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Question about tuning in FM Stations

DSChamber

DSChamber

Well-Known Member
Hey guys/gals,

I own an Akai AT-2650 and I have a question about tuning in FM Stations.

The local radio station I usually listen to is 97.5 ...

Situation

During the day time I can tune this station in very well. My signal strength nearly "pegs out" and sits usually between 4.5 and 5 (with 5 being the top of the scale). I get FM Stereo lock and the FM stereo light lights up. Sound quality is fairly good, some faint static in the background but fairly clear. The FM selector is set to FM stereo auto

Now, fast forward to the night time, after the sun goes down I get the following behavior. Without moving the tuning dial from where I had it set in the daytime I lose FM Stereo lock and the FM Stereo light flicks in and out, there is a lot more static. The signal strength indicator meter, weirdly enough, stays nearly pegged out between 4-5. If I turn the FM selector knob to Mono I can listen to the station without any static.

Some observations I have noticed with my tuner.

1. When tuning in a station, lets use 97.5 for example, I notice that if I roll down to 97.0 and then start rolling up towards 97.5 I will have to go past 97.5 and the station will actually start coming in as I pass 98.0 and "lock" at say 98.1... then I can roll back to almost 97.5 without losing the station.

2. My FM tuning meter doesn't move at all (the one with the two bars on either side and you have to get the needle in the middle). On my Pioneer SX3600 my FM tuning meter moves so I know that it should.

3. The above behavior doesn't matter if I have the Noise Cancel ON or OFF, it also doesn't matter if I have the FM Mute ON or OFF.


Any suggestions on what to look for? I would love to get this tuner working 100% because I can listen to the tuner with it in MONO fine but you definitely lose sound quality when not in Stereo Mode. Plus it is a really nice looking silver faced tuner.

TIA!
 
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yup

+1 atmospheric.
I tend to get better reception in the evening.
Back in the middle of ND, we could pick up a great Chicago rock station in the evening and at night. Usually down by the river near the big @$$ power lines that crossed the river. Clear as a bell. Nothing during the day.
 
So even though the Signal Strength remains the same, atmospheric distortions will play havoc with the FM Stereo broadcast?
 
Atmospheric effects as others have said, but probably more linked to barometric
pressure, humidity and the like rather than to the presence or absence of the sun.
Ionospheric effects are very marginal at those VHF frequencies.

A better antenna, or better orientation of the antenna you have, should boost
signal strength at all times and improve your situation.
 
You have Adobe installed? I can take the link just fine. Or are you behind a proxy at work or something?
 
Weird... it won't load the page when I use Firefox.... but it will open using IE 7..

Anyway...I'll have a read of that... I know a bit about atmospheric refraction and all of that good stuff when it comes to transmission inside the ionosphere so I wasn't surprised by the day/night thing..

What I was wondering about more specifically was my two observations about my tuner.... is this normal operation? I would think not... but I don't claim to know everything about vintage tuners, lol... I'm a newb at the basic level.

1. When tuning in a station, lets use 97.5 for example, I notice that if I roll down to 97.0 and then start rolling up towards 97.5 I will have to go past 97.5 and the station will actually start coming in as I pass 98.0 and "lock" at say 98.1... then I can roll back to almost 97.5 without losing the station.

2. My FM tuning meter doesn't move at all (the one with the two bars on either side and you have to get the needle in the middle). On my Pioneer SX3600 my FM tuning meter moves so I know that it should.
 
Sounds to me as though the I.F, detector, and/or front end oscillator sections are not in proper alignment. The effect you mention could also be caused by a strong signal adjacent to the frequency you are tuning to. If the effect is noted on ALL stations, it is a matter of alignment.
 
Just out of curiosity, do FM stations change their power settings at night like some AM stations? I doubt ionospheric issues matter since there is little effect at 3 metres which is approximately where FM is. Power changes may have more effect than anything else.
 
2chanman said:
Sounds to me as though the I.F, detector, and/or front end oscillator sections are not in proper alignment. The effect you mention could also be caused by a strong signal adjacent to the frequency you are tuning to. If the effect is noted on ALL stations, it is a matter of alignment.
Click to expand...

Agreed, if the center tuning meter does not move, something is wrong. Also the noted anomaly regarding the need to tune beyond the station and come back is not normal. The tuner needs service. Unless one has the service manual and good experience with RF electronics and proper instruments, it's best to let a pro fix it. The one thing that can be done easily is to clean the tuner gangs. See Sticky on this topic

On atmospheric conditions - in my location, usually reception is *better* at night, not worse. It worse during the day, especially on very bright sunny days.
Bob
 
Read the sticky on cleaning the tuner. You issue is even addressed in the very first post.

John
 
FM is next to TV channel 6.

If this were due to atmospheric conditions, it would be popping up a lot there.

Most likely atmospheric conditions would be ducting, common during the summer.

Some AM broadcast stations cut their power back, or go off the air because their signal bounce off the F-layer. During the day the layers below F absorb and block AM broadcast signals. This is a function of the transmitted frequency, not the mode, AM or FM. The higher the frequency, the shorter the wave length, the more likely the signal penetrates the ioniosphere. the shorter the wavelength the more likely it is to get trapped in a layer or duct. Since FM broadcast signal don't bouncer the F-layers, they don't have to cut back power or got off the air at night.

To check you signal strength meter disconnect your antenna, insert a short piece of wire and tune for a strong station and then a weak one.

Best from Tucson
Bob
 
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