I would echo Tim's remarks. I bought a bunch of Russian caps on EPAY for
a 160 meter amplifier and they overheated and changed value. One blew
up. They were horrible as a plate coupling cap. The seller advised me
that they were only good for uncritical bypassing chores. Now I have a
pile of
I had a cap like that in my Viewstar PT2500 that I bought new in 1985.
After a second or two of transmitting - the power output dropped and I had
to retune the loading control. Fixed it with a stack of 10,000 pf silver
micas in series.
I am going to transmit for a minute or two with full power
I would caution against using Russian military surplus doorknobs, or
Chinese doorknobs, in a tuned circuit without understanding their
dielectrics. I tried a couple and was very disappointed.
With HEC 7.5kV doorknobs, you would want to make it out of values of 170pF
or below. Below 170pF they
Unless you use LMR 600 or Andrew heliax a cap made from standard RG-8 or
213 has its limitations. eBay has a ton of high current fixed caps very
close to the value you need. Some are from Ukraine (Russian military
surplus) and are very inexpensive. You might also consider a home-brewed
sandwich
I usually use the complex impedance as my guide here. What is the resistive
component vs the model? If the SWR is flat it is often because the
resistive ( R ) portion is too high and dominating the frequency dependence
of the X portion. Adding radials can improve that as well as the loss of
the
On 10/15/2018 10:43 AM, Tree wrote:
I replaced the variable cap with a home made cap using RG8. I had one
Sometimes, capacitors made from coax are lossy. I modeled your
coaxial capacitor using Simsmith (very easy to do) and the Q turns out
to be 340, if I did it correctly. So the
Maybe someone can put together a web page with examples of successful gamma
match configurations for towers.
Here is what I found this weekend with my new tower.
Tower height - 97 feet.
Top loading - 10 foot mast and essentially a 34 foot 3" boom at 98 feet.
This is my Steppir with all of the
