[amsat-bb] Re: Full band transverters for satellite operations?

Grant Hodgson grant at ghengineering.co.uk
Thu Jun 14 14:26:47 PDT 2007

Tony Langdon wrote:
> Neat.  Hopefully I can look at getting the uWSDR going once I get my 
> HPSDR up and running.  Just a comment.  Firstly, I notice there are 
> plans for Rx only on 2400 MHz.  

There might be a cut-down, 2.4GHz-only version, but the only cost 
savings would be the TX power amplifier (100mW-200mW o/p) on the RF 
board and maybe the TX D/A converter on the baseband board, which is 
only a few dollars and might be offset by the fact that it would be a 
different build.  If there is a lot of demand we'll look into the 
possibility of it but I don't think the cost savings will be significant.

I should point out that the VK
> terrestrial weak signal segment is 2403 MHz, so if I was to obtain a 
> 13cm module, I would want Tx and RX on the 2400-2404 MHz segment (Rx for 
> 2401, Tx/Rx for 2403).

The 2.3-2.4GHz amateur band is the most fragmented band that we have; 
there are at least 6 regional variants that I'm aware of.  One of the 
goals is that we want to cover the whole 2.3-2.45GHz band, and we now 
have a paper design that will do just that without compromising key 
parameters such as out-of-band filtering etc.  I'm not aware of any 
other amateur radio product that will cover the whole 150MHz at 13cms.
> I'm also interested how the Ethernet and UDP/IP interface and 
> communications goes.  

I believe that the transmission of the digitised audio has already been 
successfully demonstrated over Ethernet using UDP.  The use of Ethernet 
allows for long cable runs enabling the uWSDR to be mounted at the 
masthead and just running power and CAT5 cable into the shack.  No need 
for lengthy runs of coax.

All other SDRs I've seen use a soundcard(ish),
> USB2 or Firewire interface.
The uWSDR approach is similar to that of the HPSDR, i.e. we have 
designed our own sound card, and after some considerable work we have 
opted for the same very high performance D/A converter that the HPSDR 
uses.  This way we have absolute control of all the key parameters, and 
it's also cheaper than buying a Delta-44.



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