Input For LTR

[ecps92]

I'm assuming, but maybe what someone thought was input/output was actually a Console Patch from a 420 system to a UHF 460 system.

Interesting, but I would hazard a guess that any system using a 429 input and a 460 output is improperly constructed at the least, and probably improperly licensed (or illegal).

Still wondering where this supposed system is?

 

[N_Jay]

I'm assuming, but maybe what someone thought was input/output was actually a Console Patch from a 420 system to a UHF 460 system.

Maybe so.

I always find it interesting when stuff like this gets tossed into a thread and not questioned.

Unquestioned rumors seem to develop the belief they are facts.

 

[w8jjr]

then there are others that confuse things Input of 429 and output of 460.
Rare but there are split input freq's.

First let me clear up its a MOT repeater not GE I was only making remark that there are strange splits out there. Not always 5 mhz although 99% are.

Example off the top of my head is Oakland County Michigan William Beaumont Hospital has a output of 460.650 and the input is (channel 6) 429.900 and (Channel 5 ) 465.650. Another is input of 466.0375 with output of 461.775. They use HT1000 so I know the split is there. We verified it using a freq counter and security radio in the ER one day. It received on 461.775 but xmited on 429.900. I also see it on my scanner. They may be using some kind of link to do this. It may be there to allow interop between their MOT repeaters and their LTR system. I know its strange but they are out there.

We have been using 421-429 for many years here in Detroit area. Non-Government land mobile service is allocated on a primary basis in the bands 421 - 426 MHz within 80 kilometers (50 statute miles) of Detroit, MI. Ham is not allow on those freqs.

Also some of the band is allowed in Cleveland and Buffalo.

 

[zzdiesel]

Barely hear as in scratchy, or barely hear as in soft?

The base is weak. The modulation is real low and it sounds like the "motor boat" in the background anytime the mic is keyed. I don't know how since it's not supposed to be digital.

 

[N_Jay]

I would bet if you are seeing two inputs to the same repeater, you are actually looking at a link, and not the repeater input.

I also believe that non-standard inputs in UHF is illegal in Part 90, but I am not 100% sure of that.

 

[zzdiesel]

Here is the system. It is the Steele MO tower I'm talking about and the Dunklin County Sherriff TG

Scanner Frequencies: Battles Communications - UHF (SEMO/AR) Trunking System, SouthEast MO, Multi-State

 

[w8jjr]

I would bet if you are seeing two inputs to the same repeater, you are actually looking at a link, and not the repeater input.

I also believe that non-standard inputs in UHF is illegal in Part 90, but I am not 100% sure of that.

I thought that to for along time also. Just that the 429.900 freq keys the 460 repeater and not the 424.900 repeater which seems to have another input, not 429.900. I've got some time the next couple of weeks to check this system out more and go talk to a couple of people in the CT dept there.

One security officer told be they did change the radios cause they were getting illegal radios on the system at times. I need to verify that also.

Also for those in the area the new Kenwood digital is online at Troy location

 

[kb4mdz]

I'm gonna wade in here, just to confuse the issue a bit..

zzdiesel's location is in Missouri; infact, he references the system in another post; so all this talk about 'odd offset inputs' seems to be null & void; doesn't apply here, because the system in not anywhere near Line A, yadda, yadda.

& thanks for the link about system credentials; very good. So, LTR or similar eh?

Another (very good) question asked was the quality of the signal; scratchy, or low modulation?

On first level analysis, scratchy would imply the RF getting into the receiver is weak, not too far above the squelch threshold. Bad/broken antenna for the base, low RF output power, etc.

Low audio/low modulation would imply something like the user isn't speaking into the microphone well (hand mic at arm's length, or desk mic across the room, etc.)

Back to the ORIGINAL question, is there an input; yes, standard input frequency on UHF, even in an LTR system, is 5 MHz above the repeater's TX freq; so if you hear the repeater at 452.66250 MHz, you should be able to hear (assuming you're physically close enough to the transmitting unit!) on 457.66250 MHz.

Now, (sorry, going into lecture mode here, bear with me) since this seems to be a trunking system, & I've concluded you're using a LTR-capable trunked scanner, (based on what you list under your signature), you would have to be pretty quick to grab any audio on the other input frequencies used. But, I'm sure you could do it.

