[600MRG] Fwd: Re: Fwd: Re: Testing new Transmit downconverter

[pat bunn]

-------- Original Message --------
Subject: 	Re: [600MRG] Fwd: Re: Testing new Transmit downconverter
Date: 	Thu, 25 Apr 2013 13:46:00 -0400
From: 	pat bunn <pbunn at patbunn.com>
To: 	John Langridge <jlangridge at sbcglobal.net>



For CW QSOs  a transverter is probably OK.  I have not heard of many HF
rigs that stay stable within 1-2 Hz while transmitting for long periods.
Most are stable enough for receiving.

Easiest way to get on the band for non linear modes in my opinion is
with a class D transmitter. A 12 volt rig in PP is an easy 110 watts
that can be built for $35. All that you need to drive it is a CMOS level
square wave. At 500 KHz, transmitters and power is cheap and easy.

W1JR has a nice driver circuit that uses a 2X logic signal - I have also
used the Microchip driver with a built in inverter that uses a 1X signal.

I have found that if you use high voltage good FETs like the Fairchild
FQA series rated at 200 -  400 volts at 40 amps or so, two will get an
easy 500 watts and a pair will go to a KW. That is with a 50 -60 volt
power supply. The Mean Well switchers are not expensive and make great
fixed voltage power supplies at 48 volts.

Just heat sink the FETs and a use  variable voltage supply to allow
going from 100 to 1000 watts with four FETs that you can get for a
couple $ each. Even at a KW they are over 90% efficient so the heat sink
is well within an easy to get size.




Pat
N4LTA