[hpsdr] Some things worthy of your attention

[jeff millar]

k3bu at optonline.net wrote:

> Another application for
> SDRs, becoming more of interest is the remote RX site, like having bunch 
> of Beverages in a cluster, converting portion of the band and feeding it 
> to the main site. Also need for control to switch the antennas or just 
> feed individual ANT/RXs via remote link. Ethernet/Internet or wireless 
> links would be preferred. With creeping real estate restrictions this is 
> of interest for bunch of low banders who could share the site.
> 
> Yuri, K3

That an interesting point.  But I'll stick with betting USB for the 
interface between FPGA and microprocessor.  You will will win on 
Ethernet connecting the microprocessor to the operating station.

Many modern embedded micros have both Ethernet and USB interfaces. It 
necessary to put a micro between a network connection and a remote 
digital receiver.

The micro handles complex control algorithms, such as
	- radio tuning, filter selection
	- AGC, networking, etc.
	- clock synchronization for phasing multiple of these remote Rx

The FPGA handles
	- all the glue logic
	- A/D down sampling, NCO, filtering
	- Maybe a DDC like the AD6620?
	- USB interface to the micro

The Ethernet link transmits a digitized sub-band of frequencies (such as 
the whole DX window) back to the operation station.

The operating station computer makes network connections to all the 
remote Rx and performs a range of functions
	- Final tuning and signal selection within the passband
	- Beamforming, interference nulling by phasing several remote Rx

Several operating station computers could share the same remote antenna.

Or a station could use an antenna at a better location in the world 
(probably cheating for most contests and QSL contacts).

jeff, wa1hco

 1168055730.0