TACN mobile transmissions garbled to dispatch

[CFD288]

I am usually able to monitor my home area a good part of each day (Cleveland/Bradley Co TACN North Bradley site). I have pretty good luck reception wise but we all have cussed and discussed the limitations on consumer grade scanners and I do have some garbled Donald Duck transmissions from time to time.

However in this post I'm referring to garbled mobile transmissions where dispatch immediately responds back with "repeat can't copy" or "radio is garbled" or everyone's favorite "can't copy-your radio went digital". In these cases I know it's not my scanner unable to handle the transmission, it's a problem with the mobile unit on the TACN system. I don't have any statistics to back me up but it seems to happen more than just once a day. And it doesn't seem to matter whether the mobile unit is in the city or county.

I know that no radio system can operate 100% perfectly 100% of the time in 100% of the service area and that every area has notorious "dead spots" behind high terrain and so forth. I assume if a mobile unit is close to high voltage lines or a commercial radio or cell tower there can be problems also.

My question: is this just the nature of the radio beast and not much can be done about it....or are there tweaks the radio techs can make? Does the TACN system have the ability to electronically monitor and report these dropped transmissions.....or is it each agency's responsibility to track and report these to the techs?

I understand there may be a new TACN tower going up in south Cleveland so this issue could be in the process of being addressed here locally. Obviously one garbled mobile transmission in a life and death situation could have a very bad outcome.

Thanks to all for your responses and for reading my long post,

Scotty

 

[INDY72]

Busies it records. Amount of ptt it records. Drops and garbles no. Those have to be reported then techs can study fixes. Once the new site is online that should help hugely.

Sent from my LG-K330 using Tapatalk

 

[n4yek]

.....in this post I'm referring to garbled mobile transmissions where dispatch immediately responds back with "repeat can't copy" or "radio is garbled" or everyone's favorite "can't copy-your radio went digital".

What really blows your mind is when one or the other has said that to each other but YOU heard both of them clear as a bell.

 

[INDY72]

Danny, that has always confused me on some systems. Makes me wonder if I built an tower how much I could charge for rent from radio systems since it looks like I have the better location than the PROS who designed the system picked...

 

[xlr8]

What really blows your mind is when one or the other has said that to each other but YOU heard both of them clear as a bell.

When this happens, you actually have a better line of sight to the TACN tower than either of the units talking on the system. As frequency increases, line of sight becomes more important. This is especially true at 700 and 800 MHz. where most of the TACN sites are at in the radio spectrum. There may be a ridge or mountain between the communicating units and the TACN tower that they are near.

My question: is this just the nature of the radio beast and not much can be done about it....or are there tweaks the radio techs can make? Does the TACN system have the ability to electronically monitor and report these dropped transmissions.....or is it each agency's responsibility to track and report these to the techs?

It is the nature of digital radio and TV signals to become distorted due to packet loss (remember that digital signals are really just a bunch of 1's and 0's) as signal strength decreases. As digital signals become weaker and more "lossy", they can tend to sound garbled, or as many hams refer to it, the signals become "R2-D2", sounding like everyone's favorite astromechanical droid from Star Wars. Digital signals at or near the limits or their range (or adequate line of sight to the repeater tower, whichever the case may be) will also tend to "drop off the face of the earth" or have a "cliff effect". See: https://en.wikipedia.org/wiki/Cliff_effect. While analog signals become more noisy (picket fencing sound in mobile units), digital signals will remain at full strength and then finally, "fall off the cliff".

I'm not sure if there are any settings that can be tweaked on the system, but yes, it is each agency's responsibility to report any anomalies to the maintenance techs.

 

[tsmooth]

I've heard the dispatch say that as well "10-9 you came in digital" I'm really thinking about getting a Yagi antenna even though my 800mhz antenna is doing a great job I think i'm still missing some transmissions.

 

[drayd48]

I believe the term that you are saying when they say that the unit went digital is static when talking on digital. When there is "static" on digital, it comes in as a distorted manner

 

[xlr8]

I've heard the dispatch say that as well "10-9 you came in digital" I'm really thinking about getting a Yagi antenna even though my 800mhz antenna is doing a great job I think i'm still missing some transmissions.

If dispatch is telling the other unit that "you came in digital", chances are, the units on the radio need the better antenna or location into the repeater. When you hear those particular units on the air, make a note of what TACN site they are on and note what the signal strength is on your scanner. If you are receiving the site with at least two or three of bars of signal strength, you may not need a better antenna at all. You may not be the one missing the transmissions, the reception at the TACN site may be the culprit.

 

[richard4537312]

Rule of thumb for monitoring TACN in Bradley County: Don't trust scanner to select site. Manually choose North Bradley, Oswald Dome, or Chattanooga Simulcast, according to your monitoring location. With a little creative programming, you can switch sites with two, maybe three, keystrokes.