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AM Stereo

A

audioguy

I am interested to know: is anyone here operating an AM stereo Part 15 station? If so, what equipment do you use?

I am considering going stereo. I bought a Chris Cuff exciter last year. It works OK, but the output circuit is not designed (or intended) for efficient operation. I will probably use it as an exciter, which means that I will have to build a new PA and antenna matching stage. I would be interested to hear how others have gotten on the air in stereo successfully.
 
I never carried it out, but I had an idea to do two different audio paths AM modulated at something like 100 khz, where it's easy to build high-q selective circuits by hand, then feed each path the seperate audio, follow each with a tuning network to cause upper and lower sidebands when summed, to be normal bandwidth, yet different from each other. Then I planned to select out that 15kz slice and mulitiply up to intended output frequency.

I've never had enough time to try everything I'd like to try.
 
Does anyone still make an AM Stereo receiver? Also, IMHO it would seem that like with FM, a weak signal in stereo would be suseptible to more interference than you already have to deal with on your fringe areas. How far does your Part 15 get out?
 
B Lewis said:
Does anyone still make an AM Stereo receiver? Also, IMHO it would seem that like with FM, a weak signal in stereo would be suseptible to more interference than you already have to deal with on your fringe areas. How far does your Part 15 get out?
Click to expand...

Only GM/Delco (and maybe Ford) were the only ones I knew of. I seriously doubt any home stereo manufacturers hopped on the bandwagon....never saw any at Radio Shack or professional home stareo dealers . Mind you (along with that) there were TWO systems that were FCC apporoved... the Motorola C-QUAM and the Harris system...neither one were compatible with each other along with Kahn-Hazletine system. The ball got dropped right then and there there when a singular (and compatible) system was not narrowed down to one....much to the delight of the arch conservative tabloid-style trash talkers who sank AM broadcasting down to new lows.
 
I was also told that the old Radio Shack (Accurain) HD radio had a chipset that would also decode C-QUAM AM stereo transmission. I don't own one personally but another engineering I know does. Perhaps I'll be able to borrow it to test.

In my own personal collection I have four Sony units, The SRF-A1 and SRF-42 Walkmans, the CFS-6000 boom box and the SRF-A100 table portable. Its said Sony makes a newer version of the 100, the SRF-A300, but you have to find one of the few merchants that import the radio into the states.
 
Radio Shack did make a standalone AM stereo tuner for CQUAM. It's the only AM stereo radio I have at home. I also have a GM/Delcom AM stereo ETR in our 1990 GMC Starcraft van... fantastic sounding radio if you can find a good enough station to show if off! (Like your own...)

As others have pointed out, there's virtually no hit on coverage with CQUAM stereo.
 
Bill DeFelice said:
I was also told that the old Radio Shack (Accurain) HD radio had a chipset that would also decode C-QUAM AM stereo transmission. I don't own one personally but another engineering I know does. Perhaps I'll be able to borrow it to test.

In my own personal collection I have four Sony units, The SRF-A1 and SRF-42 Walkmans, the CFS-6000 boom box and the SRF-A100 table portable. Its said Sony makes a newer version of the 100, the SRF-A300, but you have to find one of the few merchants that import the radio into the states.
Click to expand...

I will give it a try... I have an Accurian and WLS is reasonably strong.
(pause)

No C-QUAM decode here on the north side of Chicago with an Accurian. There no real noise here, and I've aimed th loop for maximum pickup.
On the the other hand, the Accurian is the most bizarre sounding AM radio I've ever heard.
The continuously varying IF bandwidth while listening to an analog AM is maddening.
It works backwards, opening up bandwidth when there's no modulation, and as soon as there's audio it narrows.
As soon as there's crashing high-frequency modulation, you can hear the bandwidth actively slamming down to something quite narrow.
What did they think they were dong with this mode?
Sounds like a Collins 390-A on 2 khz, but as heard over a internet stream.
In fact, it kinda makes everything sound like an internet stream, without low bitrate artifacts.
I suspect this is because the analog detector output is then digitized to the amp.
 
I just checked, and WLS is decoding just fine on my Radio Shack tuner. It is a model TM-152 AM-AM Stereo tuner.

