Spectra tac aligment
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Spectra tac aligment
I am in the process of setting up a uhf voting system with a MTR2000, a spectra tac comparator and Micor voting receivers. I have read through Motorolas level setting procedures and have a question about -13db and 0db level settings for status tone. The manual doesn`t give an explanation as to the advantages of one over the other. In operation which is the better? Forgot to mention that I will be using lease lines. Thanks
The -13 setting is normal for most applications to avoid crosstalk. It may be required by your Telco for a lease line.
A steady tone level of -13 is about equivalent to a peak voice level of 0 which is why tone levels of -13 or less are usually specified.
If a 0 level is specified, it will usually be attenuated to a lower level by the Telco or private network equipment before it hits the network.
A steady tone level of -13 is about equivalent to a peak voice level of 0 which is why tone levels of -13 or less are usually specified.
If a 0 level is specified, it will usually be attenuated to a lower level by the Telco or private network equipment before it hits the network.
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N4DES
- was KS4VT
- Posts: 1234
- Joined: Thu Dec 25, 2003 7:59 am
- What radios do you own?: APX,XTS2500,XTL2500,XTL1500
In addition to K2HZ comments, make sure that you order RTNC lines that are engineered for -10 db loss. It's easier to do the math when setting up the -23 status tone and -10 peak voice levels on the back of the comparator as well as any equalization that you may have to do to flatten out the audio responses.
Just take your time in setting up the levels and sweeping the lines 100 Hz at a time and you will be very happy with the results.
Just take your time in setting up the levels and sweeping the lines 100 Hz at a time and you will be very happy with the results.
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psapengineer
- Posts: 175
- Joined: Thu Oct 07, 2004 10:00 am
Leased Lines
It kind of depends on which kind of leased line you ordered. That said, in general, you should use -13dbm status tone for leased lines.
Bellcore standards, for a traditional voice grade circuit, require that any steady tone be -13 or below in level and that voice peaks cannot exceed 0dbm.
This comes from the old analog AM microwave days where if everyone put steady tone on the respective channel card that if the levels were high enough it would drive the modulator into a non-linear region and kill all of the channels.
Some telephone companies requrie -16 peak; in which case, your voice peak ends up at -16 and your status tone ends up at -29. This is normally done by setting 0 and -13 and installing a -16 pad in place of the bridge clips on the "66" block. http://www.laruscorp.com/analog.htm
Lastly, beware that long leased copper lines attenuate the high frequency noise and can cause the "copper" site to vote even with bad audio if the other sites are, as an example, on microwave channels. Often we order "C2" line conditioning to help with this problem.
Good Luck, Bob
Bellcore standards, for a traditional voice grade circuit, require that any steady tone be -13 or below in level and that voice peaks cannot exceed 0dbm.
This comes from the old analog AM microwave days where if everyone put steady tone on the respective channel card that if the levels were high enough it would drive the modulator into a non-linear region and kill all of the channels.
Some telephone companies requrie -16 peak; in which case, your voice peak ends up at -16 and your status tone ends up at -29. This is normally done by setting 0 and -13 and installing a -16 pad in place of the bridge clips on the "66" block. http://www.laruscorp.com/analog.htm
Lastly, beware that long leased copper lines attenuate the high frequency noise and can cause the "copper" site to vote even with bad audio if the other sites are, as an example, on microwave channels. Often we order "C2" line conditioning to help with this problem.
Good Luck, Bob
I just went through setting this up tonight on three receivers...
My issues:
1. I cannot get 0dbm out of the SpectraTAC Receiver. I can get about -4dbm and thats max.
Am I not running enough deviation into the receiver??
2. My notches on my SECURENET DIGITAC sound like hell - instead of a crisp click when the mobile signal disappears, I get a sloppy blorpish kinda click... I've verified that Transmitter Notch is enabled in the DIGITAC personality. I've also verified using an HP TIMS that the status tone is dead nuts on 2175Hz.
The receivers are all on-site and on dedicated copper runs back to the comparator.
My issues:
1. I cannot get 0dbm out of the SpectraTAC Receiver. I can get about -4dbm and thats max.
Am I not running enough deviation into the receiver??
2. My notches on my SECURENET DIGITAC sound like hell - instead of a crisp click when the mobile signal disappears, I get a sloppy blorpish kinda click... I've verified that Transmitter Notch is enabled in the DIGITAC personality. I've also verified using an HP TIMS that the status tone is dead nuts on 2175Hz.
The receivers are all on-site and on dedicated copper runs back to the comparator.
"...I cannot get 0dbm out of the SpectraTAC Receiver...."
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Check for JU-8 on the audio control module. This jumper is installed for applications where lower line levels are desired. If the jumper is removed you should be able to set the line level above 0dBm.