Could be just that the audio in that particular base is badly aligned;

Sounds like an interesting problem to be solved.

 

[zzdiesel]

I'm gonna wade in here, just to confuse the issue a bit..

zzdiesel's location is in Missouri; infact, he references the system in another post; so all this talk about 'odd offset inputs' seems to be null & void; doesn't apply here, because the system in not anywhere near Line A, yadda, yadda.

& thanks for the link about system credentials; very good. So, LTR or similar eh?

Another (very good) question asked was the quality of the signal; scratchy, or low modulation?

On first level analysis, scratchy would imply the RF getting into the receiver is weak, not too far above the squelch threshold. Bad/broken antenna for the base, low RF output power, etc.

Low audio/low modulation would imply something like the user isn't speaking into the microphone well (hand mic at arm's length, or desk mic across the room, etc.)

Back to the ORIGINAL question, is there an input; yes, standard input frequency on UHF, even in an LTR system, is 5 MHz above the repeater's TX freq; so if you hear the repeater at 452.66250 MHz, you should be able to hear (assuming you're physically close enough to the transmitting unit!) on 457.66250 MHz.

Now, (sorry, going into lecture mode here, bear with me) since this seems to be a trunking system, & I've concluded you're using a LTR-capable trunked scanner, (based on what you list under your signature), you would have to be pretty quick to grab any audio on the other input frequencies used. But, I'm sure you could do it.

Could be just that the audio in that particular base is badly aligned;

Sounds like an interesting problem to be solved.

Thanks kb4mdz. You are making things a bit more clear. You say the offset is likely 5 MHz above. Would that stay the same based on the home channel or would it change if someone else was talking there first and the repeater assigned another channel based on that?

 

[kb4mdz]

Thanks kb4mdz. You are making things a bit more clear. You say the offset is likely 5 MHz above. Would that stay the same based on the home channel or would it change if someone else was talking there first and the repeater assigned another channel based on that?

The input frequency follows the repeater channel assignment;

452.66250 repeater output means input on 457.66250,
452.11250 output means input on 457.11250,
451.73750 output means input on 456.7375,
etc., etc.

And while it may be a fine point, it's not the repeater itself that assigns the particular repeater or channel, but the LTR controller system.

Are you familiar with any of the details of an LTR system, like how the various channels get assigned & conversations run between the different channels? If not, I'll try to explain the 'backbone' of it, and that should help make it clearer.

Now, considering the size of the system listed, there are probably other places for this 'low audio' issue to crop up.

Much could depend on the actual structure of how the system is set up.

Is all of the dispatch audio low? Or just sometimes?

 

[silverbk]

Sorry for the thread hijack. I can't resist learning new stuff, like 420 in use in North America.

Back to the original thread question.

Have you verified each frequency in the FCC database? This site sometimes has inaccurate information posted.

After you do that I would strongly consider getting LTR analyzer running. It will help you verify the correct home repeater and any talkgroups in use.

A scanner would not be able to track a trunked system properly using an input frequency. The control data from the controller is not present. You could however listen to that frequency in conventional mode, but because of the way a LTR system works you will certainly miss transmissions, as they change repeaters and frequencies depending on the load on the system.

 

[kb4mdz]

After you do that I would strongly consider getting LTR analyzer running. It will help you verify the correct home repeater and any talkgroups in use.

A scanner would not be able to track a trunked system properly using an input frequency. The control data from the controller is not present. You could however listen to that frequency in conventional mode, but because of the way a LTR system works you will certainly miss transmissions, as they change repeaters and frequencies depending on the load on the system.

What he said; that I didn't get around to!

If you've got another scanner, program it for conventional mode, using the input freqs, while your first scanner is doing trunking; if it's anywhere in your physical neighborhood, you should be able to pick it up.

Now, the dispatch may be coming in from another path; I'm not familiar with how such a large LTR system would handle the dispatch (outbound from the console) audio; they may have some sort of switch arrangement that takes the console TX audio, routes it thru the system, to whatever appropriate site(s), and out. But, I just don't know.

