Listening to SCA

[poltergeisty]

Has anyone did this? I don't know if I'm doing this right, but I can only tune 67 KHz and not tune up to 92 KHz in SDR#.

I have HDTune tune a FM broadcast frequency and then that audio is fed via VB Cable to SDR# where I select USB and tune to 67 KHz. So far I have not heard any SCA broadcasts. I'm assuming something isn't set right. I don't know, and I can't tune to 92 KHz in SDR#. I do have a 192 KHz capable soundcard and I have selected that in my soundcard's options for the VB cable and audio output.

Anyone do this? I would think I could hear some SCA broadcast out of Denver but I none.

 

[dave3825]

Can you post a pic of your settings?

 

[EricCottrell]

Hello,

SCA is a FM subcarrier modulated on the main FM signal, so the mode should be set to FM. The audio output from HDTune needs to be "flat" with no de-emphasis set. If you look at the spectrum display in SDR# you should see the main channel audio from 0 to 15 KHz, a spike at 19 KHz (if Stereo), the stereo subcarrier from about 24 to 52 KHz (if stereo), a spike at 57 KHz (if RDS). If the station has SCA then you should see signals centered around 67 and 92 KHz.

You need a fairly good signal on the main FM receiver for good demodulation of SCA.

73 Eric

 

[poltergeisty]

The audio output from HDTune needs to be "flat" with no de-emphasis set.

How do I do that? And I think you mean HDSDR, not HDTune in the HDD scanning program.

 

[poltergeisty]

Here's what I got going. I'm not uploading this video to YouTube since I'm sure they would pull it.

Box

Video will be removed in a week.

It looks like the reason why I can't tune to 92 KHz in SDR# is due to the sound settings. But I have full 192 KHz capability so I don't know why I can't. I reversed the way I'm doing this by tuning a broadcast station in SDR# instead of HDSDR and feed the audio with VB Cable to HDSDR. In HDSDR I was able to tune to 92 KHz and beyond, but still no SCA.

I have bought a better antenna for my SDR and I'm just waiting for the SMA to MCX connector.

 

[ka3jjz]

Not every station carries SCSO (which is, I think, the more proper name for the service). What did you reference to find this out?

The FM Atlas and Station Directory (once edited by the now-silent-key Dr. Bruce Elving) used to carry this information, but it's long out of date....Mike

 

[ka3jjz]

Not SCSO, SCA is still correct, my bad....Mike

 

[poltergeisty]

Got my new antenna working and stations do come in better, but still no dice on SCA. I may just feed a radio into my computer and see what happens.

 

[poltergeisty]

Piped audio from my radio into my computer and tried to do this in SDR# and still no dice. Though, this radio may put out mono only and I saw a narrower bandwidth in the audio.

 

[EricCottrell]

Hello,

Audio output from a radio will not work since it goes through de-emphasis. You need a FM radio that has Detector Output or Multiplex Output.

How strong are the signals with the new antenna? You need reasonably strong signals. The example you showed is very weak.

73 Eric

 

[ko6jw_2]

From the FCC:

In general, tunable subcarrier receivers are prohibited because they violate Section 605 of the Communications Act of 1934, as amended, which states that no one may receive, or assist in receiving, any radio communication to which they are not entitled and use that information for their own benefit. In addition, 18 U.S.C. Sections 2510 through 2521 prohibit the manufacture, assembly, possession, and sale of any device primarily useful for the surreptitious interception of such radio transmissions. See KMLA Broadcasting Corp. v. Twentieth Century Cigarette Vendors Corp. 264 F. Supp. 35 (D. Cal. 1967); see also Letter to Dr. Haghighi from Richard B. Engelman, Chief, Technical Standards Branch, OET. (One exception was made in 1984 for a tunable subcarrier receiver for a data service in which (1) the receivers could not receive other SCA transmissions, (2) subscribers who had not met their contractual obligations to the service provider were denied access.)

FM stations no longer, in general, need FCC authorization for SCA.

 

[ka3jjz]

Well that never stopped folks from actually listening - there was/is a whole sub culture within the FM DX community that does...Mike

 

[dlwtrunked]

Here's what I got going. I'm not uploading this video to YouTube since I'm sure they would pull it.

Box

Video will be removed in a week.

It looks like the reason why I can't tune to 92 KHz in SDR# is due to the sound settings. But I have full 192 KHz capability so I don't know why I can't. I reversed the way I'm doing this by tuning a broadcast station in SDR# instead of HDSDR and feed the audio with VB Cable to HDSDR. In HDSDR I was able to tune to 92 KHz and beyond, but still no SCA.

I have bought a better antenna for my SDR and I'm just waiting for the SMA to MCX connector.

First of all, SCA/SCS is relatively rare today and 92 kHz is even rarer. (Note it is "kHz" not "KHz"--kilo is always small case "k".) It is best to tuned the FM station in SDR# then the subcarrier after VBCable in HDSDR to tune the subcarrier as you can pull in the sides of the HDSDR filter to improve signal-to-noise.

 

[EricCottrell]

Hello,

How do you setup SDR# to output 192KHz flat audio? I can not get the audio rate above 48K using virtual audio cable.

73 Eric

 

[poltergeisty]

It may be your sound card capability. But if your sound card has the 192kHz ability then go under your recording settings and adjust.

I'm also using the HiFi cable, but I had no issues with the normal VB cable either.

 

[dlwtrunked]

Hello,

How do you setup SDR# to output 192KHz flat audio? I can not get the audio rate above 48K using virtual audio cable.

73 Eric

(It is kHz" not "KHz".) As shown in another post, you must configure the software. I had trouble with paid VAC and found free VBCable better. Please all note that 192000 sample/sec means 96000 Hz without aliasing (half the sample rate).

 

[poltergeisty]

I'm guessing there are no SCA broadcast in my area, though I see the song ID and what not in SDR# from that data. The only sure fire way of knowing is to buy an SCA radio which are all on eBay.

From the FCC:

In general, tunable subcarrier receivers are prohibited because they violate Section 605 of the Communications Act of 1934, as amended, which states that no one may receive, or assist in receiving, any radio communication to which they are not entitled and use that information for their own benefit. In addition, 18 U.S.C. Sections 2510 through 2521 prohibit the manufacture, assembly, possession, and sale of any device primarily useful for the surreptitious interception of such radio transmissions. See KMLA Broadcasting Corp. v. Twentieth Century Cigarette Vendors Corp. 264 F. Supp. 35 (D. Cal. 1967); see also Letter to Dr. Haghighi from Richard B. Engelman, Chief, Technical Standards Branch, OET. (One exception was made in 1984 for a tunable subcarrier receiver for a data service in which (1) the receivers could not receive other SCA transmissions, (2) subscribers who had not met their contractual obligations to the service provider were denied access.)

FM stations no longer, in general, need FCC authorization for SCA.

Wow, 1934, huh?

Fact of the matter is that SCA provides services for the blind and what not. It's not like a super duper encrypted channel or anything.

 

[EricCottrell]

Hello,

Song data does not come from SCA, but from RBDS. It is a digital data subcarrier. HD Radio stations usually also have RBDS on the analog side.

Radio Data System - Wikipedia

en.wikipedia.org

RBDS is also how the non-satellite traffic data (TMC) gets transmitted.

Traffic message channel - Wikipedia

en.wikipedia.org

73 Eric

 

[poltergeisty]

I know it's not sub carrier audio. Was saying that I can see the data as to say I have a good fix on the station broadcast to receive SCA if it were present.