TenTec Radio Kit - Model 1054 Update #3

My longtime readers will remember I built a TenTec Model 1054 regenerative shortwave receiver kit a while back. At the time I posted to this blog about the apparent bad customer service I received from TenTec when complaining about the erratic regeneration control. Just week, there has been another development.

This past week I have been working feverishly to get all my ham and shortwave equipment up and running. After an exhaustive and *fruitless* search online, trying to find any information I could on the TenTec 1054's regeneration control issue, I decided to try once more to contact TenTec's customer service people. TenTec apparently has NO PHONE number to reach them at; apparetly one must email them as I had before. And so I did.

The following day I got an email back from one of their service technicians stating that my original email had gone into his email "spam folder". He also stated, contrary to the instruction manual, that the regeneration will start 1/4 of the way from one end of the potentiometer's travel, that regeneration will start rather suddenly, and that from my description the radio seemed to be working correctly. ANOTHER tech later wrote me and said that he thought there was a defect in either one of the two FET transistors in the regeneration circuit or that the regeneration threshold adjustment trim potentiometer was bad. He offered to send me new parts free of charge if I sent him my address. I did just so; I'll see what happens.

If they do not end up sending me the parts (I'm NOT holding my breath, under the circumstances), after studying the schematic at some length I have some ideas as to how I can modify the circuit to work better.

All this said, I still have the issue of what to do about the housing, since the box TenTec sent me is basically unusable. As mentioned in my original post I intend to do some circuit modifications such as adding a dual 9-volt regulator circuit that can be fed from an external 12 volt battery, and possibly adding a band spread control for better selectivity in crowded bands. I want to build my own improved audio section based on a decent audio chip. I would also include an active filter for CW reception and a limiter to prevent hearing damage from loud noises. Regarding the dual 9-volt regulator, the circuit currently uses separate batteries for the regenerative receiver itself and the audio section. This is no doubt to eliminate any issues from feedback and oscillation between the radio part and the audio section. But for my purposes I need the whole thing run from one 12 volt battery.

Here are the links to my prior posts regarding the TenTec Moel 1054 radio:

http://inkarlslab.blogspot.com/2011/04/ten-tec-short-wave-receiver.html

http://inkarlslab.blogspot.com/2011/05/ten-tec-model-1054-shortwave-radio.html

Shortwave Radio Converter

I built this about 27 years ago to receive international shortwave broadcasts through a car AM radio. This circuit tunes the 9.5 to 10 MHz and 12 - 12.5 MHz shortwave bands. Back in the day I would listen to the BBC World Service, Radio Canada, Radio Moscow, Deutsche Welle, Radio Australia, and many others. Radio France gave excellent reports on the radiation cloud that rolled across Europe from the Chernobyl mishap in 1986. Several times daily, they would read off a list of all the major cities in Europe, along with the radiation levels in each one. I was "glued" to my radio following the progress of this. The information was of good enough detail and quality one could actually plot it on a map, graphically monitoring the progress of the situation.

The VFO and mixer circuits were taken from the 1979 issue of the ARRL Radio Amateur's Handbook. I built them from the publshed schematics, then tweaked some of the component values for better performance. The VFO coils are wound on glass 3AG fuses that had their elements removed. I heated the end caps with a soldering iron, removed them, took out the fusable element, and glued the caps back on. Then I wound the coils using #28 magnet wire, using the metal caps to solder the wires onto. I used Bohning "Fletchtite" archery glue to secure the windings so they wouldn't move. The variable capacitors were very old, surplus units bought I-can't-remember-where. Looking at the left-hand-side of the photo: The control on the left-hand front of the box is the band selector switch. Next to that is a variable capacitor used to tune in stations. On the rear of the box (in the right-hand-side of the photo) there is a solitary variable capacitor used to tune the antenna for whichever band one is listening to. The whole unit is built in modular form - the VFO has its own board and the mixer is on a separate board. This allowed me to develop and refine the system one module at a time. The VFO is built using "ugly" or "dead-bug" type construction. Its circuit board was made by scoring a copper-clad circuit board with a knife into a grid pattern. The mixer board was actually laid out, then etched using ferric chloride solution.

After many years of sitting unused in an RV, being subjected to all kinds of temperature extremes and even a roof leak, this little device still works. Not only does it still work, the tuning has held calibraton!!! It is within 5 or so KHz of where it was when built. This attests to the quality of the components I used to build it, as electronic components generally drift in value with age.

If I can ever find the original schematic I drew, I'll post it in a future blog entry.

Within the past several years, I have heard China Radio International, Radio Australia, various Spanish-speaking stations, etc. on this unit. Regrettably, the BBC has gotten away from broadcasting quality news programming on shortwave, instead focusing on satelite broadcasts aimed at various target audiences - telling them either what they want to hear or whatever the Powers That Be WANT folks to hear.

To use the converter, simply tune the car radio to an empty spot on the AM dial between 1.40 and 1.55 MHz. Connect the converter between the external antenna and the antenna input on the radio. The converter runs on the car's 12 volt supply; an internal zener diode regulates the supply voltage for the circuit to 9 volts. Use the band selector switch to choose the band to listen to. Reach around the back of the box and turn the peaking control for maximum signal. Then simply tune the right-hand front panel control to tune around for a station. The lower band - the 9.5-10 MHz band, offers the WWV time station from Ft. Collins, Colorado. These WWV signals are very useful not only for checking your watch, but also the RF and audio signals provided are extremely accurate and may be used for equipment calibration. WWV may be heard on 5, 10, 15, and 20 MHz - these broadcasts are done around the clock, 365 days a year. Again I mention those because they are an excellent way of checking the calibration and even the operation of a shortwave radio. Basically, if you can't hear WWV, you will likely NOT hear much else, either.

Soon, in a future post I will delve into the features to look for when buying a shortwave receiver and what to listen for on your radio.