Firefighter comms questions

[speedway_navigator]

My COM T instructor did emergency comms for TN. I told him I worked Bonnaroo, he had worked there too. He said he questioned the Bearcom tech as to why he used repeaters for a small flat area when all his testing showed simplex was fine.
Then the gates opened and 40,000+ fans streamed in and his simplex failed.

Maybe it was the smell from the pot heads.

 

[speedway_navigator]

Years ago I saw a study of such and there are two losses of the human body. With the portable tight against the body (near field) you have the -10 db regardless of frequency. Beyond that the the body becomes more a clutter loss (far field loss). The signal flows (refracts) around the body. The industry standard TSB 88 has a table of clutter losses by frequency but a human body is not one of them. Maybe it is ignored because the human moves around rather than like a tree or building.

Breaking Boundaries in Wireless Communication: Simulating Animated, On-Body RF Propagation | Remcom

This paper discusses how RF propagation simulations empower engineers in the design and development of wireless devices for body-worn applications.

www.remcom.com

 

[speedway_navigator]

But I still remember that while he’d approve the STX, & MTS2000, he would not allow MTX8000’s to be used on the system. .

Something like that happened to me many years ago. I bought my own radio since I was doing consulting for the Speedway PD, chief Dine gave me a letter saying I had permission to be on the system. The guy who programmed it at the Indy radio shop called me a few months after that to say he had to change it because a Motorola sales guy said my model could shut down the system.

The guy told the tech my radio would not do a shift from 12.5 kHz to 25 kHz, I think the interops were wide at the time. I think I had an MTS2000, I showed the specs to the tech and he let me off. I was with Racing Radios back then in the pre-internet days. During May about 6.30 pm I would get the daily track report from the IMS press room and fax it to a bunch of folks, he was one, so that probably helped.

the good old days, when social media was CB channel 19.

 

[NavyPhil]

Portables usually have the same receive ( we geeks call it RX) sensitivity as mobiles. You have less signal strength inside than out, a mobile has an advantage of a better antenna system from the metal ground plane (roof) it is mounted on. You have a downlink (repeater to mobile/portable) signal strength problem from terrain issues from what you describe.

I don't think a mobile will RX much better than a portable in your hand at head height in your truck, but it only takes a 1 or 2 decibel difference between the radio working or staying mute, so the mobile antenna might be the difference. Putting the portable in the center of the hood or roof will help. I knew a cop whose Hytera portable would hit the repeater from his living room but his mobile did not from certain spots in the driveway.

The mobile has an advantage in TX due to more power and better antenna efficiency.
Any idea how high your antenna is and how much gain it has? Gain antennas force more RF horizontally at the cost of reducing strength at ground level if it is too high.

I am not sure of the gain on my mobile but it is about 24” long and is supposed to be right for 450-480 mhz.

Phil

 

[NavyPhil]

Something like that happened to me many years ago. I bought my own radio since I was doing consulting for the Speedway PD, chief Dine gave me a letter saying I had permission to be on the system. The guy who programmed it at the Indy radio shop called me a few months after that to say he had to change it because a Motorola sales guy said my model could shut down the system.

The guy told the tech my radio would not do a shift from 12.5 kHz to 25 kHz, I think the interops were wide at the time. I think I had an MTS2000, I showed the specs to the tech and he let me off. I was with Racing Radios back then in the pre-internet days. During May about 6.30 pm I would get the daily track report from the IMS press room and fax it to a bunch of folks, he was one, so that probably helped.

the good old days, when social media was CB channel 19.

Yes I recall being on CB long ago. Does anyone use CB anymore?

Phil

 

[NavyPhil]

I am a volunteer firefighter in Alabama and want to install a mobile transceiver in my truck. I need 9600 baud and ADP encryption. Can the basic ham radios (budget) do these programming points? Any suggestions would help. I have a vertex vx6000 I picked up at a yard sale but works vhf and our county uses uhf. Thanks.

Thanks for the input from all. I did speak with the comms director and he told me although they want to move to P25 (I believe that was it), currently the repeater could be used without trunking and just needed the repeater info plugged into the radio.

All comms are in the 450mhz range so I am tempted to purchase a mobile that can work there (I’ve seen mobiles advertised for 420-490 mhz or close to it). If it doesn’t work I could still transmit on ham bands I am licensed for.

Phil

 

[mmckenna]

All comms are in the 450mhz range so I am tempted to purchase a mobile that can work there (I’ve seen mobiles advertised for 420-490 mhz or close to it). If it doesn’t work I could still transmit on ham bands I am licensed for.

Just make sure the radio you are looking at has a valid FCC issued Part 90 certification. That is a requirement to use the radio on the fire frequencies, no exceptions.
That's not hard to do, but you need to be really careful looking at the low buck Chinese radios. Many of them don't have it, and are not what you want for public safety use, anyway.

