A.M. Broadcasts on 450 MHz

[SCPD]

I know this has been covered in previous posts, in fact, I looked at a thread going back to 2007, so I know that lots of people have heard A.M. stations such as KABC, KFI, KFWB and KNX broadcasting in the 450 MHz band. And these are actual program broadcasts, not a mobile unit talking to a base, etc.

But what I couldn't find in these posts is the reason WHY you can listen to these radio programs over your scanner as if you were listening to a simple transistor radio.

Is it because these stations are transmitting their programs to Mount Wilson over UHF for rebroadcasting through their A.M. transmitters at anything from 5,000 to 50,000 watts? Or is it simply that they simulcast their programs over the frequencies that their mobile units use to check in, file reports, etc?

Believe me, it's great to pop on KNX in the 450 MHz band when there's an earthquake. It makes it so much easier to then check in on the public service frequencies. I don't have to fool around with two radios. But still, I'd like to know why KNX finds it necessary to simulcast their programming on the 450 MHz band.

Dave
KA6TJF

 

[RadioDaze]

Or is it simply that they simulcast their programs over the frequencies that their mobile units use to check in, file reports, etc?

That's always been my understanding. There's camera crews and reporters out in the field who need to hear it. But maybe someone knows more than I do.

I used to listen to KFI's feed, although I can't find it now, and it ran without a delay. So if someone called in to a talk show and said something that should be censored, I'd hear the raw version of it. Pretty funny at times.

 

[KMA367]

The explanation I heard years ago, and it seems to make sense, is that it's for the benefit of the reporters in the field, specifically when they have a live shot coming up. By listening to the 450 multicast, they can hear their cue from the "anchor" directly and with no time delay when they're preparing to transmit their live report. And they need only their UHF radio and don't have to be monitoring the AM broadcast separately.

If that's what you're asking.

I know this has been covered in previous posts, in fact, I looked at a thread going back to 2007, so I know that lots of people have heard A.M. stations such as KABC, KFI, KFWB and KNX broadcasting in the 450 MHz band. And these are actual program broadcasts, not a mobile unit talking to a base, etc.

But what I couldn't find in these posts is the reason WHY you can listen to these radio programs over your scanner as if you were listening to a simple transistor radio.

Is it because these stations are transmitting their programs to Mount Wilson over UHF for rebroadcasting through their A.M. transmitters at anything from 5,000 to 50,000 watts? Or is it simply that they simulcast their programs over the frequencies that their mobile units use to check in, file reports, etc?

Believe me, it's great to pop on KNX in the 450 MHz band when there's an earthquake. It makes it so much easier to then check in on the public service frequencies. I don't have to fool around with two radios. But still, I'd like to know why KNX finds it necessary to simulcast their programming on the 450 MHz band.

Dave
KA6TJF

 

[gmclam]

Ifb

When you hear "program audio" being repeated on one of these frequencies, it is usually what the broadcaster calls an IFB channel. IFB stands for Interruptable FoldBack. Foldback should have been called feedback, but that already had a different meaning, and didn't sound like something good. Foldback is used so that talent can hear all or part of the program.

The interruptable part in this case is so that a producer or director can interrupt the program audio and give direct cues to the talent. Most of the time these are closed circuit signals in a studio, but when the talent is not in a studio they might use a radio signal (or cell phone).

I have as many of these frequencies as I know of (for California) programmed into my scanners. I end up locking them out during times of live news, but they can be interesting to hear other times or during emergencies.

 

[WA1ATA]

If you listen closely to those 450MHz channels, you may sometimes hear some studio-TO-remote messages. I've heard the same in the 160MHz range.

When the studio isn't talking to the remote person, they just leave the current programming going out over the link. Since these remote links are active for many hours before and after the remote broadcasts, it will seem like they are just a simulcast of the broadcast.

 

[RadioDaze]

The interruptable part in this case is so that a producer or director can interrupt the program audio and give direct cues to the talent.

I have heard that many times, such as "Get ready, you're on in five" or something similar. Or "Can you head up to Southgate for some shots of that barricade thing? We can use them at noon."

 

[SCPD]

That's always been my understanding. There's camera crews and reporters out in the field who need to hear it.../QUOTE]

The explanation I heard years ago, and it seems to make sense, is that it's for the benefit of the reporters in the field, specifically when they have a live shot coming up...

When you hear "program audio" being repeated on one of these frequencies, it is usually what the broadcaster calls an IFB channel. IFB stands for Interruptable FoldBack... Foldback is used so that talent can hear all or part of the program...

Thanks all. This makes sense, since I'm not hearing simulcasts of EVERY L.A. radio station, just those stations that have active news operations and reporters in the field. Why go to all the trouble to listen to two radios when you can hear everything, including cues, through your VHF/UHF channel?

What about TV stations? I used to hear channels 2, 4 and 9 broadcasting a feed of their program audio on 450 MHz, but I can't seem to pick those up anymore.

Dave
KA6TJF

 

[K6PCW]

L.A. area media frequencies

Los Angeles Area Media Frequencies

(Note that the webpage says it was last updated in 2006.)

Also check out this massive frequency resource...
http://www.n6lhv.net/valleyscan.html#newsmedia

 

[gmclam]

Don't forget the remote link frequencies

What about TV stations? I used to hear channels 2, 4 and 9 broadcasting a feed of their program audio on 450 MHz, but I can't seem to pick those up anymore.

