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<DIV><FONT size=2 face=Arial><SPAN class=487250913-05082010>Allow me to
introduce myself. I'm Steve, K1RF. I'm an electrical engineer over
40 years but in the management chain now. While I'm not a verilog or
VHDL programmer or softrware programmer, I know enough to get by and I
understand and appreciate different architectual concepts. I recently became
totally fascinated by the software defined radio concept. I've been
following the HPSDR Wiki for awhile. I was actually considering taking
ideas from prior HPSDR projects to make a simple transceiver pc board and lo and
behold, I came across Hermes and Apollo hidden somewhat down at the bottom of
the wiki page. Wow! Right along the lines I was thinking. I looked at the
schematic and loved it. The only main thoughts I have on it now are in two
areas. One is the front end, the other is to add Verilog code in the FPGA
to allow, along with a simple 2-line alphanumeric display and some controls, a
totally self contained transceiver without the need for a PC. It could have two
modes of operation, the standard mode using an external PC with communication
over USB or Ethernet for full capability, and a self-contained mode. Transmitter
code concepts would be along the lines of the Digimit transmitter (See <A
href="http://www.microtelecom.it/digimit/">http://www.microtelecom.it/digimit/</A> with
more on SSB modulator architecture defined in detail at <A
href="http://microtelecom.it/ssbdex/">http://microtelecom.it/ssbdex/</A>.
The amount of FPGA firmware for the transmit function would be fairly modest and
should easily fit with room to spare. Additional code would be needed for a
self-contained basic receiver without the full capabilities of the PC based
software.</SPAN></FONT></DIV>
<DIV><FONT size=2 face=Arial><SPAN
class=487250913-05082010></SPAN></FONT> </DIV>
<DIV><FONT size=2 face=Arial><SPAN class=487250913-05082010>With regard to the
front end, I saw a lot of discussion about preamp vs no preamp, etc. I also
looked at a QS1F front end discussion. My conceptual design would have used
a 1.6MHz high pass filter (always in) to eliminate strong AM broadcasts if you
happen to live near one) followed by a 60MHz high pass filter (always in)
followed by a programmable 0-31.5db HMC472 Hittite attenuator which allows
0.5dB attenuation steps followed by a mini-circuits GALI-74+ preamp (always in)
followed by a 6dB resistive pad attenuator to cut the gain down some on the high
gain preamp. This would eliminate any relay switching, provide finer
control of RF attenuation while trading off maximization of IP3 (would need
additional FPGA I/O and associated firmware). I would not add any other
filters, to minimize complexity and to depend on the inherent filtering of
the antenna itself. I would not add any filter switching, to keep things
simple. I prefer simplicity to having ultimate control of switching things
in and out. I'd rather have one smoothly continuous RF knob like in the
old days.</SPAN></FONT></DIV>
<DIV><FONT size=2 face=Arial><SPAN
class=487250913-05082010></SPAN></FONT> </DIV>
<DIV><FONT size=2 face=Arial><SPAN class=487250913-05082010>Ultimately, it would
be nice to have a DSP chip on the transceiver board to allow future software
coding to replace the external PC with an internal high performance processor,
and a more sophisticated front panel with a dot matriz graphics display. I
envisioned all these as a growth options using the PC initially but
eventually switching over to the DSP chip and high end front panel. One could
keep both paths available for future software development and providing a high
performance, self-contained capability.</SPAN></FONT></DIV>
<DIV><FONT size=2 face=Arial><SPAN
class=487250913-05082010></SPAN></FONT> </DIV>
<DIV><FONT size=2 face=Arial><SPAN class=487250913-05082010>So those are my
thoughts.</SPAN></FONT></DIV>
<DIV><FONT size=2 face=Arial><SPAN
class=487250913-05082010></SPAN></FONT> </DIV>
<DIV><FONT size=2 face=Arial><SPAN
class=487250913-05082010>Regards,</SPAN></FONT></DIV>
<DIV><FONT size=2 face=Arial><SPAN
class=487250913-05082010></SPAN></FONT> </DIV>
<DIV><FONT size=2 face=Arial><SPAN class=487250913-05082010>Steve,
K1RF </SPAN></FONT></DIV></BODY></HTML>