VHF LTR Programming

[zues2054]

I recently put some equipment on a VHF LTR system (PM400s & CDM1550LS+) my problem is low audio volume on all radios. When I monitor the other users on my Spectra their volume levels are normal. Since this is my first attempt at programming on a LTR system is it possible that I missed a step? Thanks

[zues2054]

Looking for a VHF LTR code plug that I could work off of to compare to mine (PM400 or CDM1550LS+).

[txshooter]

Check how your channel spacing is setup between radios.....25, 12.5? This will cause a difference in audio volume.

[zues2054]

I'm sure this very basic to you, but I've never got a clear answer to how I can tell what the proper channel spacing should be?

[txshooter]

Well, I guess I will start to say I have never seen a LTR Spectra.....I would love to have one ...LOL Sorry if this answer is a little blunt and to the point, but much of this has been hashed out here on the board many times before.

Second, is this your LTR System, what system is this you are talking about? Where and what frequencies? Are you authorized to be putting additional radios on the system? A Spectra would not be put on a LTR System as they are not capable of LTR. How exactlly are you monitoring the LTR system with this radio.

Third, CDM's, and PM's are extremely different radios from a Spectra. The Spectra in my opinion has better audio than these radios, Period.

My suggestion is you simply need to get with thte system owner or authorized service and programming system for the system in question. This would be the easiest solution to your problems and keep you from causing any possible interference to someones LTR system.

This has been hashed out here many times in the past concerning trunking radios and the unauthorized programming of information and frequncies. In a Topic here called..... "Why we tell people to buy a scanner......"

A little info on channel spacing from another source....this may help some who don't know what channel spacing is get a slightly better understanding. This info is from http://www.woodanddouglas.co.uk Directlly copied since I did not want to spend a great deal of time coming up with a orginal answer for this.

Channel spacing is the most difficult term to understand as it can be used to define two quite different aspectsof the radio performance that may not necessarily be related.The first and most common use of this term is to define the step sizes that the radio can increment in to movefrom one channel to the next. This is described in the prior section. It should be remember this could be equalto or be a multiple of the basic synthesiser resolution or raster size.The second more complicated and probably more confusing use of this term is where it defines the technicalperformance of the radio link.All the energyin the radio signal must be contained in the channel that it has been allocated for the transmission.The process that keeps this energy contained is not perfect and the channel can never be ‘filled’ to capacity asa result. A dead zone or guard band must be provided either side of the main transmission to ensure that thetransmission energy does not spread over into the adjacent channels and also to allow some drift withtemperature. Each of these guard bands are around 20% of the channel capacity. For example a radio operating in a 25kHz channel spacing system will move in 25kHz steps from one channelto the next but the energy in the transmission will be contained in only 15kHz of the possible 25kHz spacebetween the channels centres.This reduction in channel capacity is an important issue that must be considered. A 25kHz channel spacingsystem does not have a 25kHzwide channel to send the energydown but only15kHzand pro-rata with a 12.5kHzsystem this would only by around 7.5kHz.This reduced bandwidth within the channel that carries the real energyof the transmission is called the occupiedbandwidth. The occupied bandwidth defines how much data can be passed across the link.The important aspect is that channel spacing refers to the incremental step size that the synthesiser in the radiowill step which in most cases will also define the technical specification of the radio. This will ensure that theenergyfrom the transmission is contained within the occupied bandwidth. This affects the design characteristicsof the filtering used in both the receiver and transmitter.Notice that this applies in most cases. In certain circumstances the authorities might take the view that theywill permit a non standard approach to this.Where it is unlikely that there would be two signals present on adjacent channels at the same time in the samegeographical area an overlappingof conventional channel spacingmight be allowed.. In these circumstances theauthorities might impose a narrow channel spacing regime that defines the centre frequencies but allows theenergyfrom the transmission to spread over more than the normal recognised occupied bandwidth. This is veryunusual but it does happen. When considering a specification, alarm bells should ring if the specified figure forthe transmission deviation looks high compared to the channel spacing being specified

[zues2054]

Thanks for your input! I'm an authorized user/renter on a system that is owned by a bus company. Their radio shop is 150 miles from me and does not service/program Motorola products. Their local shop has faxed me the basic programming information. I never said the Spectra was on the LTR system only that I monitored the system/repeaters with it (to see what the reception was like). Like you I would rather use my Spectras than the LTR radios that Motorola is selling. I agree with you on the audio quality differences, but my issue is with low repeated volume.Thanks for the channel spacing resource. Any other thoughts on the volume issue?

[txshooter]

A normal business that rents space ona LTR System does so on a per unit basis. I have never seen oen that tells the end user to program their own equipment, but there is a first for everything.

The above explanation should be enough to explain what the volume problem could be.....That is the difference in the radios, or the way you are programming the channel spacing. Again, contact the system owner, he should know the channel spacing he is using and tell you how you need to set your radios up, even if he does not program Motorola Equipment. Channel spacing is universal and common between all types of radios. You may have your radio set on wideband when it needs to be set on narrowband. Again, there are those here on the board that would be glad to help you more if you in fact told us what system this was which you have been previously asked to do. This does lead one to believe you may not be authorized to be on the system........ The programming instructions you have recieved from the system owner should also have told what you should have the setting on. Radio Reference Databases don't tell you the channel spacing. A simple mistake in how you have the channel spacing set can cause your so called volume issues....

If you contact the System Owner he will be glad to tell you the proper setting for his system!

[zues2054]

I missed your request for the "system". Lamers Bus Lines Inc. "WPQK447" The Radio shop is Dal Santo Communications Inc. Green Bay WI. I will certainly call Dal Santo to get my questions answered. I thought this forum could possibly help me out, but I guess you "radio" guys run pretty parinoid about hacking. I will do a better job of presenting my credentials in the future.