Help identifying possible frequency range of antenna?

[model2guy]

Calling any antenna experts on here. I’ve been struggling with this for awhile now. This antenna is on an emergency warning siren. I’m trying to find the activation frequency they use. (It’s not listed anywhere that I can find, and nothing found on the FCC database is helpful). I don’t know if anyone here knows a possible frequency range for this antenna, or who makes it, but any information would be appreciated. Just trying to narrow it down until I can find the frequency. I have talked to the EMA guy, and he wouldn’t give me an exact frequency, but he said it’s all analog, and high band UHF, if memory serves me correctly. Any information past that is helpful. Thanks!

-Dayen James

 

[dave3825]

Most of those guys (EMA) (who know it) won’t give out the freq for obvious reasons.

 

[prcguy]

Knowing the frequency range of the antenna will get you maybe within 20MHz of the siren frequency.

 

[merlin]

That is in the 900 MHz data telemetry range. Specific frequencies are probably classified for reasons.

 

[merlin]

Knowing the frequency range of the antenna will get you maybe within 20MHz of the siren frequency.

Probably some data format for the siren control.

 

[wtp]

some more info would help,
town/city/county
is it around some big business

 

[model2guy]

Knowing the frequency range of the antenna will get you maybe within 20MHz of the siren frequency.

That’s enough for me to use a spectrum analyzer to find.

 

[model2guy]

some more info would help,
town/city/county
is it around some big business

Tooele county, in Utah. They have 27 sirens spread across the county.

 

[model2guy]

That is in the 900 MHz data telemetry range. Specific frequencies are probably classified for reasons.

That’s what I expect. I just want something more than high band UHF. The data telemetry range is 902-928, correct?

 

[KevinC]

Could they be on the county trunked system?

Tooele County Public Works Trunking System, Tooele, Utah

Tooele County Public Works Trunking System Profile

www.radioreference.com

 

[model2guy]

Most of those guys (EMA) (who know it) won’t give out the freq for obvious reasons.

Could they be on the county trunked system?

Tooele County Public Works Trunking System, Tooele, Utah

Tooele County Public Works Trunking System Profile

www.radioreference.com

From what I was told, it's all analog.

 

[nd5y]

The data telemetry range is 902-928, correct?

For some unlicensed stuff.
It could be on Part 101 microwave frequencies below 960 MHz if it's not on 700/800/900 MHz PLMR conventional or trunked.

 

[model2guy]

Calling any antenna experts on here. I’ve been struggling with this for awhile now. This antenna is on an emergency warning siren. I’m trying to find the activation frequency they use. (It’s not listed anywhere that I can find, and nothing found on the FCC database is helpful). I don’t know if anyone here knows a possible frequency range for this antenna, or who makes it, but any information would be appreciated. Just trying to narrow it down until I can find the frequency. I have talked to the EMA guy, and he wouldn’t give me an exact frequency, but he said it’s all analog, and high band UHF, if memory serves me correctly. Any information past that is helpful. Thanks!

-Dayen James

Update to the post, not sure if it helps at all, but I do have a tinySA spectrum analyzer I've been using to try to locate the frequency. Its not the ultra version, so it operates between about 1MHz, and 960MHz. I've kinda hopped all around the spectrum, taking chunks of about 40mhz and watching them. I haven't found anything with it so far though.

 

[prcguy]

I might be inclined to open the box attached to the antenna and get a make and model of whatever is inside. Then start lookin up specs.

 

[mmckenna]

Likely you would only find the system transmitting when activated. If they do a monthly/weekly test, that would be the time to look.

 

[model2guy]

Likely you would only find the system transmitting when activated. If they do a monthly/weekly test, that would be the time to look.

That's what I've been doing. They test every Wednesday at 4. I go out there to record the sirens running, and scan while I'm out there

 

[mmckenna]

That's what I've been doing. They test every Wednesday at 4. I go out there to record the sirens running, and scan while I'm out there

It's likely just a command to turn on, and then a command to turn off. You are looking for extremely short transmissions that may not even show up on a spectrum analyzer like that. It's quite the proverbial needle in a haystack, and the needle only exists for a few hundred milliseconds to a few seconds if it's something like DTMF, MDC or other system.

If it's on a trunked system, you'll have a hard time picking that out of the rest of the traffic.
If it's a 900MHz data system, it's going to be a very short burst of data.

