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C-L-C update
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Ok, here is why a....? C1 -? resonant choke -? C2? cap is? 1 step forward and? ?6 steps backwards.?? Ditto? with a? classic? ( henry radio style)? ?.. resonant choke -? Cap? config.? When you resonate the choke, at 120 hz,? ?you now have a glorified? 120 hz? notch filter.? ? You no longer have a? good? LP filter, with a low freq? cut off.? ? Reason is.... the small cap that's in parallel with the choke (used to resonate the choke)? will? simply pass all the? harmonics, like? 240/360/480/ 600? hz? ?etc, etc.?? Typ value parallel? resonating caps have low? XC? at? >240 hz.? ?The ONLY thing that is killing the harmonics is the cap on either side of the choke ( in the case of a C-? resonant choke - C filter).......? or the output cap ( in the case of a? ...Resonant choke -? C filter.? ?Ok, now you know why? FM broadcast? TX..that use the? classic? ?resonant choke +? cap setup.... also follow it up with a? 2nd choke? +? 2nd cap.? ?The? 2nd choke (NOT resonated)? ?+? 2nd cap is? there strictly to kill the harmonics.? ?Now in essence? they end up with a resonant choke notch filter..... followed by a? ?C-LC? filter.?? With a simple? ?C- choke - C? ?filter.... it forms a bonafide? real deal? LP? filter..with a real low freq? cut off.? ?In my case, the? cut off freq is real low, like 3.7 hz.? ? ?Attenuation at 120 hz? is? -131 db ... and lower still on the? harmonics? at? 240/360/480/600/ etc.? ? ? Max? gross overkill,? I like it.? ? So do the glass tube? audio geeks. I can see why the FM broadcast folks? want? loads of? 120..and also? 240/360/480? etc? ?harmonic redux? (this is on single phase? B+? supplies).? ? FM is about the only mode I can think of, that sucks max plate current.... with no modulation / audio / program? material /? music? applied to the TX.? ?IE:? 100 kw? ERP? and during pauses? etc, if there is any 120/240/360? etc products, they? will be heard on the RX end.? ?Esp if the? 100 kw erp station is fairly local,? full quieting, and? S meter? pegged.? A few folks? tried? 75M? ?FM late one night..that was an eye opener.? ?Locally,? FM is used on 11 M band !? later.... Jim? ?VE7RF |
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I? made a serious? error? when plugging numbers into the PSUD-2? ?power supply software.? Like an idiot,? I used the? wrong? plate xfmr? ?DC? primary? resistance.? I was plugging in? ".1 ohm"..... when it shoulda
been? ",01 ohm" .? ? ?Well that? makes a helluva? difference? to the calculated? ?source? Z? of the? plate? xfmr.?? I did have the? secondary? ?DC? resistance correct though? ( 4.5 ohms? across the 3900? tap....and? 6 ohms across the? 5200? tap).? On the 3900 tap, source? Z? is actually? just 7.411? ohms.....? and? NOT? ?33.61? ohms.? ?? On the? 5200? tap,? source Z? ?is actually just 11.61? ohms.... and NOT? ? 57.6? ohms.? B+? ?V drops? under a steady...or? varying load are of course? much improved.? ?Hardly any drop at all.? The resonant choke? setup is still? a dud? though.? ?It's? a glorified? 120 hz? notch? filter...and let's all the? harmonics? pass on through.? ?? Too? easy to make? errors.? Jim? VERF? |
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Did you try tuning the choke about 30 Hz
higher?
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Carl
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Re: [ham_amplifiers] Re: C-L-C updateExpand Messages
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¿ªÔÆÌåÓýI've seen mention on this list of Rauch trying to blow himself up doing something with resonant chokes, but I wasn't privy to the actual event. What was the story there? 73 Randy KZ4RV On 6/8/2019 10:47 AM,
jim.thom@... [ham_amplifiers] wrote:
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RAUCHEN VERBOTEN!!! Unless he sets himself on fire....
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<I've seen mention on this list of Rauch trying to blow himself up doing something with resonant chokes, but I <wasn't privy to the actual event. What was the story there? <73 <Randy <KZ4RV ##? simple really.? His choke resonated at aprx? 117hz- 119hz..with just bleeder load.? Once the real load was applied, the choke XL? drops a tiny bit... and? resonance? freq? increases a bit.? ?Once it hit? 120 hz... with a load on it,? all hell broke loose.?? ##? He was? using the? classic? ? resonant choke - filter cap? config.... like henry radio and collins used...except they resonated on the high side of? 120 hz....? which increases in freq? even more..with? max load.? ##? In the above? resonant choke - cap? config, the? resonant choke is getting hammered? by? 60% ripple, coming out of the? rectifiers.? ? And the? ripple freq? coming out of the? rectifiers is? 120 hz...or? 2F.? ##? Think? of how parallel? resonant traps? work on a triband? yagi.? ? You end up? with? extremely high peak? V on the capacitor section of the trap....and extremely high current? flowing through the coil.? ?When the sign wave flips? polarity,? you get a huge? back emf from the coil..which charges up the cap.? ?The cap then discharges through the? coil..producing? high currents through the coil.? ?It just goes back and forth forever? ( with power applied..and a big load).? ##? The other issue with the classic? resonant choke - Cap? ?setup is the B+? is only .9 X xfmr sec.? Henry radio used a 6000 vac? sec on it's? 8K ultra....fed into a FWB.... then into the resonant choke - cap? filter..and a big 300 watt? bleeder.? ? The 8 K ends up being just? 6000 X .9 =? 5400 vdc.... no load.? ?Which drops down to? 4800 vdc? with a 1.25A? load.? 6 kw dc input..and? 3.5 kw? rf output.? ?So it drops? 600 vdc... which is nothing to? write home about.? ##? A? 3600 vac sec? with a FWB..or a 1800 vac sec? and a? FWD? ?would have done the job... and a C input filter.? ##? Put the? $$$? into the xfmr.... not a? choke.?? Gotta run, a ton of stuff going wrong this AM.? Jim? VE7RF |
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Henry had been using the resonant choke PS since before many on here were born and they worked fine until the resonating cap developed leakage and the value changed.
