I've had a couple of requests to post a short review of this receiver,
so here goes:
Figure about 15-25 hours to build, depending on your experience. There
are several typos in the early manual, so be careful. The ones that
affect construction are:
1) L17 is .27 uh as identified in the master parts list, not .39 uh as
identified elsewhere.
2) C20 is installed in Phase 2, not in Phase 3 (it's noted in both
places).
3) C68 is .01 uf, not .1 uf (mistakenly noted on P 43 of the manual).
These teething problems aside, the kit went together quite easily in
about 16 hours. The test-as-you-go design not only verifies each stage
after building, but enables you to catch any mistakes right away. I
managed to get one of the VCO switching diodes in backwards, but found
it in a few minutes.
Alignment is very easy, requiring only a voltmeter to accomplish. I did
find a frequency counter useful, as I had to set the VCO control voltage
lower limits to 2.5 volts instead of the 3.5 volts called for in the
manual to get full range on the VCOs. You'll know you need to do this if
you can't get the radio to tune all the way to 30 MHz.
The radio is a direct (no RF preamp) dual conversion design. The first
IF frequency is 45 MHz and the second is 455 kHz. Much attention has
been paid to filtering in the front end and IFs, necessary to get good
performance from such a design. While performance is good with a short
antenna, the receiver really shines on an outdoor wire antenna, easily
receiving anything I can hear on my DX-398 (and then some), and sounding
quite good while doing it. The Ten Tec is less susceptible to
overloading than the DX-398 as well. Of course it doesn't have all the
fancy doodads that the DX-398 or the DX-394 (used to have one) have.
It's just a good basic receiver.
Pluses:
1) Good audio quality
2) Small size
3) Operates directly from 13.5 VDC
4) Excellent sensitivity and selectivity
5) Excellent dynamic range (100-105 dB, by my estimate)
6) Easy to read display
7) Excellent Ten Tec support
Minuses:
1) Display shows only 2.5 or 5 kHz steps. The clarifier is used to tune
between these.
2) No S meter.
3) The RCA connector used for the antenna seems a bit fragile. I'll
probably replace mine with a BNC jack.
Surely you can buy a comparable used receiver (low end Lowe, etc.) at
about the price of the 1254, but I'm not sure you can buy a new one of
this quality for this price. Of course, you can always do better if you
have a deep pocketbook. IMHO, the fancy portables don't measure up in
their RF engineering to this rig, so I won't count those as 'real' basic
SWL receivers. I emphasize the word basic. There aren't lots of frills
on this radio, just solid RF design and performance.
Conclusion: a great basic radio at an affordable price. The eureka
experience of building your own certainly can either draw you or scare
you away. Builders should have at least one simple kit under their belts
before attempting this one.
Specifications:
Frequency coverage: 100 kHz to 30 Mhz, continuous
Modes: AM, SSB/CW
Main Tuning: Normal or Fast tuning (2.5 kHz SSB, 5.0 kHz AM, or 100 kHz
Fast mode for either)
Clarifier Control: allows +-1.5 kHz tuning between 2.5 kHz steps for
SSB/CW
also works in AM mode
Front Panel Controls: Power switch, Tuning, Volume, Clarifier, Mode
Select, Memory Write, VFO/Memory Tuning, Tuning
Rate Select
Memories: 15 programmable memories (mode & frequency)
Circuit: 45-75 MHz first local oscillator (direct conversion)
45 Mhz 1st IF, 455 kHz 2nd IF
Sensitivity: AM mode, 2.5 uV for 10 dB S/N at 30% modulation
SSB/CW mode, 0.5 uV for 10 dB S/N
Selectivity: 4 kHz @ -6 dB
Frequency/Memory display: 6 digit green LED with mode indicators
Power supply: 12-15 VDC, 250 ma zero signal current consumption. 400-600
ma at max volume. 15 VDC @ 800 ma wall transformer
included with kit
Antenna connector: 50 ohm input, RCA-style phono jack
Audio: 1.5 watts audio output to internal 3" speaker, plus 1/8" stereo
phone
jack for headphones or feed to data interface
Semiconductors: 10 ICs, 26 transistors, 16 diodes
Size: 2.25" H x 6.5" W x 6.5" D
Construction: Steel clamshell case, aluminum internal chassis, molded
front
panel
--
chuck
Chuck Murcko The Topsail Group West Chester PA
USA
chuck@topsail.org
--
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