Mal,
I have a 2 uF C in series to the primary coil. I am using a homemade H
bridge switching mode PA. The circuit is currently just in my mind but
maybe i can draw and publish it soon. The impedance level of the
primary side is about 150 Ohm.
73, Stefan
Am 17.08.2010 16:38, schrieb mal hamilton:
Stefan
Are u using an audio amp, if so do u
have a capacitor in series with the link winding otherwise the winding
might appear as an almost short cct because of the low dc resistance.
73 de mal/g3kev
-----
Original Message -----
Sent:
Tuesday, August 17, 2010 12:46 PM
Subject:
Re: LF: Earth electrodes antenna tests[Contest results]
Mal,
I am using a galvanic decoupled primary winding at the bottom of the
water barrel where the coil is wound on. Adjust the primary number of
turns so that enough power is fed into the system. Watch the photo on
my qrz.com page named "new amperemeter". There you see the primary
winding just above the amperemeter.
73, Stefan
Am 17.08.2010 13:38, schrieb mal hamilton:
Stefan
I am talking about matching the
amp 8 ohms to 50 ohms not about resonating the antenna. My antenna is
already resonated for 9 Kcs, or 137 as required.
I was referring to your kite
antenna and what method you used for matching amp to antenna.
de mal/g3kev
-----
Original Message -----
Sent:
Tuesday, August 17, 2010 12:22 PM
Subject:
Re: LF: Earth electrodes antenna tests[Contest results]
Mal,
Are you talking about a earth electrode antenna or your vertical
antenna? I assume you mean the vertical ;-)
You will get several kV, most probably above 10 kV rms on your antenna.
That's why a ferrite transformer is not a good choice for a large ( C )
antenna in addition with QRO! For your 5 W tests it may work with a
ferrite coil L but not at 500 W and above.
There is no alternative to wind an air coil if you want to
generate a signal that can be watched in the far field.
And if you want to generate a signal that can be heared in CW across EU
i recommend a power supply like i had as i worked in Darmstadt last
year: http://www.hst.tu-darmstadt.de/index.php?id=173&L=1
;-)
Transforming to 50 Ohm is not wrong but it is not necessary. You can
just resonate the antenna and match the load to something suitable for
the audio amp (4...8 Ohm). A 50 Ohm impedance level is just necessary
if you want to filter your signal with a precise dimensioned low pass
filter that properly works at 50 Ohm input and output impedance (in my
opinion). Essential is, that the power is pushed into the antenna! ;-)
73, Stefan
PS: On an earth antenna, which is not resonated (!), you just have to
apply a proper output voltage to the antenna that causes the DC input
power at the PA that you want to generate.
Am 17.08.2010 12:51, schrieb mal hamilton:
Stefan
What method do u use to couple the amplifier to the electrodes? Is the amp
output impedence 8 ohms.
My method for my antenna using an audio amp would be to use a ferrite
transformer to step up the 8 ohms to 50 ohms (x 6.250) turns Prim 8 and
Secondary 20 turns. This way I can use my existing test equipment for swr
etc.
mal/g3kev
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