[Amps] Amps Digest, Vol 151, Issue 6

[Jim Thomson]

Date: Wed, 08 Jul 2015 19:44:56 -0600
From: Steve London <n2icarrl at gmail.com>
To: amps at contesting.com
Subject: Re: [Amps] Amps Digest, Vol 151, Issue 6

Thanks everyone for the responses, both on the reflector and direct.

Is there any particular reason the L-C-L T-match is better or worse than 
the more standard C-L-C pi network in this application ?

Thanks,
Steve, N2IC


###  caps have WAY less  loss vs  coils..esp on 6m.   On a friends GS35B
6m  triode GG amp, a  L-C-L  was tried 1st.   No way in hell could he get the swr
down flat.  best was 1.5:1  Spent hrs tweaking the pair of coils  plus variable cap. 

##  switched to a C-L-C... and presto,  dead flat swr.   Don’t use small ga wire for the
coil, too much loss.  Use something bigger like  10-8-6 ga.   You can also use  copper
strap, thin stuff, aprx .25 inch to .375 inch wide.... and wind the coil  from that. 
easy to wind, holds its shape nicely, virtually no loss at all. 

##  To increase eff on 6m, you can also install a fixed npo cap, like 25-75 pf... between cathode
and chassis.   Then use less C2 cap on the tuned input.  C1-L-C2.     You can also parallel 2 x 50 ohm
coaxs  from tuned input to cathode to simulate the  fixed cap between cathode and chassis.  
Both schemes will work.   2 x 75  or  70 ohm coaxs  will also work.  So will a 75 /70  coax in parallel
with a 50 ohm coax. 

##  The tuned input  has to be done right.... or the eff will go to hell. 
You can also use flat copper strap, for the main tank coil on the kw PI net, but use wider stuff,
like .5 inch. 

Jim  VE7RF