[Amps] SB221 Low Output

Ron Youvan ka4inm at tampabay.rr.com
Mon Sep 12 07:24:10 PDT 2011

Alex DV1TBX Barbon wrote:

> I am working with an SB221 amp, can't get the power output to go higher than
> 400watts either AM or SSB voice peak. The tube is confirm good from a
> working amp.

> Here is my reading

> *20m, AM mode ( no modulation )

> *Plate current = 680mA
> Grid current = 180mA
> HV= 2750V SSB
> Drive = 90~100watts
> Output = 450watts

   I don't know anything about SSB, (what ever that is) but with 25 - 30 Watts of drive you should 
get about 350 Watts (carrier only) out of it, it looks (to me) like you are over driving it a lot.
That is the legal maximum, pretty much.
     Are you using a peak reading Watt meet of known accuracy?
    Ron  KA4INM - Ifen my mother in law were to boil water
                  it would taste funny ... Earl Pitts 9-1-11

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