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[TenTec] Ten Tec 1254 Rcvr done! (Long)

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Subject: [TenTec] Ten Tec 1254 Rcvr done! (Long)
From: rohre@arlut.utexas.edu (rohre)
Date: 7 Dec 1998 18:40:13 -0600
After a long hiatus since building the display board for this LF-HF superhet, 
PIC microprocessor controlled kit receiver, I finally took the bull by the
horns and spent every evening on the main board until finished at 4AM last
Sat. morning.  Took about 22 plus hours total, with sessions as much as 4
hours at a time.  (This was my warmup to the K2, since this had over 400

This is a great SWL receiver.  It is a good entry level receiver for someone
aspiring to be a ham, and wanting to listen around to both ham bands and SWL
bands.  Now I am NOT saying it is an entry kit!!!!  Nor is it set up for
transceiving.  But it runs circles around the S38D I started with in 1957!

It requires a magnifier and small tipped iron, a couple sizes of solder to get
good looking joints, and patience!  It is all discrete parts and transistors
and IC's, no surface mount.  Only the microprocessor is socketed.  Coils are
prewound, or are transformers.  You do install cans on some coils, and around
RF and VCO stages after they are in the board.

However, there are NO toroids to wind!

It does need a shielded antenna lead in, to avoid the last 15 feet of lead in
picking up the harmonics of the multiplexed display digits, as they say in the
manual.  There is likely a fix that could be done by spray on shielding inside
the plastic front panel, and ensuring that the clam shell steel case top and
bottom pieces make a tight RF seal, by perhaps use of additional fasteners, or
shielding the front display board.  I mainly noticed this on 10M, and only
above the CW portion at that.  Those who have reported on this before might
want to check the bonding of the circuit board grounds to the brackets and
solder the brackets to the chassis, instead of relying on the rivets to
provide adequate grounding.  This has not been tested, but just an

However, it is a very sensitive receiver front end, and I found it did a
better job with weak stations on 80M and 160M than my Kenwood 450! with or
without its RF amplifier!  A transceiver receiver 10 times more 
expensive was outclassed on receive by one 1/10 as expensive!

The receiver pulled in a U.K. ham this morning on 12 Meters on the Gap
vertical.  The built in speaker is adequate, but an enclosed speaker used in
the headphone jack does sound better with its baffle. 10M has been pretty busy
as well as the other ham bands.

Over the weekend, the first SWL DX was NHK Tokyo, Saturday mid morning;
broadcasting on 9 MHz band to Thailand, in a regional SW broadcast, probably
directional, and thus coming to my Texas vertical on long path.  The signal
character and QSB confirmed its origin was not by a relay broadcast.

Other DX ham stations have been heard all over South America, Mexico, France,
and Canada with just cursory listening.  The stability is excellent, in
copying some special event stations over several hours, and being able to come
back to the same frequency by memory recall, or direct tuning.  The tuning
steps are set up for SWL use, and take some getting used to, for ham band use.
 There is a CLARIFIER control, for fine tuning CW and SSB, and to a lesser
extent, AM.  But the steps are 100k Hz, 5 kHz and 2.5 kHz.  Thus, signals seem
to drop into the IF filters at 45 MHz and 455 kHz.  Even though set up for SSB
use, the CW selectivity in copying is not any worse than many older tube era
receivers of general coverage, and in fact, it sounded a lot like a more
stable version of my old Hallicrafters, but with cleaner CW tones, and no
drift!  The 100 kHz step is used to go from band to band, or quickly go from
CW to high end of 10M.  

It is really neat to have a receiver that could be tested as I went with no
more test equipment than itself as a signal source, a DVM, and finally with
off the air signals of CHU and WWV to set the microprocessor clock right on,
for all the digital freq. readouts to be accurate.  It was fun to switch from
20 MHz, to 10, and to 5 and hear WWV not vary one bit!

I do not really have a LF antenna, but I did hear the LF beacons below the MF
broadcast band.  This radio does a fine job of MF AM reception, of course, but
is really pleasant with its product detector for SSB and CW as well.  The RF
(AGC controlled) attenuator is neat as well.  You have it stomp down on over
5,9 stateside full gallons talking to DX, and then you hear it and the noise
floor come back up, when it jacks up the DX signal to useable level at only
half way up the audio gain pot.  It is smooth and pleasant to listen to.

This radio is not a current miser, thus, it is not likely a candidate for
backpacking.  But how many backpack radios have 15 memories?  With the steel
case, it is very stable on the desk, and feels great.

What I got this radio for, and what I think it fulfills nicely, is to have a
really good looking, small all band SW receiver in the living room, which I
can place next to the easy chair, and while watching TV check on band openings
using stereo headphones so as not to disturb the family.  I think I will
experiment with perhaps a rotor cable dipole set under the eaves outside the
living room window, since that is the long side of the house, and I could
probably get a 20M full size dipole out there, and I already found the
receiver did a good job on lower bands when reception was done on my attic 20M
tri dipole system, (20,15,10).
For receive only, either small coax, or even the small diameter shielded audio
mic cable from Radio Shack would be suitable lead in.

The parts were good quality, (except for having a bad thread on one
countersunk speaker shelf screw).  The manual exceeds Heathkits' best, and is
broken into logical circuit subsections which can be tested as you go.  This
kit is well worth the $195 price.  This is a fun kit!

73 and 72,
Stuart K5KVH

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