> # say what? On ssb, the duty cycle at most is only 30-50%.## why would
> you want to suck the B+ way down as low as it will go with a cxr ?
REPLY:
Because tuning with a full carrier and then operating with a normal
SSB duty cycle gives you a wee bit of headroom to avoid clipping and
splatter. I don't believe in tying to squeeze the last watt out,
ESPECIALLY on SSB.
73, Bill W6WRT
## You got it wrong Bill. UNLESS you have perfect B+ regulation,
Tuning with a CXR, then switching to SSB is a waste of time.
## On SSB, your B+ voltage, is going to be a heck of a lot higher
than it ever will be with a cxr. Your pep input /output will be higher too.
## Your plate load Z will also be higher. If you tune with a cxr, you will
get a mis- tune every time.
## Pulse tune..1st, then switch to ssb, THEN you have some head room !
## ever watched the typ old geezer, with his 1st amp ? [ newbie] ...
tuning with a cxr. Typ will be at some point, he will be almost pegging the
plate current meter , with 500 w showing on the wattmeter. Meanwhile,
his SB-220, etc, is sucking 3 kw dc input and he has 500 w out. Anode diss
is 2.5 kw, tubes are bright orange, and meltdown is about to occur.
## he will repeat the process, every time he qsy's 20 khz. His heath
500VA plate xfmr is about to burst inside his SB-220.
## Pulse tuning @ 25- 30% duty cycle WILL provide the headroom required,
EI: Pulse tune amp to 1.6 kw pep out, switch to SSB, then back drive off a
tiny bit,
till pep meter shows 1.5kw. Now the amp is properly tuned up, and you also
have some headroom. Now if the amp is off resonance while pulse tuning,
no big deal, nothing will blow up.
later..... Jim VE7RF
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