[AMRadio] K4KYV monitor scope

Jim Wilhite w5jo at brightok.net
Thu Mar 31 20:51:22 EST 2005

What model do you have Don?

73  Jim

> 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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