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Re: Tuned input
开云体育I should have a complete 8k ultra soon that will be stripped . Parts sold piece by piece?Not interested selling as a whole or fire sale? Not a good pa numerous design flaws , I had a basket case come in on a parts trade over 10 years ago. Fixed ?it , tested used on the air then sold. Took the money and ran.? Will keep posted? Amp guy llc Amprepairguy.com YouTube Amp repair guy 203-892-4119 On Jan 20, 2024, at 4:34 PM, W7WRX <clark@...> wrote:
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Re: Tuned input
The RF flows into the center common pins in and out.? The coils are across the common pins when keyed.? These relays are labeled DPDT but the common pins are tied together!!!!!!!!!!!!!!!!!!!!!? ?? C |
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Re: Brand new updated PS board for Command Technology amplifiers
I would like to obtain two of these boards.? Please forward the email address for AJ___VE3HJ to me at k7nj@....
Thanks. 73 Riki, K7NJ |
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Re: Tuned input
WTF?? ? ?On paper, what should be required is a DPST..... NO relay (Normally Open when coil de-energized).? ? ?You can also get? single throw relay's in normally closed config.? ? One pole used to switch the input buss to the individual? tuned input.? ? 2nd pole used to switch the output of the individual tuned input....to the output buss.? One relay per tuned circuit. ? There is NO? bypass mode.? With no relay coils energized, the xcvr see's a wide open.? ? What a gong show.? Glad you got it sorted out.? ?Apparently? you can buy a SPDT? relay.... which actually consists of a DPDT relay.... but with contacts internally paralleled.... presumably for more current.?? |
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Re: Brand new updated PS board for Command Technology amplifiers
From: A J <iamfromcanadaalso@...> ? ##? Lou, AJ already has a ton of these boards.? That might just save you some time.? ? Jim? ?VE7RF |
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Re: Brand new updated PS board for Command Technology amplifiers
开云体育Is it really worth it , not to many inquiries for repairs on them. Have yet to see a power supply board issue on any of the ones I have fixed?73 Scott Kb1sel? Amprepairguy.com YouTube Amp repair guy 203-892-4119 On Jan 19, 2024, at 8:10 AM, Louis Parascondola via groups.io <Gudguyham@...> wrote:
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Brand new updated PS board for Command Technology amplifiers
Recently I had occasion to have to rebuild THREE ?power supply units ( located under the chassis) of the Commander line of amps. ?Two HF2500’s and one? VHF2000. ?Both use the same power supply board. ?Unfortunately all 3 boards were damaged by heat and the traces flaked off the boards in many spots. ?The traces that didn’t lift normally did when tried to unsolder and resolder new parts. ?The old boards are basically unsalvageable to rebuild. ?The boards are obviously old technology. ?They are a one time board as far as I’m concerned! ?As usual confronted with the need, I’ve developed a brand new board using new technology on boards with masking etc. ?I need these?boards to professionally rebuild the power supplies in these amps. ?I don’t trust Gerry rigging these old decrepit boards. ?The whole amplifier RF deck must be removed from the amp chassis to get to the power supply. ?You don’t want to go back on after using??band-aid?methods on the old boards. ?These amps are terrific amps and can go another 35 years with the breath of life from an all new board. ?Hopefully within the next month I will have these boards ready. ?I ordered extra for my supply for further repairs and for those who would like to attempt their own replacement I will have a limited supply I’ll be offering them?fully assembled and ready to install?The price is unknown at the moment until I can fully asses the expenditure. ?If interested I’ll take orders on a FCFS basis. ?I’m going to be installing one in my own personal amp as well. I have my own transformer for testing so if you don’t feel confident in doing the replacement yourself I only need the RF deck and can?do it here. ?It’s a shame??to see these good old amps sidelined for lack of parts. Thanks for reading Lou
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Re: Tuned input
PROBLEM SOLVED. I feel like hurting someone.? ?The Relays contacts are in parallel!!!!!!!!!!!!!!!!! WTF??????????????????? ?Its 6 terminals. The part number is CORRECT on the relay and order!!!!!!!!!!!!!!!? It says DPTDT 24 volt.? Its actually SPDT with 6 contacts!!!!!!!!!!!? ?I measured these things TWICE and the NC and NO where working perfect.? I never thought to measure ACROSS the common or center pins.?
What a HUGE waste of time!!!!? ? I ordered new Omron relays from mouser.? These are the same but show in the PDF they are NOT linked and are DPDT.? ?I will have to test them when I get them in my hand. Now I will rewind all the cores to the data sheet and add all the padders back in.? So when I get the relays, it should finally work. C |
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Re: Tuned input
开云体育This board does not use band pass networks.? My friend ran them through and found they are only low pass chebychev Filters.? He sent me the graphs. I can post them tomorrow.?
This board is only low pass with each band having a sharp cutoff to prevent harmonics.? It also only provides as tested about 30 to 40 ohms of matching.
This should work for a 50 ohm tube.? Remember,? the L is fixed.? You can only adjust the caps.
For other tubes where you need more matching range, I think an adjustable L/pie would be best.?
I ordered new t68-2 cores.? I will wind a new 40 with one when they arrive and report back. I am at a loss as to why the cores he sent with the correct wire and turns has double the L.
