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From: "Dick" <knaap159@zonnet.nl>
To: <rsgb_lf_group@blacksheep.org>
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Date: Sun, 13 Aug 2006 10:23:42 +0200
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Subject: LF: PA4VHF tests/problems?
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Status: O

Thanks Alan for the suggestion.

Well while tuning the variometer everything seemed working as it should be.
The SWR nice dropped to zero, while the antennacurrent raised.
With help of a separate receiver I was able to figure out that I was
certainly not tuning on a harmonic.

So, there really might be some extra capacitance produced by the
coilwindings etc.

About the antenna current, one reason might be an insufficient earth, as I
just connected the ground tap
to a groundrod with 5m wire to my groundrod 'somewhere' in the garden.

I built up the transmitter again, but now connected to a 50Ohm dummyload,
instead of the coil antenna etc.
Used exact the same coaxial cables.
SWR/PWR meter shows same value as with the loading coil/antenna connected,
and also DC input power
seems the same.
So, that gives me reason to believe it's ok.

Question however is the exact amount of power, hi.

I am measuring 140 Volt top-top on a oscilloscope parallel with the 50 Ohm
dummy load. (at the dummy load)
DC input is 13.0V/7.5A (that's 97.5W DC input)

For some reason I can't figure out the right formula to calculate the power
into the dummy load.
I get wrong figures al the time.

I'm more a practical man, hi

73

Dick, PA4VHF


my testfrequency as always is around 136.1kHz from an X-tal
oscillator/divider.