[Boatanchors] Harvey-Wells VFO stabilization etc

[Sandy]

I second the motion on the loading capacitor in the Pi-network, especially 
on 80 and 40 meters.
All the TBS-50 series suffered from needing more output capacity easily 
added with a 1 kv mica cap or an old BC band radio tuning cap in parallel 
with the output.  The Heathkit DX-40 also had this "problem" as I recall.

73,
Sandy W5TVW

-----Original Message----- 
From: Rob Atkinson
Sent: Sunday, January 27, 2013 5:51 AM
To: Ian Wilson
Cc: boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] Harvey-Wells VFO stabilization etc

Leave the VFO running and work on the backwave problem.

Without knowing the load Z and the input to the final your power out
is not all the info we need.

if the load Z is low, the standard 50 ohms these days, check the load
cap setup if it has a pi output network.

you may need more load C.   this is what happened to me with a knight
T-50.  I could never get the plate to dip to ~ 100 ma.

I finally noticed the load cap was never connected right--one section
and the padder were never in the circuit.  I connected them and
everything fell into place.

73
Rob
K5UJ

On Sun, Jan 27, 2013 at 12:33 AM, Ian Wilson <ianmwilson73 at gmail.com> wrote:
> I have a TBS-500D ready to go on the Classic Exchange tomorrow.
>
> Two things I'd like to impove:
>   - VFO stability (on 40m) isn't great
>   - output power is about 25W
>
> I am keying the VFO as well as the driver/output stage. Could do
> better by leaving the VFO running but then would have a problem
> with backwave. Perhaps I would do better by not attempting to do
> break-in keying?
>
> There is plenty of drive to the final stage. Dipping/loading seems
> rather shallow. 25W is OK but I do better with more power from this
> QTH. I wonder if it's worth trying another 807.
>
> 73, ian K3IMW
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