[HCDX] new toy: Ten-Tec RX-320D

[MarkWA1ION@xxxxxxx]

I recently purchased a Ten-Tec RX-320D computer-
controlled "black box" receiver.  This compact
unit, described at "http://www.tentec.com/TT320.htm";,
runs off a 15 VDC wall-wart and connects to a
PC through a serial port control cable.  If audio
is to be transferred to the PC's sound card, a
separate audio cable is connected for that.
Alternately, you can connect headphones or a
speaker directly to the radio.

The supplied software provides a simple-to-use
graphical user interface.  One cool feature is
the spectrum chart, much like the old Heath
panadapters or a rudimentary version of spectrum
analyzers used in professional test and measurement
labs.

There were a few things I wanted to do that I
couldn't figure out.  Apparently a recording
function is not integrated into the software.
I wanted to record MP3 or WAV files straight
from the receiver software without having to
open up other software.  Another thing I want
to do is have the receiver take in an Excel
or tab-delimited text file of times and
frequencies for unattended "robot" DXing /
recording.  Maybe DXers, on their own, have
developed C/C++ or Visual Basic code that
can do exactly what I want.  This would be
to record desired frequencies at specified
times / dates and also put out a data file
consisting of signal strength readings.
I could use the receiver as a propagation
analyzer or spectrum occupancy study aid.
Nick Hall-Patch has done this successfully
with another receiver.  Conceivably, software
could be structured to make decisions such as
"If you find this, then go look for that,
otherwise go to a different test to decide
what to do next".  Such disciplined scanning
would simulate the actions of a real-life DXer
at the dials.  Who knows what goodies you might
find in the morning on your PC in the MP3 and
data summary files if you have this capability ?

All this said, how did the receiver perform ?
On its built-in whip antenna, a lot of PC,
TV, and other house-based hash & oddball buzzy
carriers were noted.  On a real antenna,
fortunately, all that went away.  Reception
was quite similar to the Drake R8A without its
preamplifier engaged.  Since I was using a
Flag antenna with fairly low output, some
daytimers receivable on the R8A (such as CHTN-
720) were in the noise floor on the RX-320D.
With a less efficient antenna such as a Pennant or
Flag, an extra 10 dB of low-noise preamplification
would be a great thing.  Since this radio is
touted more for shortwave than medium wave,
sensitivity was probably ratcheted down a bit
since SW antennas tend to be much more efficient
and closer to a resonant length.

I did not note any spurs / intermods, not bad
since 50 kW WRKO-680 is less than 3 miles /
5 km away.  Even 1360 (=680*2), a perennial
overload channel here, had clear WLYN instead
of the WRKO overload that my car radio gets.
With a bigger antenna, or an amplified one,
I might not be quite as lucky.

The fast AGC setting didn't seem quite fast
enough for quick adjustments of loop, phaser,
or variable termination resistance derived
nulls.  There's a bit of lag time on the PC
screen "S-meter".

The IF filter selections were good and they
seemed effective.  I would have liked DSP
based continuously-variable bandwidth, but
what can you expect for $300 ?  It will be
interesting to set this up during a decent
opening and bag some TA's with it.  

Its need for the laptop and a +15V supply
probably means that I won't be using it in
the car on mini-DXpeditions to the seashore.
Running this arrangement in a dark, cramped,
and (often) cold vehicle doesn't seem likely.

Use on a house-based DXpedition (e.g. Cappahayden,
Grayland, Chamberlain, Miscou Island, or Sheigra)
could be worthwhile however.  I'm not sure what
the airport security people would make of the
little black box.  Having the radio integrated
to the laptop can be a good thing since logging
programs, Geoclock, Euro-MWLog and Pacific Log
PDF's could all be accessed.  John Bryant, Nick
Hall-Patch, and the rest of the Grayland crew
have certainly proved this.

The D model is supposed to be usable to decode
DRM broadcasts.  For a review of an earlier version
see "http://www.anarc.org/naswa/issues/1298/equip1298.html";.

Once I get the unattended recording schemes
worked out, I'll be having a lot of fun with
this radio.

Mark Connelly, WA1ION - Billerica, MA

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