>>
>> Well, it would be difficult for my bandswitch to fail as it is a big B&W
>> coil/bandswitch unit. And no, no other stuff. I did have a weird thing
>> happen that blew out some resistors a couple of weeks ago. But it turns
>> out that the tube was bad. IMHO, it had to have been an oscillation with
>> "unseen" stuff, but again, it was a bad tube.
>
>As you found out, most of the failures attributed to "parasitics" are
>really just component failures. You change the bad part, and add some
>needless voodoo, and the thing works.
>
Hmm...read again, Tom. I think my failure WAS a parasitic of some sort.
To make a 3 watt, 1 Ohm metal film resistor fail, one would need several
amps of current. To make a parallel combination of a one ohm 3 watt and
a one ohm 2 watt fail, one would need far more current than is probably
available. And it happened again yesterday. More on that in another
note.
>
>Nothing wrong with that shotgun method, as long as you don't care
>about efficiency. Another problem is can also reduce harmonic
>suppression, especially if you use the nichrome in series with the
>tuning cap modification I've seen people use.
Not using that.
>
>> >What king of load cap do you use that is fully meshed on ten meters,
>> >or is the amp a "ten meter only" amp?
>>
>> It's a standard 4 section cap. No idea of it's value though since I
>> didn't build the amp originally. It seems to like to operate near the
>> meshed position a lot of the time. Maybe I am not tuning the amp up
>> correctly. 15 meters has a false tune point when the cap is meshed but
>> tunes up better when you decrease the capacitance about half way. Maybe
>> I am doing the same thing on 10. It's a 80 thru 10 amp, BTW.
>
>Sounds strange. How are the wires routed along the loading cap? Trace
>the goesinto and goesoutta path, and see if it is "goofy". The proper
>way to pass RF through a multi-terminal air variable is in one
>corner, and out the other far end opposite corner to the RF output,
>with straps down each side in multisection caps.
OK. I don't follow you. So let me describe my setup.
The Tune C is mounted on a bracket above the Load C. The Tune C is a
Jennings Vacuum variable. A line runs from the Tune C to the B&W
inductor. The output of the inductor goes two places: One to the RF
output, the other to the load C. The Load C is connected with a piece of
copper strap about 1.25 inches wide. The strap is probably about 4 or 5
inches long total (yes, it's not the best, but I have wanted to avoid
changing the tank circuit layout). The copper strap is hooked to the
sections on the top part of the cap. The sections are all connected by a
piece of wire. The case and the other plates of the cap are grounded.
Other than the long piece of copper strap running to it, the rest of it
looked fine to me.
I guess I don't follow your logic. This is not an insult. A circuit
node is a circuit node. So wether you connect the output of the amp and
the input to the cap in exactly the same spot, or as you suggest above, I
see no difference. As long as all the sections of the cap are properly
wired together, I do not see a technical reason as to why your suggestion
works better. Perhaps there is some practical reason I am missing.
Now as for relaying stuff out - I just don't see how I would do it. It
would be really difficult and I wouldn't preserve the mechanical workings
of the cabinet as they are now.
73,
Jon
KE9NA
>
>The proper RF wiring method can make about 20 dB or more
>improvement in high order harmonics, as well as often prevent the
>"false peaks" you experienced.
-------------------------------------
Jon Ogden
KE9NA
http://www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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