In article ,
Bob Schreibmaier wrote:

In article , says...
- Restricting to ham-band-only probably doesn't buy you all that
much in savings or performance, these days, due to the large
number of bands. In order to gain big savings, I suspect you'd
have to limit yourself to a monoband radio.

Restricting to ham bands only buys a HUGE difference
in performance. Check out the Elecraft K2 and see
what kind of strong signal handling performance you
can get from an inexpensive radio if you have single
conversion right to the high-selectivity crystal
filter.

Third order IMD performance at 2 kHz is more than 10 dB
better than many of the expensive radios with general
coverage receivers, such as the FT-1000D and FT-1000MP
series, and is approximately equal to the 10 kilobuck
IC-7800! All because of the ham-band-only design and
some careful attention to design.

You're quite right, of course. I overstated my argument.

I think it's probably fair to say, though, that the sort of advantages
that the K2 family (and similar radios) gain in performance by
eschewing general coverage, might be very difficult or impossible to
achieve at the price-point that the original poster was hoping for. A
lot of the K2's improved IMD performance appears to come from having
band-specific double-tuned bandpass filters in the front end, switched
in via relays. This seems to be a technically excellent approach, but
I can't believe that it "comes cheap". Reed relays seem to run a
dollar or more each, in large quantities.

PIN diode switching of bandpass filters is another possible approach,
but I don't think you'd get the same sort of performance out of it.

At a sub-$200 retail price (which probably works out to under $50
bill-of-materials cost) the designer is going to have to make some
pretty hard decisions about where the money is to be spent. The
additional performance available from a band-optimized design (e.g.
the K2) might not be "in the budget" at the lower price point.

Consider that the K2 is between three and six times the price that the
OP was looking for... and it's a kit, has only 15 watts of output,
doesn't include a power supply, and I don't think it includes a
microphone either.

There would be some very, very interesting tradeoffs and design
decisions to be made, in any project to develop a sub-$200
mass-market-acceptable SSB HF rig. Possibilities:

- Run the finals on 24 volts, so that acceptably-linear operation could
be achieved from cheap power MOSFET parts?

- Use some of the new hybrid FPGA/DSP/microcontroller chips, to put
all of the control logic, audio filtering, etc. on a single chip?

- Limited duty cycle, to reduce the need for heavy/expensive heatsinks
and fan cooling?

--
Dave Platt AE6EO
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