HT750 emphasis, expansion, compression settings

boomer632 · Post by **boomer632** » Sat Jun 14, 2003 6:19 pm

My radio works on a conventional dispatch..no repeaters or trunked systems. What is the proper settings for these fields under the conventional personality in the advanced tab. Should I disable all of the selections? What do you guys have them set at?

In the scan list, which I have three of, what is proper setting for the signalling type?

We dont use any MDC or DTMF or quick Call through our dispatch.

RKG · Post by **RKG** » Sun Jun 15, 2003 7:11 pm

For 25 kHz channels, use pre-emphasis and de-emphasis on.

For 12.5 kHz channels, you have to experiment with compression and expansion; Motorola intended them to be used to compensate for the narrow bandwidth, but a lot of folks believe the radios sound better with them off.

The most reliable (in terms of falsing) unmute/mute combination is "AND" "OR". This means that the radio will not unmute until it had detected both valid freq and valid tone, and that it will mute if it loses detection of either. According to Motorola, this combination suffers a bit in terms of range, but that has not be our experience.

kmoose · Post by **kmoose** » Tue Jun 17, 2003 6:41 am

Speaking of compression/expansion, I am wondering something. Will the Motorola radios set up to use compression/expansion be able to distinguish between receive signals that are NOT compressed? In other words, if I have a Motorola handheld that is set up to use exapnsion and I it receives a signal that is NOT compressed, will it still try to expand it, and cause problems?

Post by **wavetar** » Tue Jun 17, 2003 9:16 am

kmoose wrote: In other words, if I have a Motorola handheld that is set up to use exapnsion and I it receives a signal that is NOT compressed, will it still try to expand it, and cause problems?

Yes! That's a big reason why this series of radio can sound like crap when mixed into a fleet full of different models, and not programmed correctly.
In 95% of situations, I have found the best settings are to leave pre & de-emphasis enabled, and expansion/compression disabled.

Todd

kmoose · Post by **kmoose** » Tue Jun 17, 2003 1:05 pm

Thanks, wave. We often are contracted to do construction work, and have to have communications between our aircraft, and our Service Van, to the guys on the ground that we are contracting with. I was wondering how much I am going to need to know about their programming, as I program ours. That is one of the first things that I keyed in on, expansion and compression. From now on, I will try to get a copy of one of their codeplugs, before I set up our radios.

kmoose · Post by **kmoose** » Wed Jul 16, 2003 6:07 am

As it turns out, in this case, the problem was not with companding.......it was that the prime contractor's UHF repeater was programmed for Narrow Band operation, and our UHF handheld, in the helicopter, is a wideband radio. This created deviation issues. No one bothered to tell us, when we sent the aircraft to the job, that the channel they were using was narrow band. We found a guy up in Fairbanks that was able to adjust the deviation on the B/K handheld in the helicopter down to work on a narrow band channel. It gets even better, though. We had a customer of ours call the other day, and say that they had a helicopter workingon a power line job up in Alaska, and was having UHF FM problems. Same symptoms as what we were seeing. Guess what job they were working on? Yep, the same one we were. And they have a Wulfsberg FM in the helicopter, which is not narrow band capable. We ended up looking like geniuses, for so quickly diagnosing their problem.

Nand · Post by **Nand** » Wed Jul 16, 2003 2:16 pm

Expand works well if turned on with narrow band systems. It cuts down the white noise significantly on weaker signals. If you do turn it on, all the radios in the system on that channel should also have it turned on. You cannot mix the expand feature with radios that do not use it. A repeater in the system is transparent to the expand feature. The deviation has to be correct as you said.
I was impressed with the ability to reduce the white noise even when using wide band. I guess both Wavetar and RKG are not convinced.

Nand.

RKG · Post by **RKG** » Wed Jul 16, 2003 4:54 pm

The bulk of my experience with narrow banding (and it involves Waris portables) is a Fire Department. Typically, comms are sent by a firefighter or officer standing next to a big diesel running at 1,500-2,000 rpm -- that is to say, in a high noise environment. We seem to observe that compression and expansion results in ragged overdriven Tx audio in a high noise environment.

A question for Nand: on the point (which seems intuitively reasonable) that if compression/expansion is used, all radios must use it, how do you handle the base station? I didn't set up the Quantar for the FD in question, but I did later on read it, and consistent with my Quantar experience generally, the audio filter provisions (page 2 of the Channel Info screen) has no provision for compression/expansion. Is this handled in the console configuration? Or not at all? Or does it matter?

