Direct/Rpeated??! lol

[ksjdklhsjkfdhsjkdfh]

Has anyone here ever ran into a department where the repeater turn off real fast, and you have to really know your stuff to know if it is repeated or not? I went for years thinking my department was direct... lol. Anyone else ever have this prob? lol I'm John by the way nice to meet everyone!

[lcsdguy]

With DCS it's hard to tell, but with PL's a repeater freq. will usually have an echoey sound to it, where as direct won't. Anyone agree with this?

[safetyobc]

How in the world do you remember your longin name? ksjdklhsjkfdhsjkdfh. Nice to meet you too btw

[KCChiefs9690]

With DCS it's hard to tell, but with PL's a repeater freq. will usually have an echoey sound to it, where as direct won't. Anyone agree with this?

I agree. If you listen to the input freq of a repeater system, or if someone is using talkaround, if they are pretty close to you the sound is clearer in my expirience than listening to a unit using the repeater the same distance away.

[Voyager]

Originally Posted by lcsdguy

With DCS it's hard to tell, but with PL's a repeater freq. will usually have an echoey sound to it, where as direct won't. Anyone agree with this?

The only time I've ever heard an 'echoey' sound is on a digital voice transmission where the transmitter (person) has another radio on in the backround or if the repeater has an audio delay duilt in.

The only difference I can attribute to repeaters is that the repeated audio many times lacks the fidelity of a non-repeated transmission.

Joe M.

[Al42]

Originally Posted by lcsdguy

With DCS it's hard to tell, but with PL's a repeater freq. will usually have an echoey sound to it, where as direct won't. Anyone agree with this?

Only if the repeater audio path has something wrong with it. In fact, if the processing in the path is good enough, the repeater output can sound better than the input.

[Voyager]

Originally Posted by Al42

Only if the repeater audio path has something wrong with it. In fact, if the processing in the path is good enough, the repeater output can sound better than the input.

That's a technical impossibility. The best repeater will sound EXACTLY like the input signal - not altering it in ANY way other than the transmitted frequency. You can alter the audio to emphasize highs or lows, but that does not make it better. It may sound better on some radios, but it will also sound worse on others depending on how the audio is set up in the radio. If it sounds better on a particular radio that is because the repeater is compensating for a shortcoming in the radio.

For example, if the audio circuit in a radio is tinny, adding bass on the repeater may make the audio sound more realistic on that radio, but it will sound bassy on a radio that has a properly designed audio circuit.

The best repeater will repeat EXACTLY what is transmitted on the input and will not alter the audio at all. It will sound just like a simplex signal. The best processing is NO processing. That's the only way to retain the full charactoristics of the original signal.

Joe M.

[loumaag]

Originally Posted by ksjdklhsjkfdhsjkdfh

Has anyone here ever ran into a department where the repeater turn off real fast, and you have to really know your stuff to know if it is repeated or not? I went for years thinking my department was direct... lol. Anyone else ever have this prob? lol I'm John by the way nice to meet everyone!

Welcome John.

To return to the topic at hand, in answer to your question, yes. Lots of times; however, it is is often easy to tell (analog signals that is) when you are hearing repeated as opposed to simplex operations because if you are stationary, the signal retains the same signal strengh on repeated operations, but simplex will be variable. As a matter of fact, a ham repeater I used to maintain was purposely set for about .25 sec drop so that it allowed for smoother cross-band operation (not the repeater obviously, but users cross-banding into it.)

[kb2vxa]

Hi Lou and readers,

"As a matter of fact, a ham repeater I used to maintain was purposely set for about .25 sec drop so that it allowed for smoother cross-band operation (not the repeater obviously, but users cross-banding into it.)"

I'll echo that comment, (;->) but not only linked systems have that typical quarter second delay. Digital audio delay (part of the processing chain) is used to kill squelch tails in single band repeaters. It came in handy once, I had a mean echo while running net control one Halloween.


Icsdguy:
"With DCS it's hard to tell, but with PL's a repeater freq. will usually have an echoey sound to it, where as direct won't. Anyone agree with this?


Al42:
"Only if the repeater audio path has something wrong with it. In fact, if the processing in the path is good enough, the repeater output can sound better than the input."

Louder may not be better, check this out.

Voyager:
"That's a technical impossibility."

That depends on what one considers "better". An extreme example is CBers who aren't happy unless the audio overmodulates and sounds like it's going through a cheese grater. A little "punch" is desirable because it increases range by giving a better S/N ratio at the receiver but sounds crappy if carried to the extreme.

"The best repeater will sound EXACTLY like the input signal - not altering it in ANY way other than the transmitted frequency. You can alter the audio to emphasize highs or lows, but that does not make it better. It may sound better on some radios, but it will also sound worse on others depending on how the audio is set up in the radio."

Agreed absolutely.

" >>> If it sounds better on a particular radio that is because the repeater is compensating for a shortcoming in the radio. <<< "
(Emphasis mine.)