C
On Jan 16, 2024 4:25 PM, "Jim VE7RF via groups.io" <jim.thom@...> wrote:
Ok,? I just checked my own manually tuned, tuned input, which cover 160-15m.? Tuned for 3750 khz, (1:1 sq swr) ,? swr rises at 4 mhz...and also 3.5 mhz.? And rises even more the further I go below 3500...or? above 4000 khz.? ? Same deal on all bands. This is for the hb 3x3 amp. On my L4B's.... flat input swr at 3750 khz..... which rises at both band edges.....and again rises even more, the further above or below the band edges.? ? Just got off the phone with scott.? He previously tested the new manually tuned, tuned input on 160-15m.? Same deal..... forms a bandpass response.? ? That WD7S (paul hewitt, now sk)? setup has always worked in the past.? ? Dunno what the deal abt measuring a toroid? (in this case a powdered iron, red core with a mu-2...... or the yellow cores with their MU=6)? ?with a lcr meter is.? I never had issues in the past.? ?? ? Those powdered iron cores are all colour coded.? Red / yellow / blue.? ? One thing to check is,,,,? put watt meters on both sides of the tuned input.......and make sure u are not losing anything.? ? Something is amiss somewhere.? ?IMO, 22/20 ga wire is on the small side....for the amount of current flowing, but that's a non issue right now.? Those tuned inputs should work, and also show a bandpass response on each band.?? This kind of stuff drives me nuts.? |
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Re: Tuned input
Update.?
I got a good measurement and found the 40 toroid 1.8uh.? ?Way to much.? Why??? It's 13 turns of 20 on a t68-2 core.? ? I removed about half.? 7 turns.? ?Measured 1.1. This is much better. Not perfect but in the ball park... Why??? I got the t50-6 cores from a local friend today at lunch. I would 11 turns on 20awg for 20 meters.? Installed it onto board. BINGO.? 1.0, 52 ohms. Sharp cut off past 8 mhz.? ? Did the guy send . Me the wrong cores.??? |
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Re: Tuned input
On Mon, Jan 15, 2024 at 07:35 PM, Mike Feher wrote:
? ##? ur making a mountain out of a mole hill.? Just a 50 ohm resistor on the output..... and any mfj-259B / favourite analyzer of the week/ VNA will work.? Or a? xcvr feeding 10-50 watts? into the input side..... then into a heath DL? will work. Something else is severely screwed up....and even though the PI net is a LP filter, in this application it will indeed show a bandpass type response...always has.? |
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Re: Tuned input
Ok,? I just checked my own manually tuned, tuned input, which cover 160-15m.? Tuned for 3750 khz, (1:1 sq swr) ,? swr rises at 4 mhz...and also 3.5 mhz.? And rises even more the further I go below 3500...or? above 4000 khz.? ? Same deal on all bands. This is for the hb 3x3 amp. On my L4B's.... flat input swr at 3750 khz..... which rises at both band edges.....and again rises even more, the further above or below the band edges.? ? Just got off the phone with scott.? He previously tested the new manually tuned, tuned input on 160-15m.? Same deal..... forms a bandpass response.? ? That WD7S (paul hewitt, now sk)? setup has always worked in the past.? ? Dunno what the deal abt measuring a toroid? (in this case a powdered iron, red core with a mu-2...... or the yellow cores with their MU=6)? ?with a lcr meter is.? I never had issues in the past.? ?? ? Those powdered iron cores are all colour coded.? Red / yellow / blue.? ? One thing to check is,,,,? put watt meters on both sides of the tuned input.......and make sure u are not losing anything.? ? Something is amiss somewhere.? ?IMO, 22/20 ga wire is on the small side....for the amount of current flowing, but that's a non issue right now.? Those tuned inputs should work, and also show a bandpass response on each band.?? This kind of stuff drives me nuts.? |
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Re: Tuned input
开云体育I ran the board into a dummy load with an FT450.? It shows flat with relay off in pass through.? Engaged it shows 1.0 with Trimmers at zero.
?Any attempt to adjust the caps from zero raises SWR.? Even added ladders and adjusted all the way to 1200pf.? It only raises SWR and rig cuts back.
I then ran the board into a 2 to 1 load.? ?It shows 2 to 1 on xcvr meter in pass through and with zero trimmer.
Any attempt to dial Trimmers up increases SWR.
Obviously the toroid is wrong.? I am told you can't stick a toroid Into an LCR. You will get a false reading.? You must use a grid dip or, a sig generator, scope and a known cap to resonate it.? Then you can find out where it dips and then work
backwards to the L of the toroid.
