[AMRadio] Amplifier to use with my DX-60

Jim candela jcandela at prodigy.net
Fri Mar 17 10:59:40 EST 2006


   Your approach as always is a good one, and can be made to work out quite
well. This extra box will allow about a 6DB increase in power from what a
screen modulated 6146 can do. The DX-60 with carrier control can arguably
better match up to a linear amplifier, but must of us would agree that
carrier control as done on this rig is too much, and annoying to those
copying a weak signal that goes into and out of the noise with modulation
peaks. Now consider these options:

1.) Modify the DX-60 for non carrier control screen modulation. That should
provide about 20 watts carrier with room for + 100% modulation.

2.) Modify the DX-60 for plate modulation. This might require a 6146 bias
change for proper class C plate modulation bias. You will also have to deal
with modulating the screen grid. The plate tuning capacitor might flash
over, and other components may need to be beefed up to handle the higher
peak power. Once done, you will have a fine 45-50 watt AM rig that you could
be proud of.

3.) Combine option 1 with this: Mate up the modified DX-60 to a linear with
1000 watts of dissipation available (like two 3-500Z's). Now you can easily
run 250 watts AM or more (maybe 375) of quality AM.

4.) Use the DX-60 as is (stock), or with an amplifier as you wish.

The choice is yours,


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net]On Behalf Of John E. Coleman (ARS
Sent: Thursday, March 16, 2006 9:10 PM
To: 'Discussion of AM Radio'
Subject: RE: [AMRadio] Amplifier to use with my DX-60

	I still say, forget the linear, and use less money to build a plate
modulator for the DX60.  It will work better, sound better, cost less, and
heat the shack up less. As I recall the DX 60 has a 6146 in the final for
class C CW and puts out about 40-50 watts of carrier if it were plate
modulated it would do at least 200 watts PEP and sound great.  There is a
number of different ways to do the modulator.  A lot of guys just find and
old PA and a transformer to match to the final.  Some build the modulator
output stages only, input XFMR tubes and modulation XFMR.  Then they drive
it with a small microphone amp.  That's more stuff to set around on the desk
but it works.  There are a lot of self contained 25 and 50 watt modulator
circuits around and probably a lot of complete one piece store bought
modulators as well.  As I recall, EICO had a pretty nice one that was to go
with the EICO model 720 but it was used on many different rigs as well as
being used as a driver for big modulators.  A buddy of mine had an ECIO 720
and built a nice home brewed modulator for it using 1625s in AB1. It sounded
real good.  I built one similar to it with less power output for my Knight
Kit T60.  The T60 had the same control carrier AM that the DX60 does.  What
a difference it made when it was plate modulated.  Very little modification
is necessary in the DX60 to accommodate the external modulator.


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