I modified this tuner quite some time ago to improve the bass response. I also changed out the ceramic IF filters for some slightly wider ones. During the heyday of AM stereo broadcasting, the quality of the received audio rivaled that of most FM stations. It also compared favorably to my Scott Philharmonic. I used to have some recordings of WGN when they were broadcasting in stereo... they sounded phenomenal! I wish they would bring it back!
 
Just to avoid any confusion, here's a picture of the Radio Shack/Accurian table radio that is suppose to decode C-QUAM.

Long before I engineered the AM daytimer the operations manager who I was friends with gave me the SRF-A1 portable. I drove down the street to K-Mart to pick up some batteries. I blind tuned the unit to where I thought the station was and turned it on. I swore I had the unit on FM, but it was the station in AM Stereo (they ran the Kahn ISB system). Clean, very nice fidelity and very good stereo separation. The engineers at the time did some major work on the directional array to improve it for AM stereo and it was well worth their efforts.

Personally, I would take that over IBOC any day. In fact I refuse to purchase an HD radio.
 
I remember the early days of AM Stereo. I had one of those Radio Shack tuners. I agree, AM stereo is quite good.
 
I had seen the older Rat Shack tuner but never heard how it sounded. The few stations that I had been at used a variety of AM stereo monitors. Kahn had their own rack mount demodulator for their system. One station I was at used a Sony AM Stereo car radio for their off-air monitor source while another station used the Sony SRF-A100 for their air monitor. I don't know if these radios were just more convenient than a typical broadcast monitor or if they may have performed better.
 
AM Stereo had it's day...but, you can't avoid the migration to digital now. Like it or not, the currently accepted standard for digital radio is being shoved down broadcast radio's throats. C-quam AM stereo used 30 kHz of bandwidth of precious spectrum..no wonder it "sounded like FM". These days 20 kHz is the max allowed to be used for analog AM. What's ironic, is that presently HD Radio needs about 30 kHz to work. But, lose the analog component, and the and it fits in 20 kHz. That should aleviate most of the adjacent channel interference issues that plague it presently. However, my feeling is that the Codec will never sound as good as an analog transmission. The benefit of program associated ond other data, seems to be a major factor in it's reluctant acceptance. In the end, the very environmental factors that plagued the MW band since the begining of time will still affect any form of modulation there. That can't be engineered away.

Give it to the Hams, and call it a day...
 
AM stereo is feasible for Part 15 Community Radio applications. HD Radio is not, due to the proprietary licensing agreement and high cost of the equipment. I also doubt that it would be receivable over a useful distance at the power level permitted for Part 15 AM band operation. It certainly would not provide any usable range for a Part 15 FM band system!
 
I know there have been at least two college campus stations that had taken commercial broadcast AM stereo exciters and connected them to their carrier current transmitter systems. This only works well when there is one transmitter and, if required, signal boosting is performed via amplifiers fed via coaxial cable. This has been a successful and repeatable using standard engineering practices.
 
I had heard sales reps with the old WPAT back in the B/Ez days talk about how good their music sounded in AM stereo. Never had the chance to hear them, but I did hear 560 in Philadelphia when they were B/Ez as "Easy 560". Great sound. Just as good as their FM station.


Beat IBOC hands down.
 
I just picked up a Carver TX 11a at a good price. I can hardly wait to use the AM stereo tuner again. I owned one of these right after they came on the market and I was blown away at how good WDRC AM 1360 in Hartford sounded at the time. Better than any FM station at the time. I think WRCQ AM 910 in Hartford was also broadcasting in CQUAM at that time as well.
 
Bill DeFelice said:
I have the Greek0made ASMAX-1 C-QUAM rig and it's quite nice. I'm using it to test AM processing for both mono and stereo.
Click to expand...

ASPiSYS, the company that makes the ASMAX-1, will soon be offering a 100 watt C-QuAM TX, the ASM-100. This would be perfect for a licensed LPAM service (it would also be fun to match it to an appropriate antenna and fire it up just for testing for a couple of days).

http://www.aspisys.com/asm100.htm

Don't know what the power rating is for this antenna but it's an interesting design:

http://www.theradiosource.com/products-vp9000.htm

c5
 
The early 2000's Chrysler product radios had AM stereo and were superb sounding. Even my non-technical girlfriend remarked on how good the station (at the time, WOKY in Milwaukee) sounded.
I have one of those "Alfredo Lite" Chris Cuff transmitters and I agree, it's pretty wimpy. Not familiar with a "Greek0made"...
 
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