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Author Topic: AM STEREO  (Read 2206 times)

Offline ROKFRED

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Re: AM STEREO
« Reply #15 on: June 17, 2023, 1508 UTC »
Oh Boy.....that wasn't a good thing to read. And looking online I do hear clips of X-FM who uses C-Quam and the fading signal can be annoying as the pilot comes and goes. The "stereo image" was stable. I didn't detect movement. Both audio clips are below.
I think they figured out how to reduce/eliminate the moving platform effect for regular "DX" of AM broadcast stations, quite a while ago.


https://swling.com/blog/2014/02/listening-to-shortwave-radio-in-stereo/

Offline M R I

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Re: AM STEREO
« Reply #16 on: June 17, 2023, 1802 UTC »
Give it a try on shortwave and see how well it works for you. I have been working on a method with two independent sideband channels that would not be subject to propagation fading. The receiving method would be on SDR with standard available modes like dual receiver function.
Mix.Radio.International [at] ProtonMail [dot] com

Offline nitroengine

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Re: AM STEREO
« Reply #17 on: June 19, 2023, 0555 UTC »
If you have the ability to do AM-stereo, you might as well do it. Those using mono radios won't be able to tell the difference. It gives those using rigs capable of decoding C-QUAM something extra to experience. Gives you something that sets you apart from most other pirates too.

It would be interesting to see how the later advanced Motorola decoder chips handles a shortwave signal with selective fading. The later chips tackled the problem of platform motion that the early MC13020 can exhibit. Platform motion was really only a problem in the late evenings and overnight on AM, and maybe in areas where there is a strong enough co-channel carrier.

The decoder in the Kiwi is one that does exhibit platform motion.
Receiver: Unlisted KiwiSDR configured to 3-channel wideband mode.
Ant: Homemade "Wellgood" 1m amplified loop normally kept in a fixed position (NNW/SSE) to keep 1500 KSTP in the null.

Offline ROKFRED

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Re: AM STEREO
« Reply #18 on: June 19, 2023, 1423 UTC »
OK NitroEngine
At least make use of the investment of the C-QUAM generator I bought on eBay. My present 1620khz signal is using a different model Panasonic C-QUAM generator that only goes up to 2mhz RF carrier.
The latest purchase generator goes up to 280mhz.
You gave hope to continue to carry the C-QUAM torch.
Fred

Offline ThaDood

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Re: AM STEREO ? When possible.
« Reply #19 on: June 26, 2023, 1840 UTC »
When time allows, I've simulcasted my Part 15 stations' programming to the Sean Cuthbert C-QUAM AM Stereo transmitter. https://radiojayallen.com/cuthbert-am-stereo-c-quam-transmitter/   I want to change mine over to a different, metal, case. And, I've modified a Sony SRF-42 AMAX Walkman to be an AM / FM Stereo VU OTA Monitor. https://www.minds.com/group/876322093051867136/feed     (Scroll wayyyyyyyyyyyyyy down when the page finally loads-up.) I'm set-up in my audio chain for 2 Channel audio, where the only MONO sections are the AM transmitters. So someday, I hope to be AM Stereo full time.
I was asked, yet another weird question, of how I would like to be buried, when I finally bite the big one. The answer was actually pretty easy. Face-down, like a certain historical figure in the late 1980's, (I will not mention who, but some of you will get it, and that's enough.) Why??? It would be a burial that will satisfy everyone: (1) My enemies will say that it will show me where to go. (2) On the same point, I can have my enemies kiss my butt. (3) It will temporarily give someone a place to park a bicycle. See??? A WIN / WIN for everyone.

Offline redhat

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Re: AM STEREO
« Reply #20 on: June 26, 2023, 1857 UTC »
Decoding C-QUAM as QAM eliminates much of the platform motion with a bump in low frequency distortion caused by intermodulation.  There were hacks to the older C-QUAM demodulator chips where you could disable cosine correction and force the chip into QAM mode.  In software this should be easy to do, and when the Kiwi folks added CQUAM demodulation, I advised them to add a QAM mode to get around the platform motion issue.  I'm not sure that this was done, however.

On HF, ISB would likely be a better choice.  You still would have phasing effects, but the complete channel reversal and wobble under fading conditions would go away.  I chose C-QUAM initially because of receiver support.  At the time, there were no software decoders available for ISB, and to date the only one I'm aware of is onboard the Kiwi.

+-RH
« Last Edit: June 26, 2023, 1903 UTC by redhat »
Somewhere under the stars...
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Please send QSL's and reception reports to xfmshortwave [at] proton [d0t] me

Offline Pigmeat

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Re: AM STEREO
« Reply #21 on: June 28, 2023, 0129 UTC »
Dood, our mutual friend seems to have AM stereo down pat. I listen to his station 2-3 times a week.

Offline M R I

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Re: AM STEREO
« Reply #22 on: June 28, 2023, 0557 UTC »
Transmitting in ISB stereo with suppressed carrier is effectively DSB mode. I mostly transmit in sideband anyway. I may get around to working on this at some point.
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Offline nitroengine

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Re: AM STEREO
« Reply #23 on: July 10, 2023, 0400 UTC »
I'd like to hear a pirate trying Kahn ISB AM-stereo sometime.
Receiver: Unlisted KiwiSDR configured to 3-channel wideband mode.
Ant: Homemade "Wellgood" 1m amplified loop normally kept in a fixed position (NNW/SSE) to keep 1500 KSTP in the null.