I think you need more info. But getting someone to spill the beans on a system like that might be difficult. I don't share info about any of our systems like that just to reduce the chances of someone meddling with it. It falls under the "Security by Obscurity" heading.

Happy hunting.

 

[model2guy]

It's likely just a command to turn on, and then a command to turn off. You are looking for extremely short transmissions that may not even show up on a spectrum analyzer like that. It's quite the proverbial needle in a haystack, and the needle only exists for a few hundred milliseconds to a few seconds if it's something like DTMF, MDC or other system.

If it's on a trunked system, you'll have a hard time picking that out of the rest of the traffic.
If it's a 900MHz data system, it's going to be a very short burst of data.

I think you need more info. But getting someone to spill the beans on a system like that might be difficult. I don't share info about any of our systems like that just to reduce the chances of someone meddling with it. It falls under the "Security by Obscurity" heading.

Happy hunting.

I've been in the EMA office and seen a demonstration of the encoder that runs the system. It keys up for about a second before a strand of DTMF that lasts a second or two. It's a Whelen Engineering system.

 

[mmckenna]

I've been in the EMA office and seen a demonstration of the encoder that runs the system. It keys up for about a second before a strand of DTMF that lasts a second or two. It's a Whelen Engineering system.

Well, then you know what to listen for.
But finding the RF signal is going to be a challenge if it's only a few seconds.
There's a couple of challenges, though...

Don't trust that the EMA manager knows anything about radio. Our EMA managers radio knowledge pretty much stops at "push to talk, release to listen".

DTMF doesn't necessarily mean it's on an analog RF channel.

All you know for sure is that it uses DTMF and it's probably 800MHz, based on the antenna.
It could be a stand alone 800MHz frequency that's only used for siren activation. Might want to search the FCC database for a license that looks like that and has a transmitter site listed as the EMA office.

The transmitter at the EMA office will transmit the activation/deactivation. So you'd probably want to start by being close to that site. The sirens may not acknowledge, so you may have a hard time hearing anything if close to those.

Since they have an 800MHz DMR trunked system, it's entirely possible they are using that system. Finding that on your spectrum analyzer may be a challenge since it's a TDMA system and a short duration signal. But it's a place to start.

Maybe start looking at where the Yagi's are pointed. If they are pointed directly at the EMA office, then it's probably a conventional system.
If the antennas are pointed at their trunked system site(s), then that would be a clue.

 

[model2guy]

Well, then you know what to listen for.
But finding the RF signal is going to be a challenge if it's only a few seconds.
There's a couple of challenges, though...

Don't trust that the EMA manager knows anything about radio. Our EMA managers radio knowledge pretty much stops at "push to talk, release to listen".

DTMF doesn't necessarily mean it's on an analog RF channel.

All you know for sure is that it uses DTMF and it's probably 800MHz, based on the antenna.
It could be a stand alone 800MHz frequency that's only used for siren activation. Might want to search the FCC database for a license that looks like that and has a transmitter site listed as the EMA office.

The transmitter at the EMA office will transmit the activation/deactivation. So you'd probably want to start by being close to that site. The sirens may not acknowledge, so you may have a hard time hearing anything if close to those.

Since they have an 800MHz DMR trunked system, it's entirely possible they are using that system. Finding that on your spectrum analyzer may be a challenge since it's a TDMA system and a short duration signal. But it's a place to start.

Maybe start looking at where the Yagi's are pointed. If they are pointed directly at the EMA office, then it's probably a conventional system.
If the antennas are pointed at their trunked system site(s), then that would be a clue.

First of all, thank you a ton. This is incredibly helpful. I have reason to believe the EMA guy does know about radio, as he is listed on the EMA page as communications manager, and is the guy who is carrying out the police reband from the old MOT system to the new P25 system.

Next, the antennas are all pointed towards the EMA office, and other sites in other areas of the county. As after as my knowledge goes, there is 4 transmitter sites, according to what the EMA manager told me.

The county does have a DMR system in the 800MHz band, which I will check next week just to be sure. I do have a BCD325P2 that can do the DMR system. However, he did say it's all analog. However, I'm not confident in his Information. It wouldn't surprise me if he gave me vague information and told me it was analog just to throw me off the trail.

Thank you a ton for the help, I really appreciate all the information.