind. ? Reminds me; at about grade 10 in school, and in the pursuit of getting more weak signals from Heathkit AR-3, ?I somehow connected an If output from the AR-3 into the early IF stage of an old console with a good AF amp and speaker; and man oh man; did I get stations… all over the dial from 540 kilocycles to 3o MCees. ?I had not yet discovered resonance, let alone intermod! Don VA3DRL ? ? Thanks, Mike!? In contrast, National often used all 6SG7’s in their IF design (such as in my HRO-60).? The difference is an interesting point. ? 73 – Steve, KW4H ? Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901 (505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ? ? All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? ? 73 – Steve, KW4H ?
|
Don, ? Very interesting!? Well, as we all know a lot of this old equipment was designed for a specific price point and target audience.? There were receivers with weak front ends that had awesome audio (particularly the ones with auxiliary input), and there were radios with great front ends, but audio sections that were maybe one step above a handheld transistor radio.? A few were spectacular on both ends of the spectrum, but not many.? One example is my HRO-60, which has fantastic push-pull audio and (for the day, anyway) a highly sensitive front end (if you align it correctly and can deal with the coil drawer design). ?A Hammarlund HQ-180A, by comparison had only so-so audio, but fairly sensitive and selective reception.? Hallicrafters had them all over the scale as well.? ? I’ve never owned a SX-110 before and am admittedly fairly new to Hallicrafters designs (never had a Hallicrafters in my younger years), but am learning fast.? My impression so far is that the SX-110 (and its twin the SX-99) were midrange.? The audio isn’t push-pull, but it’s good enough.? The reception – I’m not sure about yet – I’m still working my way through the restoration, but have been working backwards from the audio output. ? 73 – Steve, KW4H ? Just thinking.. if the intent of the receiver was to function only with weak signals? present, the extra gain of the 6SG7 would be preferable, but if? there were strong in-band signals, the 6SK7 might be preferred. Seems to me ?there must be trade-offs depending on the rf gain[s], the AVC and any bypassing of an Rf amp ?for lower frequencies.. so 6SK7 or 6SG7 isnt a one size fits all. Intermod {IMD} must be in the designer’s mind. ? Reminds me; at about grade 10 in school, and in the pursuit of getting more weak signals from Heathkit AR-3, ?I somehow connected an If output from the AR-3 into the early IF stage of an old console with a good AF amp and speaker; and man oh man; did I get stations… all over the dial from 540 kilocycles to 3o MCees. ?I had not yet discovered resonance, let alone intermod! Don VA3DRL ?
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From: [email protected] [mailto:[email protected]] On Behalf Of KW4H via groups.io
Sent: Thursday, October 27, 2022 5:22 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design? Thanks, Mike!? In contrast, National often used all 6SG7’s in their IF design (such as in my HRO-60).? The difference is an interesting point. ? 73 – Steve, KW4H ? Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901 (505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ? ? All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? ? 73 – Steve, KW4H ?
|
Steve I agree with your comments, which I believe, apply to various big old consoles as well as communications receivers.? Your original comment “6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.” Is quite an observation of info that really does not stand-out. Hope your restoration proves interesting and successful. Don VA3DRL ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of KW4H via groups.io
Sent: Thursday, October 27, 2022 7:41 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design? Don, ? Very interesting!? Well, as we all know a lot of this old equipment was designed for a specific price point and target audience.? There were receivers with weak front ends that had awesome audio (particularly the ones with auxiliary input), and there were radios with great front ends, but audio sections that were maybe one step above a handheld transistor radio.? A few were spectacular on both ends of the spectrum, but not many.? One example is my HRO-60, which has fantastic push-pull audio and (for the day, anyway) a highly sensitive front end (if you align it correctly and can deal with the coil drawer design). ?A Hammarlund HQ-180A, by comparison had only so-so audio, but fairly sensitive and selective reception.? Hallicrafters had them all over the scale as well.? ? I’ve never owned a SX-110 before and am admittedly fairly new to Hallicrafters designs (never had a Hallicrafters in my younger years), but am learning fast.? My impression so far is that the SX-110 (and its twin the SX-99) were midrange.? The audio isn’t push-pull, but it’s good enough.? The reception – I’m not sure about yet – I’m still working my way through the restoration, but have been working backwards from the audio output. ? 73 – Steve, KW4H ? Just thinking.. if the intent of the receiver was to function only with weak signals? present, the extra gain of the 6SG7 would be preferable, but if? there were strong in-band signals, the 6SK7 might be preferred. Seems to me ?there must be trade-offs depending on the rf gain[s], the AVC and any bypassing of an Rf amp ?for lower frequencies.. so 6SK7 or 6SG7 isnt a one size fits all. Intermod {IMD} must be in the designer’s mind. ? Reminds me; at about grade 10 in school, and in the pursuit of getting more weak signals from Heathkit AR-3, ?I somehow connected an If output from the AR-3 into the early IF stage of an old console with a good AF amp and speaker; and man oh man; did I get stations… all over the dial from 540 kilocycles to 3o MCees. ?I had not yet discovered resonance, let alone intermod! Don VA3DRL ? ? Thanks, Mike!? In contrast, National often used all 6SG7’s in their IF design (such as in my HRO-60).? The difference is an interesting point. ? 73 – Steve, KW4H ? Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901 (505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ? ? All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? ? 73 – Steve, KW4H ?
