[AMRadio] Re: Need list of good AM radios to start looking


Jim candela jcandela at prodigy.net
Wed Nov 16 13:53:06 EST 2005



Dan,

    I like your suggestion. I never tried it, so I am no authority on this
modification. In general, this would change the modulator load impedance,
and the RF pi network formulas would suggest juggling the L/C ratio to
maintain the same 'Q'. I might be tempted to use some sort of negative cycle
loading to contain the modulator, and minimize splatter by keeping the
negative modulation below 100%, and letting the positive peaks fly upward
beyond 100%. Doing this however may raise the PEP drive power too high for
the linear, so that's another issue to contend with. Running both modulator
and final RF stage at reduced B+ may still be the best approach when driving
an amplifier with low drive requirements. Another option is to use the 2e26
and low B+ for really low drive amplifiers.

Regards,
Jim

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net]On Behalf Of dw73454 at alltel.net
Sent: Wednesday, November 16, 2005 10:57 AM
To: Discussion of AM Radio
Subject: Re: RE: [AMRadio] Re: Need list of good AM radios to start
lookingfor .




> You do usually need to drop the
> power a bit to keep from over driving most linears. One >modification is
to
> run the RF Final 6146 and modulator off the low B+.
>
> Jim WD5JKO

I have also heard that you can just replace the
6146 with a 2E26 and do nothing else. Is this true?
And....what are the tradeoffs, if any?

73 de Dan -- WAØJRD ..


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