SCA channels

IBOC, HD Radio, FM eXtra, DRM, Importers, Exporters, Exgines...digital radio spoken here!
Post Reply
kc8gpd
Posts: 192
Joined: Sun Aug 02, 2009 10:32 am
Location: Arvada, Co 80004
Contact:

SCA channels

Post by kc8gpd » Tue Dec 23, 2014 5:38 pm

with the advent of FM IBOC what is going on with SCA channels these days?

have stations dropped SCA entirely or have they gone digital?

the other post regarding analog pre-emphasis on HD got me thinking about this topic.
kc8gpd

"The scientists of today think deeply instead of clearly. One must be sane to think clearly, but one can think deeply and be quite insane."

User avatar
Deep Thought
Posts: 3124
Joined: Thu Mar 20, 2008 9:23 am
Location: La Grange, IL
Contact:

Re: SCA channels

Post by Deep Thought » Wed Dec 24, 2014 8:52 am

Hybrid FM IBOC mode is compatible with normal subcarrier operations.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

User avatar
BroadcastDoc
Site Admin
Posts: 2723
Joined: Tue Nov 13, 2007 3:34 pm
Location: Milwaukee, WI
Contact:

Re: SCA channels

Post by BroadcastDoc » Wed Dec 24, 2014 5:04 pm

I'm actually leasing out honest-to-god analog audio programming on mine! (And I'm running IBOC)
Christopher "Doc" Tarr CSRE, DRB, AMD, CBNE
Help support the Virtual Engineer, use our 1&1 Affiliate link if you need good, cheap hosting.
Virtual Engineer. The Broadcast Engineering discussion forum

kcbooboo
Posts: 434
Joined: Sat Dec 10, 2011 4:53 pm
Location: East of the Mississippi

Re: SCA channels

Post by kcbooboo » Thu Dec 25, 2014 7:38 am

While the digital carriers are primarily in the 100-200 kHz (offset from the carrier) range, there can be some interference if you're using SCAs of 67 kHz or higher AND additional HD channels. The additional HD channels start encroaching on the lower end of the digital carrier range and can be a problem with the higher frequency SCAs. You can lower the quality or bit rate of the HD2 etc channels to help this situation a bit. It's a tradeoff, but the two systems can operate successfully together. RDS is a sort of SCA and it too runs just fine along with HD.

If the SCA injection level and/or deviation level is too high, that can cause problems with HD2 and higher, but if it's too low, some receivers may have a problem decoding it.

Bob M.

User avatar
BroadcastDoc
Site Admin
Posts: 2723
Joined: Tue Nov 13, 2007 3:34 pm
Location: Milwaukee, WI
Contact:

Re: SCA channels

Post by BroadcastDoc » Thu Dec 25, 2014 3:14 pm

To clarify a bit: In standard (MP1) mode HD and HD2-3-4 channels use the same 96k data partition and won't interfere with SCA's or vice-versa - the carriers for the whole 96k partition are active no matter how many services you're using.

If you move into "extended hybrid" (MP3) mode, that adds a small partition closer in to the analog carrier. In this mode, you can encroach on the extended digital partitions if your baseband modulation exceeds 110%, though it doesn't have much of an effect on narrowband audio SCA's at 67kHz. I did try data at 67kHz with extended hybrid many years ago, and it didn't seem to affect anything, but it was far from a scientific test!

In MP3 mode the second partition is not added to the 96k primary partition - you're essentially getting another, separate 16k partition. You can put ancillary data in there, or throw in an additional audio channel (or two). Again though, it doesn't matter how much of that data is used - once the carriers are on, they're on. In theory if you exceed 110% analog baseband you could cause errors on that one 16k partition, but not the main, 96k one.