|
Richard , and gang ? I believe Steve was talking about the tubes in the original design, and not discussing swapping tubes, but your notes about swapping seem valid, but are likely are only some of the considerations. I wonder if tube noise is a factor below 30 Mceees, but agree that the best performance I hard to find, and must have been lots of trial and error 6o years ago too. Don VA3DRL ? ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow
Sent: Thursday, October 27, 2022 7:38 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design? It isn't the gain but the Internal noise.? ?One can have too much gain.? The internal noise of a tube is roughly proportional to its Gm.? A 6SG7 has about four times the Gm of a 6SK7.? One problem with just plugging a "better" tube in is that the load resistances and other characteristics will be different.? For the better tube to be optimum the associated RF coils will have to be designed to match.?? While the higher Gm tube will be quieter it may not make s lot of difference at communications frequencies where atmospheric noise often exceeds receiver noise by many times.? ? Another factor at least for these two tubes is the range of control grid voltages.? A 6SK7 requires about 40 volts to be cut off,? 20V will cut off a 6SG7.? A 6BA6,? which is si.ilar to the 6SG7, also takes about 40 to 50V to cut off.? So the AVC and gain budget must be designed for the particular tube.? Minimising IMD also requires the correct voltages and transformer design. It's not a trivial problem. -------- Original message -------- From: don Root <drootofallevil@...> Date: 10/27/22 3:59 PM (GMT-08:00) Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design Just thinking.. if the intent of the receiver was to function only with weak signals? present, the extra gain of the 6SG7 would be preferable, but if? there were strong in-band signals, the 6SK7 might be preferred. Seems to me ?there must be trade-offs depending on the rf gain[s], the AVC and any bypassing of an Rf amp ?for lower frequencies.. so 6SK7 or 6SG7 isnt a one size fits all. Intermod {IMD} must be in the designer’s mind. ? Reminds me; at about grade 10 in school, and in the pursuit of getting more weak signals from Heathkit AR-3, ?I somehow connected an If output from the AR-3 into the early IF stage of an old console with a good AF amp and speaker; and man oh man; did I get stations… all over the dial from 540 kilocycles to 3o MCees. ?I had not yet discovered resonance, let alone intermod! Don VA3DRL ? ? Thanks, Mike!? In contrast, National often used all 6SG7’s in their IF design (such as in my HRO-60).? The difference is an interesting point. ? 73 – Steve, KW4H ? Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901 (505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ? ? All, A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? ? 73 – Steve, KW4H ?
|
Thanks, Don.? I’m admittedly a bit fussy about a couple of things – one is that I try to restore as true to the original as possible.? This can be particularly challenging when a radio has been – shall we say – “molested” by a mad scientist.? The other thing is that I enjoy writing articles about my restoration adventures and try to gather as much technical and historical information as possible.? The use of the 6SK7 as the 2nd IF caught my attention because what I’m used to seeing in most IF chains is a lineup of identical tubes.? For example, the HQ-180A is 6BA6’s.? The HRO-60 has a train of three 6SG7’s.? The Hallicrafters S-40 has two 6SK7’s in a row.? The NC-98 has two 6BD6’s in a row.? The use of a 6SG7 followed by a 6SK7 is very interesting! ? 73 – Steve, KW4H ? Steve I agree with your comments, which I believe, apply to various big old consoles as well as communications receivers.? Your original comment “6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.” Is quite an observation of info that really does not stand-out. Hope your restoration proves interesting and successful. Don VA3DRL ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of KW4H via groups.io
Sent: Thursday, October 27, 2022 7:41 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design? Don, ? Very interesting!? Well, as we all know a lot of this old equipment was designed for a specific price point and target audience.? There were receivers with weak front ends that had awesome audio (particularly the ones with auxiliary input), and there were radios with great front ends, but audio sections that were maybe one step above a handheld transistor radio.? A few were spectacular on both ends of the spectrum, but not many.? One example is my HRO-60, which has fantastic push-pull audio and (for the day, anyway) a highly sensitive front end (if you align it correctly and can deal with the coil drawer design). ?A Hammarlund HQ-180A, by comparison had only so-so audio, but fairly sensitive and selective reception.? Hallicrafters had them all over the scale as well.? ? I’ve never owned a SX-110 before and am admittedly fairly new to Hallicrafters designs (never had a Hallicrafters in my younger years), but am learning fast.? My impression so far is that the SX-110 (and its twin the SX-99) were midrange.? The audio isn’t push-pull, but it’s good enough.? The reception – I’m not sure about yet – I’m still working my way through the restoration, but have been working backwards from the audio output. ? 73 – Steve, KW4H ? Just thinking.. if the intent of the receiver was to function only with weak signals? present, the extra gain of the 6SG7 would be preferable, but if? there were strong in-band signals, the 6SK7 might be preferred. Seems to me ?there must be trade-offs depending on the rf gain[s], the AVC and any bypassing of an Rf amp ?for lower frequencies.. so 6SK7 or 6SG7 isnt a one size fits all. Intermod {IMD} must be in the designer’s mind. ? Reminds me; at about grade 10 in school, and in the pursuit of getting more weak signals from Heathkit AR-3, ?I somehow connected an If output from the AR-3 into the early IF stage of an old console with a good AF amp and speaker; and man oh man; did I get stations… all over the dial from 540 kilocycles to 3o MCees. ?I had not yet discovered resonance, let alone intermod! Don VA3DRL ? ? Thanks, Mike!? In contrast, National often used all 6SG7’s in their IF design (such as in my HRO-60).? The difference is an interesting point. ? 73 – Steve, KW4H ? Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901 (505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ? ? All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? ? 73 – Steve, KW4H ?
|
I must look at the schematic to see if I can figure out the reason for this.? It's not too unusual to see different tubes used in rf stages but is in if stages.? ?
