Topband: Moon and the Ionosphere : YO3FFF

Tom Rauch w8ji at
Fri Mar 16 10:17:33 EST 2007

> This could also be done with exisiting low frequency BC 
> beacons that are
> there every day - for example, a W6 listening to an Asian 
> beacon every
> day at the same time for a year as you suggested.

But you would have to know and record the absolute signal 
level changes referenced to some starting point  for a long 
period of time every night for many nights. I would guess at 
least a year.

The receiving antenna could not change, the receiver 
calibration could not change, it would have to have enough 
signal to noise during measurement periods to know the real 
signal level (and not S+N level), the transmitter ERP in 
your direction could not change. When you are all done with 
that, someone has to average the signal levels and even 
perhaps compare peaks if that is what you want to know.

A few spot checks would never produce anything useful.

> I'm not aware of the active beacons on 160m (in the last 
> 10 years I was a "2m DX guy" HI). If someone can point me 
> to a WEB page or to send me a file with this information, 
> I'll appreciate that.

In the USA, we are not allowed to have unattended beacons 
except on specific bands. 160 meter and 80 meter beacons 
must have a control operator present. I don't know anyone 
who would follow that rule for a single night, let alone a 
year of nights.

> - a stable RX from the amplitude/temperature point of 
> view; should be calibrated at lease 3 times/day (in the 
> morning, at the mid day and in the evening/night) the best 
> will be to inject a known calibrated signal together with 
> the received signal - this should be done automatically; 
> the BW of the receiver should be as low as possible (less 
> than 500Hz, preferable 10Hz - this could be achieved with 
> PC software); the dynamics of the receiver should be 
> greater than 80dB; the noise floor should be at 
> least -125dBm; AGC should be OFF; if AGC is ON than the 
> AGC voltage should measured in order to achieve a linear 
> response at the output of the receiver.
> - a PC software to measure the detected signal of the 
> beacon; a good example should be Radio SkyPipe; The best 
> will be an audio spectrum analyzer like Spectran but the 
> recorded file will be huge! the advantage of an 
> time/frequency recording is the doppler information but is 
> not mandatory for this experiment;
> - a PC, preferable a laptop in order to minimize the power 
> consumption and the possible interference with the radio.
> - antenna - this is a point to be discussed; is it better 
> to use a directional antenna or not. is it better to use 
> vertical or horizontal polarization (or both); is it 
> better to use a vertical low angle or a high angle 
> antenna?
> IMHO one should use at least two antennas; one directional 
> antenna toward the beacon and another one omni directional 
> but with low vertical angle. Each antenna will feed a 
> separate receiver (so 2 RX is needed!) than the tow 
> signals will be logged.

The antenna would have to be gain stable under all weather 
conditions. That would rule out most receiving antennas 
people use on 160.

73 Tom

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