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Hi Marcel the original idea came from a Pat Hawker
Technical Topics column. It was originally in a Canadian BC Journal and
recommended for short free standing MW BC antennas. We did the experiments
you found in the web pages on 136kHz. Gary up in Preston made one too. The
problem with them is the windage of the spiral, Garry G4WGT had his
destroyed in a light gale. They can work but as our experiments showed
top-load capaitance is far more effectinf at reducing ground loss and increasing
the efficiency. Hence the additional tests with capacitance added above the
spiral. wirespacing was 5 to 10 cm from memory and not too critical, yes it you
need the inductance you can wing out below the stays and back in again above
then and get 4 times the inductance. You will not need so much inductance at
475kHz. It is also possible to helically wind the vertical. The gain achieved is
relatively low measured at an increase in Rrad of about 10%.
Best Wishes
Alan
G3NYK
----- Original Message -----
Sent: Monday, June 01, 2015 10:11
AM
Subject: LF: Top loaded vertical spiral
antenne
Members,
My backyard is in the city 8 x 8 m. My
intention is to do some experiments on 472 khz. Ready: RX converter
0-500 khz 10 mhz osc. and K3, RX ant. pa0rdt whip and receiving
loop TX: GW3UEP 100 watt, RF meter, and variometer 30 uh -600
uh Now i'm looking for a antenne. Found a article from Finnbar
EI0CF and Alan G3NYK about the spiral toploaded vertical. Has any
body tryed this antenne, is the original article availble. What is
the distance between the wire's of the spiral? Also talking
about a double spiral? So who is gone help me out ore has
some better suggetions for a antenne in my backyard http://www.xeropage.co.uk/g3nyk/spiraltop.htm#aerials tnx
in advanced Marcel PA9M
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