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-------- Original message -------- From: "KW4H via groups.io" <reedsteve@...> Date: 10/27/22 8:57 PM (GMT-08:00) Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design
Thanks, Don.? I’m admittedly a bit fussy about a couple of things – one is that I try to restore as true to the original as possible.? This can be particularly challenging when a radio has been – shall we say – “molested” by a mad scientist.? The other thing is that I enjoy writing articles about my restoration adventures and try to gather as much technical and historical information as possible.? The use of the 6SK7 as the 2nd IF caught my attention because what I’m used to seeing in most IF chains is a lineup of identical tubes.? For example, the HQ-180A is 6BA6’s.? The HRO-60 has a train of three 6SG7’s.? The Hallicrafters S-40 has two 6SK7’s in a row.? The NC-98 has two 6BD6’s in a row.? The use of a 6SG7 followed by a 6SK7 is very interesting! ? 73 – Steve, KW4H ? Steve I agree with your comments, which I believe, apply to various big old consoles as well as communications receivers.? Your original comment “6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.” Is quite an observation of info that really does not stand-out. Hope your restoration proves interesting and successful. Don VA3DRL ? ? ? Don, ? Very interesting!? Well, as we all know a lot of this old equipment was designed for a specific price point and target audience.? There were receivers with weak front ends that had awesome audio (particularly the ones with auxiliary input), and there were radios with great front ends, but audio sections that were maybe one step above a handheld transistor radio.? A few were spectacular on both ends of the spectrum, but not many.? One example is my HRO-60, which has fantastic push-pull audio and (for the day, anyway) a highly sensitive front end (if you align it correctly and can deal with the coil drawer design). ?A Hammarlund HQ-180A, by comparison had only so-so audio, but fairly sensitive and selective reception.? Hallicrafters had them all over the scale as well.? ? I’ve never owned a SX-110 before and am admittedly fairly new to Hallicrafters designs (never had a Hallicrafters in my younger years), but am learning fast.? My impression so far is that the SX-110 (and its twin the SX-99) were midrange.? The audio isn’t push-pull, but it’s good enough.? The reception – I’m not sure about yet – I’m still working my way through the restoration, but have been working backwards from the audio output. ? 73 – Steve, KW4H ? Just thinking.. if the intent of the receiver was to function only with weak signals? present, the extra gain of the 6SG7 would be preferable, but if? there were strong in-band signals, the 6SK7 might be preferred. Seems to me ?there must be trade-offs depending on the rf gain[s], the AVC and any bypassing of an Rf amp ?for lower frequencies.. so 6SK7 or 6SG7 isnt a one size fits all. Intermod {IMD} must be in the designer’s mind. ? Reminds me; at about grade 10 in school, and in the pursuit of getting more weak signals from Heathkit AR-3, ?I somehow connected an If output from the AR-3 into the early IF stage of an old console with a good AF amp and speaker; and man oh man; did I get stations… all over the dial from 540 kilocycles to 3o MCees. ?I had not yet discovered resonance, let alone intermod! Don VA3DRL ? ? Thanks, Mike!? In contrast, National often used all 6SG7’s in their IF design (such as in my HRO-60).? The difference is an interesting point. ? 73 – Steve, KW4H ? Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901 (505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ? ? All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? ? 73 – Steve, KW4H ?
|
Hi again steve Interesting stuff.. hope you unravel the design differences for us. I don’t recall the 6SG7 as a kid; but my very hazy memory thinks it was a later octal. the tung-Sol sheets I just saw were ?dated 1948; ?If you allow a few years for it to be recognized, as a good bet, it would be too late for many receivers, But it was in use in 52 or 53 in that HRO-60. ?to check? all receivers would be a lot of work. so dunno?? ?Just a thought don VA3DRL ?
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From: [email protected] [mailto:[email protected]] On Behalf Of KW4H via groups.io
Sent: Thursday, October 27, 2022 11:58 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design? Thanks, Don.? I’m admittedly a bit fussy about a couple of things – one is that I try to restore as true to the original as possible.? This can be particularly challenging when a radio has been – shall we say – “molested” by a mad scientist.? The other thing is that I enjoy writing articles about my restoration adventures and try to gather as much technical and historical information as possible.? The use of the 6SK7 as the 2nd IF caught my attention because what I’m used to seeing in most IF chains is a lineup of identical tubes.? For example, the HQ-180A is 6BA6’s.? The HRO-60 has a train of three 6SG7’s.? The Hallicrafters S-40 has two 6SK7’s in a row.? The NC-98 has two 6BD6’s in a row.? The use of a 6SG7 followed by a 6SK7 is very interesting! ? 73 – Steve, KW4H ? Steve I agree with your comments, which I believe, apply to various big old consoles as well as communications receivers.? Your original comment “6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.” Is quite an observation of info that really does not stand-out. Hope your restoration proves interesting and successful. Don VA3DRL ? ? ? Don, ? Very interesting!? Well, as we all know a lot of this old equipment was designed for a specific price point and target audience.? There were receivers with weak front ends that had awesome audio (particularly the ones with auxiliary input), and there were radios with great front ends, but audio sections that were maybe one step above a handheld transistor radio.? A few were spectacular on both ends of the spectrum, but not many.? One example is my HRO-60, which has fantastic push-pull audio and (for the day, anyway) a highly sensitive front end (if you align it correctly and can deal with the coil drawer design). ?A Hammarlund HQ-180A, by comparison had only so-so audio, but fairly sensitive and selective reception.? Hallicrafters had them all over the scale as well.? ? I’ve never owned a SX-110 before and am admittedly fairly new to Hallicrafters designs (never had a Hallicrafters in my younger years), but am learning fast.? My impression so far is that the SX-110 (and its twin the SX-99) were midrange.? The audio isn’t push-pull, but it’s good enough.? The reception – I’m not sure about yet – I’m still working my way through the restoration, but have been working backwards from the audio output. ? 73 – Steve, KW4H ? Just thinking.. if the intent of the receiver was to function only with weak signals? present, the extra gain of the 6SG7 would be preferable, but if? there were strong in-band signals, the 6SK7 might be preferred. Seems to me ?there must be trade-offs depending on the rf gain[s], the AVC and any bypassing of an Rf amp ?for lower frequencies.. so 6SK7 or 6SG7 isnt a one size fits all. Intermod {IMD} must be in the designer’s mind. ? Reminds me; at about grade 10 in school, and in the pursuit of getting more weak signals from Heathkit AR-3, ?I somehow connected an If output from the AR-3 into the early IF stage of an old console with a good AF amp and speaker; and man oh man; did I get stations… all over the dial from 540 kilocycles to 3o MCees. ?I had not yet discovered resonance, let alone intermod! Don VA3DRL ? ? Thanks, Mike!? In contrast, National often used all 6SG7’s in their IF design (such as in my HRO-60).? The difference is an interesting point. ? 73 – Steve, KW4H ? Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901 (505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ? ? All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? ? 73 – Steve, KW4H =======trimd
|
? ?The 6SG7 dates from at least as early as 1940.? It is used as both RF and IF stages in the RCA AR 88 I don't know what other receivers of that Era it is found in.? It's also found as? the RF? stage in the Hallicrafters S 40B. It is a metal octal tube also supplied with a low loss base wafer.? The closest miniature is the 6BA6.? The two are similar in characteristics but are not identical. The 6BA6 is very widely used.??
