[AMRadio] Amplifier to use with my DX-60


Jim candela jcandela at prodigy.net
Sat Mar 18 12:43:31 EST 2006


Harry,

    You will need to find a suitable modulation transformer for the
impedances, and power levels used. If the amp uses metal 6L6's, consider
pathways towards a little higher power, as 25 watts is a little light for
this job. I might be wrong but my recollection is that a 6146 is good for 65
watts DC input on AM. Backing that down to 50 watts DC input to better match
your PA amp power is another option. You might be able to use another audio
output transformer to raise the voice coil impedance back up, but if you do
this look at a single ended transformer designed to handle DC current flow
(these have gapped cores). There are some in the 25 watt category that
audiophiles use, but don't expect a cheap price. Alternatively you could use
another push pull output transformer, a choke, and an AC capacitor to shunt
the 6146 plate current away from the non-gapped 2nd transformer. The use of
back to back transformers is not usually the best choice, but with the
limited availability of modulation transformers, the back to back
transformer idea has a certain appeal to it.

    Once these details are worked out, you need to make a mod to disable the
modulator when you are not transmitting. You might add a relay and hook that
into the transmit PTT circuit. The details on how this goes will depend on
the circuitry in your own equipment, and whatever choice you prefer.

  If you could post the schematic somewhere of that PA amp, maybe the group
could offer suggestions on how to adapt it to modulator usage.

Regards,
Jim
WD5JKO

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net]On Behalf Of Harry Vaught
Sent: Friday, March 17, 2006 7:13 AM
To: Discussion of AM Radio
Subject: Re: [AMRadio] Amplifier to use with my DX-60


Ok, tell me this:

I have a DX-60A and a 25 watt P-P 6L6 Webster Electric PA amp with a
large selection of output impedances.  What would I have to do to plate
modulate my DX-60?

There are obviously greatly varying levels of knowledge out there, and
mine is probably below median.

Harry, KT4AE
Maryville, Tennessee
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