Improving clock radio FM reception
 

I am having a very specific problem with two radios in my apartment. One is a clock radio; the other is a shelf audio system. Both have digital tuners and happen to be made by Sony.

The only FM station I listen to is 93.9, which is my local public radio station. Neither of these radios has ever had a problem receiving this station in the past (I live right downtown). I moved apartments and now both of these radios (a) have trouble receiving this station and (b) often play a different station, 95.5, when tuned to 93.9.

I have tried various antenna configurations for the shelf system and placements of the clock radio. Sometimes I can improve the reception of 93.9, but other times, my efforts just increase the interference from 95.5 to the point where all I hear is that station.

What's going on here?

NB: There is also an analog-tuned clock radio on the other side of the bed, which seems to have no trouble with this.

Improving clock radio FM reception
 

On Thu, 13 Jan 2011 20:02:39 +0000, Jake W.
wrote:


I am having a very specific problem with two radios in my apartment.
One is a clock radio; the other is a shelf audio system. Both have
digital tuners and happen to be made by Sony.

The only FM station I listen to is 93.9, which is my local public radio
station. Neither of these radios has ever had a problem receiving this
station in the past (I live right downtown). I moved apartments and now
both of these radios (a) have trouble receiving this station and (b)
often play a different station, 95.5, when tuned to 93.9.

I have tried various antenna configurations for the shelf system and
placements of the clock radio. Sometimes I can improve the reception of
93.9, but other times, my efforts just increase the interference from
95.5 to the point where all I hear is that station.

What's going on here?

NB: There is also an analog-tuned clock radio on the other side of the
bed, which seems to have no trouble with this.

Hi Jake,

Sounds like the two Sonys are being overwhelmed by a strong local
station. They have no front-end tuning to make them as selective as
your, as you describe, analog tuned clock radio.

73's
Richard Clark, KB7QHC

That seems odd because both stations broadcast from the same place (the antenna cluster on top of the Empire State Building). The station I want to hear (93.9) has an effective power of 5,400 watts and the interfering station's (95.5) is 6,700.

Does this seem like a situation where the one is likely to overwhelm the other, especially considering that they're not exactly neighbors on the dial? As a general matter, is it normal for a tuner to pick up separate frequencies when tuned to one?

Improving clock radio FM reception
 

On Fri, 14 Jan 2011 23:08:21 +0000, Jake W.
wrote:


Richard Clark;729027 Wrote:

Sounds like the two Sonys are being overwhelmed by a strong local
station. They have no front-end tuning to make them as selective as
your, as you describe, analog tuned clock radio.


That seems odd because both stations broadcast from the same place (the
antenna cluster on top of the Empire State Building). The station I
want to hear (93.9) has an effective power of 5,400 watts and the
interfering station's (95.5) is 6,700.

Hi Jake,

The problem is with a radio station you are NOT listening to that
overwhelms you receiver and silences the other (or forces a new
station over the) station you ARE listening to. This comes from the
lack of a tuned circuit in the receiver.

Your manual tune radio apparently has just such a tuned circuit which
you adjust by hand with the twist of a knob (old-school). Cheap sets
are tuned digitally (even though some of them, too, have a twist knob
to do it) and have no tuned circuit. What you describe is the classic
difference between the two, and living in a dense urban environment
increases the number AND proximity of strong stations that could lead
to this problem you describe.

If you have the provision for attaching an external antenna to the
problem receivers, then using a "rabbit ears" antenna, with careful
length adjustment might help (but it would seem unlikely). Notch
filters would also offer help, but this may be too sophisticated for
you if you are not a Ham or techie, and you are just visiting our
forum to tap our experience (which is perfectly OK).


Does this seem like a situation where the one is likely to overwhelm the
other, especially considering that they're not exactly neighbors on the
dial? As a general matter, is it normal for a tuner to pick up separate
frequencies when tuned to one?

It is found in all single conversion receivers and is called "Image"
reception. It can be observed when the interfering station is
different from the one you are listening to by twice the Intermediate
Frequency. For FM, the IF (Intermediate Frequency) is generally 10.5
MHz. Now, given the FM band is only 20MHz wide, this condition is not
commonly found in FM receivers. However, there are other transmitters
nearby in the TV low VHF bands (if they have not gone dormant due to
the DTV conversion). The aviation band is above FM, but it would seem
unlikely to be the source of your problem by this mechanism.

Then it could be a very strong signal crowding its way in.

73's
Richard Clark, KB7QHC

Improving clock radio FM reception
 

Andy comments:
You mean 10.7 mhz instead of 10.5.......

Andy in Eureka, W4OAH

Yeah, adding a notch filter to a $29 clock radio seems like an overkill (especially considering that it has no external antenna connections and I have no idea where my soldering iron went).

I think I'll just try replacing it with a $15 "old-school" model.

Thanks,
Jake