At 18:28 01/07/2003 +0100, you wrote:
In ref to Ian's comment about receiving SAQ. I would be surprised if I
could not copy this signal on 17.2 khz because of my antenna system. I
resonated my 90m loop for the event whereas others probably used odd bits
of wire and hoped for the best!!!!! Perhaps they will tell us if this is
incorrect.
I also have a proper LF RX Hagenuk EE 430 10 - 30000 Khz plus two
Pegelmessers W & G and Siemens dedicated for LF activities. I also have
space diversity facilites using at present 2 antennas, the 90 m loop and
the vertical array, both resonated at the frequency required.
The SAQ signal is of the order of 100s 0f uV/m over much of Europe - so it
is quite a strong signal, and can still be received if the antenna and RX
are far from optimum. The usual limiting factor is the high noise level in
this frequency range - for more distant stations, QRN can reach 100uV/m or
more in CW bandwidth at this time of year. Local interference is a more
severe limitation at times - for some reason, my washing machine generates
the equivalent of several mV/m of noise in the mains wiring around the
house, so has to be switched off during SAQ broadcasts. If you read the
various reports, QRM and QRN were the factors preventing reception, not
antenna/receiver performance - it would seem the vast majority of people
who tried were able to receive at least parts of the broadcasts.
On Sunday, I got good reception on my electro-mechanical RX, using the
usual 40m inverted L wire. This has "gain" of -20dB between the antenna and
the headphones, but the QRN was clearly audible in the background under the
signal. I also used a 2m x 2m un-tuned loop and preamp, and a tuned ferrite
rod antenna, with perfectly good results from conventional receivers. In
the past, I have used various odd bits of wire, down to about 2m long -
provided these are tuned somewhere near resonance, ample signal is
obtained. Longer bits of wire don't even need to be resonant, allthough
some sort of low-pas filtering is very desireable. Active whips should also
work fine - provided you don't live in Brookmans Park! Just about anything
capable of detecting a few 10's of uV at 17.2kHz, and rejecting adjacent
frequencies can be used as a receiver - try listening to the excellent
recording KK7KA made with a loop antenna and a sound-card.
Cheers, Jim Moritz
73 de M0BMU
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