1088 FM problem

3/28/2009 12:17:06 PMBubba

Hi, on my 1088. FM only the stations are duplicate and some bleed into each other. For example when you tune a tation in then move the dial over a half an inch it also comes in. I think it is called imaging. Anyone familar with this model might give me a hint? It is clear when tuned. I'd just like the stations to stop bleeding into each other and appearing in duplicates beside themselves.

3/28/2009 3:07:01 PMLewis L

:Hi, on my 1088. FM only the stations are duplicate and some bleed into each other. For example when you tune a tation in then move the dial over a half an inch it also comes in. I think it is called imaging. Anyone familar with this model might give me a hint? It is clear when tuned. I'd just like the stations to stop bleeding into each other and appearing in duplicates beside themselves.

Well, I don't know the manufacturer of your radio, but imaging is a phenominum that occurs at exactly twice the IF of the radio. If you work at an airport, for the FM band the image will be 2 X 10.7, or 21.4 mHz above the FM band. The aircraft navigation band starts at 108.0 mHz, and switches to communication at 118.0 mHz thence to 135 mHz. So the upper limit of FM is 108.0, the image would be at 129.4. Believe me, I worked at a very busy airport for 35 years, and listening ot FM was about of the question on the stations that had images in the aircraft band. I think Atlanta has a radio on every frequencv known to man. So, if you are getting IF stations at several places on the band, I would suspect the IF is passing several frequencies.
Lewis

3/28/2009 9:44:03 PMEdd

And would that 1088 be the Model, and would that then be a ?

GRUNDIG 1088

HALLICRAFTERS 1088

TELEDYNE 1088

EMERSON 1088

TRUETONE 2D 1088 A

WARDS GSE 1088 A

RCA RC 1088

REALTONE TR 1088

CONTINENTAL MDSE. CO. TFM 1088

Relevant to the "image"":
The most common FM IF is 10.7 megglinghertz, so would that be in agreement with, say , finding a station at mid band and finding it replicated at either +10.7 or -10.7 Mhz , which you could possibly only BARELY do once at the center of the band , what with the FM band only being < 20 Mhz wide.

I might suspicion an extra " mixer" problem in the RF front end, in the respect of a poor connection / galvanic corrosion acting as a "semiconductor" and throwing some spurious signals in CONSIDERING there is a strong local signal nearby to you that could be providing the strong RF for that additional mixing action
.

AM stations, could also included, for that source of their continuous sourced RF.

Next thought, deterioration of bypass / decoupling caps in the RF- IF sections upsetting the RF with the possibility of spurious oscillations occurring.

Mis-alignmentt of the IF-RF stages ?.

Which is the sets brand ?

73's de Edd

4/20/2009 10:44:26 AMBubba

Sorry it's a grundig 1088

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: And would that 1088 be the Model, and would that then be a ?
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:GRUNDIG 1088
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:HALLICRAFTERS 1088
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:TELEDYNE 1088
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:EMERSON 1088
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:TRUETONE 2D 1088 A
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:WARDS GSE 1088 A
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:RCA RC 1088
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:REALTONE TR 1088
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:CONTINENTAL MDSE. CO. TFM 1088
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:Relevant to the "image"":
:The most common FM IF is 10.7 megglinghertz, so would that be in agreement with, say , finding a station at mid band and finding it replicated at either +10.7 or -10.7 Mhz , which you could possibly only BARELY do once at the center of the band , what with the FM band only being < 20 Mhz wide.
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:I might suspicion an extra " mixer" problem in the RF front end, in the respect of a poor connection / galvanic corrosion acting as a "semiconductor" and throwing some spurious signals in CONSIDERING there is a strong local signal nearby to you that could be providing the strong RF for that additional mixing action
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:AM stations, could also included, for that source of their continuous sourced RF.
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:Next thought, deterioration of bypass / decoupling caps in the RF- IF sections upsetting the RF with the possibility of spurious oscillations occurring.
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:Mis-alignmentt of the IF-RF stages ?.
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:Which is the sets brand ?
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:73's de Edd
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4/20/2009 6:23:43 PMEdd

Vell, at der least, ve done bin havink vit der schematic-er-er here:

Is it replicating that condition on every station or possibly only the STRONG ones, and I assume that degree of frequency shift / replication being the same on all situations . . . . right ?

And most assuredly . . .being higher in frequency, if you can differentiate between the two, considering
that one is the weaker of the two signals.

73's de Edd

GRUNDIG . . . . Model 1088. . . . . . SCHEMATIC :

4/20/2009 6:23:45 PMEdd

Vell, at der least, ve done bin havink vit der schematic-er-er here:

73's de Edd

GRUNDIG . . . . Model 1088. . . . . . SCHEMATIC :