Nate, your statement about trying a ferrite loopstick for transmission has me digesting thoughts, but I'm not sure if I'm learning or just building a bigger question.
Based on your discovery that ferrites absorb rather than radiate, perhaps that explains how they contribute to reception. As the ferrite absorbs medium wave energy from the air, the loopstick gathers some of the RF as it passes through.
If ferrite is unable to radiate RF energy it has no use in the transmission of radio waves. It's only purpose is to act as a "soak", which also would explain it's usefulness in filter circuits.
Is that a smart statement, or one that misses the point (?)
Nate,
I have the ase2 exciter, and you are quite right, the output replaces the main rf frequency at ttl level, and it phase modulates the carrier frequency, in quadrature.
I am going to feed this ttl level in to the amt5000, in place of the amt's synth output.
I can get the AMT5000 to output flat wideband am mod, on the bench, by feeding the output through a series 47pf cap, in to a 50 ohm dummy load/attenuator.
I can sweep the audio in, and monitor the attenuators output on the scope for modulation envelope, and it is flat, and i mean flat between 20hz to 15khz+, we are talking 0.2db or better here !
Of course i have bypassed the audio processor ic, as discussed before.
Also do get it super flat i used a small cap to compensate the amt's modulator, to get it ruler flat.
It is a lot harder to do a c-quam add on for existing transmitters, as it requires some knowledge to apply it.
Also to get the phase/amplitude to match over the entire band, as in the Aspisys AMAX-1 requires the phase modulator/osc to be at a fixed frequency, and then mixed with a synth oscillator to produce the final frequency.
The upshot of this is that it does tune the entire band without peaking circuits, and the phase/am mod is consistent to give the same channel seperation.
Btw i have fired up the Cyprus C-Quam exciter, all i can say is it is total crap, power varies across the band dramatically, and the am envelope is badly distorted, and the 25hz pilot is a squarewave from a 555 ic !
The ASMAX-1 pilot tone is at least a dds squarewave with basic rc filtering, so i added a bandpass filter to make it resemble a decent sinewave.
Paul.
The Sony SRF-42, SRF-A1, and SRF-A100, Realistic TM-152, and MCS-3050 AM Stereo tuners are all common finds on eBay, although some sellers ask much more than what they're worth. The controls on top of the SRF-A100 are a dust magnet, but just pull off the knobs and spray some contact cleaner into them, and that'll get rid of the scratchiness.
Many HD Radios also support C-Quam, but not all, and this feature was never officially promoted by the manufacturers, so you have to do some Internet searching to find out which models support it. Many HD Radios do not give any visual indication of when a C-Quam broadcast is being received and they can take anywhere from 10 to 30 seconds to begin decoding, so you just have to be patient and listen for the stereo separation to open up.
Also HD Radios tend to be picky about the C-Quam pilot tone. If it's not exactly dead on 25 Hz and 5% modulation they often will stay in mono. However I was able to get my Directed Electronics HD Radio to decode 890 WLS in AM Stereo via 700-mile skywave under pretty poor signal conditions:
Curious about coverage of Am stereo back in it's heyday? Here's a coverage map of C-Quam stations from 1988!
http://www.ironrangecountry.com/cquam1988.pdf
TIB
I remember that year. And I remember the promos from a couple of local stations in Wichita Falls running A.M. Stereo. But, I didn't listen to them because they carried a format I didn't like at the time. One was the old KNIN 990. It was a fairly nice "powerhouse" that had been on the air for years. I believe it went dark in the 90s. The call letters moved to FM 92.9, not sure now if they are in use. I will have to look.
Regardless, things have definately gone downhill for A.M. stereo and A.M. in general.
So what breally happened to Stereo AM? Looks like a lot of staions invested and then stopped?
The sharpest decline happened in the mid to late '90s when Clear Channel was buying stations by the hundreds, and they had a policy of turning off the AM Stereo at any station they acquired, even if it had a music format.
And then another decline happened in the early to mid 2000s when IBOC DAB (HD Radio) was the hot new thing, and since C-Quam and IBOC are incompatible with each other, numerous big-market stations switched off their C-Quam "in preparation for upgrading to HD Radio", regardless if they ever actually implemented HD Radio or not.
Thus, with a few exceptions like 890 WLS in Chicago, most stations using AM Stereo today are small-market stations which were able to escape corporate takeover and never had the budget to use HD Radio.
That is good info. Makes sense. I guess CC thought that AM stereo was competing against their FM stations?
Interesting to see a few stations missing from that map that I know were running C-QuAM in '88 in Texas. 820 WBAP at 50kW, 1400 KGVL at 1kW. Eventually KAAM/KMKI 620 would run AM Stereo as well.
I had forgot that "K double A M" went stereo back when they were on 620. I still listen to them these days on 770. I wasn't aware of 820 being in stereo since they have been news talk since the early 80's (I think). I remember the day they switched. I was not impressed as a listener.
Stereo talk is effective if the staion is doing live talk with two persons, one on each channel.
Wasn't there talk in the 1970s of some stations going Quad (4-channel)?
Maybe that was just for FM, but I don't think it ever happened.
Quad LPs were on the market for a year or two.
Then more recently we heard big talk about 5.1 sound.
They always want to load us down with big box appliances.
Very interesting. I don't listen to talk radio, I have enough opinions of my own without getting upset about other peoples opinions. But it makes sense.
Interesting, short bit on quad broadcasting, with an interesting list of recordings as well:
http://www.surrounddiscography.com/quaddisc/quadradi.htm
And of course, since all the trendsetting in broadcasting is done here in Minnesota, details on a quad broadcasting project:
http://www.oldradio.com/archives/warstories/md-quad.htm
I still have some Quad LP's. And I remember a classmate in high school did his science project on quad sound, and had set up a booth with a speaker in each corner and sound effects of trains, airplanes, some symphonies (much like early stereo demonstration records) where those interested could sit in the center and hear the train, etc actually go around them from speaker to speaker.
TIB
Hi, are you able to rerun that map for 2016, I'd like to see the stereo landscape of today.