"Diversity Tuning" used in car radios? - Canadian TV, Computing and Home Theatre Forums
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post #1 of 8 (permalink) Old 2016-04-04, 08:53 PM Thread Starter
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Question "Diversity Tuning" used in car radios?

Don't most newer cars come with FM diversity reception? I remember way back in the day (1980's) when I paid an exorbitant amount of money for an aftermarket car radio that did diversity reception. This was the next best thing to sliced bread. I lived in London Ontario at the time and came home on weekends from a job in Toronto. With that radio set up, I could listen to Q107, full quieting all the way to Ingersoll.

I thought all new cars utilized diversity reception for FM these days. No?

Delhi SFA 1483, Antennacraft Suburban VHF, CM7778
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post #2 of 8 (permalink) Old 2016-04-04, 09:37 PM
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Diversity reception requires at least 2 antennas. I haven't seen that on any car.

I haven't lost my mind. It's around here...somewhere...
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post #3 of 8 (permalink) Old 2016-04-05, 02:22 AM
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I've never seen it either, and I did not know about car FM radio use of it until now. Here's a brief mention of Diversity Tuning in car radios in an article from 1989:
Another option available to the consumer is to replace the standard tuner with one that supports "Diversity Tuning" techniques. A system utilizing diversity tuning consists of a specialized tuner and two antennas located on opposite sides of the vehicle. When listening to the radio, a special electronic circuit monitors the signal strength at both antennas and electronically selects between the stronger of the two. The speed at which this switching process occurs is so rapid that the listener does not even perceive that it has taken place.

Diversity Tuning did not take off in the consumer car autio industry. Here's the Wikipedia link on "Diversity Schemes" used in telecommunications: https://en.wikipedia.org/wiki/Diversity_scheme
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post #4 of 8 (permalink) Old 2016-04-05, 07:52 AM
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I can't see this feature returning either as more cars come equipped with HD Radio. On an HD Radio data stream, the bits are buffered. Thus, negating 'picket fencing' and moderate multipath effects.

Whereas, Diversity Tuning was designed to get around these effects. Optimum spacing between the two antennae helped as one antenna would be in a "peak" and the other in a "null". Thus the switching in the radio for best reception.

I'm an ancient radio hack from a long time ago, so I remember these things... :-)


DAB listener 12/2003-11/2011 (DAB Off-Air since 11/2011)
HD radio Listener since 06/2010
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post #5 of 8 (permalink) Old 2016-04-05, 08:22 PM Thread Starter
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I have a 1998 Volvo S70 in the driveway that has diversity reception for FM.There are two antennas in this vehicle. A power retractable vertical antenna on the rear fender and a fixed antenna inside the plastic front bumper. This arrangement works very well with no noticeable "picket fence" noise while travelling down the road on weak FM signals.

My first experience with diversity radio was an ideal setup. I had two, half wave Hirschman vertical antennas on the rear of the vehicle. Each one mounted on opposite fenders. The performance on my Sony aftermarket diversity radio was excellent. As I mentioned in my earlier post, I was able to listen comfortably to Q107 all the way to Ingersoll without issue. Those were the days.

Delhi SFA 1483, Antennacraft Suburban VHF, CM7778
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post #6 of 8 (permalink) Old 2016-04-05, 08:47 PM Thread Starter
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If anyone is interested or so inclined, here is an article on building a diversity reception device for car radios.


Delhi SFA 1483, Antennacraft Suburban VHF, CM7778
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post #7 of 8 (permalink) Old 2016-04-14, 07:58 AM
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Collinear Car Antenna

I had an electrical antenna (glued to the glass) from the beginning.
I removed the antenna, and made a simple Collinear Antenna.
Much better it was.

I used high-quality cable (50ohm) to antenna length of about 2 meters.

I made it and one boosters.
Much better. A simple amplifier with one transistor BFR91
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post #8 of 8 (permalink) Old 2016-04-15, 01:32 PM
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My 1998 Volvo V70 Sportwagon also has Diversity Antennas for (Analog) FM Tuner (Dual-DIN mount), each located in the huge rear window behind the doors....one more reason I haven't upgraded to an integrated NAV System with Digital FM Tuner....I COULD install/adapt something from the junk yard....if only they could DEMONSTRATE that the security code worked.

A professional installer for the U.S. market says that there are NO current Aftermarket FM Radios that support these Diversity Antenna Systems:

BMW has FM Diversity Antennas in many of their 80's thru Current models...which of course caused "issues" when trying to fit an aftermarket Tuner/NAV system:
DIY - E60 NBT retrofit diversity antenna - Bimmerfest - BMW Forums

Toyota Tacoma trucks [and 4Runner SUV's] have FM Diversity Antennas, one in the Rear Window, the other in the Front Bumper Assembly. Some recent Camry's and Sienna Van also come with it:

Nissan also has FM Diversity Antennas in some of their vehicles sold in USA from mid-80's to Current....and some Subaru's (e.g. Outback) and many Audi/VW's from at least 2002 to today, some with Antennas in the two Side Mirror Pods:

BTW: It is apparently MUCH EASIER to implement a Maximal Ratio Combiner (MRC) for DVB-T Diversity Antennas (esp in cars) than ATSC, based on the easy availability of the former for automobiles vs the ALMOST complete lack of aftermarket ATSC Diversity Receivers for Cars/Vans/Buses/Limos in North America....ATSC's biggest problem is that signals turns to rubbish when moving, working ONLY when stuck in stop-and-go traffic or driving VERY slowly. ATSC 3.0 should change this in a few years.

More info re MRC vs Selection Diversity and Diversity Combiners in general found in my fol. post [continue reading down in Thread]:
Smart Antennas, Adaptive Arrays, Automated OTA Gear
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Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands

Last edited by holl_ands; 2016-04-15 at 03:27 PM.
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