On Jan 16, 2024 9:17 AM, "Jim VE7RF via groups.io" <jim.thom@...> wrote:
One added note for LP filters....like used on the output of SS amps.? The harmonics don't get absorbed by the LP filter, nor are they routed to grnd.? ?They get reflected by towards the final PA. The LP filter looks like a HIGH Z to harmonics ABOVE? the LP filter cut off freq.? That's why Flex used a diplexer on it's PGXL.? ?Each high power rated LP filter has a mating low power HP filter...( input of each is bonded).? Harmonics from the HP filter are routed to a 400 watt DL.? In the old ARRL books, they called that a ...' absorption typ LP filter'.? That combo of LP + HP filter is not as easy as it looks.? ?When the inputs of both filters are bonded..... they filters interact with each other, screwing up the response of the LP filter..... which then requires some re-tweaking of the coils. In the case of the LP filter on the PI tuned input for the GG / cathode driven amp....the harmonics are generated at the cathode....and will feed backwards toward the xcvr.? In this case, the PI tuned input is a LP filter, but with harmonics being? The other somewhat semi popular tuned input is the T filter....which consist of 2 x coils in series, with a cap from the junction point to chassis.? It too is a LP filter...BUT when used as a tuned input, will not present a high Z to harmonics being generated at the cathode...and being fed backwards to the xcvr.?? ? We dumped the idea of a T? tuned input on that 6m 10 kw amp....and went with a conventional PI tuned input.? It's manually tuned, with 2 x air caps and one coil.......and covers the entire 50-54 mhz.? ? None of this explains why Clarks tuned input board is screwed up.? |
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Re: Tuned input
One added note for LP filters....like used on the output of SS amps.? The harmonics don't get absorbed by the LP filter, nor are they routed to grnd.? ?They get reflected by towards the final PA. The LP filter looks like a HIGH Z to harmonics ABOVE? the LP filter cut off freq.? That's why Flex used a diplexer on it's PGXL.? ?Each high power rated LP filter has a mating low power HP filter...( input of each is bonded).? Harmonics from the HP filter are routed to a 400 watt DL.? In the old ARRL books, they called that a ...' absorption typ LP filter'.? That combo of LP + HP filter is not as easy as it looks.? ?When the inputs of both filters are bonded..... they filters interact with each other, screwing up the response of the LP filter..... which then requires some re-tweaking of the coils. In the case of the LP filter on the PI tuned input for the GG / cathode driven amp....the harmonics are generated at the cathode....and will feed backwards toward the xcvr.? In this case, the PI tuned input is a LP filter, but with harmonics being? The other somewhat semi popular tuned input is the T filter....which consist of 2 x coils in series, with a cap from the junction point to chassis.? It too is a LP filter...BUT when used as a tuned input, will not present a high Z to harmonics being generated at the cathode...and being fed backwards to the xcvr.?? ? We dumped the idea of a T? tuned input on that 6m 10 kw amp....and went with a conventional PI tuned input.? It's manually tuned, with 2 x air caps and one coil.......and covers the entire 50-54 mhz.? ? None of this explains why Clarks tuned input board is screwed up.? |
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Re: Tuned input
I don't get it.? Sure, the PI network is a LP filter.? BUT when tweaked for? 1:1? swr at the middle of a band, the swr rises when u go below / above the band edges.? I'm gonna re-check this in the next 2 days...and on a bunch of bands.?? ? On a side note, per JI's? tuned input writeup, the function of the PI filter is to kill harmonics at the cathode from going BACKWARDS towards the xcvr.? In that case, the PI filter has to have LOW Z on all the harmonic freqs.? "An RF power amplifier's tuned input circuit is more than just impedance matching. While reasonable impedance matching can be important for proper exciter operation, the tuned input circuit of a grounded-grid or cathode driven radio frequency power amplifier provides multiple important functions for the amplifier:
A tuner between the amplifier and radio,? a matching circuit some distance from the cathode, or a high pass or broadband network will NOT do all of the above." "Harmonics Current in the CATHODE shares the SAME path through the tube as current in the anode, with an additional current that flows in the grid-cathode path in class sub-2 amplifiers. (AB1?amplifiers have no grid current, while AB2?amplifiers have grid current.) The cathode of a vacuum tube essentially contains the same time-varying current as the anode, and if there is ANY grid current that additional current is also harmonic-rich current." ? "Input Impedance The driving impedance of a cathode driven amplifier always varies some amount with power level and tuning. We can say the input impedance of a cathode driven stage is?dynamic, with the tube's driving impedance changing with parameters like drive power and how the amplifier is loaded or tuned. The input impedance changes dynamically because the output system is in SERIES with the input system. The SAME plate current flows through both cathode and anode systems. Varying anode load impedance, because the same very same current flows through both, CHANGES the input impedance. In general the lower tube mu, the greater the effect of output tuning and power level on driving impedance. This is because a low-mu tube generally has a high driving impedance, making cathode impedance a larger percentage of anode impedance.?The higher cathode impedance increases negative feedback, and increased negative feedback causes the input impedance to vary more with anode load impedance changes. The tuned input's resonance or "flywheel effect" does not stabilize this impedance variation, but additional losses brought into the cathode system by tuned input circuit components helps dilute or "swamp out" dynamic changes in driving impedance. An attenuator pad would do the same of course, but would not filter harmonics or sharpen conduction point transitions. The dynamic cathode impedance, where cathode impedance changes with drive level, PREVENTS? us from accurately adjusting the tuned input system of a typical cathode driven amplifier at very low power. This prevents accurate use of an antenna analyzer to adjust the tuned input while using the operating PA tube as a load. The input system should always be adjusted near full output power under normal operating conditions, or with a suitable dummy load replacing the tube's dynamic impedance. A reasonable approximation of tube input impedance, for circuit adjustment purposes, would be a small non-inductive resistor from each cathode pin to a control grid pin at each tube. This resistor should be the approximate value of the tube input resistance when driven near full power with normal tuning and loading. Filament power and HV should be off and the tubes left in place, and the input driven normally as if the amplifier was running but with a low power antenna analyzer substituting for the the normal exciter. ? |
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Re: Tuned input
Peter.??
