GTR Wire Line

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mobile4
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GTR Wire Line

Post by mobile4 »

I am looking for the minimum and maximum input levels for the wire line input on the GTR. I am trying to set levels from the console to the repeater with a 4 wire configuration. I have been looking though the service manual and I cant find the information. Any help would be appreciated. Tom SMith
Jim202
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Re: GTR Wire Line

Post by Jim202 »

mobile4 wrote:I am looking for the minimum and maximum input levels for the wire line input on the GTR. I am trying to set levels from the console to the repeater with a 4 wire configuration. I have been looking though the service manual and I cant find the information. Any help would be appreciated. Tom SMith


Are you talking about the GTR8000?

If you have to ask, you shouldn't be making any adjustments. Lack of knowledge and understanding of what your doing will make matters worse.

Have you tried reading the installation information? There is some very good information there that will guide you in your mission. Try reading the manual 6871020P77-A for what you need. It's available for downloading off the MOL site.

One very important point to remember, your test equipment being used to measure the line level should be in the bridged mode and not in the terminate mode.

Jim
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Re: GTR Wire Line

Post by gtriever »

My agency typically uses -6dB for a level, unless paging is involved. Others will recommend -10dB, which I personally feel is better. I disagree with Jim that the TIMS should be used in bridge mode, however. I've seen an error as great as 1.5dB in bridged mode. I would set the equipment up while it's disconnected from the wireline, using the TIMS in Terminate mode, then would hook the equipment up and tweak as needed.
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Bill_G
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Re: GTR Wire Line

Post by Bill_G »

gtriever wrote:My agency typically uses -6dB for a level, unless paging is involved. Others will recommend -10dB, which I personally feel is better. I disagree with Jim that the TIMS should be used in bridge mode, however. I've seen an error as great as 1.5dB in bridged mode. I would set the equipment up while it's disconnected from the wireline, using the TIMS in Terminate mode, then would hook the equipment up and tweak as needed.
My TMS works fine in bridge mode.
Jim202
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Re: GTR Wire Line

Post by Jim202 »

gtriever wrote:My agency typically uses -6dB for a level, unless paging is involved. Others will recommend -10dB, which I personally feel is better. I disagree with Jim that the TIMS should be used in bridge mode, however. I've seen an error as great as 1.5dB in bridged mode. I would set the equipment up while it's disconnected from the wireline, using the TIMS in Terminate mode, then would hook the equipment up and tweak as needed.


As most remote telco circuits today are now tone, let me give you a simple way of doing level adjustments. Unplug the console mic and just key the radio circuit. Put the TIMS set across the circuit in the bridged mode. Measure the low level guard tone (LLGT) level. It should be someplace between a neg 25 and a neg 35. Adjust it to where you want it. The people on the radio system only hear the station keying up and not the annoying 1004 Hz tone that most people use to adjust audio level on a tone remote controlled radio. Been doing it this way for years. It is fast, doesn't bother users on the radio system and allows you to have a clan way of doing the adjustments.

If you forget to put the TIMS set in the bridged mode, your levels will be about 3 db off from where they should be. The TIMS set will load the line down and you will end up with the levels being hot.

Jim
gtriever
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Re: GTR Wire Line

Post by gtriever »

I'm in complete agreement with you about the effects of "double terminating" a circuit. The only thing I've seen is, as I stated, a difference in recorded levels between bridged mode and terminated mode on the TIMS units that I've been provided with. If you guys don't see it with your equipment, great. Also, we never align a circuit while the system is "live". The station is always connected to a service monitor while we adjust anything, and the dispatchers are always warned to expect test tones at their end so they can either crank the volume down or temporarily mute the channel.
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The Pager Geek
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Re: GTR Wire Line

Post by The Pager Geek »

gtriever wrote:My agency typically uses -6dB for a level, unless paging is involved. Others will recommend -10dB, which I personally feel is better. I disagree with Jim that the TIMS should be used in bridge mode, however. I've seen an error as great as 1.5dB in bridged mode. I would set the equipment up while it's disconnected from the wireline, using the TIMS in Terminate mode, then would hook the equipment up and tweak as needed.
Sounds like you're not adjusting it correctly.

Initially, going from wireline into TIMS WITHOUT the radio, should be terminated. The TIMS then acts as the radio termination point. It's a good way to set initial values prior to connecting the radio.

Once the radio is connected to the wireline, the TIMS should be changed to bridged to "monitor" the line, not weight it down.

If you make adjustments with the TIMS in terminate, as soon as you disconnect the TIMS, the line level will jump about 3db (as mentioned.)

As a rule, if the radio is connected, it should be in bridged mode. (some exceptions, but unique at best)

tpg
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gtriever
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Re: GTR Wire Line

Post by gtriever »

I can assure you that with 30 years of experience with Tone Remote Circuits I am definitely "adjusting it correctly". If it needs more clarification to make what I've been saying more clear: I see a slight difference in level when bridged across a console to radio circuit as opposed to console to terminated TIMS. It's not that big a deal, it's not rocket science, it's just a small equipment error... but I prefer to do circuit alignments to a terminated TIMS at the end point, and then hook the equipment up for a final check. I'd be interested to know what equipment you guys are using, because I've seen this happen with all 4 different TIMS that I've been issued in the past (Halcyon 704A, Sage 930A, HP4935A, and Electrodata ATS-2).

To the OP: Sorry for getting sidetracked here...
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The Pager Geek
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Re: GTR Wire Line

Post by The Pager Geek »

gtriever wrote:I see a slight difference in level when bridged across a console to radio circuit as opposed to console to terminated TIMS.
That's typical. The termination value of the radio will vary from product to product. The TIMS termination "should" be a calibrated 600ohm termination. Radios can vary (I've seen 400-900ohms.) This is why you should use bridged mode as opposed to terminated in the final steps. It allows the radios termination circuit to be used for final adjustment, not both radio and TIMS (if TIMS is still terminated.) The terminated TIMS will increase the load, thus making the circuit a higher level as soon as you disconnect the TIMS.

Annually calibrated HP4934A

Lastly, I doubt anything anyone says will change your mind with your "30 Years Experience" etched in stone.
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gtriever
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Re: GTR Wire Line

Post by gtriever »

You still incorrectly assume that I'm advocating double-terminating the darned circuit in the final stages. Thank you though, for proving my point that a bridged TIMS and a terminated TIMS will display a different level. Lastly, maybe you could learn sometime from us old-timers... like comprehending what you read.
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The Pager Geek
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Re: GTR Wire Line

Post by The Pager Geek »

gtriever wrote:You still incorrectly assume that I'm advocating double-terminating the darned circuit in the final stages. Thank you though, for proving my point that a bridged TIMS and a terminated TIMS will display a different level. Lastly, maybe you could learn sometime from us old-timers... like comprehending what you read.
You old guys are funny... let's review:

In your first post:
gtriever wrote: I disagree with Jim that the TIMS should be used in bridge mode... I would set the equipment up while it's disconnected from the wireline, using the TIMS in Terminate mode, then would hook the equipment up and tweak as needed.
Reading that indicates you would still be double terminated (never changed to bridged)

Your post a few below:
gtriever wrote: ...but I prefer to do circuit alignments to a terminated TIMS at the end point, and then hook the equipment up for a final check.
Reading that also indicates you would still be terminated (never changed to bridged)

So, if you ARE changing to bridged after connecting to the radio, you are not indicating that in your writing.
If you are NOT changing to bridged, you are double terminating.

?
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