Hopefully that makes sense!
Christopher "Doc" Tarr CSRE, DRB, AMD, CBNE
Help support the Virtual Engineer, use our 1&1 Affiliate link if you need good, cheap hosting.
Virtual Engineer. The Broadcast Engineering discussion forum

kc8gpd
Posts: 192
Joined: Sun Aug 02, 2009 10:32 am
Location: Arvada, Co 80004
Contact:

Re: SCA channels

Post by kc8gpd » Thu Dec 25, 2014 3:44 pm

Doc in your opinion what would a typical SCA (or HD Sub Ch) lease cost on average for a metro area like Denver.

i have been trying to think of some legal backdoor ways of putting a FM signal on the air here in Denver without having to outright spend millions (which i don't have) on a existing station or new construction.

i was thinking of leasing an SCA or HD Sub and feeding a translator (or network of part 15 AM's) with it.

i have been trying to think of some unique programming idea's that are not heard around here. do something really community oriented with live DJ's.

the oldies and old time radio formats are already here.

maybe an outlet for alternative (unsigned artists) on FM.

my friend runs a neutral loaded carrier current am up in Casper, Wyoming covering about 4 miles over the power lines and the response to his alternative format has been great. if it can work in a small out of the way mid western town like there i bet it would go over great in a major metro area like Denver.

any way it has just been an idea on my mind for a number of years now.
kc8gpd

"The scientists of today think deeply instead of clearly. One must be sane to think clearly, but one can think deeply and be quite insane."

User avatar
BroadcastDoc
Site Admin
Posts: 2723
Joined: Tue Nov 13, 2007 3:34 pm
Location: Milwaukee, WI
Contact:

Re: SCA channels

Post by BroadcastDoc » Thu Dec 25, 2014 7:01 pm

That's a tough one - it's one of those "whatever two people agree to" sorts of things.

Based on what some groups are paying in smaller markets, I'd say somewhere in the neighborhood of $2500-$4000/mo for an SCA lease in Denver on a full-market signal. HD sub channel would likely start around $5K in your area.

Of course, then you have to get SCA radios in the hands of the public in order to be heard. At that point, you're better off doing internet broadcasting - you'll have a bigger audience (same could probably be said for HD sub channels as well).
Christopher "Doc" Tarr CSRE, DRB, AMD, CBNE
Help support the Virtual Engineer, use our 1&1 Affiliate link if you need good, cheap hosting.
Virtual Engineer. The Broadcast Engineering discussion forum

w9wi
Posts: 807
Joined: Tue Feb 05, 2008 11:40 am
Location: Pleasant View, Tennessee
Contact:

Re: SCA channels

Post by w9wi » Thu Dec 25, 2014 7:04 pm

kc8gpd wrote: i was thinking of leasing an SCA or HD Sub and feeding a translator (or network of part 15 AM's) with it.
Are you sure the FCC will let you carry a SCA on a translator? (nothing explicitly says you can run a HD sub either, but they obviously allow it. But I don't know of anyone carrying an SCA & would be careful about spending too much $$ without getting an answer.)
--
Doug Smith W9WI
Pleasant View, TN EM66

User avatar
BroadcastDoc
Site Admin
Posts: 2723
Joined: Tue Nov 13, 2007 3:34 pm
Location: Milwaukee, WI
Contact:

Re: SCA channels

Post by BroadcastDoc » Thu Dec 25, 2014 8:03 pm

Well, that and there's the whole "getting a translator" thing in Denver. At the prices they're going for, no mere mortal can afford one - they're selling for the same kind of money as full signals.
Christopher "Doc" Tarr CSRE, DRB, AMD, CBNE
Help support the Virtual Engineer, use our 1&1 Affiliate link if you need good, cheap hosting.
Virtual Engineer. The Broadcast Engineering discussion forum

User avatar
Deep Thought
Posts: 3124
Joined: Thu Mar 20, 2008 9:23 am
Location: La Grange, IL
Contact:

Re: SCA channels

Post by Deep Thought » Fri Dec 26, 2014 4:49 pm

SCA on a translator is a non-starter. There is no provision for this anywhere in the Rules. HDx on a translator is the method of choice for some of the big broadcast groups to get around the ownership caps and hog available frequencies which would better serve the audiences you seek to reach, but that ship has sailed and is covered by a rather loose reading of the Rules which allowz a "main" broadcast audio program (which all HDx subchannels are considered) to be repeated on a translator. SCA is by definition not a "broadcast" signal.

