I still dont understand KKMJ's HD Signal, it seems to be the weakest signal out of all of the HD signals in Austin. I can recieve the analog signal fine, but when it goes to the call letters it says HD-U not even the KKMJ's Call sign. Could it be possible they are running on low power? I was able to raise my antenna a bit more, it helped out my reception out to San antonio better, but still I just cant understand KKMJ. I like their oldies HD-2 channel.
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KKMJ's HD Signal...
- Thread starter jras20
- Start date
jras20 said:I still dont understand KKMJ's HD Signal, it seems to be the weakest signal out of all of the HD signals in Austin. I can recieve the analog signal fine, but when it goes to the call letters it says HD-U not even the KKMJ's Call sign. Could it be possible they are running on low power? I was able to raise my antenna a bit more, it helped out my reception out to San antonio better, but still I just cant understand KKMJ. I like their oldies HD-2 channel.
Have you called the station? Sounds like they have some other problem not related to signal strength.
R.F. Burns said:Have you called the station? Sounds like they have some other problem not related to signal strength.
I emailed they acted like nothing was wrong.
jras20 reported:
Nope. That's how it is supposed to work.
Poorly.
I emailed they acted like nothing was wrong.
Nope. That's how it is supposed to work.
Poorly.
jras20 said:I still dont understand KKMJ's HD Signal, it seems to be the weakest signal out of all of the HD signals in Austin. I can recieve the analog signal fine, but when it goes to the call letters it says HD-U not even the KKMJ's Call sign. Could it be possible they are running on low power? I was able to raise my antenna a bit more, it helped out my reception out to San antonio better, but still I just cant understand KKMJ. I like their oldies HD-2 channel.
I've experienced that here in Nashville: WPLN-FM and WNRQ are Class C stations on the same tower, but WPLN's HD is MUCH more reliable than WNRQ's. (good thing, as WPLN's programming is decent; WNRQ's isn't!)
In many (most?) cases a FM station's HD signal is generated by a separate transmitter and then combined with the analog. It seems some stations are using less-powerful transmitters for the HD. And that in some cases the combiner is more or less efficient. In a nutshell, two HD stations may have different digital powers even if their analog stations' power is identical.
M
Mike Walker
Guest
Stations are still learning about HD, but that's really no excuse. They need to get their s##t together. There's too much shoddy engineering...hd off with nobody noticing, distorted audio, etc. Of course the vast majority is still listening to the analog signal. BUT, this is the time when people are getting their first taste of HD. Plus the stations have spent such a large amount. I hate to go past the engineer, but I wonder sometimes if the most effective measure wouldn't be to talk to the General Manager, and if that didn't work, the owner or corporate office.
I worked for a guy more than 20 years ago who was anal about everything being "just so". I don't know how many cart labels I've re-typed because there was a smudge, or tapes I've re-dubbed because, with the fader at the marked level, the audio was 2db too hot (or "cold"). "TAPE SENSITIVITY VARIES BY THAT MUCH FROM BATCH TO BATCH", I would plead with him, to no avail. "There's only one way to do things...the right way. Not because I say so, but because it's RIGHT!" Ya' know what? That lesson stuck with me. If you're going to do something, do it right. Or don't bother. Going to do HD? DO IT RIGHT! Make sure the text on the screen matches what listeners are hearing. Make sure your audio is pristine. NO AUDIBLE DISTORTION ON ANY SOURCE! Make sure stereo balance is PERFECT. NEVER ALLOW ANY DEAD AIR. I don't care if there are 30 listeners, or 30 million...if you're going to do it, DO IT RIGHT! I know what it's like to have "one more thing" dumped on you.
When I was doing mornings at an FM station a decade ago, and also had the responsibilities of operations manager/program director, production mgr., and bottle washer, they suddenly made the AM talk station my responsibility as well. They (the owners...who naturally had never worked in radio...are you listening Jeff and Margie?) would actually yell at me DURING MY SHOW to go fix the AM automation system. The FM, which covered maybe 20 counties was to be abandoned so I could fix the automation on the AM which barely covered three. Astounding. But that's what we sign up for when we do radio these days. Too many responsibilities falling on too few shoulders.
My advice? Just find a way to do it, and do it right, or move on and let someone else!
I worked for a guy more than 20 years ago who was anal about everything being "just so". I don't know how many cart labels I've re-typed because there was a smudge, or tapes I've re-dubbed because, with the fader at the marked level, the audio was 2db too hot (or "cold"). "TAPE SENSITIVITY VARIES BY THAT MUCH FROM BATCH TO BATCH", I would plead with him, to no avail. "There's only one way to do things...the right way. Not because I say so, but because it's RIGHT!" Ya' know what? That lesson stuck with me. If you're going to do something, do it right. Or don't bother. Going to do HD? DO IT RIGHT! Make sure the text on the screen matches what listeners are hearing. Make sure your audio is pristine. NO AUDIBLE DISTORTION ON ANY SOURCE! Make sure stereo balance is PERFECT. NEVER ALLOW ANY DEAD AIR. I don't care if there are 30 listeners, or 30 million...if you're going to do it, DO IT RIGHT! I know what it's like to have "one more thing" dumped on you.
When I was doing mornings at an FM station a decade ago, and also had the responsibilities of operations manager/program director, production mgr., and bottle washer, they suddenly made the AM talk station my responsibility as well. They (the owners...who naturally had never worked in radio...are you listening Jeff and Margie?) would actually yell at me DURING MY SHOW to go fix the AM automation system. The FM, which covered maybe 20 counties was to be abandoned so I could fix the automation on the AM which barely covered three. Astounding. But that's what we sign up for when we do radio these days. Too many responsibilities falling on too few shoulders.
My advice? Just find a way to do it, and do it right, or move on and let someone else!
Your right Mike, they need to get their stuff together. I dont have time to be calling them all the time. Most of the day yesterday their HD signal had no audio in both channels! I'd half to give KVET some credit though, they acually knew what they were talking about when their channel was out.
w9wi said:In many (most?) cases a FM station's HD signal is generated by a separate transmitter and then combined with the analog. It seems some stations are using less-powerful transmitters for the HD. And that in some cases the combiner is more or less efficient. In a nutshell, two HD stations may have different digital powers even if their analog stations' power is identical.
By definition, the HD signal is supposed to be 20db down from the analog signal, so yes, when separate transmitters are used, the HD version is a lot smaller than the analog transmitter. This is an attempt to lessen interference issues, because the HD signal actually is contained in the adjacent channels of the main signal. That is the problem in a nutshell. Running your HD signal any lower than 20 db below analog is not only a waste of electricity (since few people will be able to receive it) but it also does not conform with the standard, which is in the process of becoming a part of the FCC rules.
There are several methods which are used to convert to HD. The best and also most expensive is to replace the entire transmitter and usually the antenna too. Under this scenario, the new transmitters' exciter handles both the analog and digital signals. The digital signal is injected the required 20db down from the analog signal. From there, both signals are amplified to the desired power level and fed to the antenna which has sufficient bandwidth to pass the entire envelope. Still, the HD portion of the signal is 20 db lower than the analog signal. This is very straight-forward approach, but as I mentioned, is also the most expensive alternative.
Sometimes, an existing transmitter can handle the bandwidth requirement, and the antenna can too, so it is possible to just replace the analog exciter with a new one that handles both HD and analog signals. The Harris Flex-Star is a good example. This is a good cure for stations that have fairly recent vintage transmitting equipment.
Another common method is to use a separate, lower powered transmitter that provides the HD signal. Its output is combined with the analog transmitter's output at the feed line that goes to the antenna. They call this method High Level Combining. You’ll find that this is a fairly common approach. The down side is the combiner inserts a loss, so both the analog and HD transmitters need to have sufficient power to overcome that loss. If your existing analog transmitter is already maxed out to make your licensed effective radiated power, you have a problem. It is never a good idea to run any transmitter wide open. A little headroom is a very good thing, and you will be rewarded by increased component life and less electronic failures.
A third approach uses a separate HD transmitter with an antenna that is interleaved with the analog antenna. This is called "Space Combining." It is probably the cheapest to do, but it seems to yield the worst results, unless you get very lucky. There are a lot of variables in antenna design. Combining signals this way approaches the realm of a "black art." It can be done, but the first time you have an ice storm (even with radomes protecting the antennas) all bets are off. Stations that I know of who have done this report very strange results, especially close in to the antenna.
Back to the original point, the HD signal is always lower level than the analog signal. The theory is that digital devices do not require a high signal to noise ratio to work properly. That is true, but eventually, there is a point of diminishing returns, even for digital signals. If the HD signal was at or near the power level of the analog signal, it would work great, but the interference generated would be intolerable. Therein lies the problem.
