[Central-Electronics] Drive a Johnson KW

[George Maier]

Well Jimmy, the first thing you will encounter is a lot of envy from those
of us that do not have a Desk KW!!!!!!

I've often thought about the same combo you're describing just as a brain
teaser to consider the options that are available.  Jim & Colin both
provided good advice with options for using or ignoring the built-in Johnson
modulator.  If you don't have a high quality audio driver, Jim's suggestion
for linear operation is both practical and easy, and will provide good
sounding AM up to the legal power limit.  The only kink is that when you
turn the RF output power control on the 200V down to a safe drive level, the
200V scope trace will no longer be useful.  If you have a CE MM-2 scope, you
should hook it to the output of the Desk KW to check modulation depth; I
suspect it's a fairly critical adjustment with such a combination. The other
part that WD5JKO hit on was the need for an attenuator. On my 200V, the
minimum power out is around 10W with the  control down as far as it will go;
probably too high for linear operation.  In the past, I've used a 200V on AM
to drive a 3-1000Z in grounded grid linear, and it's  worked fine.  The
drive requirement is quite a bit higher that your Desk KW would be, but
getting the 200V AM modulation percentage spot on  is still a bit touchy
even so.  

Given your situation, I think I'd look for, or build a good clean audio
driver and use the built-in AM modulator;  those desk KW's sound really
sweet with the high level modulator.   The Johnson 10W audio driver that
Colin referred to is part number 250-33, but they are extremely scarce and
overpriced when you do find one.  

Good luck with it Jimmy!

73, George - W1LSB

PS - Sorry to  have been so quiet lately, been busy with real life for a
spell - ugh!   Good to be back !


-----Original Message-----
From: central-electronics-bounces at mailman.qth.net
[mailto:central-electronics-bounces at mailman.qth.net] On Behalf Of Jimmy
Green
Sent: Saturday, November 03, 2012 11:07 PM
To: central-electronics at mailman.qth.net
Subject: [Central-Electronics] Drive a Johnson KW

Would some tell me what I will incounter using my 200V to drive my Johnson
KW on AM.
Thank You,
Jimmy K5CSU
______________________________________________________________
Central-Electronics mailing list
Home: http://mailman.qth.net/mailman/listinfo/central-electronics
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Central-Electronics at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html