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-------- Original message -------- From: don Root <drootofallevil@...> Date: 10/27/22 11:05 PM (GMT-08:00) Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design
Hi again steve Interesting stuff.. hope you unravel the design differences for us. I don’t recall the 6SG7 as a kid; but my very hazy memory thinks it was a later octal. the tung-Sol sheets I just saw were ?dated 1948; ?If you allow a few years for it to be recognized, as a good bet, it would be too late for many receivers, But it was in use in 52 or 53 in that HRO-60. ?to check? all receivers would be a lot of work. so dunno?? ?Just a thought don VA3DRL ? ? Thanks, Don.? I’m admittedly a bit fussy about a couple of things – one is that I try to restore as true to the original as possible.? This can be particularly challenging when a radio has been – shall we say – “molested” by a mad scientist.? The other thing is that I enjoy writing articles about my restoration adventures and try to gather as much technical and historical information as possible.? The use of the 6SK7 as the 2nd IF caught my attention because what I’m used to seeing in most IF chains is a lineup of identical tubes.? For example, the HQ-180A is 6BA6’s.? The HRO-60 has a train of three 6SG7’s.? The Hallicrafters S-40 has two 6SK7’s in a row.? The NC-98 has two 6BD6’s in a row.? The use of a 6SG7 followed by a 6SK7 is very interesting! ? 73 – Steve, KW4H ? Steve I agree with your comments, which I believe, apply to various big old consoles as well as communications receivers.? Your original comment “6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.” Is quite an observation of info that really does not stand-out. Hope your restoration proves interesting and successful. Don VA3DRL ? ? ? Don, ? Very interesting!? Well, as we all know a lot of this old equipment was designed for a specific price point and target audience.? There were receivers with weak front ends that had awesome audio (particularly the ones with auxiliary input), and there were radios with great front ends, but audio sections that were maybe one step above a handheld transistor radio.? A few were spectacular on both ends of the spectrum, but not many.? One example is my HRO-60, which has fantastic push-pull audio and (for the day, anyway) a highly sensitive front end (if you align it correctly and can deal with the coil drawer design). ?A Hammarlund HQ-180A, by comparison had only so-so audio, but fairly sensitive and selective reception.? Hallicrafters had them all over the scale as well.? ? I’ve never owned a SX-110 before and am admittedly fairly new to Hallicrafters designs (never had a Hallicrafters in my younger years), but am learning fast.? My impression so far is that the SX-110 (and its twin the SX-99) were midrange.? The audio isn’t push-pull, but it’s good enough.? The reception – I’m not sure about yet – I’m still working my way through the restoration, but have been working backwards from the audio output. ? 73 – Steve, KW4H ? Just thinking.. if the intent of the receiver was to function only with weak signals? present, the extra gain of the 6SG7 would be preferable, but if? there were strong in-band signals, the 6SK7 might be preferred. Seems to me ?there must be trade-offs depending on the rf gain[s], the AVC and any bypassing of an Rf amp ?for lower frequencies.. so 6SK7 or 6SG7 isnt a one size fits all. Intermod {IMD} must be in the designer’s mind. ? Reminds me; at about grade 10 in school, and in the pursuit of getting more weak signals from Heathkit AR-3, ?I somehow connected an If output from the AR-3 into the early IF stage of an old console with a good AF amp and speaker; and man oh man; did I get stations… all over the dial from 540 kilocycles to 3o MCees. ?I had not yet discovered resonance, let alone intermod! Don VA3DRL ? ? Thanks, Mike!? In contrast, National often used all 6SG7’s in their IF design (such as in my HRO-60).? The difference is an interesting point. ? 73 – Steve, KW4H ? Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901 (505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ? ? All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? ? 73 – Steve, KW4H =======trimd
|
About the 6SG7… Another receiver from the same Era than the RCA AR 88 is the Canadian Marconi Co. CSR-5A. 1st RF: 6SK7, 2nd RF: 6SG7, 1st IF: 6SG7, 2nd IF: 6SK7. The CSR-5A is also the first receiver (to my knowledge) using a miniature tube in the local oscillator: a 9002. From 1943, the RCA AR-88LF became the Canadian Army “standard receiver” but the CSR-5A became the Royal Canadian Navy counterpart. ? There is also more tubes that are close to the 6SG7 characteristics, including the 6AB7 (1853) used in the SX-28/28A. See: ? 73, Jacques, VE2JFE in Montreal ? Richard Knoppow wrote?: ? The 6SG7 dates from at least as early as 1940.? It is used as both RF and IF stages in the RCA AR 88 I don't know what other receivers of that Era it is found in.? It's also found as? the RF? stage in the Hallicrafters S 40B. It is a metal octal tube also supplied with a low loss base wafer.? The closest miniature is the 6BA6.? The two are similar in characteristics but are not identical. The 6BA6 is very widely used.??
