Hello, Everyone,
In doing the transmitter checks, a scope with two reliable channels was
needed for the ScopeMatch and for troubleshooting. The local TV repair shop
is going out of business and sold me a Hitachi V-680 Dual trace digital
storage scope for a very good price.
I have the service manual, but neither the operating manual nor the
specifications could be located through a websearch which was done earlier
today.
Does anyone have the operating manual or know where a copy can be obtained?
Hitachi has been contacted and their webpages searched, but they do not even
show an Oscilloscope.
Any tips or clues would be appreciated.
Also, does anyone know the advantages and disadvantages of using Bifilar
windings on amp output transformers for Push-Pull amps? I do not know if
this is usually the case, but when I used the straight winding method, the
amplifier ran a lot more power but when I switched to the bifilar winding
the output waveform has just a little bit less even order harmonic content.
By the way... The amp is working very much better now, with one small
caveat.
It is also interesting that when the good scope was put in service, it
became apparent that the channel on the old scope which had been
intermittent also had been indicating a slightly better antenna match than
the new scope does.
On the Push Pull amp prototype, there is a small amount of high frequency
damped wave ringing which occurs just before the positive and negative peaks
of the amp output voltage and current waveforms. These damped waves are
very small, but will they may be a harbinger of troubles to come if they are
ignored, or are they a normal occurrence in these inverter type amps... are
they important?
The output transformer will be rewound from bifilar to conventional winding
and if it has any effect on the damped waves, I will let the group know.
Thanks to all for the help getting the transmitter working... There were
several problems, all related to being in the VY1JA shack... :o) The main
problem was that I misunderstood or my memory failed. I thought the amp was
set for input frequency divide-by-two and it was set for divide-by-four.
When the HF rig output was doubled from 13.778 to 27.555 MHz, the output
waveform of the rig tamed right down.
This explains why I was having those really bad antenna waveforms a couple
of months back whenever I switched to the prototype amp. When I build my
amp shortly, it will only divide by 2 so that I can use the frequency output
display of the HF rig. Here too, thanks to all who worked with me to try to
solve the antenna matching problem.
With a good rig and scopematch in hand, I am looking at revisiting the
Variometer. If you remember, I removed it and replaced it with a simple
single layer tapped solenoid, with a separate link-coupled air-core
impedance matching transformer. Perhaps it is due to the size of the
antenna, but the antenna holds its match well even in rain and wind. Yes,
the trace moves slightly around but not enough to require a trip outside.
When the variometer is redone, I am considering winding it with #12
Thermoplastic insulated building wire, is there any drawback to this in a
situation where little inductance is required?
73,
J.
[email protected]
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