Very clear SS comms on Satcom UFO freq 255.550 @ 2:21 CST on Apr 21st 2008.
My location is South Central Texas.
My location is South Central Texas.
Satellite is presumably geosynchronous so it is going to be at least 36,000 km away even if it was right overhead.
Path loss (dB) is 32.5 + 20*log10(MHz) + 20*log10(km)
So in this case 32.5 + 20*log10(256) + 20*log10(36000)
= 172dB
Now I don't know what the ERP of the satellite is but lets take a guess and say its 10 watts on that particular frequency. Thats 40dBm. Therefore, received signal will be somewhere around -172 + 40 = -132dBm. Assume antenna has 3dB gain over isotropic. That's still -129dBm. That's 0.08uV. How many receivers have this kind of sensitivity? Yet I hear people describing receiving these with just the whip antenna on their receiver. I don't understand this. Certainly with a good gain antenna reception should not be a problem. But with just a whip antenna or even a discone? Unless my assumption of the satellite's ERP on that frequency is way low.
Frank KG9NZ
Satellite is presumably geosynchronous so it is going to be at least 36,000 km away even if it was right overhead.
Path loss (dB) is 32.5 + 20*log10(MHz) + 20*log10(km)
So in this case 32.5 + 20*log10(256) + 20*log10(36000)
= 172dB
Now I don't know what the ERP of the satellite is but lets take a guess and say its 10 watts on that particular frequency. Thats 40dBm. Therefore, received signal will be somewhere around -172 + 40 = -132dBm. Assume antenna has 3dB gain over isotropic. That's still -129dBm. That's 0.08uV. How many receivers have this kind of sensitivity? Yet I hear people describing receiving these with just the whip antenna on their receiver. I don't understand this. Certainly with a good gain antenna reception should not be a problem. But with just a whip antenna or even a discone? Unless my assumption of the satellite's ERP on that frequency is way low.
Frank KG9NZ
Sure. I can hit the AO-51 amateur satellite with my 5 watt HT, no problem. Ain't no obstructions straight up into space!How are these people doing that?
Talking on satcoms?
with a 10 watt radio?
Sure. I can hit the AO-51 amateur satellite with my 5 watt HT, no problem. Ain't no obstructions straight up into space!
How are these people doing that?
Talking on satcoms?
with a 10 watt radio?
How are these people doing that?
Talking on satcoms?
with a 10 watt radio?
How are these people doing that?
Talking on satcoms?
with a 10 watt radio?