[AMRadio] Amplifier to use with my DX-60

John E. Coleman (ARS WA5BXO) wa5bxo2005 at pctechref.com
Fri Mar 17 12:57:16 EST 2006

Well first of all Harry I am not familiar with the Webster Electric PA amp
but 25 watts output is a little on the light side but is usable if you don't
load the DX60 to more than 40-50 watts plate input power.  You could
probably use a 25 watt audio output XFMR rated of single ended use, so it
would handle the DC from the final.  I have used a 200 watt power XFMR from
old television sets as a modulation XFMR.  Use the HV Secondary as the final
side (experiment as to whether using all of the secondary or one half) and
input from the PA (16 ohm to 12V) or (500 ohm to 110V).  Experimentation
might be necessary.  Basically, if the 6146 rig is 500V and 100ma it would
require 25 watts at 353 V RMS (0.707 X 500) to modulate it.  Find the
transformation windings that give you the closest match to get this voltage
output.  Your 25 watt amp is capable of putting out 
20 volts RMS into 16 ohms or 
about 14 volts into 8 ohms 
or 112 volts for 500 ohm line.

If you had more audio power available then your options would be more.

If the power XFMR is about 360 volts either side of CT then use CT to one
one side (half of the secondary) for the plate circuit and input 500 ohms to
the 115 Volt AC of the primary.

You will use the DX 60 in the CW mode and connect the HV secondary of the
outboard matching XFMR so that the B+ for the final and the screen resistor
connection point are together and their current has to pass thru the XFMR to

Check with other diagrams of 6146 plate modulated rigs in the older
handbooks and you will get the idea.

Good Luck John, WA5BXO

-----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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