This is NOT a band pass filter?? I am confused here.? I expected each band slot to have a band pass for that band and a cut off above and below. What I see is that I can adjust the match to 1.0 to 1.0 at near 50 ohms.? But the band pass is only a cut off ABOVE the primary. Example: 10 meters.? ?Low SWR from 1.8 to 40MHZ.? past 40 it shoots up. 40 meters,? Low SWR from 1.8 to 18 MHZ, Past that it shoots up. Is this expected behavior??? C |
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Re: Tuned input
开云体育Yes, a real easy way to tell is to look at the transfer function with omega equal 0. A non mathematical way is simply, if you put DC in will you get DC out? 73 – Mike ? Mike B. Feher, N4FS 89 Arnold Blvd. Howell NJ 07731 848-245-9115 ? From: [email protected] <[email protected]> On Behalf Of Peter Voelpel
Sent: Monday, January 15, 2024 11:45 AM To: [email protected] Subject: Re: [ham-amplifiers] Tuned input ? Yes,those are? 5 turns. ? A pi-filter with capacitors as shunt elements is a low pass filter, not a band pass filter. ? Differences from the instructions to the real world might be caused by stray and input capacitances which have to be deducted from the theroretical values. ? Just use a non inductive resistor as a load in parallel to the output? and adjust for minimum swr on a VNA or swr meter. ? 73 Peter, DJ7WW ? ? ? -----Original-Nachricht----- Betreff: Re: [ham-amplifiers] Tuned input Datum: 2024-01-15T17:10:46+0100 Von: "W7WRX" <clark@...> An: "[email protected]" <[email protected]> ? ? ? ? So this would be 5? ? I have tried 7, 6 and 5 turns.? NO band pass. Only a cut off past 40mhz. ? As I remove turns I require less and less cap on each side.?? ? With this winding it's 0pf on each side.? If I add even 10pf swr raises.?? ? I am lost now.? Maybe try 8 turns?? ?The instructions say 100pf, 7 turns and 100PF ? C ? On Jan 15, 2024 9:01 AM, "Mike Feher via groups.io" <n4fs@...> wrote: If a wire goes through the center of a toroid, it counts and acts as a turn. It does not need to be looped around. 73 – Mike ? Mike B. Feher, N4FS 89 Arnold Blvd. Howell NJ 07731 848-245-9115 ? From: [email protected] <[email protected]> On Behalf Of W7WRX ? I removed 2 turns and still do not see band pass.? What I see is a high pass at 40mhz.? Below that it's pretty flat down the bands.? ? ? It's supposed to be 7 turns of 20awg.? ? Do the wire ends as they loop over the donut count as a turn? ? C ? On Jan 15, 2024 7:27 AM, "Jim VE7RF via groups.io" <jim.thom@...> wrote: On Mon, Jan 15, 2024 at 12:26 AM, W7WRX wrote:
## I design and run the PI tuned inputs through software every other week...then verify on the bench.? For a overall network Q? of '4'? (input Q = 2....and output Q =2)? ?on 10m,(28.5 mhz) when matching 50 ohms from xcvr to 50 ohm tube input Z....?it should be 223.4 pf? - .22 uh? - 223.4 pf.? ## For an overall network Q of? ? '1.8'? (input Q =.9......and output Q = .9) on 28.5 mhz, it's then 100 pf - .28 uh - 100 pf.? ? ##? if ur caps are only 25-35 pf, then ur Q is through the floor...and the coil has way too much uh.? ? ## either remove a turn or maybe 2, and? / or spread the turns? a bit.? Tweak the coil till both caps are in the 100-140 pf range.? Ok, at that point, you will see the 1:1 swr @ 28.5 mhz..... which should remain flat between? 28.0? and 29,0...then rise when u go below 28 mhz...and above 29 mhz. ? ##? with the Q through the floor, it all goes to hell...and you won't get a? proper bandpass response.? ? ## Have u tested al the other bands yet ?? ? IE: installed caps and toroid's for the other bands...and tested other bands.? ? ##? Note on the above,? only when matching 50 ohms to 50 ohms? (or any 2 x equal Z's)? is the C1 + C2 caps both the same value.? On software, we only tweak the overall network Q.? ?The C1 input Q? ?+ the C2 output Q = overall network Q.? ##? For a PI network for the kw output side, (High tube Z? down to 50 ohms), typ an Overall network Q of....'12' is used....which consist of an input Q of 10...and an output Q of 2.?? ##? In the old ARRL books (and also Eimac's? 'care + feeding'), they only used the INPUT Q...which is why they said? to use a Q of? '10'.? ?They did the same thing with PI tuned inputs.? When they said to use a Q of..'2'? ?what they really meant was to use an overall network Q of 4.? ? ##? For tuned inputs that are tweaked once ..in the middle of the band,? you want low swr? across the entire band.? ?500 khz on 80m is like 1mhz wide on 40m..and 2 mhz wide on 20m..and 4 mhz wide on 10m.? This is where you can do some creative tweaking.? Each band is different....with 160m only 200 khz? wide, 80m = 500 khz, 40m = 300 khz, 30m = 50 khz,? 