CoMIRS Metro Boston Overlay Simulcast

[n1moy]

My initial experimentation with CoMIRS has been to receive control signals. Using a 9 element 13dBi yagi antenna, reception of the 'Logan Airport/Massport' site is possible from the town of Hull. Route is mostly over water, Boston Harbor.

The 'Metro Boston Overlay Simulcast' is more of a mystery to me. The RadioReference database provides a location coordinate of Logan Airport. [42.3698, -71.0107] I'm not seeing any control signal in that direction. Perhaps the listed location is original or antiquated. There are also no locations posted on the FCC site for WPTZ789.

Requesting site location details for the 'Metro Boston Overlay Simulcast' to point a yagi. Also, are there multiple transmitter locations for this site ?

Thanks in advance,

 

[ecps92]

My initial experimentation with CoMIRS has been to receive control signals. Using a 9 element 13dBi yagi antenna, reception of the 'Logan Airport/Massport' site is possible from the town of Hull. Route is mostly over water, Boston Harbor.

The 'Metro Boston Overlay Simulcast' is more of a mystery to me. The RadioReference database provides a location coordinate of Logan Airport. [42.3698, -71.0107] I'm not seeing any control signal in that direction. Perhaps the listed location is original or antiquated. There are also no locations posted on the FCC site for WPTZ789.

Requesting site location details for the 'Metro Boston Overlay Simulcast' to point a yagi. Also, are there multiple transmitter locations for this site ?

Thanks in advance,

Massachusetts Commonwealth Interoperability Radio System - Scan New England Wiki

www.snewiki.com

the known multiple sites for the 700 are:
Arlington, Revere, Milton, Quincy and 4 different sites in Boston

For Hull, I might say try Revere if you are getting Logan ok

As to site info from the FCC Database there is/will be none for that callsign
Since those frequencies are assigned to the State they can be placed anywhere they wish within the Market (like TV/Radio)

 

[W1KNE]

The 'Metro Boston Overlay Simulcast' is more of a mystery to me. The RadioReference database provides a location coordinate of Logan Airport. [42.3698, -71.0107] I'm not seeing any control signal in that direction. Perhaps the listed location is original or antiquated. There are also no locations posted on the FCC site for WPTZ789.

The radio reference location is for the "center of the circle". Meaning it is the expected minimum area you should receive any of the sites. The actual distance varies by all the normal factors. It is not a point of transmission. So Logan isn't a site, it's just the center reference.

As Bill stated above, that it is a market license. The locations have only been unofficially determined by users. The system is designed to cover the area within 128. That means it is optimized for coverage there, but not so for locations out near where you are. By the fact we're stuck in using circles vs geometry for these coverages, it shows you have coverage when it is plausible you don't.

Make sure you are using a simulcast capable receiver such as a SDR, SDS or the like. And aim towards downtown, there is a known site on one of the roofs there.

 

[n1moy]

Thank you for this information!

Is the Quarry Hills Drive tower the Quincy location ?
[42.247009, -71.048219]

Revere also looks like a possible option.

Thanks again,

 

[W1KNE]

Thank you for this information!

Is the Quarry Hills Drive tower the Quincy location ?
[42.247009, -71.048219]

Revere also looks like a possible option.

Thanks again,

Likely so.

 

[n1moy]

Favorable results !

Not the strongest of signals. My route is not without obstacles.

Pointed the yagi in the general direction of the Quincy, Quarry Hills Drive tower and received a -60dBFS control signal. Also aimed ~60° further to the north and received a lesser signal, possibly Revere.
[image attached]

During my test the signal was infrequent, perhaps current traffic on this site is sparse.

Thanks again for your assistance,
-Bob

 

[nikronzo]

you should use a program like SDR trunker or unitrunker to follow the simul better rather than just a single voice channel which can be used infrequently or at random. the current CC is 774.58125.

 

[n1moy]

I was using this grid to determine the control channels.

Site Frequencies​

769.20625	769.93125	770.15625	770.45625	770.90625	770.95625
773.05625	773.28125	773.53125c	773.58125c	774.33125c	774.58125c

 

[W1KNE]

To reiterate Nik's point, about following the trunk, here are the following, currently active voice channels.
From monitoring for the last 2 hours.
769.93125
770.15625
770.45625
770.90625
770.95625
773.05625
773.28125
773.53125

 

[n1moy]

Mike, Curious what you are using to track active voice channels on the site ?

 

[W1KNE]

Simple, as I was at work. Proscan on my 536HP. With a highly directional antenna aimed downtown.

 

[n1moy]

Constructed a 772 MHz ground plane for indoor use with a Uniden SDS200. Used a BNC male chassis mount with some 10 & 24 ga wire. Measured SWR 1:1.22 with a NanoVNA. Antenna hung from the ceiling above the radio scanner with paracord. Receiving the site successfully with the addition of a 20 dB GaAs FET preamp. RSSI is about -85 dBm.
[image attached]

 

[ecps92]

Favorable results !

Not the strongest of signals. My route is not without obstacles.

Pointed the yagi in the general direction of the Quincy, Quarry Hills Drive tower and received a -60dBFS control signal. Also aimed ~60° further to the north and received a lesser signal, possibly Revere.
[image attached]

During my test the signal was infrequent, perhaps current traffic on this site is sparse.

Thanks again for your assistance,
-Bob

Also depending.... pointing toward Quincy is also right at GBH (Canton)

 

[n1moy]

Experimentation with the outdoor yagi was mostly to confirm if site reception was possible. Ground plane antenna fabrication followed. The line drawn on the attached Google Map is from Great Blue to Quarry Hills and beyond, north of Hull.



Currently receiving the 'Overlay' site using the indoor omnidirectional ground plane without problems. Many of peaks on the attached tinySA image are site signals. About -82dBm is above the noise floor and more than enough signal. Glad that I was able to avoid an outdoor antenna.