Just to clarify, that's in the case of the transmitter the repeater is hearing, assuming we're talking about the same receiver listening to the repeater.

"For example, if the audio circuit in a radio is tinny, adding bass on the repeater may make the audio sound more realistic on that radio, but it will sound bassy on a radio that has a properly designed audio circuit."

I agree. I have heard what you're talking about, things sound worse overall, the repeater sounds bassy or muddy and lacks definition like you said. That was fairly common in the early days when hams BUILT repeaters and still had to figure out when to use pre-emph and when not to.

"The best repeater will repeat EXACTLY what is transmitted on the input and will not alter the audio at all. It will sound just like a simplex signal. The best processing is NO processing. That's the only way to retain the full charactoristics of the original signal."

I tend to agree with that but peak limiting at least is needed to mash down somebody's hot audio, Alinco 2M rigs are known for that. (They tend to have weak PL too and the repeater drops out.) If a repeater doesn't employ at least minimal processing it can be too hot at times and interfere with adjacent ones while at other times the audio can barely be heard. We had our share of problems with the club 2M repeater after getting complaints from up north. The new controller was too hot out of the box and caused some problems before the techs had time to tweak it properly. Yes, it was all in the processing.

Overall I agree that a repeater should sound like it's not adding anything to the audio, technically it's known as color. Good audio processing sounds natural or in other words it sounds like no processing at all. I remember a classical music station in New York that used barely enough limiting to prevent overmodulation and it was the best sounding station on the band. Frankly I hate the rock stations that hammer down on it, grates on the nerves. When it comes to repeaters and I'll include FM simplex, the only processing needed is just enough to keep it legal and not cause interference, we're not working DX here.

Back to the original post, most public service repeaters have very short tails (hang time) and some have none at all. I have come across one or two ham repeaters like that so I can see how it would confuse someone unfamiliar with what he's listening to. Frankly I was too for a moment the first time I encountered one. I suppose like digital delay it eliminates the squelch tail, you can't tell the repeater's from your own.

[Al42]

Originally Posted by Voyager

That's a technical impossibility. The best repeater will sound EXACTLY like the input signal - not altering it in ANY way other than the transmitted frequency.

So if the signal on the input is a bit noisy the output signal shouldn't be cleaned up?

There are many characteristics of the input signal that should be, and are, modified in repeater controllers, and have been for years. Remind me to never buy a repeater copntroller you design.

(BTW, how many commercial repeater system designs have you been responsible for over the years?)

[Voyager]

Originally Posted by kb2vxa

Voyager:
"That's a technical impossibility."

That depends on what one considers "better". An extreme example is CBers who aren't happy unless the audio overmodulates and sounds like it's going through a cheese grater. A little "punch" is desirable because it increases range by giving a better S/N ratio at the receiver but sounds crappy if carried to the extreme.

When I say 'better', I mean 'it sounds like the ORIGINAL signal. Anything that changes the signal may sound better to some, but it will sound worse to others.

" >>> If it sounds better on a particular radio that is because the repeater is compensating for a shortcoming in the radio. <<< "
(Emphasis mine.)

Just to clarify, that's in the case of the transmitter the repeater is hearing, assuming we're talking about the same receiver listening to the repeater.

Well, the repeater can be altered to compensate for a poor audio circuit of a TRANSMITTER on the input, OR a poor audio circuit in a RECEIVER listening to the output. Either could make the audio sound tinny or bassy.

But the point is that ANY alterations you make to the signal will adversely affect how close it sounds to the original signal when using properly designed audio circuitry. A repeater that adds base can compensate for a tinny TX or a tinny RX, but will make a bassy TX or RX sound worse.

The overall effect is that ON THE WHOLE it will make radios sound worse unless they have the same shortcoming as was compensated for.

"For example, if the audio circuit in a radio is tinny, adding bass on the repeater may make the audio sound more realistic on that radio, but it will sound bassy on a radio that has a properly designed audio circuit."

I agree. I have heard what you're talking about, things sound worse overall, the repeater sounds bassy or muddy and lacks definition like you said. That was fairly common in the early days when hams BUILT repeaters and still had to figure out when to use pre-emph and when not to.

Actually, many ham-built repeaters sound much BETTER than commercial units as long as the person knows wha they are doing. The best audio usually comes from what are called 'flat audio' repeater systems. That's one where the input and output voltages match for any given audio frequency. What goes in is what comes out. Typically, the audio is NOT de-emphasized on the RX and is not pre-emphasized on the TX, and de-emphasized audio is fed straight into the transmitter modulator (with necessary LPF and limiting, of course).

Most repeater designs de-emph the RX audio and then TRY to MATCH the pre-emph to the de-emph exactly, which is darn hard to do. It's this processing that usually creates a bias toward the low end or the high end of the audio spectrum, and makes the audio sound tinny or bassy. By not de-emph'ing the audio, you don't have to worry about trying to UNDO the de-emph.

