For those of you in South Melbourne and Palm Bay - you have a BIG problem receiving Z-88. There is a low power station in Palm Bay on 88.5, right next to Z-88's assigned frequency of 88.3.

Fortunately - for the technically minded (which includes a lot of the people in the area) - there IS a solution.

OK - if you don't know how to solder and don't know what you are doing, don't bother reading the rest of this page. And a mandatory safety note - unplug the thing before you work on it! And those big filter capacitors on the power supply are an energy hazard - if you short them - you could have some big sparks and melt your tool! If you happen to be holding onto the tool - hands don't melt, they BURN. BADLY! Do not wear rings or watches or any other type of metal jewelry while working. They are potential shorts and snags. We assume no responsibility if you electrocute or burn yourself, or if you hopelessly destroy your radio. Enough said?

There is one area where even good audio gear skimps - and it is called "test-selecting" parts. They don't do it because it is expensive and labor intensive. Which parts am I talking about? I am talking about little parts the size of your fingernail, called "IF ceramic filters". For those familiar with electronics, they look like little ceramic disk capacitors, except they have three leads on them instead of two. Here is an enlarged picture:

The majority of these filters are manufactured by two manufacturers - Murata and Toko. They come in several varieties, or bandwidths. Almost without exception, what is installed in your tuner is a 280 kHz variety. Since FM stations are spaced every 200 kHz, this means that they are wider than they have to be for each station. The reason for this is that they are not precise, they can be a little high or low. If you use 280 kHz, you are guaranteed of covering the whole station.

So - by test selecting filters that are all centered the same, you would only need 200 kHz. Standard filter values,or bandwidths are: 280, 230, 180, 150, 100, and 90 kHz. So you should use 230, right? WRONG!!! The way FM is actually transmitted, you only need a little over half of the 200 kHz bandwidth for stereo reception. The rest of the channel is used for elevator music, paging, telemetry, and other things that you don't need at all. A good compromise is to use the 150 kHz ceramic filters, matching them carefully for center frequency. This will yield superb selectivity, and you will notice a big increase in sensitivity as well. The reason for this is a thing called the "gain/bandwidth product". As the bandwidth goes down, the gain goes UP! It isn't hard to understand the conceptual reason - instead of amplifying parts of adjacent channels and all the sub-carrier stuff you don't need, you are focusing right on just the important portions of the station you are interested in. You aren't wasting energy and resources on noise. It is VERY important to match the filters. If they are not matched, your stereo receptions will suffer BADLY! The best way for an amateur without the necessary equipment is trial and error. It is pretty easy if your stereo only has two of these filters. If it has three, the best thing to do is leave the first one alone and just change out the second two. Then you can go back and change the first one to match the other two if you want. It won't make that much difference.

(1) Before doing anything else, you need to order the parts you need. The quickest way is to order them from Digi-Key (1-800-344-4539). They can accept credit card orders, so have your credit card handy. Think ahead - most radios have 2 FM ceramic filters, so order 2 for each radio you want to modify. They don't cost that much. The part number you want is: TK2308-ND Single pieces are 72 cents, it is $6.27 for 10. The description is "FM ceramic filters" (with 150 kHz bandwidth). The Toko part number is: SK107M4-AO-10. Here is the catalog page:

If you are modifying a portable radio that does NOT have stereo reception, you can substitute a TK2309-ND / SK107M5-A0-10. It is slightly more expensive but will reject 88.5 much better.

(2) You need to find the FM ceramic filters in your radio (described above). Some portables may have only one, most other radios 2 or 3. You may have to do a fair amount of disassembly to find them. You will need to be able to get to the underside of the PC board to unsolder them.

(3) Make note of location of the polarity marker on the old ceramic filter(s). It is usually a red dot. Carefully unsolder each ceramic filter in the radio, cleaning the traces and holes after you get it out. Solder wick or a vacuum de-soldering tool is very helpful. Solder in the new ceramic filters with their polarity markers in the same direction as the old. Trim excess lead length and re-assemble.

(4) Enjoy! I live very close to the tower of the offending station, and have no trouble at all - but you might have to turn your antenna away from the 88.5 tower (near the intersection of Minton and I-95).