The AM Forum

With the apparent demise of AM stereo and the present push to digital IBOC technology, I don't think many AM stations are still transmitting in stereo, nor are any receivers being produced to receive it (not that there ever were, in significant numbers).

I wonder what has happened or will happen to all the stereo generators that were out there, but have been taken out of service, now that this has fallen into the class of dinosaur technology.  These things could have all sorts of possibilities for amateur radio experimentation, and by now should about be at the free-for-the-taking stage, like hollow-state AM transmitters were starting a few years ago.

Maybe some of you with close ties to the present-day broadcast industry could shed some light on the issue.  Just like Gates, RCA, Collins, Raytheon and other modulation iron, it would be a real shame to see these units end up in the landfill because "nobody could possibly have any use for that old junk".

Wouldn't it be interesting to hear a beer/chili belch in stereo?

I still hear a few AM Stereos out there. The radio in the Chrysler has a stereo detector.

Either I'm picking up the occasional stereo stations when WEEI fades on 850 and when WZON fades on 620, or those stations are about 20 Hz off and the heterodyne is falsing the decoder.

My old pickup has a stereo AM receiver in it.  I listen to WBAP in Ft. Worth from time to time and they broadcast in stereo. I haven't listened in a while but think they may have pulled the card.

Are you wanting one to add to your Gates Don?  Wouldn't that be fun on 3.885?

Motorola, Delta Electronics and Broadcast Electronics were some of the major producers of CQUAM exciters for transmitters when it was the thing. Search for them when looking on epay or wherever.

Wasn't Motorola the company that developed that system (CQUAM)?

I don't think the stereo decoder chips are still available unless one could pull one from a junked car radio.

For a while, Denon made component home tuners that would decode AM stereo, look for a TU-680NAB. I suppose one could use one with a mixer converter up front.

I will ask around and see if there's an encoder gathering dust around town somewhere.

I recall someone came up with a circuit for a synchronous detector some years ago, built around a stereo decoder chip.

There's always stereo AM using independent sidebands..

Heck, fire up two transmitters at once. 3885 and 3685. Left and right.
The other end uses two receivers.

Heh. Is simultaneous FM and AM still illegal?

it would have to be double-ended to be stereo, if you know what i mean.

No.  The FeeCee (inadvertently?) deleted that prohibition with the R&O of bandwidth Docket 20777.  They also deleted the maximum 100% modulation rule, when they revamped the Technical Standards section.

So, Timtron's SBE rig is legal.

I've often considered using my Gonset GSB-100 as an exciter for the Junkyard Dawg, phase-modulating the Gonset with left-minus-right and amplitude-modulating the Junkyard Dawg with left-plus-right, but the results would probably be iffy at best. Besides, I don't have a stable 20 Hz generator for the stereo pilot.

ISB receivers (at least,in the professional grade realm) are fairly common - the WJ 8716, Harris RF-590, assorted Racals.  TMC made some ISB exciters back in the 50s and 60s which turn up from time to time at hamfests.  Wouldn't be too hard to do.

I thought about this too a few years ago, but why bother?
as hams we are supposed to be experimenters of cutting edge technologies, not dumpster diving junk collectors.
why not experiment with DRM on 75m, encode stereo at a decent bitrate.
no more selective fading, static crashes and it will chase the slopbuckets away.
im sure this can be achieved on a decent tube rig, so no solid state required (except for encoding/decoding)

For that matter, any AM Stereo signal can be easily generated by an SDR.

I disagree. 

90% of my station is recycled from stuff somebody else didn't want.  What could be more in the spirit of genuine amateur radio than creating something out of nothing, from what someone else considered "junk"?  The latest and greatest is not always the best.  That's one of the things wrong with our society, that has  resulted in the mess we are in to-day - we throw away (waste) too much good stuff to the point that our whole economic system is based on waste, spending money we don't have for stuff we don't need.

The cutting edge of technology is but one facet of the many that make up amateur radio.

Hi:

I was the first to broadcast in err, "AM Stereo" in the mid 1980's. I phase modulated my Valiant with L-R and amplitude modulated with what else...mono!

Years ago Radio Shack had a mini AM stereo tuner. I just bought one for $5.00 at the Shelby hamfest this year in hopes to making a sync detector with it.

Have not seen many AM stereo exciters hitting the market yet though.

73,
Dan
W1DAN

I agree Blaine. This technology stereo whatever is old news. Who cares. Amateurs should help advance the technologies that are available and moving forward. DRM for amateur radio use sounds like a great place to play. Here's some great background:
http://www.arrl.org/tis/info/pdf/x0301049.pdf


I wonder if this is another amateur who's into total recycling

I experimented quite a bit with 'Part 15' AM transmitters a few years back. One of my concoctions managed to make the AM stereo capable receiver in my 2000 Ford Taurus switch to stereo. It actually sounded pretty good. I treated it as a problem to solve and managed to clean up the signal enough to stop it. Never figured out what was going on. Maybe a 20Hz pilot was somehow being generated... dunno. The transmitter was not crystal controlled and had a lot of FM even though the oscillator was not being modulated as in most Part 15 transmitters put together by tinkerers.

I suppose but DRM is at least ten years old now - hardly cutting edge.

Pic looks like a rennie selling his spare garb, likely dug out of the ash heaps from the festival in the last town he was in.

What a person does with their own station is their business. Aside from the bean burrito's push-pull revenge, or the occasional guest in the shack, what would two channels would be good for?

I did just read that article on DRM. Not sure how the CODFM signal is going to fit through the class B modulator without a fuss.

It sounds cool but for voice it seems if little use. You can hear what it sounds like at the link below.


http://www.amwindow.org/audio/mov/wa2fnq.mov

Hey Don,
You have the same views I do about the old tube transmitters. Everyone is phasng them out for their solid state replacements.
What value do the old 250 watt - 5kw tube transmitters have now??
Why would third world countries have any interest in energy guzzling transmitters that are beyond 25 yrs old???

Fred