20m = 350 khz, 17m = 100 khz, 15m = 450 khz, 12m = 100 khz, 10m = 1700 khz.? ( 6m = 4000 khz). ? ## here is the other thing u gotta worry about.? The tube's input C? is directly in parallel with the C2 of the tuned input. Say a 3CX-3000A7.... with it's 38 pf input C (grid to cathode C).? Now you have to subtract 38 pf from the calculated C2 values of ALL the various tuned inputs for each band.? ##? here's the other thing to deal with.... the XL of the bifilar fil choke (since it's RF grnded at it's cold end...and hot end of fil choke goes to the cathode) is also directly in parallel with the tube's input cathode to grid C.? ##? On a SB-220, they used a 9 uh (per winding) fil choke.? ?XL @ 3.75 mhz =? 212 ohms.? ?You now require 212 ohms of XC to cancel out the XL.? ? 200 pf @ 3.750 mhz = 212 ohms of XC.? On an SB-220, the C2 cap of the 75m tuned input has to be increased by 200 pf? vs it's calculated value.? But since the tube's input C on a pair of 3-500Z's is 16.6 pf,? it's then 200-16.6 pf =? 183.4 pf. ## The fil choke primarily affects the lower bands. On the upper bands it's less of an issue.? ? 9 uh is 1611 ohms of XL @ 28.5 mhz.? ? ? 3.465 pf = 1611 ohms of XC.? ? ?That amounts to dick on 28.5 mhz...and the pair of 3-500Z's still has 16.6 pf...so now it's 16.6 - 3.465 pf = 13.135 pf.? 13.135 pf has to be subtracted from the calculated C value of the tuned input. ? ##? If you are doing say a PI network for a 3CX-3000A7,? wire the relay switched tuned input? into the cathode.....and temp wire a 50 ohm resistor between one cathode lug....and chassis....and also plug the tube into the socket.? With no fil or B+, all voltages off....and TR relays activated, put ur analyzer on the input...and tweak both arco's for each band for 1:1 swr.? ?50 ohm resistor removed.? Apply B+ and fil V.... and test the amp.? ? It will be sorta close, and perhaps some minor C1 + C2 tweaking required.? That depends on drive level, bias used,? loaded B+ used, amp tuned to max PO.... and perhaps loading increased till PO drops 1-2%, and cable length between xcvr and input to amp.? ##? if the relay switched, tuned input board is below the chassis, near the cathode, it may or may not be possible to tweak all the arco caps.? ?The board would have to be mounted to rear apron, with holes to access the caps..or to chassis..pita. If amp is fan cooled, you might be able to remove bottom lid.? If a chimney is used, removal of bottom lid means? zero airflow.?? ? ##? This is why I went to the pair of broadcast caps + tapped coil, manually tuned, tuned input setup on the hb amps.? ? Jim? ?VE7RF ? ? |
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Re: Tuned input
开云体育Yes,those are? 5 turns. ? A pi-filter with capacitors as shunt elements is a low pass filter, not a band pass filter. ? Differences from the instructions to the real world might be caused by stray and input capacitances which have to be deducted from the theroretical values. ? Just use a non inductive resistor as a load in parallel to the output? and adjust for minimum swr on a VNA or swr meter. ? 73 Peter, DJ7WW ? ? ? -----Original-Nachricht----- Betreff: Re: [ham-amplifiers] Tuned input Datum: 2024-01-15T17:10:46+0100 Von: "W7WRX" <clark@...> An: "[email protected]" <[email protected]> ? ? ? ? So this would be 5?
?
I have tried 7, 6 and 5 turns.? NO band pass. Only a cut off past 40mhz.
?
As I remove turns I require less and less cap on each side.??
?
With this winding it's 0pf on each side.? If I add even 10pf swr raises.??
?
I am lost now.? Maybe try 8 turns?? ?The instructions say 100pf, 7 turns and 100PF
?
C
On Jan 15, 2024 9:01 AM, "Mike Feher via groups.io" <n4fs@...> wrote:
If a wire goes through the center of a toroid, it counts and acts as a turn. It does not need to be looped around. 73 – Mike ? Mike B. Feher, N4FS 89 Arnold Blvd. Howell NJ 07731 848-245-9115 ? From: [email protected] <[email protected]> On Behalf Of W7WRX
Sent: Monday, January 15, 2024 10:25 AM To: [email protected] Subject: Re: [ham-amplifiers] Tuned input ? I removed 2 turns and still do not see band pass.? What I see is a high pass at 40mhz.? Below that it's pretty flat down the bands.? ? ? It's supposed to be 7 turns of 20awg.? ? Do the wire ends as they loop over the donut count as a turn? ? C ? On Jan 15, 2024 7:27 AM, "Jim VE7RF via groups.io" <jim.thom@...> wrote: On Mon, Jan 15, 2024 at 12:26 AM, W7WRX wrote:
## I design and run the PI tuned inputs through software every other week...then verify on the bench.? For a overall network Q? of '4'? (input Q = 2....and output Q =2)? ?on 10m,(28.5 mhz) when matching 50 ohms from xcvr to 50 ohm tube input Z....?it should be 223.4 pf? - .22 uh? - 223.4 pf.? ## For an overall network Q of? ? '1.8'? (input Q =.9......and output Q = .9) on 28.5 mhz, it's then 100 pf - .28 uh - 100 pf.? ? ##? if ur caps are only 25-35 pf, then ur Q is through the floor...and the coil has way too much uh.? ? ## either remove a turn or maybe 2, and? / or spread the turns? a bit.? Tweak the coil till both caps are in the 100-140 pf range.? Ok, at that point, you will see the 1:1 swr @ 28.5 mhz..... which should remain flat between? 28.0? and 29,0...then rise when u go below 28 mhz...and above 29 mhz. ? ##? with the Q through the floor, it all goes to hell...and you won't get a? proper bandpass response.? ? ## Have u tested al the other bands yet ?? ? IE: installed caps and toroid's for the other bands...and tested other bands.? ? ##? Note on the above,? only when matching 50 ohms to 50 ohms? (or any 2 x equal Z's)? is the C1 + C2 caps both the same value.? On software, we only tweak the overall network Q.? ?The C1 input Q? ?+ the C2 output Q = overall network Q.? ##? For a PI network for the kw output side, (High tube Z? down to 50 ohms), typ an Overall network Q of....'12' is used....which consist of an input Q of 10...and an output Q of 2.?? ##? In the old ARRL books (and also Eimac's? 'care + feeding'), they only used the INPUT Q...which is why they said? to use a Q of? '10'.? ?They did the same thing with PI tuned inputs.? When they said to use a Q of..'2'? ?what they really meant was to use an overall network Q of 4.? ? ##? For tuned inputs that are tweaked once ..in the middle of the band,? you want low swr? across the entire band.? ?500 khz on 80m is like 1mhz wide on 40m..and 2 mhz wide on 20m..and 4 mhz wide on 10m.? This is where you can do some creative tweaking.? Each band is different....with 160m only 200 khz? wide, 80m = 500 khz, 40m = 300 khz, 30m = 50 khz,? 20m = 350 khz, 17m = 100 khz, 15m = 450 khz, 12m = 100 khz, 10m = 1700 khz.? ( 6m = 4000 khz). ? ## here is the other thing u gotta worry about.? The tube's input C? is directly in parallel with the C2 of the tuned input. Say a 3CX-3000A7.... with it's 38 pf input C (grid to cathode C).? Now you have to subtract 38 pf from the calculated C2 values of ALL the various tuned inputs for each band.? ##? here's the other thing to deal with.... the XL of the bifilar fil choke (since it's RF grnded at it's cold end...and hot end of fil choke goes to the cathode) is also directly in parallel with the tube's input cathode to grid C.? ##? On a SB-220, they used a 9 uh (per winding) fil choke.? ?XL @ 3.75 mhz =? 212 ohms.? ?You now require 212 ohms of XC to cancel out the XL.? ? 200 pf @ 3.750 mhz = 212 ohms of XC.? On an SB-220, the C2 cap of the 75m tuned input has to be increased by 200 pf? vs it's calculated value.? But since the tube's input C on a pair of 3-500Z's is 16.6 pf,? it's then 200-16.6 pf =? 183.4 pf. ## The fil choke primarily affects the lower bands. On the upper bands it's less of an issue.? ? 9 uh is 1611 ohms of XL @ 28.5 mhz.? ? ? 3.465 pf = 1611 ohms of XC.? ? ?That amounts to dick on 28.5 mhz...and the pair of 3-500Z's still has 16.6 pf...so now it's 16.6 - 3.465 pf = 13.135 pf.? 13.135 pf has to be subtracted from the calculated C value of the tuned input. ? ##? If you are doing say a PI network for a 3CX-3000A7,? wire the relay switched tuned input? into the cathode.....and temp wire a 50 ohm resistor between one cathode lug....and chassis....and also plug the tube into the socket.? With no fil or B+, all voltages off....and TR relays activated, put ur analyzer on the input...and tweak both arco's for each band for 1:1 swr.? ?50 ohm resistor removed.? Apply B+ and fil V.... and test the amp.? ? It will be sorta close, and perhaps some minor C1 + C2 tweaking required.? That depends on drive level, bias used,? loaded B+ used, amp tuned to max PO.... and perhaps loading increased till PO drops 1-2%, and cable length between xcvr and input to amp.? ##? if the relay switched, tuned input board is below the chassis, near the cathode, it may or may not be possible to tweak all the arco caps.? ?The board would have to be mounted to rear apron, with holes to access the caps..or to chassis..pita. If amp is fan cooled, you might be able to remove bottom lid.? If a chimney is used, removal of bottom lid means? zero airflow.?? ? ##? This is why I went to the pair of broadcast caps + tapped coil, manually tuned, tuned input setup on the hb amps.? ? Jim? ?VE7RF ? |
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Re: Tuned input
开云体育So this would be 5?
I have tried 7, 6 and 5 turns.? NO band pass. Only a cut off past 40mhz.
As I remove turns I require less and less cap on each side.??
With this winding it's 0pf on each side.? If I add even 10pf swr raises.??