------------------------------------------------------------------
Check for JU-8 on the audio control module. This jumper is installed for applications where lower line levels are desired. If the jumper is removed you should be able to set the line level above 0dBm.
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N4DES
- was KS4VT
- Posts: 1234
- Joined: Thu Dec 25, 2003 7:59 am
- What radios do you own?: APX,XTS2500,XTL2500,XTL1500
I shouldn't see why not Rob. I got back from Orlando last night (2 trips in one week) from APCO and the hamfest, so it will be a few days.FMROB wrote:Mark,
If you have the time, could you write up a short "primer" on the intitial set-up on voting systems, and the do's and dont's. Also, maybe some test equipment pointers.
You seem to have an handle on it, and some pointers would be awesome.
It is a hard subject to compile info on.
Thanks, Rob
Mark
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psapengineer
- Posts: 175
- Joined: Thu Oct 07, 2004 10:00 am
Watch out for Double Terminate
Here's a "watch out" for you:
If the Spectra-Tac is connected to the circuit be sure that your TIMS is "bridged" and not "terminated". If you double terminate the test you may not be able to get to 0 reading since you're really trying for +6.
I know that occasionally I have to catch myself doing just that and end up performing the setting a second time.
If the Spectra-Tac is connected to the circuit be sure that your TIMS is "bridged" and not "terminated". If you double terminate the test you may not be able to get to 0 reading since you're really trying for +6.
I know that occasionally I have to catch myself doing just that and end up performing the setting a second time.
This would be great info for the Knowledge BaseKS4VT wrote:I shouldn't see why not Rob. I got back from Orlando last night (2 trips in one week) from APCO and the hamfest, so it will be a few days.FMROB wrote:Mark,
If you have the time, could you write up a short "primer" on the intitial set-up on voting systems, and the do's and dont's. Also, maybe some test equipment pointers.
You seem to have an handle on it, and some pointers would be awesome.
It is a hard subject to compile info on.
Thanks, Rob
Mark
My two bits worth:
The reason for the -13DBMO is that the early A version SQM had status tone at test tone level.
This caused problems by occupying too much band width on analog microwave systems.
Not to mention cross talk.
Speaking of cross talk, I highly recommend using the alternative tone, 1950.
Status tone cross talk can cause an un related TRC system that shares certain facilities such as microwave multiplex or phone cables to lock up on transmit for no apparent reason.
B version and later SQM cards have a switched 13DB attenuator in the front end of the card.
The card is squelched when the status tone is present.
The 13 DB pad is by passed, the sample and hold circuit samples the AGC detector.
When the status tone is lost, the card switches the pad into the audio path, locks the AGC voltage is locked by the sample and hold capacitor.
The audio out put of the comparator should have equal test tone on every channel.
It is not necessary that the status tone be set to -13DBM0.
It is necessary that all the channels be set exactly the same.
The delays, and band width and levels should be equal for all channels.
If you are using digital microwave, you will have to delay the local receiver by putting it on a loop back channel.
Noisy telephone lines, as well as RF links can cause problems of their own.
Noise bursts can cause the status tone detector to fire for a moment, re setting the AGC for more attenuation. The result is that the status tone detector can no longer detect the status tone, so the tone is voted until the activity timer times out or the card is manually reset.
A bad noisy phone line can cause the card to vote on the noise until time out or it is manually disabled.
Nothing like an emergency service call at 3 AM during a storm.
Spectra Tac, as well as Micor receivers are a bit along in years.
I would expect that there are electrolytic caps that are at the end of their life span.
The ones in the power supply, as well as the caps on the boards.
Use D5 on the contact pins. Inspect the pins to be sure that the pins couple properly. It is possible that a pin can get bent, by passing the socket.
Inspect everything for corrosion, as well as contamination.
Rodents can make a mess at a remote site.
The reason for the -13DBMO is that the early A version SQM had status tone at test tone level.
This caused problems by occupying too much band width on analog microwave systems.
Not to mention cross talk.
Speaking of cross talk, I highly recommend using the alternative tone, 1950.
Status tone cross talk can cause an un related TRC system that shares certain facilities such as microwave multiplex or phone cables to lock up on transmit for no apparent reason.
B version and later SQM cards have a switched 13DB attenuator in the front end of the card.
The card is squelched when the status tone is present.
The 13 DB pad is by passed, the sample and hold circuit samples the AGC detector.
When the status tone is lost, the card switches the pad into the audio path, locks the AGC voltage is locked by the sample and hold capacitor.
The audio out put of the comparator should have equal test tone on every channel.
It is not necessary that the status tone be set to -13DBM0.
It is necessary that all the channels be set exactly the same.
The delays, and band width and levels should be equal for all channels.
If you are using digital microwave, you will have to delay the local receiver by putting it on a loop back channel.