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The transformers were old design high impedance and used 866A, 872A, 8008, 575A, or equivalent/similar in xenon such as 3B28, 4B32. Nobody ever complained about hum (harmonics) in any ham mode or AM broadcast use even after the transformers were the modern design and retcifiers were SS. The 8K 600V drop is only for key down and at 9% regulation is no big deal. For intermittent loads the dynamic regulation is much better and could be improved with a bit more output C. I dont understand what all the fussing is about these days. Carl ----- Original Message -----
From: jim.thom@... [ham_amplifiers] To: ham_amplifiers@... Sent: Tuesday, June 11, 2019 9:47 AM Subject: Re: [ham_amplifiers] Re: C-L-C update <I've seen mention on this list of Rauch trying to blow himself up doing something with resonant chokes, but I <wasn't privy to the actual event. What was the story there? <73 <Randy <KZ4RV ## simple really. His choke resonated at aprx 117hz- 119hz..with just bleeder load. Once the real load was applied, the choke XL drops a tiny bit... and resonance freq increases a bit. Once it hit 120 hz... with a load on it, all hell broke loose. ## He was using the classic resonant choke - filter cap config.... like henry radio and collins used...except they resonated on the high side of 120 hz.... which increases in freq even more..with max load. ## In the above resonant choke - cap config, the resonant choke is getting hammered by 60% ripple, coming out of the rectifiers. And the ripple freq coming out of the rectifiers is 120 hz...or 2F. ## Think of how parallel resonant traps work on a triband yagi. You end up with extremely high peak V on the capacitor section of the trap....and extremely high current flowing through the coil. When the sign wave flips polarity, you get a huge back emf from the coil..which charges up the cap. The cap then discharges through the coil..producing high currents through the coil. It just goes back and forth forever ( with power applied..and a big load). ## The other issue with the classic resonant choke - Cap setup is the B+ is only .9 X xfmr sec. Henry radio used a 6000 vac sec on it's 8K ultra....fed into a FWB.... then into the resonant choke - cap filter..and a big 300 watt bleeder. The 8 K ends up being just 6000 X .9 = 5400 vdc.... no load. Which drops down to 4800 vdc with a 1.25A load. 6 kw dc input..and 3.5 kw rf output. So it drops 600 vdc... which is nothing to write home about. ## A 3600 vac sec with a FWB..or a 1800 vac sec and a FWD would have done the job... and a C input filter. ## Put the $$$ into the xfmr.... not a choke. Gotta run, a ton of stuff going wrong this AM. Jim VE7RF --- This email has been checked for viruses by AVG. |
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<Henry had been using the resonant choke PS since before many on here were?
<born and they worked fine until the resonating cap developed leakage and the? <value changed. <The transformers were old design high impedance and used 866A, 872A, 8008,? <575A, or equivalent/similar in xenon such as 3B28, 4B32. <Nobody ever complained about hum (harmonics) in any ham mode or AM broadcast? <use even after the transformers were the modern design and retcifiers were? <SS. <The 8K 600V drop is only for key down and at 9% regulation is no big deal.? <For intermittent loads the dynamic regulation is much better and could be? <improved with a bit more output C. <I dont understand what all the fussing is about these days. <Carl ##? Points? well taken, but it's not? 1954 anymore.? ?I see that? Henry radio still sells the? resonating caps on their website,? ?$120.00? ?Made by? HEC.? ? The? 8K uses? 2 of em? for? 60 hz.... and 3 of em for? 50 hz. That's a lot of? $$$, just for some resonating caps.? ? 300 watts? CCS? for the bleeders? is a bunch, but a requisite when using choke input.? ? Toss in the cost of the choke, + resonating caps...... and a low Z plate xmfr sec +? high C filter cap makes? more sense.? Put the? $$? where? it should go.? ##? I used? 816's...and the bigger? 866? back in the? day.? But you had to wait a few minutes for the mercury to vaporize.? ?The B+ output came off of the? CT? of the? fil xfmr that ran the? rectifier tubes...so a special HV? fil xfmr was used. . Peak plate xfmr? sec? current was low, so a high? Z? plate xfmr could easily be used.? IE:? high sec? dc resistance.? ? ##? The only mode where? 100 / 120hz? ripple..and harmonics are an issue is Broadcast FM.... and that's? when using single phase power.? ?Without the added? ?C-L-C? tacked onto the? output of the resonant choke, the? B+? supply won't meet? the FCC ..... 'AM? noise spec'....applied to? broadcast? FM.? ?The typ? resonant choke already has a cap on the output, so adding? one additional choke + 2nd cap is not a big issue.? ? ?FM is the only mode where the TX is operating full bore? cxr, whether modulated..or not....and plate current is max at all times.? ?During speech pauses, or between program material is when? you will hear any? ripple...or? ?ripple harmonics.? ?Typ? FM? consumer RX's? are good from 50-15 khz....and with a local? 100 kw erp? FM? station? across? town,? you? would hear em .?? ##? That's all a? moot point for? ham use.? ##? One slight advantage of the 127 lb dahl choke is..... unlikely some bozo will steal it.? Later.... Jim? ? VE7RF? ? ? |
¿ªÔÆÌåÓýSomewhere, AG6K is smiling... 73 Randy KZ4RV On 6/10/2019 11:05 PM, Jim Strohm
jim.strohm@... [ham_amplifiers] wrote:
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