Ten Tec 1254 mods
 

Having been away from swl listening for quite a few years I have been
searching for a used receiver.
While searching for a used Ten Tec 1254, which I have bought, I
came upon a couple of mods supposedly to improve the receiver. One mod
is the second 455khz mixer.
I happen to have some matched 1N5711 Schottky diodes and a
Mini-Circuits
TFM-2 mixer from projects never completed. Right now I have no way
to measure LO power level to decide if the TFM-2 will be suitable. I
have a AD8307 rf meter under construction but I will need a way to
calibrate the level meter.
I wonder if the mixer modification would accomplish much? The receiver
will be used with a MFJ-1024 active antenna since I have trees all
around the house. Thank you.

Richard

Quote:
The null is too broad to be of any use. Instead, tune the receiver
down to 15kHz

I thought the minimum frequency was 100khz??
Can you explain this?

Hi Pete

No, I am not one you sent the diodes to.

I just received the used receiver today and it sure has a lot of
birdies but I knew that when I bought it.

I have an MFJ-1024 active antenna but I did not use it yet. The
receiver schematic seems to indicate that there is DC on the antenna
connection.

I noticed in a post that you replaced capacitors in the audio chain and
front end. I am getting an order to Digi-Key ready and any suggestions
would be appreciated.

Yesterday I ordered from Alltronics.com a matched set of four
HP5082-2835 diodes. From a search I found out that these diodes are the
same as the 5711s.

I have a function gen, Tek475 scope, frequency counter, dvm and analog
meter, HP wave analyzer, AD8307 RF meter, so calibration should not be
very difficult.

Tonight I will look at the schematic and your suggestions and
familiarize myself with the receiver.

Cheers

Richard

Email address is no good. Only for logging onto google groups.

Sure, I would be glad to.....................when in the fast tune mode, you
can tune all the way down to zero kHz. From this point, you can tune
upwards, but you cannot tune down. This is how you can tune the radio to
15kHz. Since this is where you can hear the system noise floor rise because
of the phase noise from the synthesizer, you have a very good noise source
to perform the 1st mixer balance with. When adjusting the 1st mixer balance
pot, you have a very sharp null.

Pete

wrote in message
oups.com...
Quote:
The null is too broad to be of any use. Instead, tune the receiver
down to 15kHz

I thought the minimum frequency was 100khz??
Can you explain this?

Hi Pete

No, I am not one you sent the diodes to.

I just received the used receiver today and it sure has a lot of
birdies but I knew that when I bought it.

I have an MFJ-1024 active antenna but I did not use it yet. The
receiver schematic seems to indicate that there is DC on the antenna
connection.

I noticed in a post that you replaced capacitors in the audio chain and
front end. I am getting an order to Digi-Key ready and any suggestions
would be appreciated.

I just used some of the film caps that I had on hand for the audio chain. In
the front end, I used Silver Mica caps.


Yesterday I ordered from Alltronics.com a matched set of four
HP5082-2835 diodes. From a search I found out that these diodes are the
same as the 5711s.

A very good choice.

I have a function gen, Tek475 scope, frequency counter, dvm and analog
meter, HP wave analyzer, AD8307 RF meter, so calibration should not be
very difficult.

Tonight I will look at the schematic and your suggestions and
familiarize myself with the receiver.

Cheers

Richard


I think you will have fun with this receiver. Feel free to e-mail me
directly if you run into any snags. It is good to look at the addendum
sheet that is included with the manual. The specified PIN diodes, for
example, have been replaced with BA479 PIN diodes..........there are other
things as well. Instead of adjusting the tune voltage at the low end of each
VCO's tuning range for 3.5 volts, Ten-Tec now specifies 2.5 volts.
Have fun!

Pete