Easily my finest purchase .... (until I hock the XYL and buy an Orion)
It came from bankrupt/demo stock here in UKand I made an overnight 500 mile
trip to get it before anyone else did. OK; it needed a trivial mechanical
repair, but it replaced a home brew wide range ATU and it is absolute magic.
My 253 came complete with a socket for the eeprom, thank goodness. It is a
fairly old memory chip design and it has a finite life, after which it
becomes increasingly difficult to re-write/store data. Replacement is the
only sure fire fix.
I have had to swap the 253 eeprom out only once in many years. The ATU gets
used every day, but I have most band settings stored (mid-band SSB, CW and
WARC) so I do not need to run the "tune" function too often. The antenna
selector switch comes in handy for this. Position 1 is CW, position 2 is SSB
and position 3 is for the WARC bands. Three cables go to an old Heathkit coax
switch and the output of that switch goes to a second switch, so I can then
select antenna or dummy load. Messy but extremely convenient for band
hopping.
There is only one official mod I know of for the 253 and that relates to the
SWR bridge grounding. It is possible to set/adjust the null more accurately,
but you have to make a minor change to the bridge.
But there was also more than one firmware eprom for the 253. I have the second
(latest ?) in mine now and it has an occasionally very annoying feature If
you play around too much with the manual push buttons, it suddenly decides
that you do not know what you are doing and it simply sends the roller
coaster to the end stop and does a full reset.. You have wait for this
routine to finish before you can start over, but it does not wipe any other
stored settings, thank goodness.
When you turn the rig and 253 on, the SWR may be way out from the last time
you used it. I find that if you simply swap bands and then swap back, it
usually goes back to where it was when you switched off.
All other problems here are entirely my fault. Rain badly affects my ancient
wire antenna. It is a 40m dipole used on all bands, but due to operator error
there are no end insulators - just plastic rope. When first I put the thing
up, its main job was to stop the mast falling down and I never got around to
adding the insulators. Ooops. I always need to check the WX and then the
SWR.
But in practice, I can often null the SWR by manual tweaking using the push
buttons, but sometimes I have to use the tune function. How heavy is the rain
today ??
Never mind. I keep a bag of those eeproms, because there is also one hard
soldered into the Omni-V.9 and after a few years that too gets very tired.
The symptoms are the rig getting very confused about the band/mode etc.
Resetting the CPU does not cure it, so the chances are that the eeprom has
passed its sell by date and will not store new data correctly. TenTec
asuggested that when I replaced the Omni eeprom I should really save myself
some grief by also fitting a socket, so I did, using a gold plated turned pin
socket. An awkward job, but well worth it.
Should TT start making automatic ATUs again ? Good question, but not another
253. The Elecraft KAT 100 shows the way to go, tight integration with the
radio, more memories, more flexibility and no moving parts (except latching
relays.)
Now to make myself a proper antenna with insulators - if it will stop raining
long enough.
John G3JAG
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|