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Re: Loaded Plate chokes...again
¿ªÔÆÌåÓý
I can assure you the Floyd chokes do not blow up.? You know that also. It must be like you said, a different material.?
?I have used those chokes in several amps.? A Dual 3-1000Z amp with 6kv on plates, It runs 15 to 160.? never an issue. Amp does 5kw out plus.? It's been in there for maybe 6 years now.??
This amp would KILL other chokes.? I started out with a linear wound choke, That one had a burn spot and arc.? I then tried an ameritron choke and that failed. I put a Glitch resistor and a second ameritron choke. I thought maybe it had a flash over and that
took the choke out.? That did not help. The second choke failed almost immediately on 80 meter SSB.? The odd thing about it is that the ameritron would UNWIND right in front of your eyes.? You could hear a metal spooling sound and all the wires were in a ball
down low on the form.? ?I was confused at the time as to what was going on with it.? I got the first choke from Floyd and it never did this again.
I have one in the 4x10 and it runs 15 to 80 meters. 20kw out and never a problem.? ?
I did have one problem with this choke.. I installed one in a Johnson desk KW.? This is a pair of 4-400s plate modulated by 810s.? I lost 15 meters completely and had trouble getting it to load on 10.? I pulled the deck back out, Put the Johnson choke back
in and the problem was fixed.? ?I think the Desk KW actually has two chokes and that was likely my issue. I only changed the one near the finals.
I have a few of those in the parts bin. Is there a way I can test or inspect to see which material they are?
C
From: [email protected] <[email protected]> on behalf of Jim VE7RF via groups.io <jim.thom@...>
Sent: Wednesday, February 14, 2024 2:07 AM To: [email protected] <[email protected]> Subject: Re: [ham-amplifiers] Loaded Plate chokes...again ?
<Jim. Thanks for the Post.? That is a real eye opener.? Sadly, I placed a Choke very close to the back wall of my amps.? It seems to run ok but that is great information.??
?
<I remember us talking about these new chokes. I am glad you got one built!? ?Can you post a picture of it?
?
<C
?
I spoke with Floyd a few yrs back, and I think he said he used type 43. IF his beads are 2" tall, they have to be type 43.? Floyd has his 5000 sq ft new machine shop. He takes 1" solid teflon rod and machines out the inside to take the slightly bigger .767"
OD beads.... with their .400" ID. Floyd doesn't machine it to the very bottom, just to the bottom of the winding.? ?He then drills and taps the base for a 1/4-20? nylon bolt....to mount to chassis.?
?
I have no easy access to any machine shop so bought a doz 1' lengths of hollow teflon tubing from McMaster-Carr.? It's listed as 1" OD? x .125" wall thickness.? ?Then they state...'slightly thicker so u can do ur own final precision machining'.? ?Well all mine
are thicker.... at .145" wall. With an ID of now just .710" (instead of? .750")? my originally planned .767" x 2" long x .400" ID? (type 43)? beads would not fit.? I got a caseload from a local buddy, we use em to slide over 393 coax, (.393" OD)... they will
NOT slide over 213-U? ( .405")
?
Ok, so ordered the smaller .687" OD beads.? ?Got into it with W8JI.? ?He claims that where U1 and U2? cross on the graph, the Q? of the ferrite = 0.? ? And when Q=0 = kaboom.? ?Well U1 + U2 cross at exactly 7 mhz using type 43.? Your floyd choke doesn't blow
up on a 4x10..and it uses type 43.? ? So I mentioned to W8JI that type 61 has U1 + U2 crossing at exactly 45 mhz.? He? sez... still not good enough and that they will? all dissipate 5 kw, and explode immediately.? ?After analyzing this for hrs, I believe that
type 61 is the preferred material.? Even though U1 = 125 (vs 800 for type 43).... the 2 x chokes I have made so far have bucketloads of uh.? ?Type 61 has a lot higher curie temp, like > 300 deg C. (type 43 is just 150 deg C).? Resistivity is a magnitude higher
on type 61 vs type 43. ( 100 megohms per cm? ?for type 61? ?vs 10 megohms per cm for type 43.?