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RICHARD , GOOD SLEUTHING!; ?looks like you found the 6SG6 used very early; and to find 5 of them in one radio. I wonder if they were developed by RCA, well they must have been. The original question posed by Steve becomes even more interesting/ mysterious. Perhaps the AR-88’s were intended to be located in quiet areas, where the front end would not get overloaded? Don VA3DRL ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow
Sent: Friday, October 28, 2022 2:50 AM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design? ? ?The 6SG7 dates from at least as early as 1940.? It is used as both RF and IF stages in the RCA AR 88 I don't know what other receivers of that Era it is found in.? It's also found as? the RF? stage in the Hallicrafters S 40B. It is a metal octal tube also supplied with a low loss base wafer.? The closest miniature is the 6BA6.? The two are similar in characteristics but are not identical. The 6BA6 is very widely used.?? -------- Original message -------- From: don Root <drootofallevil@...> Date: 10/27/22 11:05 PM (GMT-08:00) Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design Hi again steve Interesting stuff.. hope you unravel the design differences for us. I don’t recall the 6SG7 as a kid; but my very hazy memory thinks it was a later octal. the tung-Sol sheets I just saw were ?dated 1948; ?If you allow a few years for it to be recognized, as a good bet, it would be too late for many receivers, But it was in use in 52 or 53 in that HRO-60. ?to check? all receivers would be a lot of work. so dunno?? ?Just a thought don VA3DRL ? ? Thanks, Don.? I’m admittedly a bit fussy about a couple of things – one is that I try to restore as true to the original as possible.? This can be particularly challenging when a radio has been – shall we say – “molested” by a mad scientist.? The other thing is that I enjoy writing articles about my restoration adventures and try to gather as much technical and historical information as possible.? The use of the 6SK7 as the 2nd IF caught my attention because what I’m used to seeing in most IF chains is a lineup of identical tubes.? For example, the HQ-180A is 6BA6’s.? The HRO-60 has a train of three 6SG7’s.? The Hallicrafters S-40 has two 6SK7’s in a row.? The NC-98 has two 6BD6’s in a row.? The use of a 6SG7 followed by a 6SK7 is very interesting! ? 73 – Steve, KW4H ? Steve I agree with your comments, which I believe, apply to various big old consoles as well as communications receivers.? Your original comment “6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.” Is quite an observation of info that really does not stand-out. Hope your restoration proves interesting and successful. Don VA3DRL ? Don, ? Very interesting!? Well, as we all know a lot of this old equipment was designed for a specific price point and target audience.? There were receivers with weak front ends that had awesome audio (particularly the ones with auxiliary input), and there were radios with great front ends, but audio sections that were maybe one step above a handheld transistor radio.? A few were spectacular on both ends of the spectrum, but not many.? One example is my HRO-60, which has fantastic push-pull audio and (for the day, anyway) a highly sensitive front end (if you align it correctly and can deal with the coil drawer design). ?A Hammarlund HQ-180A, by comparison had only so-so audio, but fairly sensitive and selective reception.? Hallicrafters had them all over the scale as well.? ? I’ve never owned a SX-110 before and am admittedly fairly new to Hallicrafters designs (never had a Hallicrafters in my younger years), but am learning fast.? My impression so far is that the SX-110 (and its twin the SX-99) were midrange.? The audio isn’t push-pull, but it’s good enough.? The reception – I’m not sure about yet – I’m still working my way through the restoration, but have been working backwards from the audio output. ? 73 – Steve, KW4H ? Just thinking.. if the intent of the receiver was to function only with weak signals? present, the extra gain of the 6SG7 would be preferable, but if? there were strong in-band signals, the 6SK7 might be preferred. Seems to me ?there must be trade-offs depending on the rf gain[s], the AVC and any bypassing of an Rf amp ?for lower frequencies.. so 6SK7 or 6SG7 isnt a one size fits all. Intermod {IMD} must be in the designer’s mind. ? Reminds me; at about grade 10 in school, and in the pursuit of getting more weak signals from Heathkit AR-3, ?I somehow connected an If output from the AR-3 into the early IF stage of an old console with a good AF amp and speaker; and man oh man; did I get stations… all over the dial from 540 kilocycles to 3o MCees. ?I had not yet discovered resonance, let alone intermod! Don VA3DRL ? ? Thanks, Mike!? In contrast, National often used all 6SG7’s in their IF design (such as in my HRO-60).? The difference is an interesting point. ? 73 – Steve, KW4H ? Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901 (505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ? ? All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? 73 – Steve, KW4H =======trimd
|
Steve, Jacques, Richard +?? ? i somehow found this link ?where you can go down ?to “usages” of the 6SG7 ?and click and find some interesting but uncertain information ? it shows? Sg7’s but sometimes others? … I am not very familiar with the site but.. on the second line? “31=42”??? ?does list the CRS-5A and the AR-88 as well as many other early items keeps the SG? vs SK question more interesting. ? I can’t send this as a link so remove the quotes ““ ? Jacques; your link is interesting but going to take time to digest.. for me anyhow. ? don va3drl ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Jacques_VE2JFE
Sent: Friday, October 28, 2022 1:08 PM
To: [email protected]
Cc: 'Richard Knoppow'
Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design? About the 6SG7… Another receiver from the same Era than the RCA AR 88 is the Canadian Marconi Co. CSR-5A. 1st RF: 6SK7, 2nd RF: 6SG7, 1st IF: 6SG7, 2nd IF: 6SK7. The CSR-5A is also the first receiver (to my knowledge) using a miniature tube in the local oscillator: a 9002. From 1943, the RCA AR-88LF became the Canadian Army “standard receiver” but the CSR-5A became the Royal Canadian Navy counterpart. ? There is also more tubes that are close to the 6SG7 characteristics, including the 6AB7 (1853) used in the SX-28/28A. See: ? 73, Jacques, VE2JFE in Montreal ? Richard Knoppow wrote?: ? The 6SG7 dates from at least as early as 1940.? It is used as both RF and IF stages in the RCA AR 88 I don't know what other receivers of that Era it is found in.? It's also found as? the RF? stage in the Hallicrafters S 40B. It is a metal octal tube also supplied with a low loss base wafer.? The closest miniature is the 6BA6.? The two are similar in characteristics but are not identical. The 6BA6 is very widely used.??
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The AR 88 was designed to be a very advanced performance general purpose receiver.? They were never sold commercially ?The tubed were the most advanced available at the time . They are very interesting receivers.? ?Part of the good HF performance comes from the very low loss coils used. Polystyrene formers used on the top three bands and? ceramic insulation elsewhere. The image suppression is very high for a single conversion receiver.??