 

[michaelsbus]

OK, here's my $.02

You obviously need to research your home territory better. On the trunking system page, you click on the site name and get a page about the site. Click on the site license, and you get the RR license info, including all frequencies on that license, inputs and outputs. You'll see that the inputs are all 5MHz higher than the outputs. Next, you should have known about the Warner Communications trunking system has talkgroup for the Dunklin Sheriff as well. There's some more freqs to consider. Then, there's the VHF High band conventional freqs the sherrif uses. (my guess is the northside/southside VHF freqs are patched into the Battles Communications system northside/southside talkgroups.)

Now, as far as low audio is concerned, you could have several problems. First, the dispatcher could be leaning back in the chair and relaxing while on the radio. In that case, you'd probably hear a lot of backround noise in the room while they're transmitting. Next is their volume settings. They probably have the volume up high enough to hear everything loud and clear, but the dispatcher is in a fairly quiet room, so he doesn't talk very loudly into the mic. Lastly, there's the audio link between the radio systems. Picture a VHF reciever speaker output connected to the mic input of a UHF transmitter. If the VHF's volume isn't set high enough, the sound level on the UHF system will be low.

What you could do is send them a reception report (ham-speak: QSL). Program a second scanner with all of the VHF freqs (input and output) as well as all of the UHF input freqs for both Battles and Warner systems and listen to them for a while (oh, say a week). Keep a list of the various freqs and note the signal level and quality and audio level and quality of the transmissions from the base and mobile units, and then how the transmission rates coming from the trunk system (and which trunk system), then at the end of the week, send them a copy.

I noticed the VHF license dates to 2004. In all likelyhood, they are transitioning to the trunking system and eventually pull the plug on the old freqs. They may have even been starting to go with Warner, then switched to Battles for the wide-area coverage and interop capability. If they are in the midst of a transition, they should appreciate the information. Also include the area you're in, the time period you monitored, and something about the receiving equipment. (handheld or base, whip or roof antenna)

Class dismissed

 

[zzdiesel]

The Dunklin County Sheriff has TG's on several systems around the area. They talk mostly on the Battles Steele tower when they are not on VHF. The county owns the VHF north & south repeaters, but Battles does keep them serviced. I can't see them transitioning away from these repeaters anytime in the foreseeable future. The county uses them to dispatch all of the smaller towns. They don't have the funds to upgrade very often.

The low audio on the county's base on all the LTR systems is always low. It is the same with all dispatchers. There is no background noise from the office at all unless the phone rings or something.

I learned a long time ago that they don't like outsiders talking to them about their radio equipment. They try to make a dummy out of you real quick. :roll:

 

[Packetpeeker]

429 / 460 Mhz

That is quite a split.
Are you sure that the 429 is not a rebroadcast, perhaps there is two sites and you receiving the second?
This band is usually licensed .repeater receives HI and Transmits or repeats Low.

 

[ecps92]

The other thought is image.

I routinely get 460 Mhz traffic on 415 Mhz frequencies for various Scanners.

That is quite a split.
Are you sure that the 429 is not a rebroadcast, perhaps there is two sites and you receiving the second?
This band is usually licensed .repeater receives HI and Transmits or repeats Low.

 

[detroit780]

429MHz

47CFR Part 90.273
Public Safety and Industrial/Business Pool
Frequency bands 422.1875-425.4875MHz and 427.1875-429.9875 are available for use in Detroit and Cleveland 423.8125-425.4875 and 428.8125-429.9875 available in Buffalo New York.

5 MHz split is called out in this section. control station frequencies and mobile are 5MHz higher then base station frequencies. So for this band you cannot use anything other than a 5 MHz split.

425.00-425.48125 are unpaired available for simplex or paging.

Les
W8MSP

I would bet if you are seeing two inputs to the same repeater, you are actually looking at a link, and not the repeater input.

I also believe that non-standard inputs in UHF is illegal in Part 90, but I am not 100% sure of that.

 

[kb4mdz]

zzdiesel -

Any luck on this issue you were asking about? I remain, curious.

 

[zzdiesel]

No, not really. It blew up into such a big issue that I quit reading this for awhile. I'm going to record it tonight and maybe I can post a good sound byte of what I've been talking about. Thanks for bringing it back up.

 

[zzdiesel]

Here is a file that is just over two minutes. The base is the weak one. I had to upload it Rapidshare. It was too big for here.If you listen to this; some guy killed himself with a shotgun. RapidShare: Easy Filehosting