Getting back to a comment above, the deviation (in KHz) of an FM carrier is not the same as the baseband bandwidth, which is why FM IBOC can coexist with analog subcarriers. As Doc mentioned, in some IBOC modes you have to watch the analog carrier deviation to keep the two out of each other but the subcarrier frequencies have little to do with that.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

awsherrill
Posts: 234
Joined: Fri Nov 16, 2007 10:30 pm
Location: Raleigh NC

Re: SCA channels

Post by awsherrill » Wed Dec 31, 2014 4:54 pm

We are getting ready to stick HD on our big dog FM here. The possibility of HD and analog SCA interference is of real concern to me, as we have a tenant at 92 kHz.

If we stay with MP1 mode, from what I'm hearing there should be no impact on the 92 kHz subcarrier...but if we go extended hybrid, watch out. Since the object of the game is driving translators (sorry Deep), extended mode is a distinct possibility.

I have a question that maybe Doc or somebody else can answer. Are there minimum bandwidth requirements for the various HD streams? I seem to recall HD1 had to be at least 48 kbps, and the HD2-etc. were typically 16 kbps or higher, but is there a minimum for those?

User avatar
BroadcastDoc
Site Admin
Posts: 2723
Joined: Tue Nov 13, 2007 3:34 pm
Location: Milwaukee, WI
Contact:

Re: SCA channels

Post by BroadcastDoc » Wed Dec 31, 2014 6:00 pm

There isn't a minimum for the secondary channels, though the audio isn't very good at all below 16k. I'd go ahead and try the extended mode with the subcarrier - as DT said, it's not really the location of the subcarrier that matters - deviation is deviation. The issue will be injection level. Your baseband will need to be under 110% with SCA's for extended hybrid and SCA's to behave.

Now, there is a loophole if you're feeding translators with HD sub channels. You are not required to actually feed the translator with the OTA HD signal - you can do a direct feed. However if your HD sub is off, the translator must be off as well. So, you could feed the HD sub at a lower bitrate and still feed the translator directly. That may preclude having to go to MP3 mode.
Christopher "Doc" Tarr CSRE, DRB, AMD, CBNE
Help support the Virtual Engineer, use our 1&1 Affiliate link if you need good, cheap hosting.
Virtual Engineer. The Broadcast Engineering discussion forum

kc8gpd
Posts: 192
Joined: Sun Aug 02, 2009 10:32 am
Location: Arvada, Co 80004
Contact:

Re: SCA channels

Post by kc8gpd » Wed Dec 31, 2014 6:26 pm

BroadcastDoc wrote:That's a tough one - it's one of those "whatever two people agree to" sorts of things.

Based on what some groups are paying in smaller markets, I'd say somewhere in the neighborhood of $2500-$4000/mo for an SCA lease in Denver on a full-market signal. HD sub channel would likely start around $5K in your area.

Of course, then you have to get SCA radios in the hands of the public in order to be heard. At that point, you're better off doing internet broadcasting - you'll have a bigger audience (same could probably be said for HD sub channels as well).

well that revelation just took the wind out of my sales for the idea.

i would need to get sponsorship ahead of time which i know is good luck on that.

guess i will just have to stick with my hobby radio.
kc8gpd

"The scientists of today think deeply instead of clearly. One must be sane to think clearly, but one can think deeply and be quite insane."

User avatar
BroadcastDoc
Site Admin
Posts: 2723
Joined: Tue Nov 13, 2007 3:34 pm
Location: Milwaukee, WI
Contact:

Re: SCA channels

Post by BroadcastDoc » Wed Dec 31, 2014 7:57 pm

Yeah, you still very much have to pay to play in a large market. There are no shortcuts, unfortunately.
Christopher "Doc" Tarr CSRE, DRB, AMD, CBNE
Help support the Virtual Engineer, use our 1&1 Affiliate link if you need good, cheap hosting.
Virtual Engineer. The Broadcast Engineering discussion forum

Radio Ranger
Posts: 74
Joined: Sun May 02, 2010 7:44 am

FM Extra Receivers

Post by Radio Ranger » Tue Jan 20, 2015 11:27 am

You might want to contact Hal Schardin, the CE for Minnesota State Services for the Blind. He's using FM Extra on Minnesota Public Radio stations all over Minnesota to transport Radio Talking Book. I know that he purchased a large number of receivers from someone for this project a few years back.

Hal's telephone number is (651) 642-0848

Steve Brown
Radio Rangers
Minneapolis

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest