In a message dated 1/6/99 9:27:04 AM Eastern Standard Time, km1h@juno.com
writes:
<< At 2KW input the average SB-220 will crank out a massive 900-1000W on 10M
for 45-50% efficiency. OTOH, with all that HF stuff removed and rebuilt
strictly for 6M the power out will be 60-65% efficient with good tubes.
So where does the missing 15-20% of the power go on 10M ?
>>
Same place as in Clipperton L on 160m - heating up the coil, cabinet metal,
anodes in tubes, etc. Clipperton L would produce around 1200W on higher bands,
while only abt 400W on 160. Add about 4 turns to the coil and 1k Cap on the
output C and you get about 900W out, take the top cover off, and you get at
least 1100W out.
Best efficiency and harmonic suppression can be obtained with monoband design
(like your 6m SB220). My 8877 contest amp "Monobandit" has plug in PI-L
network input circuit, PI-L plug in output circuit and the final adjustment is
done with 50 ohm full load, trying taps on coil every 1/2 turn from calculated
value and looking for maximum output while drawing minimum plate current.
Takes care of all "calculations".
With addition of 1/4 wave coax stubs and link coupled tuned circuit between
rig and amp, I managed to get suppression of harmonics with amp on by about 20
dB over barefoot exciter.
Happy and powerfull 1999!
Yuri Blanarovich
K3BU, VE3BMV
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