?
Then I also factored in the wire used for the winding.? Teflon has a dielectric constant of just 2.1? ?Magnet wire has a dielectric constant of 4.0 to 4.2? (air is 1.0)? .? This 22 ga teflon wire I got on ebay (belden)? is .060" OD, but the inner 22 ga wire
is just .028".? ?Inner core consists of 7 x strands of silver plated wire, which of course is twisted.? With turns butt? tight on the form,? it's almost like space winding turns.? Dunno how much the .016" wall thickness of the teflon insulation affects the
overall dielectric constant.? On paper, it should have 1/2 the interwinding capacitance? vs magnet? wire... and 1/2 again, since it's effectively space wound.?
?
With all the beads removed, it drops from 315 uh....down to just 33 uh.?
?
?
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8410/9500 Wattmeter Failure
I have an 8410; however, according to the schematic(s), it appears as if
it probly uses the same wattmeter as the 9500. The other day, I encountered intermittent flashover in my external antenna tuner while running around 1100 watts on 160; it would cause all the reflected power LEDs on my 8410 to light up. I managed to finish working someone, let the amp cool down for five mins, then shut it down. All front panel indicators appeared to work properly at that time (although I've never, ever, seen a grid current LED light up, nor the FAULT LED even though I once did have a real fault where I thought that LED SHOULD light... but it didn't). The output power and reflected power indicators have always been very accurate and worked fine. Later that day, I fired it up again... and was chagrined to find NO output power indicated on the front panel LEDs... neither forward nor reverse. But the amp was still amplifying normally; output power on an external wattmeter indicated full power out. I fired up the AE9K Alpha Monitor program and it, too, shows no output power. But the amp does still have full output power; so something common to both forward and reverse power that drives the front panel display failed in my amp. When the tuner flashed over, my external LP-100A power meter usually indicated something really high like over 2500 watts momentarily.. once, I think I saw 2932 watts indicated? ===8-O? Since then, I've fixed the tuner problem... but have no output power indication on either the amplifier front panel, nor with the AE9K Alpha Monitor program, even though the amp is actually still correctly putting out full power. I'm now printing out all 19 pages of the schematics, but an eyeball perusal in Acrobat hasn't yet identified exactly which connector carries the output of the tube deck to the TR system and what it plugs into on another schematic page. Meanwhile, I thought I'd ask here, in case someone else has already "invented the wheel" and fixed this kind of problem. Any help? TNX, Steve K0XP |
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Re: Loaded Plate chokes...again
<Jim. Thanks for the Post.? That is a real eye opener.? Sadly, I placed a Choke very close to the back wall of my amps.? It seems to run ok but that is great information.??
?
<I remember us talking about these new chokes. I am glad you got one built!? ?Can you post a picture of it?
?
<C
?
I spoke with Floyd a few yrs back, and I think he said he used type 43. IF his beads are 2" tall, they have to be type 43.? Floyd has his 5000 sq ft new machine shop. He takes 1" solid teflon rod and machines out the inside to take the slightly bigger .767" OD beads.... with their .400" ID. Floyd doesn't machine it to the very bottom, just to the bottom of the winding.? ?He then drills and taps the base for a 1/4-20? nylon bolt....to mount to chassis.?
?
I have no easy access to any machine shop so bought a doz 1' lengths of hollow teflon tubing from McMaster-Carr.? It's listed as 1" OD? x .125" wall thickness.? ?Then they state...'slightly thicker so u can do ur own final precision machining'.? ?Well all mine are thicker.... at .145" wall. With an ID of now just .710" (instead of? .750")? my originally planned .767" x 2" long x .400" ID? (type 43)? beads would not fit.? I got a caseload from a local buddy, we use em to slide over 393 coax, (.393" OD)... they will NOT slide over 213-U? ( .405")
?