I am lost now.? Maybe try 8 turns?? ?The instructions say 100pf, 7 turns and 100PF
C
On Jan 15, 2024 9:01 AM, "Mike Feher via groups.io" <n4fs@...> wrote:
If a wire goes through the center of a toroid, it counts and acts as a turn. It does not need to be looped around. 73 – Mike ? Mike B. Feher, N4FS 89 Arnold Blvd. Howell NJ 07731 848-245-9115 ? From: [email protected] <[email protected]>
On Behalf Of W7WRX
Sent: Monday, January 15, 2024 10:25 AM To: [email protected] Subject: Re: [ham-amplifiers] Tuned input ? I removed 2 turns and still do not see band pass.? What I see is a high pass at 40mhz.? Below that it's pretty flat down the bands.? ? ? It's supposed to be 7 turns of 20awg.? ? Do the wire ends as they loop over the donut count as a turn? ? C ? On Jan 15, 2024 7:27 AM, "Jim VE7RF via groups.io" <jim.thom@...> wrote: On Mon, Jan 15, 2024 at 12:26 AM, W7WRX wrote:
## I design and run the PI tuned inputs through software every other week...then verify on the bench.? For a overall network Q? of '4'? (input Q = 2....and output Q =2)? ?on 10m,(28.5 mhz) when matching 50 ohms from xcvr to 50 ohm tube input Z....?it should be 223.4 pf? - .22 uh? - 223.4 pf.? ## For an overall network Q of? ? '1.8'? (input Q =.9......and output Q = .9) on 28.5 mhz, it's then 100 pf - .28 uh - 100 pf.? ? ##? if ur caps are only 25-35 pf, then ur Q is through the floor...and the coil has way too much uh.? ? ## either remove a turn or maybe 2, and? / or spread the turns? a bit.? Tweak the coil till both caps are in the 100-140 pf range.? Ok, at that point, you will see the 1:1 swr @ 28.5 mhz..... which should remain flat between? 28.0? and 29,0...then rise when u go below 28 mhz...and above 29 mhz. ? ##? with the Q through the floor, it all goes to hell...and you won't get a? proper bandpass response.? ? ## Have u tested al the other bands yet ?? ? IE: installed caps and toroid's for the other bands...and tested other bands.? ? ##? Note on the above,? only when matching 50 ohms to 50 ohms? (or any 2 x equal Z's)? is the C1 + C2 caps both the same value.? On software, we only tweak the overall network Q.? ?The C1 input Q? ?+ the C2 output Q = overall network Q.? ##? For a PI network for the kw output side, (High tube Z? down to 50 ohms), typ an Overall network Q of....'12' is used....which consist of an input Q of 10...and an output Q of 2.?? ##? In the old ARRL books (and also Eimac's? 'care + feeding'), they only used the INPUT Q...which is why they said? to use a Q of? '10'.? ?They did the same thing with PI tuned inputs.? When they said to use a Q of..'2'? ?what they really meant was to use an overall network Q of 4.? ? ##? For tuned inputs that are tweaked once ..in the middle of the band,? you want low swr? across the entire band.? ?500 khz on 80m is like 1mhz wide on 40m..and 2 mhz wide on 20m..and 4 mhz wide on 10m.? This is where you can do some creative tweaking.?
Each band is different....with 160m only 200 khz? wide, 80m = 500 khz, 40m = 300 khz, 30m = 50 khz,? 20m = 350 khz, 17m = 100 khz, 15m = 450 khz, 12m = 100 khz, 10m = 1700 khz.? ( 6m = 4000 khz). ? ## here is the other thing u gotta worry about.? The tube's input C? is directly in parallel with the C2 of the tuned input. Say a 3CX-3000A7.... with it's 38 pf input C (grid to cathode C).? Now you have to subtract 38 pf from the calculated C2 values of ALL the various tuned inputs for each band.? ##? here's the other thing to deal with.... the XL of the bifilar fil choke (since it's RF grnded at it's cold end...and hot end of fil choke goes to the cathode) is also directly in parallel with the tube's input cathode to grid C.? ##? On a SB-220, they used a 9 uh (per winding) fil choke.? ?XL @ 3.75 mhz =? 212 ohms.? ?You now require 212 ohms of XC to cancel out the XL.? ? 200 pf @ 3.750 mhz = 212 ohms of XC.? On an SB-220, the C2 cap of the 75m tuned input has to be increased by 200 pf? vs it's calculated value.? But since the tube's input C on a pair of 3-500Z's is 16.6 pf,? it's then 200-16.6 pf =? 183.4 pf. ## The fil choke primarily affects the lower bands. On the upper bands it's less of an issue.? ? 9 uh is 1611 ohms of XL @ 28.5 mhz.? ? ? 3.465 pf = 1611 ohms of XC.? ? ?That amounts to dick on 28.5 mhz...and the pair of 3-500Z's still has 16.6 pf...so now it's 16.6 - 3.465 pf = 13.135 pf.? 13.135 pf has to be subtracted from the calculated C value of the tuned input. ? ##? If you are doing say a PI network for a 3CX-3000A7,? wire the relay switched tuned input? into the cathode.....and temp wire a 50 ohm resistor between one cathode lug....and chassis....and also plug the tube into the socket.? With no fil or B+, all voltages off....and TR relays activated, put ur analyzer on the input...and tweak both arco's for each band for 1:1 swr.? ?50 ohm resistor removed.? Apply B+ and fil V.... and test the amp.? ? It will be sorta close, and perhaps some minor C1 + C2 tweaking required.? That depends on drive level, bias used,? loaded B+ used, amp tuned to max PO.... and perhaps loading increased till PO drops 1-2%, and cable length between xcvr and input to amp.? ##? if the relay switched, tuned input board is below the chassis, near the cathode, it may or may not be possible to tweak all the arco caps.? ?The board would have to be mounted to rear apron, with holes to access the caps..or to chassis..pita. If amp is fan cooled, you might be able to remove bottom lid.? If a chimney is used, removal of bottom lid means? zero airflow.?? ? ##? This is why I went to the pair of broadcast caps + tapped coil, manually tuned, tuned input setup on the hb amps.? ? Jim? ?VE7RF |