Unfortunately, commercial repeaters also add high pass filters to eliminate the spectrum below 300 Hz. This takes away some of the bass components of most voices. That's another step hams can bypass. I won't debate whether or not that SHOULD be done, but without it the audio does retain much closer fidelity compared to the input signal - especially if the user transmit radio does not have high pass filters (most of the older ham radios don't).

"The best repeater will repeat EXACTLY what is transmitted on the input and will not alter the audio at all. It will sound just like a simplex signal. The best processing is NO processing. That's the only way to retain the full charactoristics of the original signal."

I tend to agree with that but peak limiting at least is needed to mash down somebody's hot audio, Alinco 2M rigs are known for that. (They tend to have weak PL too and the repeater drops out.) If a repeater doesn't employ at least minimal processing it can be too hot at times and interfere with adjacent ones while at other times the audio can barely be heard. We had our share of problems with the club 2M repeater after getting complaints from up north. The new controller was too hot out of the box and caused some problems before the techs had time to tweak it properly. Yes, it was all in the processing.

Absolutely. You do have to live with your neighbors, and a LPF/Limiter should be part of every transmitter to eliminate interference with adjacent channels. Without these, there are many signals that can extend 30 kHz or more away from the carrier. ACC controllers are somewhat famous for doing that when the charge pump caps go bad and you have a 15 kHz signal on your audio line. Without the proper filtering, the TX will pass that and you will most certainly interfere with your neighbors.

Overall I agree that a repeater should sound like it's not adding anything to the audio, technically it's known as color. Good audio processing sounds natural or in other words it sounds like no processing at all.

The best processing is no processing. (beyond what is absolutely necessary). Again, with repeaters this is usually issues involveing trying to match the pre-emphasis to the de-emphasis.

As a test, I built a repeater with discriminator audio fed directly into the modulator. While I would not leave something like that on the air, I could tell ABSOLUTELY NO DIFFERENCE between the inptu signal and the output signal whatsoever. It sounded perfect.

Back to the original post, most public service repeaters have very short tails (hang time) and some have none at all. I have come across one or two ham repeaters like that so I can see how it would confuse someone unfamiliar with what he's listening to. Frankly I was too for a moment the first time I encountered one. I suppose like digital delay it eliminates the squelch tail, you can't tell the repeater's from your own.

On commercial repeaters, even if they have no tail, they usually have the turn off code or reverse burst after the carrier drops, and that is noticable. Yes, audio delays with squelch tail elimination and a short tail can sound very much like simplex as far as the signal goes. That's where you look at the signal strength. Usually if you are getting an S-meter reading and the signal is noisy, that's a sign of a repeater, too. Most perople familiar with repeaters can tell one on the air.

Joe M.

[Voyager]

Originally Posted by Al42

So if the signal on the input is a bit noisy the output signal shouldn't be cleaned up?

If a signal is noisy, how would YOU clean it up? I wasn't talking about noisy signals before - I was talking about audio spectral purity compared to the input signal, but I GOTTA hear how you would clean up a noisy signal.

There are many characteristics of the input signal that should be, and are, modified in repeater controllers, and have been for years. Remind me to never buy a repeater copntroller you design.

Well, I won't tell you which ones I've had a hand in the design of. I'll just say that I've had a hand in some of the most popular ones on the market today. BTW, they are some of the FLATTEST, too. They aren't biased toward the low end or the high end. The audio is virtually unchanged throughout the controller from input to output.

So, what 'characteristics of the input signal' should be modified?

(BTW, how many commercial repeater system designs have you been responsible for over the years?)

Hundreds. (and indirectly, thousands).

Some of those I own don't even meet my current design goals. Sooner or later, they are being rebuilt.

BTW, if you want an example of a POS controller, but a CAT controller. I didn't have anything to do with that one, although I own one and it's the worst sounding POS I've ever owned. That's the opinion of many of the leading repeater builders, too. It's also hung up a repeater on the air with no response to control (input, control RX, or phone line) due to a firmware bug. While that bug was fixed, it didn't help my opinion of CAT at all.

So, if you want to make sure I didn't have anything to do with it, but one of those.

Joe M.

[Al42]

Originally Posted by Voyager

If a signal is noisy, how would YOU clean it up?

A DSP could do a pretty good job.

I wasn't talking about noisy signals before - I was talking about audio spectral purity compared to the input signal

Okay, granted, if the input signal is perfect, there's nothing you can do to make it better.

Not that, in 41 years, I've heard a signal that couldn't be improved.

So, what 'characteristics of the input signal' should be modified?

That's different for each individual system.

[Voyager]

Originally Posted by Al42

That's different for each individual system.

Speaking in general terms. Or list each for a few sample systems.

I think the repeater should only repeat the signal without any changes at all. If the user has a bassy radio, the person listening to the repeater should hear bassy audio (and encourage the USER to fix his radio, as opposed to encouraging the repeater owner to change the audio of the repeater to compensate for it. Because the minute you add more highs to compensate for that bassy radio, someone will come on with a radio with tinny audio which the repeater will have made even more tinny, or someone with good audio who the repeater made tinny.

Joe M.