|[AMRadio] K4KYV monitor scope|
w5jo at brightok.net
Thu Mar 31 20:51:22 EST 2005
What model do you have Don?
> I would have to dig up the documentation, but relying on my memory, I
> recall beefing up the HV filtering, rerouting the filament circuitry and
> replacing the magnetic shield on the scope tube.
> As I recall, I substituted a separate filament line for the original
> design that depended on the chassis for one side of the circuit.
> The piece of tin wrapped around the neck of the tube is worthless is a
> magnetic shield. I had an old military RTTY monitor that used a similar
> shaped scope tube, and cannibalised the special black anodised magnetic
> shield and managed to shoehorn it in place by relocating some of the
> original scope components.
> I got rid of most of the hum that shows up on the vertical trace, and the
> additional filtering got rid of the hum that modulated the brightness of
> the trace.
> I also modified it to add some astigmatism control, which results in a
> sharper, better focused and better defined image.
> The original designers could have done a much better job. The manual even
> mentions the problem; they pass it off as "insignificent" in a scope that
> is "only" designed to monitor modulation.
> Since I use mine only on AM, I pulled out the tube from the two-tone
> generator and vertical amplifier. That lightens the load on the
> failure-prone power transformer. I excite the vertical deflection plates
> directly with rf.
> Instead of running the rf feedline through the scope, I use a remote
> toroidal pickup link to feed the scope some distance away from the rf
> feedline. I had to locate it on the transmitter side of the antenna relay;
> otherwise the pickup link was inducing an intolerable level of noise from
> the scope into the receiver.
> Don K4KYV
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