Post by **wavetar** » Wed Jul 16, 2003 5:01 pm

Well Nand, I have found that using 'low level expansion' in wide band mode seems to work just fine, as long as all the radios in the fleet are HT/CDM series and programmed likewise. Trouble is, most companies (around here at least) have a mixture of other radio types. We have found the HT/CDM radios simply don't sound "right" in this situation, unless all compression/expansion is disabled. Several customers complained, so we make a habit out of not using it. I have never tried using full expansion/compression since it follows to reason it would work even worse in that situation. As far as narrow-band applications go, I have no experience...it's still virtually unused out here as of yet.

Todd

Nand · Post by **Nand** » Wed Jul 16, 2003 6:59 pm

RKG wrote: A question for Nand: on the point (which seems intuitively reasonable) that if compression/expansion is used, all radios must use it, how do you handle the base station? I didn't set up the Quantar for the FD in question, but I did later on read it, and consistent with my Quantar experience generally, the audio filter provisions (page 2 of the Channel Info screen) has no provision for compression/expansion. Is this handled in the console configuration? Or not at all? Or does it matter?

I remember that the “Expand” feature came up some time ago and since I wasn’t sure at the time if this was really useful, I tried a simple test in the shop with P1225 radios. I also found some explanation info on “Expand” from either the Manual for the P/M/R1225 or some other Motorola item. What they said was that if there was no need for anything like a wire line, then the repeater would not effect the compressed signal and does not need to use it. This seems a bit obvious. But like you said, if a wire line is used, the signal needs to be de-compressed and re-compressed someplace. I have no idea what Motorola has available for this if anything. But I also remember reading in the MSF5000 manual that there is a standard option to compand and expand the audio that can be used in 12.5 KHz systems. This was an 800 Mhz digital manual, but the board is the same for other bands.
Just looked in the Quantar RSS. It does have a “Hear Clear” setting in the channel configuration screen. Isn’t that the same thing?

Wavetar,
I had a similar experience. Because of some misunderstanding, we had a customer with some M1225’s programmed with expand and some without. It didn’t take to long to figure out what was wrong. But it was very puzzling for the customer because some radios worked fine with some and poor with other users. We don’t have that much narrow stuff either and what there is are 1225’s. I never tried it with the CDM’s.

Nand.

mancow · Post by **mancow** » Thu Jul 17, 2003 12:39 am

We use a wideband vhf system here with mostly BK EPH flexmode radios with the narrow feature disabled of course.

A friend I work with has an HT1000 with the companding enabled. The number of complements he gets about the audio is amazing. It sounds 100% better than all the other radios. The audio seems to be far more rich and full of bass. You can instantly tell it's him when he transmits even if you aren't paying much attention.

I suppose you just have to try it to tell but I'm a believer.

mancow

Nand · Post by **Nand** » Thu Jul 17, 2003 2:58 am

mancow wrote:We use a wideband vhf system here with mostly BK EPH flexmode radios with the narrow feature disabled of course.

A friend I work with has an HT1000 with the companding enabled. The number of complements he gets about the audio is amazing. It sounds 100% better than all the other radios. The audio seems to be far more rich and full of bass. You can instantly tell it's him when he transmits even if you aren't paying much attention.

I suppose you just have to try it to tell but I'm a believer.

mancow

But the HT1000 doesn't have companding. Glad to hear that Motorola sounds better though.

Nand.

mancow · Post by **mancow** » Thu Jul 17, 2003 7:59 am

Hmmm, hell I thought it did...

I must be thinking of the AGC function, whenever he speaks the background noise seems to fade out and the voice volume raises.

Either way, it does put the rest to shame.

Now I have to dig in the prog. again to see what I was thinking of.

mancow

RKG · Post by **RKG** » Thu Jul 17, 2003 8:04 am

Nand: Never paid much attention to "Hear Clear" because even on a 12.5 UHF system, the RSS won't allow me to go there. So now you make me curious, and after 20-30 minutes, I located 68P81085E35 (RSS book), which, at p. 4-38 says: "Compander: Determines whether companding (compression and expansion) is employed for transmit/receive signals. Applies to 900 MHz only; must be enabled for 900 Mhz stations." (Version is R12.10.00.)

However, now that I've found it, I'll put the book back where I'll know where it is next time.

Nand · Post by **Nand** » Thu Jul 17, 2003 5:36 pm

I should make a correction to the MSF5000 info. The companding circuitry is an option all right. The components need to be added to the board if needed.

And for the Quantar, I can change the compand option in the RSS for both a narrow and wide band UHF station. I didn’t try it with any other code plugs. Perhaps the station you tried it on does not have the feature. But I also can enable the flutter fighter and that option should not exist in a UHF station. Who knows?
Also what is the difference between “Hear Clear” as it is called with some 900 MHz equipment and “Expand” as it is called in the 1225 radios? Are the two compatible?

Mancow,
It must have been the mic AGC your friend uses, it does produce full audio. I can’t use it myself, because I leave too much dead air between words and the AGC brings up the background noise (or is it background static) when I am thinking with the key down.

Nand.