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-------- Original message -------- From: don Root <drootofallevil@...> Date: 10/28/22 11:26 AM (GMT-08:00) Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design
RICHARD , GOOD SLEUTHING!; ?looks like you found the 6SG6 used very early; and to find 5 of them in one radio. I wonder if they were developed by RCA, well they must have been. The original question posed by Steve becomes even more interesting/ mysterious. Perhaps the AR-88’s were intended to be located in quiet areas, where the front end would not get overloaded? Don VA3DRL ? ? ? ?The 6SG7 dates from at least as early as 1940.? It is used as both RF and IF stages in the RCA AR 88 I don't know what other receivers of that Era it is found in.? It's also found as? the RF? stage in the Hallicrafters S 40B. It is a metal octal tube also supplied with a low loss base wafer.? The closest miniature is the 6BA6.? The two are similar in characteristics but are not identical. The 6BA6 is very widely used.?? -------- Original message -------- From: don Root <drootofallevil@...> Date: 10/27/22 11:05 PM (GMT-08:00) Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design Hi again steve Interesting stuff.. hope you unravel the design differences for us. I don’t recall the 6SG7 as a kid; but my very hazy memory thinks it was a later octal. the tung-Sol sheets I just saw were ?dated 1948; ?If you allow a few years for it to be recognized, as a good bet, it would be too late for many receivers, But it was in use in 52 or 53 in that HRO-60. ?to check? all receivers would be a lot of work. so dunno?? ?Just a thought don VA3DRL ? ? Thanks, Don.? I’m admittedly a bit fussy about a couple of things – one is that I try to restore as true to the original as possible.? This can be particularly challenging when a radio has been – shall we say – “molested” by a mad scientist.? The other thing is that I enjoy writing articles about my restoration adventures and try to gather as much technical and historical information as possible.? The use of the 6SK7 as the 2nd IF caught my attention because what I’m used to seeing in most IF chains is a lineup of identical tubes.? For example, the HQ-180A is 6BA6’s.? The HRO-60 has a train of three 6SG7’s.? The Hallicrafters S-40 has two 6SK7’s in a row.? The NC-98 has two 6BD6’s in a row.? The use of a 6SG7 followed by a 6SK7 is very interesting! ? 73 – Steve, KW4H ? Steve I agree with your comments, which I believe, apply to various big old consoles as well as communications receivers.? Your original comment “6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.” Is quite an observation of info that really does not stand-out. Hope your restoration proves interesting and successful. Don VA3DRL ? Don, ? Very interesting!? Well, as we all know a lot of this old equipment was designed for a specific price point and target audience.? There were receivers with weak front ends that had awesome audio (particularly the ones with auxiliary input), and there were radios with great front ends, but audio sections that were maybe one step above a handheld transistor radio.? A few were spectacular on both ends of the spectrum, but not many.? One example is my HRO-60, which has fantastic push-pull audio and (for the day, anyway) a highly sensitive front end (if you align it correctly and can deal with the coil drawer design). ?A Hammarlund HQ-180A, by comparison had only so-so audio, but fairly sensitive and selective reception.? Hallicrafters had them all over the scale as well.? ? I’ve never owned a SX-110 before and am admittedly fairly new to Hallicrafters designs (never had a Hallicrafters in my younger years), but am learning fast.? My impression so far is that the SX-110 (and its twin the SX-99) were midrange.? The audio isn’t push-pull, but it’s good enough.? The reception – I’m not sure about yet – I’m still working my way through the restoration, but have been working backwards from the audio output. ? 73 – Steve, KW4H ? Just thinking.. if the intent of the receiver was to function only with weak signals? present, the extra gain of the 6SG7 would be preferable, but if? there were strong in-band signals, the 6SK7 might be preferred. Seems to me ?there must be trade-offs depending on the rf gain[s], the AVC and any bypassing of an Rf amp ?for lower frequencies.. so 6SK7 or 6SG7 isnt a one size fits all. Intermod {IMD} must be in the designer’s mind. ? Reminds me; at about grade 10 in school, and in the pursuit of getting more weak signals from Heathkit AR-3, ?I somehow connected an If output from the AR-3 into the early IF stage of an old console with a good AF amp and speaker; and man oh man; did I get stations… all over the dial from 540 kilocycles to 3o MCees. ?I had not yet discovered resonance, let alone intermod! Don VA3DRL ? ? Thanks, Mike!? In contrast, National often used all 6SG7’s in their IF design (such as in my HRO-60).? The difference is an interesting point. ? 73 – Steve, KW4H ? Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901 (505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ? ? All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? 73 – Steve, KW4H =======trimd
|
I have not looked at the CSR 5 handbook but suspect you have the order of the RF reversed.? The other tubes , like the 1853, are really not like the 6SG7.? They were designed for wide band television IF use.? As RF tubes they have rather low impedance making it difficult to get good selectivity .?? I have lost a word,? means non-beluever,? but I think the well loved SX 28? has some serious design flaws.? Hallicrafters liked to use hot tubes but they were not always used well.?
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-------- Original message -------- From: Jacques_VE2JFE <jacques.f@...> Date: 10/28/22 11:11 AM (GMT-08:00) Cc: 'Richard Knoppow' <1oldlens1@...> Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design
About the 6SG7… Another receiver from the same Era than the RCA AR 88 is the Canadian Marconi Co. CSR-5A. 1st RF: 6SK7, 2nd RF: 6SG7, 1st IF: 6SG7, 2nd IF: 6SK7. The CSR-5A is also the first receiver (to my knowledge) using a miniature tube in the local oscillator: a 9002. From 1943, the RCA AR-88LF became the Canadian Army “standard receiver” but the CSR-5A became the Royal Canadian Navy counterpart. ? There is also more tubes that are close to the 6SG7 characteristics, including the 6AB7 (1853) used in the SX-28/28A. See: ? 73, Jacques, VE2JFE in Montreal ? Richard Knoppow wrote?: ? The 6SG7 dates from at least as early as 1940.? It is used as both RF and IF stages in the RCA AR 88 I don't know what other receivers of that Era it is found in.? It's also found as? the RF? stage in the Hallicrafters S 40B. It is a metal octal tube also supplied with a low loss base wafer.? The closest miniature is the 6BA6.? The two are similar in characteristics but are not identical. The 6BA6 is very widely used.??
