I put my Radioshark project aside for about a year and finally returned to my plan to experiment with improving it's radio reception.
My earlier article got quite a bit of checkout and it is my hope that this new series of articles helps those intrepid souls who wish to extend the functionality of their Radiosharks. In a sense we are pioneers and it does give a certain satisfaction to make such a unique toy better with a little creativity.
My particular model is a Radioshark II and the model I have just felt like a smaller circuit board than those I had seen in the MP3 car forum and the old Maine article cited below. I'm betting it is the same size for mine as the others, but it still is disturbing to see such a tiny board being used!
The goal was not deterred by tiny circuit boards. In fact, I have plenty of room to do mods in the rather spacious fin as a result of my planned hacking of the antenna system into what will be a better configuration.
As such, I felt it was time to try a gradual experimental plan to get the Radioshark to have better reception. So I decided to run a few experiments before committing to a single approach. For those familiar with the Radioshark, the manufacturer states that the use of the antenna jack will help with reception. I have found this not to be the case and decided, based on other past modification articles, to pursue either attachment to the internal antennas or to replace them entirely.
Experiment One: Find best method of adding antenna
Step One: The footer plate
So, with all of this in mind, my first issue was disassembly. It turns out that a screw on the bottom metal weighted section of the Radioshark is what opens the unit to disassembly. This screw is located in the center of the bottom plate. Just feel through the rubber to locate the depression where the screw is located.
I had to use a sharp phillips screwdriver to break the rubber covering that was in the way of taking the screw out. Rather than scrape this rubber away, I only broke through and used the screwdriver to remove the bottom plate. This turned out to be a good decision and keeps yet another part (the screw) from being lost.
Once I got the footer off the case, I heard rattling of a part inside the case. I then realized that the nut that held the footer plate was now loose. This was simple enough to fix later.
Step Two: The plastic halves
The plastic halves are pressed together with plastic pins that fit into corresponding receptacles. To get them apart, a knife blade was used to slowly expand the two halves apart until the entire system came apart. It was amazing to see how little actual circuitry was in the Radioshark itself. Upon opening it, I noted two independent antennas, one AM loop and an FM loop that went followed the contour of the fin. One could look at this arrangement and see why the system is so poorly suited to reception.
Step Three: Inspecting the circuit board and antenna connections
The inner loop is the AM radio antenna. It is not the usual sort of AM antenna I was used to seeing. Most are wound around a ferrite core in smaller AM radios. This was a simple looped arrangement with the two ends finding themselves connected to two inputs in the circuit board.
The AM Antenna
The inputs are close together. It is not clear as to what the best arrangement is for tying this into an external setup since I do not routinely design antennas. I would guess it makes sense to try a standard dipole setup or perhaps to go after one grounded lead and the other as the antenna. It will do for me to do some research on this elsewhere.
I was rather disappointed with how this was done by the manufacturer. The cost for adding proper antenna inputs and better internal antennas would have been worth it. Still, it makes for an interesting project.
The FM antenna
The amount of space inside the fin is pretty good. There is quite a bit of room to adding extra circuitry and altering the antenna arrangement as needed. Thus I'm fairly convinced that I'm going to remove both loops and use shielded coax with the shortest possible route to get the signals into the circuit board, after boosting by an auxiliary circuit.
The two leads are spaced on opposite ends of the circuit board. I'm not used to seeing this sort of arrangement. Usually the antenna inputs are closer together. I'll do the same with shielded coax in this setup, but do need to figure how to do this in the best manner.
The Active Antenna
Having yet to pick a design, a casual search of Google revealed a
wealth of circuits out there that can do the job for boosting AM and FM signals. I am looking at active antenna circuits that are small enough to fit into the package and which require small power inputs. I may need to provide a place for a power input of 9 volts to handle this little complication. Simple enough to solve. Stay tuned for the next article with the finalized antenna boost solution I come up with.
I live on a ranch with about 7 acres of land. As such, I've got multiple buildings spread out over quite a distance and it becomes pretty clear that if you are going to compute in such an environment, you need a decent network to cover large areas of space.
Are we getting closer to Star trek? Well, Purdue University researchers have developed a handheld sensing system, which they liken to Star Trek’s “tricorder,” to be used to study the chemical compounds of alien worlds.
