I believe Tom settled on 12-15% higher than 120 Hz as the best performing.
Its somewhere in the archives.
Carl
KM1H
----- Original Message -----
From: "Jim Thomson" <Jim.thom@telus.net>
To: <amps@contesting.com>
Sent: Sunday, February 21, 2010 7:07 AM
Subject: [Amps] resonant choke filters.
> Date: Sat, 20 Feb 2010 11:29:34 -0600
> From: "Roy" <royanjoy@ncn.net>
> Subject: Re: [Amps] 120 Hz hum from Henry...
>
>
> "Be careful if you fix this. It's not tuned to *exactly* 120 Hz because
> that
> would cause a very high voltage to appear across the choke. Use the
> specified values if
> you replace anything."
>
>
> I strongly believe the above is a perpetuated old hams' tale, totally
> untrue. The parallel-tuned circuit is a frequency-rejection filter,
> exhibiting a very high Z to the 120 Hz ripple, thus preventing high
> circulating current and its resultant voltage build up. Read the article,
> noting the careful tuning to exactly the 120 Hz resonant frequency:
> http://www.qsl.net/i0jx/supply.html
>
> 73, Roy K6XK
>
> &&& IF you resonate the filter to exactly 120 hz... the resonating cap
> WILL blow up in your face. Try it and you will see for yourself. Been
> there, done that. Ask Tom Rauch abt his resonant choke experiences,
> he just abt killed himself.
>
> &&& also note in the I0JX article. He uses SIMULATIONS. That`s
> fine, but apparently the simulations don`t show the exploding cap.
>
> && also note he advocates using swinging chokes. Swinging chokes
> are a dead loss, if used in resonant filters. Their inductance is all over
> the map,
> exactly what you don`t want. Dahl`s chokes, made for resonating, are very
> stiff, and
> only drop down in value a small amount, when a huge load is applied.
>
> && Look at his plane jane C input filter.. just ONE 15 uf cap.. 6450 vdc
> No load,
> and 6175vdc, sucking 1000ma. 6147 divided by 6450 = .957 That`s a
> 4.3% drop. That`s superb regulation. If he had increased the C to
> 50-150uf, you
> will then get a real eye opener. Loaded V is higher.. and on SSB, it won`t
> droop at all.
>
> In his henry 4 K ultra example... his No load = 4525vdc. His loaded V =
> 3950vdc.
> 3950 divided by 4525 = .873 This is a 13% DROP ! So much for the
> nonsense abt
> the infamous Henry radio resonant chokes.They are heavy alright, but they
> are not heavy duty.
>
> The 8 K ultra used a resonant choke. It also sucks 300 w of bleeder, just
> to make the choke,
> look like a choke. ( 5 x 20 k, 100 watt WW`s in series) No load is 5400
> vdc. To get that,
> they use a 6000 vac xfmr. If that had been a simple C filer, only a 3800
> vac xfmr is needed...
> (and NO choke, nor 300 W CCS bleeder) Loaded V on the 8k = 4800 vdc ,
> 4800 divided by 5400 = .888 again, no fantastic regulation here.
> (11.1% drop)
>
> IMO, ur better off to dump the resonant choke,and spend the money on the
> xfmr, and caps,
> not a bunch of excess weight. Besides, any resonant choke set up will
> not kill the harmonics
> very well. The plane jane... BIG C input filter, will kill the 120 hz
> ripple,,, and ALL the
> harmonix of 120 hz.
>
> later... Jim VE7RF
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