HFU HF Underground
General Category => General Radio Discussion => Topic started by: ROKFRED on June 14, 2023, 1429 UTC
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Hello friends
I wonder if anyone likes to tickle their ears with nice stereo audio coming in from an AM station?
I have a (sort of) part15 stereo AM station on 1620 during the daylight hours and here are 2 ways to listen in.
These are links to hear C-QUAM AM STEREO
http://music-music.blogsite.org:8000/airmon
The link above is direct from a Denon AM STEREO TUNER
http://amstereo.blogsite.org:8073/
The link above is the KIWI SDR. You may have to tune it to 1620. It's on a public network and previous users may have changed settings.
Tune for 1620 and AM (NOT AM N) And press the button next to AM for QAM and you will hear stereo. Mouse over the cursor on the "dial" ( The scroll wheel) to open up the bandwidth for REAL HI-FI audio
Enjoy
ROKFRED
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Thanks, listening via the Kiwi (15:05 UTC 14 June 2023). I could not connect to the Denon tuner.
P.S. I noticed that the signal level on the Kiwi is at S+50 and occasionally clipping. You might want to add an attenuator on the receiver's input to avoid overload.
~SIGINT~
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hmmm that's strange for the Denon link not working.
The link should open another folder in the browser and a black screen with the player. After 5 seconds or so it automatically should play. Unless the server is kicking you off.
The SDR is S-50 but no overload indicator and the audio is fine.
Thanks for the feedback
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Ohhhh
The Denon tuner server might be at its limit for listeners. I think it can handle 3.
Fred
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Hi Fred,
I get "connection has timed out" on the Denon. I will keep trying.
As for the Kiwi, I do occasionally see the "dBm" indicator flash red so it is probably just on the edge.
Good work. Sounds good. Perhaps when you have the chance you can tell us a little about the setup / equipment.
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Sure.....
I'm using Station playlist as the playout software and the "radio station sound" for AM 1620. There is some processing for audio using Stereo Tool. That audio goes to more processing using APHEX Compellor and Dominator to the RF exciter. A Panasonic VP8132A which generates the C-QUAM audio and RF set at 1620khz. The antenna is a vertical resonant at 1620khz
Fred
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Hi Fred,
Much appreciated and thank you. I was looking at the Panasonic a little while back as it is an "all-in-one" solution as opposed to having to deal with the old Motorola and miriade of external gear. Nice to actually hear the Panasonic on the air, considering it is supposed to be a piece of test equipment.
~SIGINT~
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2012 UTC song Bare footing
Nice sound via your web sdr ;D
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I listen to a friend's carrier-current AM stereo station on his SDR. I'll have to try your link after dinner.
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Sounding sweet on the Kiwi, Fred. Heard one of my late Mom's favorites, "Kansas City" by Wilbert Harrison.
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I modified a Sony ICF-2010 receiver by bringing out the both left and right channels to line level output from original CQUAM stereo synchronous AM detector IC in the radio. This with the switchable wideband Hi Fi AM filter mod sounds great. One of the best SAM stereo detectors holding lock into the noise without distortion especially on shortwave.
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thanks for reports and comments.
FYI I sign off around 8PM from the skip coming in from the many 1620's showing up. They really cut my coverage down at night......so i just turn it off and back on around 10AM.
Fred
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Welcome! I see you made it to HFU. (I'm Jacob over on the C-QUAM FB page).
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hi Jacob
Going to shaking things up on 43M band.....6955 on KRAP and using C-QUAM on shortwave.
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Unfortunately the phase method of C-QUAM that was designed for the the local AM broadcast band can’t keep the stereo and center channel from constantly drifting called platform motion on shortwave. This is because of signal propagation fading causing phase distortion. This makes it just about useless unless you are transmitting closer to the receiving station especially during the day or have no phase fading.
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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/
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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.
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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.
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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
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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.
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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
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Dood, our mutual friend seems to have AM stereo down pat. I listen to his station 2-3 times a week.
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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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I'd like to hear a pirate trying Kahn ISB AM-stereo sometime.