Am 04.03.2012 02:23, schrieb Graham:
Thanks' Stefan, . bit late in the night
50 ? That's quite low , I was expecting much
higher ? that's for a 'large' system ?
Well if you assume a loss resistance of 50 Ohm and 470 pF for the
antenna then its about 50.
OK, 470 pF is much. So then you have Q=100 if C is 235 pF ;-)
do you have a ball park figure for the max frequency
change on that ?
What kind of PA do you run? As long as it is no class E i would do some
careful tests, i.e. allow an offset and see what happens after some
minutes. However there can be overvoltage problems as well.
1:1.5 > 5% reflected power , that would reduce the
b/w again ..
Reflected, eventually this is no problem since e.g. in a H bridge the
power is then not dissipated but pushed back into the capacitor again
(which has to deal with the higher voltages then).
73, Stefan
Tnx -G..
Sent: Sunday, March 04, 2012 1:09 AM
Subject: Re: LF: Permissible QSY limits for 136
Am 04.03.2012 02:01, schrieb Graham:
Permissible QSY limits for 136
Q what is the average Q of a 136 Khz Ae system ?
(back garden + larger)
Maybe arround 50.
Q What would the maximum acceptable change in frequency
+/- Fo before swr considerations became a problem , say 10%
reflected power 1 :2 swr ? ....
That depends strongly on the PA circuit. A class E is very critical. A
H bridge has almost no problems at all (just lower output power then).
I would stay below 1:1.5 if the output power is 70% or above.
73, Stefan
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