Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Mark -
This is just a guess, having never owned an L-7.
There is a capacitor across a portion of the final plate RF choke. I'm
assuming that it is to compensate for an unwanted resonance of the RFC
on some band(s). It;s not easy to make an amplifier work over the
entire HF range covered by the L-7.
IF that capacitor shorted, it would effectively short out part of the
RFC, reducing the inductance, which would decrease the impedance at
lower frequencies, effectively shunting RF to ground, OR altering the Pi
Net match, OR... ???
Something is either shunting RF to ground, OR a series capacitor has
gone down in capacitance (or one of a parallel pair has opened up) to
decrease the coupling between stages, e.g., the plate blocking
capacitor(s) in the L-7 are a pair 752 (?) pF capacitors in parallel.
Hopefully someone will KNOW the correct answer!
73, Garey - K4OAH
St Charles, IL
MT wrote:
MT <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Howdy group
I have a couple questions about an L7.
First, I am looking for the .82 ohm resistor which did its job on
Sat. I talked to Harbach and he does not have them. Newark and
Mouser don't list them. Anyone have an idea for a source? There
were no sources listed other than Harbach in the archives of this list.
Second,
I have low output on the bottom of 80 and all of 160. I went thru the
manual steps and adjusted the tuning coils appropriately. I can get
over 1KW at 3795, but at 3510 I get 300w. 160 is the same way. All
other bands are over 1KW with no issues. The exciter does see a
higher SWR at the freqs where I have low output.
The 80m tuning coil was adjusted extensively, almost to its limit,
without much difference.
Any thoughts?
THANKS
Mark
N9UM
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