Ok, so ordered the smaller .687" OD beads.? ?Got into it with W8JI.? ?He claims that where U1 and U2? cross on the graph, the Q? of the ferrite = 0.? ? And when Q=0 = kaboom.? ?Well U1 + U2 cross at exactly 7 mhz using type 43.? Your floyd choke doesn't blow up on a 4x10..and it uses type 43.? ? So I mentioned to W8JI that type 61 has U1 + U2 crossing at exactly 45 mhz.? He? sez... still not good enough and that they will? all dissipate 5 kw, and explode immediately.? ?After analyzing this for hrs, I believe that type 61 is the preferred material.? Even though U1 = 125 (vs 800 for type 43).... the 2 x chokes I have made so far have bucketloads of uh.? ?Type 61 has a lot higher curie temp, like > 300 deg C. (type 43 is just 150 deg C).? Resistivity is a magnitude higher on type 61 vs type 43. ( 100 megohms per cm? ?for type 61? ?vs 10 megohms per cm for type 43.?
?
Then I also factored in the wire used for the winding.? Teflon has a dielectric constant of just 2.1? ?Magnet wire has a dielectric constant of 4.0 to 4.2? (air is 1.0)? .? This 22 ga teflon wire I got on ebay (belden)? is .060" OD, but the inner 22 ga wire is just .028".? ?Inner core consists of 7 x strands of silver plated wire, which of course is twisted.? With turns butt? tight on the form,? it's almost like space winding turns.? Dunno how much the .016" wall thickness of the teflon insulation affects the overall dielectric constant.? On paper, it should have 1/2 the interwinding capacitance? vs magnet? wire... and 1/2 again, since it's effectively space wound.?
?
With all the beads removed, it drops from 315 uh....down to just 33 uh.?
?
? |
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Re: Loaded Plate chokes...again
¿ªÔÆÌåÓý
I am interested in learning more RIkki.? This is how one of my respected amplifier builders always handles the plate choke. He uses two, Never switched.? Each tuned.? Sounds like a good solution. Especially if you have space limitations.? Where are the resonances
of your example?? What values are each of the chokes?? How did you build them?
From: [email protected] <[email protected]> on behalf of Riki, K7NJ via groups.io <k7nj@...>
Sent: Tuesday, February 13, 2024 11:08 AM To: [email protected] <[email protected]> Subject: Re: [ham-amplifiers] Loaded Plate chokes...again ?
Instead of a loaded plate choke with all its issues, I used two separate chokes located to eliminate (or minimize) undesirable coupling between them.? The series resonances of each individual choke are far apart.? The result of this combination is equivalent
to an ideal high impedance broadband choke without series resonances. Think about it: a short circuit in series with an open circuit is equivalent to an open circuit :-)
-- 73 Riki? K7NJ |
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Re: Loaded Plate chokes...again
Instead of a loaded plate choke with all its issues, I used two separate chokes located to eliminate (or minimize) undesirable coupling between them.? The series resonances of each individual choke are far apart.? The result of this combination is equivalent to an ideal high impedance broadband choke without series resonances. Think about it: a short circuit in series with an open circuit is equivalent to an open circuit :-)
-- 73 Riki? K7NJ |
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Re: Loaded Plate chokes...again
