30-40 Problem Question ?

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From: Bob Berlyn (bob.berlyn@chowda.com)
Date: Sat Dec 17 1994 - 04:54:00 EST


Hello All,

I just got my 30-40 done. I built it with all the mods from the most
recent issue of 72.

Installed 2N3553 Final, Q6

Installed 7.5V Zener for better TX mixer supply voltage, it's now 7.14v.

Installed 2N2222 for Q4 & Q5

Replaced the .01 Cap between the T-R bridge diodes with a
47Pf.

Problem is with the LO Freq, I guess. I cant get the rig into the part
of the band I want. Since most of the action on 30 meters seems to be on
the low end of the band I wanted to set my 30-40 up for about 10.102 as
the bottom end.

I had to remove a turn from L1 and the lowest Freq I can obtain is
10.129 Mhz.

I added a 10 Pf Cap in Parallel to L1 and got it down to 10.123 Mhz, not
good enough.

I added a 18 PF Cap and got it down to 10.119, better, but the
transmitter becomes unstable when I try to drive it over about 950
millawatts. I wanted to get a watt and a quarter if I could and it is
stable in the last two examples.

I tried unwinding another turn from L1 but than the Freq goes way to
low.

I have seen some postings in the past about this problem with the 30-40
but, cant remember what the cure is.

Can anyone help ?

Hope to see you on 30 Mtr QRP soon. Thanks

Bob

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* CMPQwk #1.4* UNREGISTERED EVALUATION COPY


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