Although I live in the Sacramento area, I am close enough to pick up media traffic from San Francisco and travel to the L.A. area often. Therefore I have all media channels listed on RR programmed into my scanners; this includes AM radio, FM radio and TV. Some are UHF and some are VHF.

Here in Sacramento we have one TV station that is very active on two 450MHz channels; one is IFB and the other is their com channel to the field (mostly their helicopter). While at least two other stations have UHF frequencies, they are not used much. They don't have aircraft in use and mostly use cell phones to communicate with their reporters on the ground.

Last time I was in L.A. (a month ago) I picked up similiar traffic. Although I must say that I am often paying more attention to CHP and fire traffic than broadcast media - other than the traffic reports on remote broadcast link channels. These are frequencies, picked up by our scanners, used to get the reports from the reporter TO the stations.

 

[n5ims]

One other issue is that with the addition of "HD Radio", which is common on FM and getting more common on AM as well, is that there is a 6 to 8 second delay in the audio due to the additional signal processing. Since the design of "HD Radio" is to allow the radio to switch from the HD digital broadcast to the normal analog broadcast when the signal drops to a point that the HD signal isn't of sufficient strength to reliably decode it, the stations add a similar delay to their analog signal as well. This isn't noticed normally, but can easily be seen while listening to a live broadcast while in the stands watching the game you're listening to.

This delay prevents the normal station's broadcast from being used as a signal to the remote reporter to start talking. [Mary at the studio ] "And now we go to Bob who is at the scene" <silence for the delayed broadcast to make it to the reporter's earpiece> [Bob on the scene] "This is Bob Roberts on the scene ...". With the undelayed broadcast sent out on the IFB channel, it's much more professional.

 

[n5ims]

What about TV stations? I used to hear channels 2, 4 and 9 broadcasting a feed of their program audio on 450 MHz, but I can't seem to pick those up anymore.

WIth the migration of HD television, it became important (for ratings and bragging rights) to have not only the studio broadcast originate in HD, but also the remote units. This required the replacement of not only the cameras in the field, but also their auxiliary equipment such as remote switchers and microwave links. For various reasons, when the microwave links were upgraded, many of them went from being one-way links (remote truck to the studio) to being two way links. This allows the station to send the signal to the remote truck to control the "red light" on their camera alerting the reporter that they're live. It also provides the IFB signal as well as additional links to allow communication between the studio director and a remote switcher operator. The new two-way links also allow for a nearly automatic setup of the remote antenna (it simply locks on the tower's microwave return signal now instead of being pointed manually by the remote engineer) and allows for both audio and textual que information to be sent back to the field reporter and their crew. Updates to the story collected at the station can be sent to the remote truck where it can be printed out and given to the reporter during while the camera is pointed away from them so they can do a better job of field reporting live.

 

[cousinkix1953]

Last time I heard, the KGO feed on 450.0125 mhz to the transmitter site under the Dumbarton Bridge was encrypted full time. Not sure why. As far as I know, the foul language heard on 450 mhz is just as illegal as hearing it on the AM station itself.

Those UHF links would be handy around here. I hear only those AM stations which stream their programs on the internet!

We get nothing but static on the AM dial most of the time. It isn't a ham radio operator or the neighbor's old power tools going 24/7 for six months. Some idiot is jamming 540-1700 khz and beyond. Don't report these criminals; because nobody cares. The FCC will put a Part 15 sticker on any piece of crap. which the electronics industry wants to sell in the stores. It's our fault if the stores don't want to sell quality merchandise. Screw the FCC's keystone kops...

 

[SCPD]

WIth the migration of HD television, it became important (for ratings and bragging rights) to have not only the studio broadcast originate in HD, but also the remote units...

I took my scanner outside today and, as a lark, decided to search 450-451 MHz. Guess what? I picked up audio from three different TV stations broadcasting programs. Can't say which stations, because I didn't want to listen for 30 minutes or more to try to figure it out, but I was definitely hearing TV audio. So I guess some L.A. stations are still running their simulcasts in Analog. My guess is the 450 MHz band is used for audio communications only between field units and their studios. Any actual broadcasting in HD is done through a microwave link. Again, I'm just guessing.

BTW, makes a HUGE difference taking my scanner out into an open area. I certainly wasn't picking up these TV stations at all indoors on my little rubber duck. Unfortunately, I can't erect an outside antenna, so I'm stuck.

Dave
KA6TJF

 

[gmclam]

I picked up audio from three different TV stations broadcasting programs. Can't say which stations, because I didn't want to listen for 30 minutes or more to try to figure it out

All you needed to do was note the frequency and CT/DC if any. Then look here in the RR DB and it is likely listed.

I guess some L.A. stations are still running their simulcasts in Analog.

LOL. I would not call these "simulcasts". They are merely feeding their program audio (IFB) to someone in the field.

My guess is the 450 MHz band is used for audio communications only between field units and their studios. Any actual broadcasting in HD is done through a microwave link.

Yes, or fiber/etc.

Radio stations will use a UHF/VHF frequency for field reports, especially traffic.

BTW, makes a HUGE difference taking my scanner out into an open area. I certainly wasn't picking up these TV stations at all indoors on my little rubber duck. Unfortunately, I can't erect an outside antenna, so I'm stuck.

There could be options. If you want to concentrate on reception in a specific band, such as 450 MHz, you can use a "portable antenna" that is designed for that band. If all the signals are one general direction from you, perhaps that antenna can be directional. Of all factors, altitude is probably the most important. Get your antenna up high and perhaps near a window toward the signal source.