The reason a 4' length of magnet wire on the carpet? ( same 22 ga) runs at room temp, vs teflon coated wire on a choke is...? the heat can escape on the 4' length.? ?I stuffed 5 amps? ccs though the magnet wire...and zero heat increase, none. With 22 ga ( silver plated and stranded) teflon coated wire wound on a 1" OD teflon? former, any heat generated in the wire can't readily escape.? ?The turns are butt tight, there is no air between turns.? ?Heat can't go through the 1" OD teflon tube either.? ?It can only escape out the upper? 60 degs of it's 360 deg total circumference.? That was another reason to use 22 ga teflon wire vs smaller gauges.? That and teflon has a dielectric constant of 2.1? ?vs 4.2? for magnet wire.? C between turns on magnet wire is double that of teflon coated wire.? ?More C shifts the series resonance freqs even lower.? That and this particular Belden 22 ga PTFE wire has thick insulation.? It's .060"? OD? (inner wires is just .028" OD).? Smaller gauges run a lot hotter, and won't work with this application.? ? Later... |
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Re: Loaded Plate chokes...again
Ok, here's the deal.? ?Room temp is 70 F.? After 2 hrs,? the hottest part of the winding hit 107.7 F.? (That's barely luke warm) Inductance was 305 uh with no current and just 70 F room temp on the winding.? ? This dropped to 302 uh when current drawn and windings at 107.7 F.? ? ? On the vna,? series resonant freq? shifted? HIGHER? when warm vs room temp.? (19.479 mhz? with winding at 70 F room temp, and no current drawn)? vs? 19.728 uh when winding is 107.7 F....and after sucking 3.222 amps for 2 hrs.? That's a? 249 khz shift upwards in the series resonant freq.? This shift has also been factored in.? As is, the choke is safe, I just want it safer, hence adding another 8.33 turns.? ?The choke can't be used +/- 750 khz from it's series resonant freq....and I want it a lot further than that..? In normal operation, plate current is 2.5 amps.? ? And worse case for RF current through the choke is on 160m.... at a calculated value of 1.217 amps. ( 7 kv loaded B+? X .6 = 4200 V rms).? (4200 vrms / 3449 ohms of XL? = 1.217 amps of RF through the choke @ 1.8 mhz).? ( That's exactly how W8Ji and also Rich Measures calculated RF current through the choke).? If I can barely get it warm after 2 solid hrs with 3.222 amps of DC current flowing through it...... it's gonna be a non issue.? At least that's the plan.? I would still suggest drilling a 1/4" hole directly below the choke, so some compressed air in the chassis plenum? will flow up through all the beads. (beads have a .374" ID).? Then the beads will run at room temp at all times.? With the choke mounted vertical, instead of horizontal, the winding's won't get as?warm.? I'm satisfied that? the choke is not gonna heat up in normal operation on any band.? ? Next step is to remove the? old 3/4" wide straps, remove the entire? 5" winding, install the narrower (1/2") wide straps....and re-wind the choke. The new winding will be 5.5" long, another 8.33 turns.? ? This will lower both series resonance freqs to where I want them.? The upper series resonant freq is a moot point since the amp is 160-80-40-20-15m.? ?I want the lower series resonant freq to ideally sit at? 17.675 mhz..... which is exactly midway between 14.350 mhz..... and 21.000 mhz.? The choke can not be used? +/- 750 khz of it's series resonance freq.? ?Factoring that in, it's still miles away from 14.350 mhz...and also 21.00 mhz.? This choke can NOT be used on 17m band.? But this is the tradeoff.? ?I can't make the choke winding any longer, due to it has to be mounted vertical, and there is only 9.25" between chassis ..and top lid.? Choke is 8.25" tall.? The tweaked up version of this choke gets wound? tonight.?