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Today I pulled out the big gun – Osterman’s book.? Looking at the IF tubes of some of the Hallicrafters (listed in order of IF) – and this is not a comprehensive list – I “think” it’s possible to derive at least part of what may have been going on.? Note that there are a lot of 6SK7’s and 6SG7’s from the late ‘30s through about the mid-‘50s.? The 6BA6’s began to appear sometime mid-‘50s, and by the early to mid ‘60s the 6SG7’s and relatives were mostly gone.? According to Radiomuseum, the first year for the 6SK7 was 1938, and the first year for the 6SG7 was 1941.? ? Now, look at the SX-110, and how it followed the SX-99.? Timing is important.? The SX-99 was in production from ’55 to ’58, and then the 6BA6’s came into favor (smaller base and other advantages).? Hallicrafters produced the SX-100 and SX-101, saw the advantages of the 6BA6 design, and may have literally tried to clear their stock of the old 6SG7’s and 6SK7’s with the retread of the SX-99 in a more “jet age” style cabinet. ? The reason for using both tubes may not have been technical, it may have been a business decision.? They may have had a large stock of 6SG7 and 6SK7 tubes and wanted to move as many out as possible before they became a liability. ? As a disclaimer – this is nothing but a wild guess based on the info below.? ? 73 – Steve, KW4H ? SX-23 (1939-40) 6SK7, 6SK7 SX-24 (1939-43) 6SK7, 6SK7 SX-25 (1940-46) 6SK7, 6SK7 SX-28A (1944-45) 6L7, 6SK7 SX-42 (1947-50) 6SK7, 6SG7 SX-43 (1947-50) 6SG7, 6SH7, 6SH7 SX-62 (1949-53) 6SK7, 6SG7 SX-71 (1949-54) 6SK7, 6SK7, 6SH7 SX-96 (1954-56) 6BA6, 6BA6 S-85 (1954-57) 6SK7, 6SK7 SX-99 (1955-58) 6SG7, 6SK7 SX-100 (1955-62) 6BA6, 6BA6 SX-101 (1955-58) 6BA6, 6BA6 SX-110 (1960-63) 6SG7, 6SH7 SX-111 (1960-63) 6CB6, 6DC6 SX-115 (1961-64) 6DC6, 6DC6, 6DC6 SX-117 (1961-65) 6BA6, 6DC6, 6BA6 SX-122 (1964-71) 6DC6, 6BA6, ? ? ? ? ? Hi again steve Interesting stuff.. hope you unravel the design differences for us. I don’t recall the 6SG7 as a kid; but my very hazy memory thinks it was a later octal. the tung-Sol sheets I just saw were ?dated 1948; ?If you allow a few years for it to be recognized, as a good bet, it would be too late for many receivers, But it was in use in 52 or 53 in that HRO-60. ?to check? all receivers would be a lot of work. so dunno?? ?Just a thought don VA3DRL ?
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From: [email protected] [mailto:[email protected]] On Behalf Of KW4H via groups.io
Sent: Thursday, October 27, 2022 11:58 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design? Thanks, Don.? I’m admittedly a bit fussy about a couple of things – one is that I try to restore as true to the original as possible.? This can be particularly challenging when a radio has been – shall we say – “molested” by a mad scientist.? The other thing is that I enjoy writing articles about my restoration adventures and try to gather as much technical and historical information as possible.? The use of the 6SK7 as the 2nd IF caught my attention because what I’m used to seeing in most IF chains is a lineup of identical tubes.? For example, the HQ-180A is 6BA6’s.? The HRO-60 has a train of three 6SG7’s.? The Hallicrafters S-40 has two 6SK7’s in a row.? The NC-98 has two 6BD6’s in a row.? The use of a 6SG7 followed by a 6SK7 is very interesting! ? 73 – Steve, KW4H ? Steve I agree with your comments, which I believe, apply to various big old consoles as well as communications receivers.? Your original comment “6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.” Is quite an observation of info that really does not stand-out. Hope your restoration proves interesting and successful. Don VA3DRL ? ? ? Don, ? Very interesting!? Well, as we all know a lot of this old equipment was designed for a specific price point and target audience.? There were receivers with weak front ends that had awesome audio (particularly the ones with auxiliary input), and there were radios with great front ends, but audio sections that were maybe one step above a handheld transistor radio.? A few were spectacular on both ends of the spectrum, but not many.? One example is my HRO-60, which has fantastic push-pull audio and (for the day, anyway) a highly sensitive front end (if you align it correctly and can deal with the coil drawer design). ?A Hammarlund HQ-180A, by comparison had only so-so audio, but fairly sensitive and selective reception.? Hallicrafters had them all over the scale as well.? ? I’ve never owned a SX-110 before and am admittedly fairly new to Hallicrafters designs (never had a Hallicrafters in my younger years), but am learning fast.? My impression so far is that the SX-110 (and its twin the SX-99) were midrange.? The audio isn’t push-pull, but it’s good enough.? The reception – I’m not sure about yet – I’m still working my way through the restoration, but have been working backwards from the audio output. ? 73 – Steve, KW4H ? Just thinking.. if the intent of the receiver was to function only with weak signals? present, the extra gain of the 6SG7 would be preferable, but if? there were strong in-band signals, the 6SK7 might be preferred. Seems to me ?there must be trade-offs depending on the rf gain[s], the AVC and any bypassing of an Rf amp ?for lower frequencies.. so 6SK7 or 6SG7 isnt a one size fits all. Intermod {IMD} must be in the designer’s mind. ? Reminds me; at about grade 10 in school, and in the pursuit of getting more weak signals from Heathkit AR-3, ?I somehow connected an If output from the AR-3 into the early IF stage of an old console with a good AF amp and speaker; and man oh man; did I get stations… all over the dial from 540 kilocycles to 3o MCees. ?I had not yet discovered resonance, let alone intermod! Don VA3DRL ? ? Thanks, Mike!? In contrast, National often used all 6SG7’s in their IF design (such as in my HRO-60).? The difference is an interesting point. ? 73 – Steve, KW4H ? Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901 (505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ? ? All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? ? 73 – Steve, KW4H =======trimd
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Richard ????getting off topic a bit but you raise the question of coil losses: are these due to the /any coil form material and its dielectric loss or a mixture of that and ?coil stranding, coil wire insulation and ?its magnetic environment. Do you have any evidence? that a few more bux could get you reduced losses.. and is there a list of materials.. and does it really matter? ?this is a question!! ?guess we need a new topic. don ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow
