Subj : Re: Moon bounce
To   : alt.ham-radio.vhf-uhf
From : Bob Bob
Date : Fri Oct 14 2005 17:49:56

From Newsgroup: alt.ham-radio.vhf-uhf

Chris

There is a lot of information out there about the basis for frequency 
selection etc. It is relatively easy to work out the link budget as you 
will be entering operating frequency, RX noise figure, bandwidth, EIRP etc.

I would expect though that the recent claims of success using lower 
power/EIRP is due to narrowband and burst digital modes like the 
FSK441/JT44 stable. ie connecting your PC to the radio. You are 
effectively decreasing the system bandwidth to that of a few characters 
over a 30 second period. Less bandwidth means less noise means better 
signal to noise for a given signal power. A "good" terrestrial SSB voice 
circuit with a mast mounted low noise preamp for example will be usable 
down to -141dBm or so (0.02uV). If you drop the bandwidth to 1Hz you'll 
get down to -174dBm or so. (This also happens to be the thermal noise 
level "limit" on earth at this b/w. Point an antenna at cold space and 
things might go lower still...)

Sorry I dont do moonbounce.

 From what I have read you have to consider all parts of the setup in 
determining which is the right frequency to use. You tend to have more 
line loss at a higher frequency but less background/galactic noise. Your 
front end noise figures also tend to be higher at a higher frequency and 
equipment may be more expensive. Frequency stability and induced phase 
noise (very important for super narrowband modes) is also harder to 
achieve the higher you go. You also have to consider the antenna system 
which there are pro's and con's for. This often ends up with the optimum 
being a 2M system with 70cm next best.

Hope you find this useful.

Cheers Bob VK2YQA



Chris W wrote:
> 
> 
> I have been reading about moon bounce on the net.  There is a lot of 
> very conflicting data.

.