[AMRadio] Broadcast transmitter rescue


John Coleman jc at pctechref.com
Sat Feb 14 21:37:50 EST 2009


If voltage is needed for the exciter a long coax line from the VFO can be tuned with a small network to provide the voltage needed at the grid of a distant buffer.

John, WA5BXO

-----Original Message-----
From: amradio-bounces at mailman.qth.net [mailto:amradio-bounces at mailman.qth.net] On Behalf Of sbjohnston at aol.com
Sent: Saturday, February 14, 2009 7:48 PM
To: amradio at mailman.qth.net
Subject: Re: [AMRadio] Broadcast transmitter rescue


Todd wrote:

>Don, I'd be curious to hear your thoughts on maximum connection
>distance electrically for a VFO.

I'm not Don but I have some thoughts:  It depends a lot on the output
impedance of the VFO, I'd think.  If it is low-Z, say less than 100
ohms, then I'd think you could run coax quite a long way.  The DDS VFO
I built and use with my Gates BC-1T has a video op-amp as the output
line driver so it is no problem to run a fair distance on regular
coaxial cable.

See

http://www.wd8das.net/DDSVFO/ddsvfo.html

which shows both the VFO circuit and the interface to the Gates AM rig.


If you have a VFO with a high-Z output, maybe the special
low-capacitance coax used for broadcast antennas on cars would help.

Steve WD8DAS

sbjohnston at aol.com
http://www.wd8das.net/
-----------------------------------------------------
Radio is your best entertainment value.
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