Sir Lim Radio Shack Special

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My hat is off to you, Sir Lim, for taking the time and patience in making the Radio Shack Special come to life for you!

And so, I am please to announce that Sir Lim Hing Thing completed his Radio Shack Special in June 2005. Below are Sir Lims' own pictures and words of his maiden journey...

The RSS is truly a wonder... and a powerful project. With just one transistor and a few other components we can have FM stations and even air traffic communications. The signals are also clear and steady.

Imagine what an experimenter can do! He can build the RSS smaller or he can add cool items like a slow motion drive for tuning and proper knobs for the volume and regeneration controls and so forth. Maybe the RSS and Islander can be combined to form a transceiver?

In this photo, you can see that I have a power on off switch, a socket for external earphone or speaker, a socket for external power source and an antenna socket. The antenna socket is on the other half of the plastic box. The built in speaker is a flat piece 4.5cm diameter. Despite the size, audio quality is good and crisp just like what we may hear in a small commercial radio.

The PCB is 4.5cm by 7cm. This is how I made the PC Board. A photocopy of the template from your article was placed over the board and the different position of the component holes marked onto the board by using a sharp needle tool.

Then, using a marker pen, I drew lines to join the points accordingly (as shown on the template) to form the tracks on the board. After that I used a curve- blade hobby tool to slowly chisel away the unwanted copper leaving only the tracks and some other unaffected island areas. No effort was made to trim the tracks or clear way these island areas. I then drill the holes for the components.

Over here in Malaysia it is not easy to get certain electronic parts especially those for VHF communication purposes. I was unable to get the specified variable tuning condenser and had to make do with a trimmer. Luckily, with the large track on the PCB I was able to drill holes to suit this trimmer.

I used a 2N3819 instead of the MPF102. The Source Coil might not be exact due to different wire measurement standards. In Malaysia we use the British standard i.e. SWG. I had used a wire size (in stock) that I deemed was suitable and wrapped around 26 turns of it on to a 8mm diameter plastic tube. Luckily it worked. The Drain Coil too might not be exact again due to wire size difference. Anyway, the tap and diameter of the coil were complied with.The tap was made at the 3rd turn but I had 6 turns overall instead of 7 turns. I thought that with lesser turns, I would be able to tune to higher frequencies. There were no difficulties getting the other component parts. It is amazing that with all these variances, the project still took off without much fuss.

Here you can see the slits in the plastic casing. The two larger holes are for adjusting purposes. A mini tool is inserted through these holes to turn the screw on the trimmer for tuning and the potentiometer for regeneration control respectively. At one half of the trimmers rotation, I get a number of FM stations while at the other half I get to hear aircraft communications. These came in at short bursts and tuning could be tricky. Anyway with patience and a steady hand, tuning for the aircraft band can still be accurately done.

I had thought of making the RSS portable but could not find a suitable enclosure. A name-card holder plastic box was available and this was pressed into use.

I drilled holes for the sockets, speaker and switch and cut grooves to allow one the cover to fit nicely once the sockets were held in place. The plastic material is of low quality and it cracks easily so great care was taken when drilling the holes. Even so I could not help to prevent some splits here and there.

I am not too impressed with my handiwork, but I am really happy that I visited Patricks' website. Anyway, once again, thank you Sir. Will be visiting you soon regarding the Islander project.

Sir Lim has just sent me new pictures his his new and revised RSS; along with an updated documentary of modifications he has done with his Radio Shack Special. So without further ado, here is Sir Lim's updated story of his new and revised RSS!

I congratulate Sir Lim for his continued quest of striving for perfection. The more one sees...the more one does ! And Sir Lim definately falls into that category!

I am glad to inform you that I have done some modifications to my RSS like replacing the plastic casing and changing the regen control with a multi turn type for more precise adjustments.

The drain coil was changed too.I have also chiseled away some of the unused islands on the PC board.The outcome is a better looking RSS. I can still tune in to some FM stations and also catch aircraft communications. Additionally I am now able to get taxi mobile radio communications. Probably this is due to the multi turn regen control providing more range or sensitivity.

Somehow I found that the set suffered from handling effects. While holding and tuning it, I could get clear and loud receptions but once I leave the set by itself there was a slight drift especially the VHF part. Also the antenna cannot be too long else there is no oscillation. I have also successfully built a second RSS, this time with external controls which make it easier for me to tune and adjust. Reception is steady and clear.

As with the first RSS I can tune in to some FM and Airband. The actual range is different as I have used a different tuning cap. I have pleasure to show some pictures of both the projects.

Sir Patrick, your RSS project is a real gem. Anyone who knows something about electronics and can do some soldering will be able to construct the RSS. They should be able to get it to work first time easily even with slight variations as to wire size and number of turns.

Having said this, however, I must highlight one very important point. Constructors must ensure that the 1K ohm regen control must be wired correctly. Wrong connections would cause the control to heat up and burned out. This happened to my 2nd RSS. When I saw some smoke coming out of the control I quickly switch off the power and check the wiring.

After changing the connections, I tested the project starting from low to high power. The control stayed cool and the RSS jump to life. Just amazing. Another thing worth noting is that we do not really need a long antenna for the little gem to pull in the stations. If you look at my pictures you can see that I have only about 2inch wire to the RCA socket which is meant to facilitate an external antenna. Both my RSS pull in stations (FM & aircraft communications) without need for any external antenna.

"Sir Patrick, hope more people will construct your RSS GEM. We get great satisfaction as well as rewards. A lot of learning here."