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Re: Loaded Plate chokes...again
I'm gonna use my 0-30 vdc @ 3 amp, current limited lab supply and run 2.5 amps CCS of dc current through it for? 10 mins...then test for heat on any of the cores..? ?and then quickly test with current off, on my lcr meter.? ? I might be able to use a dc block cap..so I can use the VNA, and slam current through it at the same time. ? For scotts project, 2.5 amps CCS is ample. On 160m, I calculated the RF current flowing down the choke is 1.2 amps.? 2 x .01uf @ 30 kv disc caps used at cold end of choke for the bypass on lower bands.? 2 x 500 pf doorknobs also used as bypass cap at cold end.... for the upper HF freqs, like 20 +15m.? ? Stay tuned.? |
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Re: Loaded Plate chokes...again
Under a brick on key condition duty cycle test
toggle quoted message
Show quoted text
On 2024-02-10 11:09, Jim VE7RF wrote:
I'm currently fabricating several versions of ferrite bead loaded |
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Re: Loaded Plate chokes...again
Can¡¯t wait to receive it and try it out
toggle quoted message
Show quoted text
On 2024-02-10 11:09, Jim VE7RF wrote:
I'm currently fabricating several versions of ferrite bead loaded |
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Re: Loaded Plate chokes...again
¿ªÔÆÌåÓý
Jim. Thanks for the Post.? That is a real eye opener.? Sadly, I placed a Choke very close to the back wall of my amps.? It seems to run ok but that is great information.??
I remember us talking about these new chokes. I am glad you got one built!? ?Can you post a picture of it?
C
From: [email protected] <[email protected]> on behalf of Jim VE7RF via groups.io <jim.thom@...>
Sent: Saturday, February 10, 2024 11:09 AM To: [email protected] <[email protected]> Subject: [ham-amplifiers] Loaded Plate chokes...again ?
I'm currently fabricating several versions of ferrite bead loaded plate chokeS. ? I used 1" OD, hollow teflon tubing (.145" wall thickness) (.710" ID).? Each of the .687" OD beads (type 61) was shimmed with tape, so they make a snug fit, when stuffed into
the hollow teflon tube.? A 1" electrolytic capacitor bracket is used to hold the base of the choke to the chassis. ?1/2" copper straps wrapped around the hollow teflon tube, and machine screwed with a single brass 8-32 machine screw etc. ? A ?1/4" to 3/8"
hole is drilled into the amplifier chassis, to allow compressed air in the plenum, to flow up though the .374" ID of all the beads.? Easy way of air cooling.? Actual top temps will be taken with a fluke 62 IR.
The actual winding is made from 22 ga, silver plated, stranded teflon wire. Insulation is pretty thick, and the OD of the wire is exactly .060". ?( wire inside is only .028" OD) Upper + lower winding terminated on the upper / lower straps, then soldered.? Lower strap is 1" ?from the top of the electrolytic bracket.? That provides 1" of exposed teflon.? On paper, should be good for 10 kv of...'surface creep'. After measuring the inductance with my LCR meter, it was time to see where the 2 x series resonance freqs are located. ? I used the S11 output, ?then a single provided coax cable to a (SMA female / BNC female adaptor)....then the BNC plugged into a dual binding post fitting, with it's BNC male connector built into the bottom end. ? ?Then 1 ?SHORT test ?lead to top of choke...and the other test lead to bottom o f choke.? Test leads have an alligator clip at one end...and other end is a banana plug. Did the usual open / short / 50 ohm calibration. ? Ok, found the 2 x series ?resonance freqs asap...on both HB ?chokes. ( I also compared to a new Ameritron choke, since I know where the 2 x series resonant freqs are on the Ameritron choke). ? I had the chokes being tested, laying on top of my bed mattress...along with vna etc. ? I then placed the choke on Styrofoam, so only the extreme ends of the choke were supported, in the horz plane. ?90% of the choke, and all of the winding was in mid air. Well that was a surprise. The series resonant freqs ?INCREASED in freq by a bunch.? Instead of 19.002 mhz laying on the bed, it