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Old 8th February 2005, 06:10 PM   #1
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Default Adding diversity reception "brain" to car

...my car came OEM with diversity reception, the only problem now is I put in an aftermarket radio which uses only one antenna. The car uses 2 in the glass style antennas, one in the front of the car, one in the rear of the car. I tried to use just one of the antennas with the aftermarket radio and it seems as though the front antennas is good for the upper 1/2 the FM band and the rear one is good for the lower 1/2. If I plug both in at the same time, the reception is very "multipathy", probably because both antennas are used at the same time effectively picking up alot of garbage and cancellation. Overall, the reception is very poor.

I was thinking if there is an externalbrain that could be used as the diversity switcher. Is there such a thing?

Unfortunately I think this may have to be done in conjunction with the radio since it is probably specific to which frequency the radio is tuned in on but I'd though I'd ask anyway.

I tried one "solution" is one of these small amplified antennas that tape onto the windshield. Unfortunately, the unit was alot smaller then I had expected, it is probably 1/8 if not 1/16 wavelength. It is amplified but it works worse then the OEM antennas.

PS I'm looking into other antenna options as well. the car is a plastic body on frame design (chevy corvette), it does not really have a large "ground plane" so to speak, other then the frame of the car itself. I really dont want to put any huge antennas on the outside of the car either, although the convertible models did have a powered "whip" style antennas I'm not too inclined to punch a hole in my car to put it on.

I'm thinking about boat antennas since many boats are of similar composite body/metal frame designs.

The rear bumper of the car has a very large area behind it, I think I may be able to fit even a 1/2 wavelength antenna back there, but horizontally. Can anybody recommend either an antenna thats premade or one that I can fabricate that will work well for my application?
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Old 10th March 2005, 06:48 AM   #2
robjak is offline robjak  United States
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Hi

An "true" external diversity box doesnt exist because as you suspected it requires a signal strength output from the radios IF chip. Antenna switching diversity is a bandaid. The best solution is to use 2 complete synchronized recievers with a DSP "adding" the signals together to cancel multipath. This essentially creates a "phased array" that can reject reflected signal while boosting the direct line of sight path.

http://www.bluespot.co.uk/twinceiver.asp

A problem with horizontal antennas is that they need to be crossed dipoles to avoid directionality issues. When I went to the SEMA show I saw a ton of minature FM and TV "diversity" antennas. If you are still interested I can look in my "bag of show swag" for some brochures. I can't guarantee how well they work though since they seemed to bend the laws of Physics a bit.

I would recommend a Blaupunkt TwinCiever to solve all of your problems. But I don't think you want to change headunits do you?

Heres some links

http://www.thezeb.com/p-Blaupunkt-Sa...ver-100748.htm
http://www.gspr.com/blau/bremen.html

Hope this helps...

PS No I am not a Blaupunkt Rep..
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