 

[northstarfire0693]

Thanks for the input from all. I did speak with the comms director and he told me although they want to move to P25 (I believe that was it), currently the repeater could be used without trunking and just needed the repeater info plugged into the radio.

All comms are in the 450mhz range so I am tempted to purchase a mobile that can work there (I’ve seen mobiles advertised for 420-490 mhz or close to it). If it doesn’t work I could still transmit on ham bands I am licensed for.

Phil

Did the comms director point you to any radios that will work with the system?

 

[Echo4Thirty]

The guy who programmed it at the Indy radio shop called me a few months after that to say he had to change it because a Motorola sales guy said my model could shut down the system.

I loved it when the sales guy would stop by with this spiel talking about other brand subscribers. I would reply "So you are telling me your system is so fragile it can be damaged by a RADIO? I need to call the stakeholders about this! THIS IS NOT GOOD!"

 

[speedway_navigator]

I loved it when the sales guy would stop by with this spiel talking about other brand subscribers. I would reply "So you are telling me your system is so fragile it can be damaged by a RADIO? I need to call the stakeholders about this! THIS IS NOT GOOD!"

I was in a meeting where a fire chief asked about Kenwood radios coming onto their Motorola system in mutual aid calls. The Moto sales guy said "we can't guarantee audio quality from a competitor's radio." I whispered to my coworker "can he guarantee all his radios will work?". The guy next to us laughed.

 

[NavyPhil]

Did the comms director point you to any radios that will work with the system?

Yes he did, although I don’t recall the brand. Ideally an 800 hz unit but the ones I saw online were $800+. I am a volunteer firefighter working for the state for free. I am not putting out money that I should not need to.

I do have the info from him to put in the specs but I don’t know enough obviously to make it talk to the repeater with my radios.

Any help would be appreciated.

 

[speedway_navigator]

Any commercial grade UHF radio will work

 

[NavyPhil]

I have an uhf radio and I thought I put the decodes in correctly along with the offset for the repeater with no luck. I guess I need to go to my mountain top to see if it works there. If so it is the valley I am in.

 

[AM909]

Any commercial grade UHF radio will work

Almost. Make sure it's narrowband-capable on the non-amateur freqs if it's more than about 10 years old.

... Ideally an 800 hz unit but the ones I saw online were $800+. ...

Not clear what you mean here. The channels shown in your spreadsheet are UHF conventional analog. A suitable used mobile less than 10 years old should run you $100-$400, depending on condition, support, etc. By comparison, MSRP for a new Kenwood NX-1800 analog mobile is about $500.

 

[dickie757]

I have an uhf radio and I thought I put the decodes in correctly along with the offset for the repeater with no luck.

It's a split DCS. Your radio needs to encode a different code on your transmission than the receive decode. If that is not correct, it will not open the repeater to repeat. On the other side, if decode is not correct, any traffic from repeater will not open your audio.

What is the make and model of radio you are trying to use?

 

[NavyPhil]

It's a split DCS. Your radio needs to encode a different code on your transmission than the receive decode. If that is not correct, it will not open the repeater to repeat. On the other side, if decode is not correct, any traffic from repeater will not open your audio.

What is the make and model of radio you are trying to use?

Due to costs, I am using a anytone 778UV. This is so I can also use it under my tech ham license as well.

I have the software and cable to program it and pretty sure I set both dcs points correctly. I can send a screenshot of this as well if it helps.

Phil

 

[dickie757]

Ask Roy if that info is for subscriber or if it is the info of the repeater. Or, do you have access to a radio that is already programmed for the system and a sdr or freq counter? Or, a scanner....

Also, what is on sheet 2 and 3?

And, dont concern yourself with ham radio right now. Has zero bearing on your situation. A "ham radio" is a radio that is not allowed to transmit outside of Part 97 priviledges. Most commercial Part 90 radios have a wide Tx/Rx swath, and usually no restrictions. It is up to the programmer with the help of the radio system admin(s) and FCC database to keep things legal.

 

[jeepsandradios]

More CCR crap on public safety channels....Where do you buy your fire fighting gear amazon ?

 

[AM909]

Ask Roy if that info is for subscriber or if it is the info of the repeater.

It's the mobile/user/subscriber programming as evidenced by the mutual aid channels. Also, UHF is standardized as mobiles TX high.

 

[MTS2000des]

More CCR crap on public safety channels....Where do you buy your fire fighting gear amazon ?

I'd be willing to send him a real duty fit UHF analog radio, a Motorola XPR7350E, for the cost of shipping. Cheap garbage pail Chinese radios have zero place in IDLH environments.