was 19.750 mhz, when in mid air. ? Same deal with the upper series resonant ?freq (aprx 32 mhz...which also increased).? I also stood the chokes vertical on the bed, and supported the very top of the choke with the handle of a wooden spoon...same deal. Resonant freq increased by 748 khz. I can see getting any plate choke near an aluminum sidewall, or large metal triode tube, can easily lower the resonant freq, but not laying on a bed mattress.? I also held my hand parallel to the choke, and once 2.5" away, resonant freq ?decreased, and decreased more, the closer the palm of my hand got to the choke. W8JI warned about getting plate chokes too close to any dielectric or insulator.? He is correct...I shoulda listened. ? Next up, knowing all this, is to replace the 3/4" wide copper straps with 1/2" wide copper straps...and rewind the choke. That will allow for an extra (.5" / .060") ?8.33 turns. ? The idea here is to lower the ?1st series resonance point, (19.750 mhz) so it's midway between ?21.000 mhz....and 14.350 mhz. (midpoint is ?17.675 mhz). ? The new 3x6 linear amplifier is not used on the 17m band ?(18.068 mhz to 18.168 mhz) ?nor is it used on 12 + 10m bands.? We have height constraints, so the completed choke is exactly 8.25" tall. (Top lid is exactly 9.25" above the chassis). ? ?The existing 5" winding will be increased to 5.5"..... by fabricating the new 1/2" narrower straps.? Wish me luck.? Existing choke measures 315 uh....which will increase a bit once the extra 8 turns are added. On choke #2, it's a full 12" tall, and uses a 8.75" winding. Measures 750 uh.? Resonates at ?9.7 mhz...and also 17.8 mhz. I will try the narrower 1/2" wide straps...so I can get another 8.33 turns on it. ?(Then the new winding will be 9.25" and uh will increase a bit). The idea here is to lower both series resonant freqs a bit. ? Midpoint between 14.350 mhz and 18.068 mhz is 16.209 mhz. ? Midpoint between 7.3 mhz and 10.1 mhz is ?8.7 mhz.? IF I'm successful on choke #2, on paper it ?should work from 1.8 to 30 mhz....(excluding ?the 2 new series resonant freqs)...and will be used on both my 160-15m hb amps. Sri for the diatribe, but getting any plate choke, loaded or not, close to dielectrics or metal is bad news, and can skew your intended results badly.? But factored in, that can also work in your favour.?? ?
?
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Loaded Plate chokes...again
I'm currently fabricating several versions of ferrite bead loaded plate chokeS. ? I used 1" OD, hollow teflon tubing (.145" wall thickness) (.710" ID).? Each of the .687" OD beads (type 61) was shimmed with tape, so they make a snug fit, when stuffed into the hollow teflon tube.? A 1" electrolytic capacitor bracket is used to hold the base of the choke to the chassis. ?1/2" copper straps wrapped around the hollow teflon tube, and machine screwed with a single brass 8-32 machine screw etc. ? A ?1/4" to 3/8" hole is drilled into the amplifier chassis, to allow compressed air in the plenum, to flow up though the .374" ID of all the beads.? Easy way of air cooling.? Actual top temps will be taken with a fluke 62 IR.
The actual winding is made from 22 ga, silver plated, stranded teflon wire. Insulation is pretty thick, and the OD of the wire is exactly .060". ?( wire inside is only .028" OD) Upper + lower winding terminated on the upper / lower straps, then soldered.? Lower strap is 1" ?from the top of the electrolytic bracket.? That provides 1" of exposed teflon.? On paper, should be good for 10 kv of...'surface creep'. After measuring the inductance with my LCR meter, it was time to see where the 2 x series resonance freqs are located. ? I used the S11 output, ?then a single provided coax cable to a (SMA female / BNC female adaptor)....then the BNC plugged into a dual binding post fitting, with it's BNC male connector built into the bottom end. ? ?Then 1 ?SHORT test ?lead to top of choke...and the other test lead to bottom o f choke.? Test leads have an alligator clip at one end...and other end is a banana plug. Did the usual open / short / 50 ohm calibration. ? Ok, found the 2 x series ?resonance freqs asap...on