Noisy telephone lines, as well as RF links can cause problems of their own.
Noise bursts can cause the status tone detector to fire for a moment, re setting the AGC for more attenuation. The result is that the status tone detector can no longer detect the status tone, so the tone is voted until the activity timer times out or the card is manually reset.
A bad noisy phone line can cause the card to vote on the noise until time out or it is manually disabled.
Nothing like an emergency service call at 3 AM during a storm.
Spectra Tac, as well as Micor receivers are a bit along in years.
I would expect that there are electrolytic caps that are at the end of their life span.
The ones in the power supply, as well as the caps on the boards.
Use D5 on the contact pins. Inspect the pins to be sure that the pins couple properly. It is possible that a pin can get bent, by passing the socket.
Inspect everything for corrosion, as well as contamination.
Rodents can make a mess at a remote site.
Aloha, Bernie
My two bits worth:
I don't think that there is anything silly about your question.
I have seen a few Doug Hall comparators. Seem to work as expected.
Providing the status tone can be a problem, especially with links.
An advantage of the status tone is that the audio level never changes as far as the system is concerned. If the input should be double terminated, the level would drop 3 DB. The Status tone also drops by 3DB the AGC compensates.
A failed line also becomes obvious.
The SQM will go off line and alarm if the status tone is lost with out activity
for a certain time. Will re set when status is detected.
I find that I can use a low power mobile with an external antenna at the comparator site I can feed a test tone to all sites for trouble shooting and alignment.
I don't think that there is anything silly about your question.
I have seen a few Doug Hall comparators. Seem to work as expected.
Providing the status tone can be a problem, especially with links.
An advantage of the status tone is that the audio level never changes as far as the system is concerned. If the input should be double terminated, the level would drop 3 DB. The Status tone also drops by 3DB the AGC compensates.
A failed line also becomes obvious.
The SQM will go off line and alarm if the status tone is lost with out activity
for a certain time. Will re set when status is detected.
I find that I can use a low power mobile with an external antenna at the comparator site I can feed a test tone to all sites for trouble shooting and alignment.
Aloha, Bernie
You put the roofing filter module in a SQM slot, logically the one next to the slot where your local receiver's SQM will reside. I usually put it in the first slot, the local RX SQM in slot 2, then put the remote receiver SQM's in the next slots over.
What you are going to do is run the receiver audio into the filter and the filter's output into the associated SQM.
On the comparator backplane, hook the line from the local RX to the top 2 screws of the first slot [the ones that connect to pins 3&4 of the card] Then run jumpers from the bottom two screws [the ones that connect to pins 19 and 20] up to the top screws of the second slot [where the local RX SQM card is]
What you are going to do is run the receiver audio into the filter and the filter's output into the associated SQM.
On the comparator backplane, hook the line from the local RX to the top 2 screws of the first slot [the ones that connect to pins 3&4 of the card] Then run jumpers from the bottom two screws [the ones that connect to pins 19 and 20] up to the top screws of the second slot [where the local RX SQM card is]
The filter is a simple audio circuit that could be used for other purposes. It is necessary for the Spectra-TAC because the SQM high-pass filters the audio before the noise detector, thus the detector responds to frequencies above the passband of microwave MUX channels and some leased lines. These typically have a high frequency response that ends near 4000 Hz.
Later voters, such as Digitac, window filter the audio [band-pass or high-pass followed by low-pass] so that the noise detector is looking at a smaller segment of the audio spectrum. These voters usually don't need window filters.
For configuration and level setting of Spectra-TAC systems, I have submitted an article into the Knowledge Base.
Later voters, such as Digitac, window filter the audio [band-pass or high-pass followed by low-pass] so that the noise detector is looking at a smaller segment of the audio spectrum. These voters usually don't need window filters.
For configuration and level setting of Spectra-TAC systems, I have submitted an article into the Knowledge Base.
Slightly off-topic, but perhaps not...
Can a regular non-coded SpectraTAC receiver be upgraded to handle SECURENET simply by replacing the AUDIO CONTROL MODULE with a DVP AUDIO CONTROL, and replacing the ENCODER MODULE with a SECURENET ENCODE/RECOVERY?
I tried this tonight on one of my receivers, but got nothing out of it. Is there a different receiver backplane for SECURENET?
Are the receiver boards themselves different?
Anyone advise??
Tks.
Can a regular non-coded SpectraTAC receiver be upgraded to handle SECURENET simply by replacing the AUDIO CONTROL MODULE with a DVP AUDIO CONTROL, and replacing the ENCODER MODULE with a SECURENET ENCODE/RECOVERY?
I tried this tonight on one of my receivers, but got nothing out of it. Is there a different receiver backplane for SECURENET?
Are the receiver boards themselves different?
Anyone advise??
Tks.