FM radio drift/static when moving...

[scoot]

I had my radio rebuilt by Walter Odometer.  It's a correct Blaupunkt Frankfurt from 1967.  It sounds fine when I'm parked in the garage.  On the road the stations drift and there is lots of interference.  My car has the radio suppression kit, although I have not checked all of the components to see if they are intact.  I'm primarily concerned with FM reception.  Having said that, is there a suggested list of things to check before going back to our pal Walter who will test it on the bench and say it works just fine?   Thanks, and I realize that this information appears in pieces in various threads (like the stuff about spark plug resistence) but I haven't managed to piece it together enough to get the radio to sound good on the road...  thanks
Scott

[Douglas]

How's the antenna? Does it have all the proper mounting hardware at its base? I think that can have a bearing on reception and interference.

[scoot]

quote:Originally posted by Douglas

How's the antenna? Does it have all the proper mounting hardware at its base? I think that can have a bearing on reception and interference.

Antenna is a new hirshman.  Re: mounting hardware, I'm not sure what you mean.  It is mounted the same as the old one was...  Is there a trick that I don't know about with respect to the antenna?  
Thanks,  Scott

[66andBlue]

Scott,
is it an automatic or manual antenna?
With "interference" do you mean interference from another, stronger station, or just noise?
When the station has drifted away during driving and you stop, does it come back?

[Benz Dr.]

I believe that radio suppresion is more about AM than FM. AM seems to be more sensitive to static from spark plug wires that don't have resistors. Back in the 60's FM radios were kind of rare in cars. In fact a lot of cars didn't have radios.

Euro radios are somewhat different that radios made here during the same time period. If it's an AM radio it won't be all that different but a lot of radios that MB used had AM, FM, LW and even SW. I had a unit from an old 300 ( 1953 ) and it was a massive radio that could pick up stations from all over the world. It was pretty high tech for its time.

In Europe the cities are closer together and there were a lot more radio stations so they used a lot more radio bands. The reception on these old radios isn't that good because they won't pick up stations from very far away. You can easily pick up FM stations 100 miles away if they beam the signal into your area with a modern radio. You can't do that with one of these old radios. 25 miles might be all you can get sometimes on the FM band.

[scoot]

quote:Originally posted by 66andBlue

Scott,
is it an automatic or manual antenna?
With "interference" do you mean interference from another, stronger station, or just noise?
When the station has drifted away during driving and you stop, does it come back?

Manual antenna, (new Hirschman).  Basically what happens is I'll be sitting in the garage with a station tuned.  Sounds fine and stays that way while I'm working on the car.  Then I start the car and it still sounds fine.  Then I start driving and the station goes out of tune a little, so I adjust the knob and it comes back, but not as well, then I'll try to get other stations while driving and they are all difficult to tune, and even if I get them, they tend to drift away.  It's not like stations overlapping, it's as if someone turned the tuner knob a little or something.   I _think_ that when I'm driving and stop (with engine still running) that it becomes easier to keep the station, but not as easy as before I started the car to begin with.

[66andBlue]

quote:Originally posted by scoot

.... Manual antenna, (new Hirschman). ....

Scott,
when you read old instructions that came with manual antennas they suggested to pull the antenna out to about 30 inch for FM reception (and different lengths for short wave and AM).  Reason is that the FM band goes from about 90 MHz to 108 MHz which corresponds to a 1/4 wave length of 33 inch to 27 inch, respectively. For optimum reception the antenna length should match the station's frequency, or 1/2, 1/4, 1/8 of that. Modern radios have higher sensitivity so no one pays much attention to this any longer.
If antenna adjustment doesn't help then I would ask the shop to test the frequency tuning lock and how well it functions.
Finally, even in the old days on some better radios one could change the sensitivity, low in cities and high in the country side.  Does yours have this switch?

[scoot]

quote:Originally posted by 66andBlue


Scott,
when you read old instructions that came with manual antennas they suggested to pull the antenna out to about 30 inch for FM reception (and different lengths for short wave and AM).  Reason is that the FM band goes from about 90 MHz to 108 MHz which corresponds to a 1/4 wave length of 33 inch to 27 inch, respectively. For optimum reception the antenna length should match the station's frequency, or 1/2, 1/4, 1/8 of that. Modern radios have higher sensitivity so no one pays much attention to this any longer.
If antenna adjustment doesn't help then I would ask the shop to test the frequency tuning lock and how well it functions.
Finally, even in the old days on some better radios one could change the sensitivity, low in cities and high in the country side.  Does yours have this switch?

I've tried different antenna lengths and that hasn't helped.  I have a different radio that has the sensitivity switch you describe, but this radio does not have that.  If I don't get anywhere with the "radio suppression" attempts, I'll take it back and have them test some more and see if there is more that they can do.  I suspect since they are going to test on a bench that they will be unhelpful, but I'll try anyway...   thanks, Scott

[mdsalemi]

Scott,

FWIW, I have a Becker Europa mono, also period correct, purchased rebuilt from Becker.  When still it sounds fine--like yours.  Under motion it isn't as good; best on the stronger stations.  There's a little ignition noise, usually on fringe stations.  It can't hold a candle to any modern radio.

I'm not really sure how good these old radios ever were.

Contact me off line; I'll put you in touch with a local MBCA friend here who repairs them.  Not that you would send it here or whether yours needs any repair, but just to get perhaps some confirmation on just how good these old radios were or to see if there is anything else you can do.  I live with my noise.

My car had the Blaupunkt Frankfurt, too, probably dealer installed, and it was dead as a doornail when I got my car.  Everyone told me to throw it out, so I did.