FM Dxing

FM E-Skip Season Starts
So it is summer and the FM Eskip season has begun! Several days ago I caught my first opening of the year. Normally the season lasts from around May 15 to August 15, and is best during the day-time with slight peaks around noon and 6pm. It lasted a little over two hours, unfortunately there was a lot of variation. Thus for perhaps 80% of the time, you couldn't hear anything. But stations would often fade in with strong signals for anywhere from 30 seconds to a couple minutes, and then everything would fade out.

Also, most of the time the MUF (maximum usable frequency) didn't get above 92 mhz - so it was hard to identify the non-commercial stations as they don't regularly identify themselves, and there are many more on each frequency.

I think there were two openings (from my location in Philadelphia). I only identified a couple stations so it was hard to say for sure. The bigger opening was to Little Rock Arkansas where I got my only ID (about 1000 miles). I think the other opening was to Florida. I heard a Spanish station on 94.9, and the only one within 1500 miles from Philadelphia is in Miami Beach - and what I heard matched that station's format.

Tropospheric Ducting
So far this season I haven't heard much by Tropospheric Ducting. If you want to see what the conditions are, you should definitely see the Forecast Maps which are generally a good indicator. With some luck I can get Norfolk, Virginia, or less-often, Cape Cod, MA.

Meteor Scatter
I don't think I've ever heard a station by meteor scatter. I have trouble recognizing it, because I live near enough the Philadelphia airport (10 miles?) to get airplane scatter. So if a signal fades in for 10 seconds, it might be the airplanes. And it's hard to ID a station with such a small sample. I just bought a Radio Shack DX-398 which has RDS (which displays a station name/slogan if the signal is strong enough), so I'm hoping that will help me hear my first station by Meteor Scatter.

Tuners
I am the happy owner of a Yamaha T-85 tuner which was originally sold in 1986 for over $400, but I fortunately picked one up on Ebay for $120 or so. Currently they sell $200-$300 on Ebay. I think the word is out that this is a quality dx machine.

I modified mine to increase the selectivity. Unfortunately I'm forgetting the exact details. I think I replaced the narrowest three filters with 180khz ones. I believe I tried the 150khz filters, but they caused too much audio distortion.

The T-85 has four filter settings, and the narrowest setting uses five filters. This gives excellent selectivity. Except for the strongest stations, I can generally receive stations that are 0.2 mhz apart. With my modification, I have slight distortion on weak signals using the super-narrow filter. But it isn't that bad. It could be that I'd be better off if my filters were better matched (the center frequencies of the filters can vary around 10.7 mhz +- 30 khz). If there isn't substantial interference from the channel above or below, the tuner often does slightly better with the filter in the wide setting as it has more sensitivity (the narrower filters have a slight insertion loss).

The tuner tunes with 0.01 mhz steps. Thus you can detune 0.01 or 0.02 away from a channel if need be.

The tuner is almost entirely immune to overload. I guess it could overload if I had a larger antenna pointed at a local station. Currently I use the Radio Shack 6-element FM Yagi.

The AM section is terrible.

The tuning system is funky. It is slower than modern digital tuners. For instance, there is a noticeable half second or so pause before it switches to a memory. This is annoying if you are trying to hear stations (like NPR) ID at the half hour or hour.

The automatic tuning will actually over-shoot a station. So if you are tuning it will go 90.9, 91.0, 91.1, 91.2, 91.1 and then stay there. I never use automatic tuning so I think it's funny.

It has an annoying CSL locking system which tries to lock on to a signal. Unfortunately lock fades in/out if you have a Eskip signal (or tropo) and it mutes the signal while losing/gaining lock. You can defeat this by hitting the manual tuning button (and by storing memories as 92.90, instead of 92.9).

The 20 memories are very nice. They store the filter-setting too.

You can download a Yamaha T-85 service manual

The Tuner Information Center has the most comprehensive set of FM tuner reviews that I've seen, including information on the Yamaha models.

I constantly monitor the TV/FM Eskip log to see if there is an Eskip opening.

RDS
I wanted to get a radio that could decode RDS signals to help identify stations that fade rapidly in/out (E-Skip and meteor scatter primarily). RDS is widely used in Europe, but is becoming increasingly used in the US. Around 1200 US stations use it.

I probably should have spent the extra money and bought a Denon TU1500 RD tuner (for $250), but they are expensive.

So I went for a Radio Shack DX-398 which isn