[hpsdr] Alex, the poor man's alternative.

[Jeff Cook]

Much though I would have liked to do so, I could not justify to myself 
the expense involved in acquiring the full Alex kit, so what to do? For 
some while now I've been running my HPSDR 0.5 W output into my aged 
TS-830S's power output stage, and so did not need a lowpass filter. 
However it was time that I moved on to using a semiconductor power 
amplifier and allowed my TS-830s to retire gracefully. So for Christmas 
my wife bought me a 140 W linear amplifier from the Communication 
Concepts Inc people in America, which of course required me to think in 
terms of a lowpass filter. After some fiddling about I eventually 
decided on a second-hand LPF board taken from a FT-757GX, this board 
also contains tx/rx switching, which meant that I could do away with my 
outboard DIY switch. It also contains circuitry to read reflected power, 
but I haven't used that up to now. I guess that the board itself must be 
something in the order of 20 years old but seems to be in very good 
condition, and I use the open collector outputs available from Penelope 
to operate the relays on the LPF board. After rummaging around on the 
second-hand market, it seemed to me that very few LPF boards 
manufactured in that era used ground switching for their relays, most 
went for positive switching, the FT-757 GX board is an exception to 
that. It cost me £45 that's about $72, which I felt I could justify as 
an acceptable spend on myself.

So if there are any other slightly less affluent members of the HPSDR 
community out there that are salivating over Alex, this just might be 
the way to go.

Jeff Cook.