both HB ?chokes. ( I also compared to a new Ameritron choke, since I know where the 2 x series resonant freqs are on the Ameritron choke). ? I had the chokes being tested, laying on top of my bed mattress...along with vna etc. ? I then placed the choke on Styrofoam, so only the extreme ends of the choke were supported, in the horz plane. ?90% of the choke, and all of the winding was in mid air. Well that was a surprise. The series resonant freqs ?INCREASED in freq by a bunch.? Instead of 19.002 mhz laying on the bed, it was 19.750 mhz, when in mid air. ? Same deal with the upper series resonant ?freq (aprx 32 mhz...which also increased).? I also stood the chokes vertical on the bed, and supported the very top of the choke with the handle of a wooden spoon...same deal. Resonant freq increased by 748 khz. I can see getting any plate choke near an aluminum sidewall, or large metal triode tube, can easily lower the resonant freq, but not laying on a bed mattress.? I also held my hand parallel to the choke, and once 2.5" away, resonant freq ?decreased, and decreased more, the closer the palm of my hand got to the choke. W8JI warned about getting plate chokes too close to any dielectric or insulator.? He is correct...I shoulda listened. ? Next up, knowing all this, is to replace the 3/4" wide copper straps with 1/2" wide copper straps...and rewind the choke. That will allow for an extra (.5" / .060") ?8.33 turns. ? The idea here is to lower the ?1st series resonance point, (19.750 mhz) so it's midway between ?21.000 mhz....and 14.350 mhz. (midpoint is ?17.675 mhz). ? The new 3x6 linear amplifier is not used on the 17m band ?(18.068 mhz to 18.168 mhz) ?nor is it used on 12 + 10m bands.? We have height constraints, so the completed choke is exactly 8.25" tall. (Top lid is exactly 9.25" above the chassis). ? ?The existing 5" winding will be increased to 5.5"..... by fabricating the new 1/2" narrower straps.? Wish me luck.? Existing choke measures 315 uh....which will increase a bit once the extra 8 turns are added. On choke #2, it's a full 12" tall, and uses a 8.75" winding. Measures 750 uh.? Resonates at ?9.7 mhz...and also 17.8 mhz. I will try the narrower 1/2" wide straps...so I can get another 8.33 turns on it. ?(Then the new winding will be 9.25" and uh will increase a bit). The idea here is to lower both series resonant freqs a bit. ? Midpoint between 14.350 mhz and 18.068 mhz is 16.209 mhz. ? Midpoint between 7.3 mhz and 10.1 mhz is ?8.7 mhz.? IF I'm successful on choke #2, on paper it ?should work from 1.8 to 30 mhz....(excluding ?the 2 new series resonant freqs)...and will be used on both my 160-15m hb amps. Sri for the diatribe, but getting any plate choke, loaded or not, close to dielectrics or metal is bad news, and can skew your intended results badly.? But factored in, that can also work in your favour.?? ?
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Re: 572's
Money maybe tight but money dropped into questionable tubes with little to no warranty is foolish. Chinese 8877s will set you back close to a grand. 4CX1500As are going for $1500 a piece. Compared to those prices the 400 dollar difference for RF Parts Tubes is trivial. Money is tight. Really ? Then have your friend to his sked up to 10 Meters. There are lots of Spots and plenty of unused Real Estate on 10. On Fri, Feb 9, 2024, 1:50 PM James Wolf <kr9u@...> wrote:
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Re: TL-922 Meter.
Here it is guys. Nice job Lou. Bob W4JFA? On Fri, Feb 9, 2024, 8:56 AM Bob via <W4JFABob=[email protected]> wrote:
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Re: TL-922 Meter.
Alek, I sent u a picture to you email. Let me know that you got it. Bob W4JFA? On Fri, Feb 9, 2024, 6:53 AM Alek Petkovic via <vk6apk=[email protected]> wrote:
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Re: TL-922 Meter.
¿ªÔÆÌåÓýYeah. Thanks Lou. That would be great. On 9/02/2024 7:43 pm, Louis
Parascondola via groups.io wrote:
Alek, o have to build one up for a customer who just ordered I¡¯ll do an extra one for you while I¡¯m at it. ?Lou |
Bob
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