ANTENTOP- 01- 2010, # 012

Some Thoughts on Regenerative Receivers

Fine tuning on the Ten-Tec 1253 is done with an additional voltage control on the tuning varactor. This is a quite satisfactory solution, in my opinion. You just have to remember to return the fine tuning control to the center position before you move up or down the band when scanning for additional stations.

The only clear problems that I experienced with the Ten-tec 1253 were:

Lack of a shielded antenna connection - I added an SO-259 connector to replace the binding post. A random length wire can be attached through a banana plug.

Ugly tuning knob - a trip to Radio Shack fixed this.

I added the "enhanced sensitivity option." I might want to re-think this. With it, the regeneration setting is somewhat "twitchy."

Calibration required borrowing a signal generator from a friend. I have to consult a chart for the band coverage. I simply stuck a chart with the tuning ranges to the top of the receiver.

The second regenerative receiver kit I built was the MFJ-8100. They take a slightly different tack in the design. They use a series of inductors with a simple multi-position switch to tap into the inductor string for band switching. They, as do Ten-tec, use simple ferrite miniature inductors, except for one that is a toroid that you have to wind. All the inductors in the Ten-tec 1254 design are miniature ferrite inductors.

MJF-8100 uses a nice variable capacitor with a vernier reduction drive for tuning. This "feels" better than the potentiometer used in the Ten-tec 1253. The tuning is a little "fast" on the upper bands, but acceptable. I admit to being a tradtionalist on the issue of real variable capacitors. I am not sure God intended us to tune circuits with varactors. The MFJ-8100 has five bands to cover most of the same range as the Ten-tec 1253, but this is due to using a variable capacitor instead of a varactor.

Again, lack of a shielded antenna connection. I added an SO-259 connector on the back panel. I did retain the supplied binding post for the antenna, however.

Lack of external power supply connection. A power jack from Radio Shack and a SPDT toggle switch took care of this. I can use an external 9 volt battery. There are eight screws to remove to get the case apart to change the battery, so an external battery is handy.

Exact calibration can effectively be done at one point. I zero beat to WWV at 15 MHz. At worst, dial seems to be off by +/- 200 kHz at the lowest or highest tunable frequencies. I made a couple of dots with a marker for CW portions of the 40 and 20 meter bands for CW QRP monitoring.

Headphone only operation. A small external speaker/amplifier from Radio Shack took care of this. I might add a more robust internal AF amplifier, as there is plenty of room in the case. A small speaker could be fitted as well. A project for the future...

MFJ- 8100

Credit Line: http://www.radiomuseum.org/r/mfj_mfj_8100.html

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