The Ten-Tec 1253 Regenerative Receiver Kit.
(April 19, 2021)

This is the second Ten Tec regenerative receiver that Lionel found at the De Anza Electronics Flea Market on the same day as the 1054 presented elsewhere on this Web site.
It is a 9-Band  Shortwave receiver, marketed around 1996, powered by internal batteries (8 "C" cell batteries) or by an external 12-14 V DC regulated power supply.
Like the 1054, the kit was complete with the enclosure. The picture below shows all the components I found when I opened the box.


1. Building the kit.
The schematic diagram is shown below (thanks Lionel for image processing).


The antenna is connected to a JFET RF amplifier Q1 followed by a 2 JFET regenerative stage (Q2,Q3): this receiver shows points of similarity to the 1054 in the RF and audio preamplifier sections. The low-level audio output  is amplified by Q4 and a TDA2611A power amplifier drives the internal loudspeaker or a low impedance headset. Tuning is accomplished by 2 controls: a large Main Tuning  knob with a circular logging scale and a smaller Fine Tuning, very helpful when listening to CW or SSB signals.
The 9 shortwave bands are : 1.760 to 1.990 MHz, 3.3 to 4.15 MHz, 5.5 to 6.9 MHz, 6.8 to 8.5 MHz, 8.5 to 11 MHz, 10.1 to 13.2 MHz, 12.5 to 16 MHz, 14.7 to 18.5 MHz and 18.5 to 21.5 MHz. Band switching, accomplished by a decade counter, is rather uncommon but not so bad.

Soldering the components on the PCB is not difficult and the Instruction Manual is a good one, with a simple theory section about regenerative radios. I suggest you read the errata pages before beginning. Check the resistors and the inductors carefully before soldering because one can be confused with some colors: if you are not sure, check the resistor with an ohmmeter.
As I don't intend to use the internal battery pack, I don't install the battery compartment in my receiver.
The receiver is built in 7 assembly phases and several optional progress tests are very helpful (audio amplifiers test, basic receiver operation test, etc.).

Here is a picture of the inside of the 1253 just before final assembly.


And this one shows the complete receiver.


2. Testing the receiver.

I tested the receiver with a small  antenna (6 m of wire going into the attic). Tuning is easy and the fine-tune control is very useful. I heard a lot of  broadcast stations on several shortwave bands. Many CW and SSB ham stations were heard on 80 and 40 meters, and  on 20 meters when the band was open.
The measured sensitivity is good : a 2 uV signal, 90% AM modulated by a 1 kHz signal, is perfectly audible in the loudspeaker. A 1 uV CW signal is easily received .

This is a good and fun radio to build and use. I got very good results with this simple receiver and I especially appreciated the Coarse/Fine tuning and the 9-Band coverage.