Hi All
Ref recent abt various antennas etc.
At present I have two antennas available for 136 khz. The 80m perimiter vert
loop and a vert system comprising 3 x inv L antennas in parallel all mounted
on the same mast at 100 ft approx.and fanned out at the top, with the horiz
sections about 450 ft long. Signals on the vert are 20 db stronger than the
loop, the loop has the advantage being N/E where the majority of signs
originate from, and greatly reduces the Rugby and French qrm on the band to
my South.
At present either antenna is available for RX but only the Vert is used for
TX and connected to my h/brew fet TX that I have been using for some years.
The present RX set up consists of a Datong UC/1 up converter IF 28 or 144
mhz out (can be used with two receivers) this if followed by and IC - 746
with a narrow CW filter and audio DSP.
There are no preamps etc but this system is very sensitive on both antennas
and comparable to the Hagenuk RX which is designed for 10 khz - 30 mhz.
This converter has a pre- selector which is useful for peaking the required
signal and is stable enough up to qrs 30.
I have not tried the mini whip because I cannot see how it would be as good
as my existing antennas.
For info, the vert system is resonated at the base by about 0.5 mh inductor
and in series with this at the bottom is a small inductor going to
earth/radials, this is used to match the antenna to 50 ohms by tapping the
coax centre wire up the coil from the earth end the braid to earth.
Both inductors are air wound, the large one about 15 inches diam and the
small one about 6 inches. No ferrite material is used around the antenna.
This system has been going for years and gives no trouble, just the odd
tweak because of WX condx
I get a perfect match 1:1
This info might help others with similar antennas, any questions just ask.
de Mal/G3KEV/Scarborough/IO94SH
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