>
>What is the true purpose of the CW/SSB switch on many of the older linear
>amps ?
>
The duty cycle for SSB is about 15%. The duty cycle for CW is about
double that. To obtain 1500w keydown output with 60% efficiency, a 2500w
HV supply would be needed. The avg. ham amplifier has a c.600w HV
supply. This is ok for 2500w pep input on SSB, however, it isn't as ok
for CW. Reducing the anode voltage and current for CW is a satisfactory
workaround. On the receiving end, who could notice c. 1/4 of one S unit?
>Was it simply to ensure that you stayed within the old power INPUT
>regulations when in CW mode, or is there some other good technical reason ?
>
> Obviously the reason I'm asking is that I can't see a good technical
>reason for the switch. Actually I see good reasons for not having it but
>I need someone to verify my understanding. (I wasn't planning on having
>one on the 4-1000 amp I'm building).
>
If you have a large enough power supply, you don't need CW/SSB switch,
Phil. On the other hand, 7kV is ideal for SSB with an 8166/4-1000a, but
it is a bit much for casual CW use. . Why not go with an 8171? It
drives easier, is easier to cool, takes up the same chassis space as an
8166, requires no filament choke, uses a simpler tuned input, and can
deliver seven more db if need be. .This can come in pretty handy to
compensate for additional path loss on 80m and 160m.
- later, Phil
Rich. Measures. Web site: www.vcnet.com/measures
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