[hpsdr] Please more info on reusing an analog rig for HPSDR

[Joe Martin K5SO]

Hello Ben,

The specifics of what to do will depend upon which analog rig you are  
trying to use but basically the general steps are similar for any of  
them.

For transmit, the idea is to break the existing exciter to power  
amplifier coaxial connection and allow the Penelope board to drive the  
PA instead.  I simply brought that line out the back of the IC-7800  
and inserted coaxial connectors so that I can directly couple them  
together for normal IC-7800 operation or break them to insert the  
Penelope rf output to the IC-7800 PA instead.  You do need to be  
careful with the rf levels though.  In the case of the IC-7800 I use  
about 33 dB of attenuation between the 0.5w Penelope output and the  
IC-7800 PA input to get the correct drive level for the IC-7800 PA.

You want Penelope running at a high output level so that you don't  
lose dynamic range so external attenuation pads are the way to do that  
most easily if 0.5w drive is too much.  Of course, if you don't want  
to use external attenuators you can simply bypass the output stage of  
Penelope and use the low level from its driver stage directly, as has  
been discussed previously here.  Using one of the open collector  
outputs on the Penelope board DB-25 connector is a handy way to switch  
the analog transceiver into Tx mode via, for example, the ACC-1 jack  
on the rear panel of the IC-7800 when the HPSDR rig is keyed; that's  
what I do.  Usually inserting the Penelope output at the input of the  
analog PA will keep the Tx bandpass filtering intact so you need not  
worry about filters for Tx.

Break-in operation works alright in this way if you setup the break-in  
keying option in PowerSDR.  Of course the T/R relay will open and  
close on each dit and dah so true break-in results in lots of relay  
clattering.  I usually set the break-in time delay for a second or  
more so that the T/R relay doesn't open and close on each and every  
dit/dah (semi-break-in)!

For receive, the idea is to use the T/R switching of the analog rig to  
provide the antenna connection to the Mercury receiver board.  Some  
rigs have rear panel connections that let you do that very simply,  
others will involve accessing the T/R relay connections internally.   
If you use the existing T/R connections directly to Mercury you will  
not have a band pass filter on Rx but unless you're in a terrible QTH  
with lots of strong out of band signals nearby that's not really a  
problem.  If it is a problem you can make your Rx connection to  
Mercury after the band pass filtering of the analog rig and use the  
bandpass function of the analog rig (or wait until Alex is available!).

A while back (Jan 10, 2009) I posted the details of how we did a  
modification to a Kenwood TS-940S to mate it with the HPSDR boards.  I  
will send that info to you separately so that I don't make this  
message too long.  If others would like it too I'll be happy to  
forward it to them as well.  As I said, the details of what exactly to  
do depends very much on the analog rig you've selected to use but the  
steps described for the TS-940S are representative to what you might  
need to do on other rigs, I think.

The Alex filter board is soon to be available so filters won't be a  
problem soon!

Hope that general description helps some!   We can discuss in more  
detail directly if you like.

73,  Joe K5SO



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