[AMRadio] Re: Gates BC250L efficiency

Brett gazdzinski Brett.gazdzinski at mci.com
Wed Sep 29 11:06:47 EDT 2004

Efficiency is often a function of the tank circuit Q.
Lower Q often gives more efficiency.

It can be quite dramatic if you are far off.
Grid bias needs to be way beyond cutoff, and with a 
lower Q, efficiency should go up.

I did some experiments on the push pull 812 rig when it was done.
I was getting 200 watts out of it, until I shorted 2 or 3 turns
on the final coils.
Power went up 50 watts!
I removed the turns to prevent weird stuff going on, but still
only got the 250 watts out, so the shorted turns were not
causing problems in my application.
Maybe try shorting some tank coil turns as a test and see what happens.

If you left a lot of turns in the coil, your Q could be above 20 or more.

>From memory, a Q of 15 is 'normal'.
A Q of 12 should be ok, who has harmonics these days?


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of K9AF at aol.com
Sent: Wednesday, September 29, 2004 10:32 AM
To: amradio at mailman.qth.net
Subject: [AMRadio] Re: Gates BC250L efficiency

K4KYV writes:
I replaced the PA grid/driver plate coil wound on the bakelite form with 
similar Miniductor coil stock and got a big boost in grid drive when I moved

it to 160. 

Don, thanks for the suggestion. Trouble is the BC250L's grid/driver plate 
coil is NOT on a bakelite form. It is a ceramic one,  2 1/2 inches in
I still get the exact same grid drive on 160 meters as I did on the
band.  My problem still remains efficiency, and maybe I'll just have to
with 61% and be happy.


Jerry K9AF ______________________________________________________________
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