Chuck said:w9wi said:In many (most?) cases a FM station's HD signal is generated by a separate transmitter and then combined with the analog. It seems some stations are using less-powerful transmitters for the HD. And that in some cases the combiner is more or less efficient. In a nutshell, two HD stations may have different digital powers even if their analog stations' power is identical.
By definition, the HD signal is supposed to be 20db down from the analog signal, so yes, when separate transmitters are used, the HD version is a lot smaller than the analog transmitter. This is an attempt to lessen interference issues, because the HD signal actually is contained in the adjacent channels of the main signal. That is the problem in a nutshell. Running your HD signal any lower than 20 db below analog is not only a waste of electricity (since few people will be able to receive it) but it also does not conform with the standard, which is in the process of becoming a part of the FCC rules.
There are several methods which are used to convert to HD. The best and also most expensive is to replace the entire transmitter and usually the antenna too. Under this scenario, the new transmitters' exciter handles both the analog and digital signals. The digital signal is injected the required 20db down from the analog signal. From there, both signals are amplified to the desired power level and fed to the antenna which has sufficient bandwidth to pass the entire envelope. Still, the HD portion of the signal is 20 db lower than the analog signal. This is very straight-forward approach, but as I mentioned, is also the most expensive alternative.
Sometimes, an existing transmitter can handle the bandwidth requirement, and the antenna can too, so it is possible to just replace the analog exciter with a new one that handles both HD and analog signals. The Harris Flex-Star is a good example. This is a good cure for stations that have fairly recent vintage transmitting equipment.
Another common method is to use a separate, lower powered transmitter that provides the HD signal. Its output is combined with the analog transmitter's output at the feed line that goes to the antenna. They call this method High Level Combining. You’ll find that this is a fairly common approach. The down side is the combiner inserts a loss, so both the analog and HD transmitters need to have sufficient power to overcome that loss. If your existing analog transmitter is already maxed out to make your licensed effective radiated power, you have a problem. It is never a good idea to run any transmitter wide open. A little headroom is a very good thing, and you will be rewarded by increased component life and less electronic failures.
A third approach uses a separate HD transmitter with an antenna that is interleaved with the analog antenna. This is called "Space Combining." It is probably the cheapest to do, but it seems to yield the worst results, unless you get very lucky. There are a lot of variables in antenna design. Combining signals this way approaches the realm of a "black art." It can be done, but the first time you have an ice storm (even with radomes protecting the antennas) all bets are off. Stations that I know of who have done this report very strange results, especially close in to the antenna.
Back to the original point, the HD signal is always lower level than the analog signal. The theory is that digital devices do not require a high signal to noise ratio to work properly. That is true, but eventually, there is a point of diminishing returns, even for digital signals. If the HD signal was at or near the power level of the analog signal, it would work great, but the interference generated would be intolerable. Therein lies the problem.
Which is why alot of commentors have suggested a new band for the digital HD frequencies, and allow the analog portions to remain as they are... in fact the digital HD broadcasters could have competed directly with satelite on a per pay basis and no one would have any grief on the new band.
Allowing such a scheme as Ibiquity and the FCC have done, they hoped to convert everyone to the digital land when alot of people could care less about HD radio.
Radiopilot
Chuck said:By definition, the HD signal is supposed to be 20db down from the analog signal, so yes, when separate transmitters are used, the HD version is a lot smaller than the analog transmitter. This is an attempt to lessen interference issues, because the HD signal actually is contained in the adjacent channels of the main signal. That is the problem in a nutshell. Running your HD signal any lower than 20 db below analog is not only a waste of electricity (since few people will be able to receive it) but it also does not conform with the standard, which is in the process of becoming a part of the FCC rules.
Oh, I fully understand that the HD signal is supposed to be considerably lower in power than the analog.
The point I was trying to make is that it appears in some cases, the HD signal is more than 20dB down from the analog. Maybe because the digital transmitter isn't big enough to overcome combiner losses, or there isn't enough cooling or primary power in the transmitter building, or the combiner isn't working properly, or ???
w9wi said:The point I was trying to make is that it appears in some cases, the HD signal is more than 20dB down from the analog. Maybe because the digital transmitter isn't big enough to overcome combiner losses, or there isn't enough cooling or primary power in the transmitter building, or the combiner isn't working properly, or ???
I can't imagine that anyone would intentionally run a station at a lower power than they are authorized, except in an emergency. It certainly is not in keeping with the standard. I think you'd have to call it mighty poor engineering, if that is really the case. As Mike has pointed out, if something is worth doing at all, it is worth doing right (or at least, as best as you can).
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