SB-102 - more troubles

[Kenneth G. Gordon]

On 14 Jul 2009 at 17:28, Glen Zook wrote:

> The problems that I have seen in the solid-state LMO in the SB-102 is
> not stability.

Agreed.

>  They seem to be as stable as the tube-types.

In my experience, they are MORE stable than the tube-types by quite a 
bit, in fact.

>  However,
> it has been my experience that the company that manufactured the
> solid-state LMOs did not perform the close calibration that TRW did on
> the tube-type.

Agreed.

>  In every SB-102 that I have worked on the LMOs were
> pretty much "spot on" at the 100 kHz points.

Not mine: if I calibrate it to be on at the high end, it gets increasingly off 
as one goes towards the low end until at the low end the adjustable hair-
line is more than 1/2 inch from where it sits at the high end. Also, my 
SB-102 won't tune lower than, say, 3502 Khz at the low end.

>  But, in between I have
> seen them as much as 5 kHz off from the dial reading.

Agreed.

> I understand that there is an amateur radio operator somewhere down in
> Florida who will work on getting the calibration of the solid-state
> LMOs just as good as the tube-type.  From what I have heard this is
> basically a "labor of love" because what he charges is very small when
> considering all the work that is required.  Unfortunately, his name
> and call escape me right now!

Well, if you should happen to figure out who he is, I would sure like to 
get that information.

Concerning stability with the Heathkit LMOs: the one in my SB-102 will 
easily hold within 10 Hz over fairly long periods of time, while that in my 
SB-301 drifts back and forth at LEAST 10 Hz within a period of one 
minute. I cannot get the two to "lock" to the same frequency for much 
longer than about 20 seconds at a time.

Also, the frequency being listened to changes as the signal level rises 
and falls, but not by much. I think the voltages to the heterodyne 
oscillator AND to the BFO oscillator should be regulated in all SB/HW 
rigs, to start with. Zener's would be a good choice as they can be 
mounted inconspicuously.

Ken W7EKB

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