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Re: Tuned input
开云体育If a wire goes through the center of a toroid, it counts and acts as a turn. It does not need to be looped around. 73 – Mike ? Mike B. Feher, N4FS 89 Arnold Blvd. Howell NJ 07731 848-245-9115 ? From: [email protected] <[email protected]> On Behalf Of W7WRX
Sent: Monday, January 15, 2024 10:25 AM To: [email protected] Subject: Re: [ham-amplifiers] Tuned input ? I removed 2 turns and still do not see band pass.? What I see is a high pass at 40mhz.? Below that it's pretty flat down the bands.? ? ? It's supposed to be 7 turns of 20awg.? ? Do the wire ends as they loop over the donut count as a turn? ? C ? On Jan 15, 2024 7:27 AM, "Jim VE7RF via groups.io" <jim.thom@...> wrote: On Mon, Jan 15, 2024 at 12:26 AM, W7WRX wrote:
## I design and run the PI tuned inputs through software every other week...then verify on the bench.? For a overall network Q? of '4'? (input Q = 2....and output Q =2)? ?on 10m,(28.5 mhz) when matching 50 ohms from xcvr to 50 ohm tube input Z....?it should be 223.4 pf? - .22 uh? - 223.4 pf.? ## For an overall network Q of? ? '1.8'? (input Q =.9......and output Q = .9) on 28.5 mhz, it's then 100 pf - .28 uh - 100 pf.? ? ##? if ur caps are only 25-35 pf, then ur Q is through the floor...and the coil has way too much uh.? ? ## either remove a turn or maybe 2, and? / or spread the turns? a bit.? Tweak the coil till both caps are in the 100-140 pf range.? Ok, at that point, you will see the 1:1 swr @ 28.5 mhz..... which should remain flat between? 28.0? and 29,0...then rise when u go below 28 mhz...and above 29 mhz. ? ##? with the Q through the floor, it all goes to hell...and you won't get a? proper bandpass response.? ? ## Have u tested al the other bands yet ?? ? IE: installed caps and toroid's for the other bands...and tested other bands.? ? ##? Note on the above,? only when matching 50 ohms to 50 ohms? (or any 2 x equal Z's)? is the C1 + C2 caps both the same value.? On software, we only tweak the overall network Q.? ?The C1 input Q? ?+ the C2 output Q = overall network Q.? ##? For a PI network for the kw output side, (High tube Z? down to 50 ohms), typ an Overall network Q of....'12' is used....which consist of an input Q of 10...and an output Q of 2.?? ##? In the old ARRL books (and also Eimac's? 'care + feeding'), they only used the INPUT Q...which is why they said? to use a Q of? '10'.? ?They did the same thing with PI tuned inputs.? When they said to use a Q of..'2'? ?what they really meant was to use an overall network Q of 4.? ? ##? For tuned inputs that are tweaked once ..in the middle of the band,? you want low swr? across the entire band.? ?500 khz on 80m is like 1mhz wide on 40m..and 2 mhz wide on 20m..and 4 mhz wide on 10m.? This is where you can do some creative tweaking.? Each band is different....with 160m only 200 khz? wide, 80m = 500 khz, 40m = 300 khz, 30m = 50 khz,? 20m = 350 khz, 17m = 100 khz, 15m = 450 khz, 12m = 100 khz, 10m = 1700 khz.? ( 6m = 4000 khz). ? ## here is the other thing u gotta worry about.? The tube's input C? is directly in parallel with the C2 of the tuned input. Say a 3CX-3000A7.... with it's 38 pf input C (grid to cathode C).? Now you have to subtract 38 pf from the calculated C2 values of ALL the various tuned inputs for each band.? ##? here's the other thing to deal with.... the XL of the bifilar fil choke (since it's RF grnded at it's cold end...and hot end of fil choke goes to the cathode) is also directly in parallel with the tube's input cathode to grid C.? ##? On a SB-220, they used a 9 uh (per winding) fil choke.? ?XL @ 3.75 mhz =? 212 ohms.? ?You now require 212 ohms of XC to cancel out the XL.? ? 200 pf @ 3.750 mhz = 212 ohms of XC.? On an SB-220, the C2 cap of the 75m tuned input has to be increased by 200 pf? vs it's calculated value.? But since the tube's input C on a pair of 3-500Z's is 16.6 pf,? it's then 200-16.6 pf =? 183.4 pf. ## The fil choke primarily affects the lower bands. On the upper bands it's less of an issue.? ? 9 uh is 1611 ohms of XL @ 28.5 mhz.? ? ? 3.465 pf = 1611 ohms of XC.? ? ?That amounts to dick on 28.5 mhz...and the pair of 3-500Z's still has 16.6 pf...so now it's 16.6 - 3.465 pf = 13.135 pf.? 13.135 pf has to be subtracted from the calculated C value of the tuned input. ? ##? If you are doing say a PI network for a 3CX-3000A7,? wire the relay switched tuned input? into the cathode.....and temp wire a 50 ohm resistor between one cathode lug....and chassis....and also plug the tube into the socket.? With no fil or B+, all voltages off....and TR relays activated, put ur analyzer on the input...and tweak both arco's for each band for 1:1 swr.? ?50 ohm resistor removed.? Apply B+ and fil V.... and test the amp.? ? It will be sorta close, and perhaps some minor C1 + C2 tweaking required.? That depends on drive level, bias used,? loaded B+ used, amp tuned to max PO.... and perhaps loading increased till PO drops 1-2%, and cable length between xcvr and input to amp.? ##? if the relay switched, tuned input board is below the chassis, near the cathode, it may or may not be possible to tweak all the arco caps.? ?The board would have to be mounted to rear apron, with holes to access the caps..or to chassis..pita. If amp is fan cooled, you might be able to remove bottom lid.? If a chimney is used, removal of bottom lid means? zero airflow.?? ? ##? This is why I went to the pair of broadcast caps + tapped coil, manually tuned, tuned input setup on the hb amps.? ? Jim? ?VE7RF |
