FM Radio External Antenna Connector

Check this out. Build an FM Antenna I don't think you need to solder anything. I'd just start touching things on the radio with the antenna lead and clip the lead to whatever makes the reception best.

Many thanks, lyn. The article shows a very nice antenna. I've built several less sophisticated than that design already and they don't get the job done. What I really want to do is put an FM antenna on the roof complete with amplifiers and rotor. That kind of serious antenna has two conductors and there has to be a decent impedance match with the radio input. My question is how to do that in a table radio that has neither 75 nor 300 ohm input plugs.

I think the clip on the telescoping antenna gives only one input. Maybe I have to hunt for a ground plane inside the radio; but then I need to know how to get the right impedance match. The current system with any antenna in the room has to fight off local interference, especially from the new electric blanket.

It seems like FCC class B requirements are no longer being enforced, especially on cheap import products. The control on the electric blanket is the second new product we have gotten that massively interferes with all the radio broadcast bands, both FM and AM reception.

Ed Weldon

1) Article about Quad antennas. http://en.wikipedia.org/wiki/Quad_antenna. The instructional PDF Lyn pointed out describes their antenna as a cubical quad, which is one of the varieties. I have had good luck extending the range of my 1970's era portable AM-FM receiver (Zenith RF86Y) with a length of insulated 26 gauge stranded wire (salvaged from a 25-pair telephone cable) soldered to an alligator clip attached to the whip. Most consumer-grade radios aren't fussy about impedance matching. I used ten feet of wire, but you can start longer and trim. Drape the wire over doorways, furniture, etc. until you get the best signal. The US FM band is mostly line-of-sight, and isn't affected by the ionosphere, so you can make a note of your successful arrangements and reproduce them later. Antenna design is about ten percent calculation and ninety per cent experiment. No lightning arrester is required for this setup.

If you decide on a more elaborate arrangement, I strongly recommend an attic-mounted antenna with an amplifier, also for safety's sake. If you have an old TV antenna lying around, you can clean that up and give it a second useful life. I used a salvaged Winegard log-periodic on a short mast of Schedule 40 PVC in the attic with a cheap Radio Shack booster in a difficult reception area for years, having rotated it for best reception through a hatchway with a 10-foot piece of dried bamboo.

2) FM is mostly immune to over-the-air interference, but RFI can be conveyed to the audio section of your receiver through the power line. I put up with the noisy switching power supply in a 386SX clone for some time because I couldn't afford a better computer. Fortunately, there are plug-in Radio Frequency Interference filters that you can interpose between the offending appliance and the rest of your household electrical supply.

3) If you have a computer with a broadband connection, you can download iTunes, which comes with an internet radio and several hundred stations. You can also download links to hundreds more stations from all over the USA and all over the world. Internet reception is noise-free and good to go as long as your service provider keeps his equipment up-to-snuff. If you don't want to run the computer to listen to the radio, C. Crane sells an internet radio that is just a radio. Happy Listening.

Check if the present antenna has an isolating cap between it and the internal radio components, if not add one in the low to middle Pico Farad range, some experimentation may be required, then add a socket to the same capacitor......

That is what I would do, but there may be a better method from someone else here, but my method should work.....

The antenna on your radio has an input impedance of 50 ohms. The cable will have an impedance of 75 ohms. Putting a cable female connector in parallel with you antenna should do the trick. The output of the cable system should adequately address the small difference in impedance.

de VE7WD

P.S. One good thing about C.Crane Rado's is that the standard plug for external antennas has a designated pin out for long wave if you are into am listening. My C.Crane Radio has a tuning nob on the side. I had it wacked by a baggage handler and it took a little work to get it to work properly as it is in a resistance configuration.

At least 6 good ideas for me to work on. For half of them I'll have to get my wife to give up her radio for a few hours.

Many thanks guys. But keep'em coming; They are much appreciated....... Ed Weldon