My software is not working to do this calculation at the moment.
What I'd like to know is how much reactance change there is, when going from
say 3500 khz UP to 3900 khz.
IE: 68' LL rotary dipole resonant on 3500. I'd like to know how much
XC there will be on say 3800, 3850 and 3900 khz. Knowing that,
I can calculate how much C is required in a motor driven vac cap.
As we move up in freq... the value of the vac cap is decreasing.
I'm contemplating this scheme vs resonating the rotary dipole at say
3900 khz... then switching in various amounts of XL.... with relay switched
coils, via a mess of vac relay's.
I'm guessing the rotary dipole, if resonant at 3500, will exhibit 75 ohms of
XL on 3800 khz ?
That would imply a 560 pf cap would be required.... and even LESS C... on 3900
khz.
I was contemplating the same thing for the 40M yagi... resonant at 7000 khz....
and then
dialing in XXX amount of pf, to resonate it progressively higher up the band..
to a max of 7300.
I have a pair of motor driven 10-1050 pf caps [15 kv, ceramic] . They only
take 2 secs to get from
min to max... so tried slowing em down by reducing vdc... which hardlyslows em
at all [3 x sec's]
The motor's are 28 vdc.. and stop spinning at 18 vdc. I went to PWM... and
this works very well.
Now I can slow em down to a crawl, and maintain almost full torque.
If i had some aprx ballpark figures to work with for reactance change VS freq
for both 80+40m
I can then calculate if this idea is even feasible.
Tnx...... Jim VE7RF
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