Sent: Friday, October 28, 2022 4:12 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design? The AR 88 was designed to be a very advanced performance general purpose receiver.? They were never sold commercially ?The tubed were the most advanced available at the time . They are very interesting receivers.? ?Part of the good HF performance comes from the very low loss coils used. Polystyrene formers used on the top three bands and? ceramic insulation elsewhere. The image suppression is very high for a single conversion receiver -------- Original message -------- From: don Root <drootofallevil@...> Date: 10/28/22 11:26 AM (GMT-08:00) Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design RICHARD , GOOD SLEUTHING!; ?looks like you found the 6SG6 used very early; and to find 5 of them in one radio. I wonder if they were developed by RCA, well they must have been. The original question posed by Steve becomes even more interesting/ mysterious. Perhaps the AR-88’s were intended to be located in quiet areas, where the front end would not get overloaded? Don VA3DRL ? ?The 6SG7 dates from at least as early as 1940.? It is used as both RF and IF stages in the RCA AR 88 I don't know what other receivers of that Era it is found in.? It's also found as? the RF? stage in the Hallicrafters S 40B. It is a metal octal tube also supplied with a low loss base wafer.? The closest miniature is the 6BA6.? The two are similar in characteristics but are not identical. The 6BA6 is very widely used.?? -------- Original message -------- From: don Root <drootofallevil@...> Date: 10/27/22 11:05 PM (GMT-08:00) Subject: Re: [HallicraftersRadios] SX-110 2nd IF Circuit Design ? Hi again steve Interesting stuff.. hope you unravel the design differences for us. I don’t recall the 6SG7 as a kid; but my very hazy memory thinks it was a later octal. the tung-Sol sheets I just saw were ?dated 1948; ?If you allow a few years for it to be recognized, as a good bet, it would be too late for many receivers, But it was in use in 52 or 53 in that HRO-60. ?to check? all receivers would be a lot of work. so dunno?? ?Just a thought don VA3DRL ? Thanks, Don.? I’m admittedly a bit fussy about a couple of things – one is that I try to restore as true to the original as possible.? This can be particularly challenging when a radio has been – shall we say – “molested” by a mad scientist.? The other thing is that I enjoy writing articles about my restoration adventures and try to gather as much technical and historical information as possible.? The use of the 6SK7 as the 2nd IF caught my attention because what I’m used to seeing in most IF chains is a lineup of identical tubes.? For example, the HQ-180A is 6BA6’s.? The HRO-60 has a train of three 6SG7’s.? The Hallicrafters S-40 has two 6SK7’s in a row.? The NC-98 has two 6BD6’s in a row.? The use of a 6SG7 followed by a 6SK7 is very interesting! 73 – Steve, KW4H Steve I agree with your comments, which I believe, apply to various big old consoles as well as communications receivers.? Your original comment “6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.” Is quite an observation of info that really does not stand-out. Hope your restoration proves interesting and successful. Don VA3DRL ? Don, ? Very interesting!? Well, as we all know a lot of this old equipment was designed for a specific price point and target audience.? There were receivers with weak front ends that had awesome audio (particularly the ones with auxiliary input), and there were radios with great front ends, but audio sections that were maybe one step above a handheld transistor radio.? A few were spectacular on both ends of the spectrum, but not many.? One example is my HRO-60, which has fantastic push-pull audio and (for the day, anyway) a highly sensitive front end (if you align it correctly and can deal with the coil drawer design). ?A Hammarlund HQ-180A, by comparison had only so-so audio, but fairly sensitive and selective reception.? Hallicrafters had them all over the scale as well.? ? I’ve never owned a SX-110 before and am admittedly fairly new to Hallicrafters designs (never had a Hallicrafters in my younger years), but am learning fast.? My impression so far is that the SX-110 (and its twin the SX-99) were midrange.? The audio isn’t push-pull, but it’s good enough.? The reception – I’m not sure about yet – I’m still working my way through the restoration, but have been working backwards from the audio output. ? 73 – Steve, KW4H ? Just thinking.. if the intent of the receiver was to function only with weak signals? present, the extra gain of the 6SG7 would be preferable, but if? there were strong in-band signals, the 6SK7 might be preferred. Seems to me ?there must be trade-offs depending on the rf gain[s], the AVC and any bypassing of an Rf amp ?for lower frequencies.. so 6SK7 or 6SG7 isnt a one size fits all. Intermod {IMD} must be in the designer’s mind. ? Reminds me; at about grade 10 in school, and in the pursuit of getting more weak signals from Heathkit AR-3, ?I somehow connected an If output from the AR-3 into the early IF stage of an old console with a good AF amp and speaker; and man oh man; did I get stations… all over the dial from 540 kilocycles to 3o MCees. ?I had not yet discovered resonance, let alone intermod! Don VA3DRL ? ? Thanks, Mike!? In contrast, National often used all 6SG7’s in their IF design (such as in my HRO-60).? The difference is an interesting point. ? 73 – Steve, KW4H ? Hello Steve!
Excellent question!
The 6SG7 has higher gain than the 6SK7.
The 6SK7 can handle stronger signals.
And the 6SK7 provides better AGC control since it’s a remote cutoff tube.? The 6SG7 is semi-remote cutoff. ? I hope this helps!
Mike/
K5MGR
__________________________________ ? Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901 (505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... ? ? All, ? A curiosity – I’m restoring a SX-110 at the moment and see that a 6SK7 was used for the 2nd IF, while a 6SG7 is used for the 1st IF.? I’m trying to understand why that is – why not use two 6SG7’s?? What was magical about the 6SK7? 73 – Steve, KW4H =======trimd
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Hi Richard, ? For the order of the CSR-5A RF tubes, absolutely not. Makes no sense (intuitively) to me also, but that’s how it was done. It is a fairly rare receiver compared to the other ones made in WWII. Maybe 1250 units made… There are still many in Canada (I have three…), and the other country where you can find some is New Zealand. ? All that you can learn about (or not) is here: ? 73, Jacques, VE2JFE in Montreal ? I have not looked at the CSR 5 handbook but suspect you have the order of the RF reversed.? The other tubes , like the 1853, are really not like the 6SG7.? They were designed for wide band television IF use.? As RF tubes they have rather low impedance making it difficult to get good selectivity .?? I have lost a word,? means non-beluever,? but I think the well loved SX 28? has some serious design flaws.? Hallicrafters liked to use hot tubes but they were not always used well.?
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Mike Langner
don Root
Jacques_VE2JFE