ISP radios

[jharris68]

At what power do the mobiles transmit at? I very seldom am able to hear anything but dispatch on dist 13, 19, and 22. At the same time I can hear 6 local county pd's just fine. I thought maybe I was missing a frequency, but I do hear them occaisionally.

 

[illini52]

Usually 100W. Do you have an outside antenna? Normally, you won't be able to hear the mobile units much more than 10 miles away unless you have a really good receive setup (tall tower, tuned antennas for VHF hi/lo). Even then 15 miles is pushing it for the mobiles.

 

[jharris68]

I have an ouside antenna, probably 20 feet, also a mobile antenna, both tuned for vhf high. I just wondered why I could hear county pd mobiles. From neighbooring counties, and not hear ISP mobiles. Your range estimation is pretty close. I know when they are fairly close to my house, I dont live very far from I57, and I24.

 

[timmer]

The county pd's are most likely on a repeater. As for state mobiles, he's right about not hearing them more than about 10 miles with your indoor antenna. I'd say more like 6 to 8 miles tops would be more accurate. I have a d-130j discone mounted on a 45 foot tower and I can recieve the mobiles about 25 miles away, tops. I also have a scanner beam that can pick them up maybe just a little bit farther, when it is pointed right at the mobiles location. (Of course, this is a pain to constantly be turning the rotor.) From what I have heard, a more band specific antenna might give you the best results. I have heard the comet gp-6 is a great antenna for vhf high band. There are others as well.

 

[K9JLR]

Most commercial scanner antennas just do not perform well on VHF-lo, probably because most monitoring activity is now concentrated in the VHF-hi and UHF segments of the radio spectrum. Some folks have the same complaints about these antennas for distand monitoring of stations in the 800/900 MHz range.

I would recommend that you either purchase a commercial antenna tuned specifically for lowband or purchase a six meter base antenna (like I did) and use it to monitor lowband. Purchasing a six meter ham antenna will save you some cash, but it won't work quite as well as an antenna tuned specifically for say 42 MHz. Another relatively inexpensive option would be a mobile to base antenna conversion kit on a stainless steel 102" whip trimmed to 72" or so (pick your optional frequency range and cut that antenna to 1/4 wave for that freq.).

 

[werinshades]

Is it possible that you don't have the Mobile frequency programmed in? Most of the State Police's VHF-Lo frequencies have both a Base Frequency and a Mobile Frequency . You have both programmed in correct ?

 

[jharris68]

I belive they operate on one frequency, because I can hear them when they are within 10 miles or so. I really don't think the local counties use a repeater either, but maybe they do.

 

[werinshades]

I belive they operate on one frequency, because I can hear them when they are within 10 miles or so. I really don't think the local counties use a repeater either, but maybe they do.

I'm no expert on ISP, but to be on the safe side, put in the Mobile frequencies with the CTCSS mentioned in the forums. You should know within an hour if thats it. When District-Chicago was using VHF-Lo, they only used one frequency, but if my memory serves me correctly, most southern Districts use both. Is it possible that they could be simulcasting from the Starcom system?

 

[RoninJoliet]

Simulcasting is correct, here in Joliet at D5 the tech has revealed that all new Starcom consoles have been installed and a few weeks ago the D5 and Elwood IL transmitters were tuned to simulcast thru these consoles for 42.60, 42.80, 154.92, Ireach, Ispern, Point to point.....

 

[timmer]

I wish they would simulcast downstate. I want to put my pro-96 to work!!

 

[RoninJoliet]

The simulcasts are "analog' not digital, but here at D5 the testing is on 700mgz in digital and so far they have been using mostly one freqys on TO 101=774.80625 and i used Win96 software to open up the PRO96,it handles the digital 700 freqy with perfect audio decoding but will not trunk the system...

 

[bessiedawg]

I used to live in Decatur back when ISP was exclusively low band. Given the size of ISP District-10, I was always amazed that a mobile unit at the far end of the district could be heard by district headquaters in Pesotum. Was that due to tower height at Pesotum, or the nature of low band signals ? I know the wattage from the mobile radios was not that strong.

 

[N9JIG]

I used to live in Decatur back when ISP was exclusively low band. Given the size of ISP District-10, I was always amazed that a mobile unit at the far end of the district could be heard by district headquaters in Pesotum. Was that due to tower height at Pesotum, or the nature of low band signals ? I know the wattage from the mobile radios was not that strong.

District 10 has remote sites at Champaign, Danville, Strasburg and Decatur. This allows them to select the closest transmitter for the car involved. They also use voting receivers, where multiple receivers are connected to a central voter (by microwave or phone line) and the voter selects the best quality audio to send to the console.

This allows ISP to cover such a large area without needing a 2 mile tall tower or a million watts of power.

 

[bessiedawg]

Right....I was referring back to the "dark ages" of the 70's. ( There was this thing called disco! ) At that time they did not have the satellite towers. Thanks for the detailed info though. I didn't realize that they had one in Strasburg. It's actually a huge district.

 

[timmer]

District 9 has several of these satellite towers, also. They have them is Springfield, Jacksonville, Beardstown, and I believe Taylorville.

 

[K9JLR]

Right....I was referring back to the "dark ages" of the 70's. ( There was this thing called disco! ) At that time they did not have the satellite towers. Thanks for the detailed info though. I didn't realize that they had one in Strasburg. It's actually a huge district.

The remote sites are not brand new technology, as they have been around for awhile. I had a conversation about ISP radios with a very long time monitoring veteran and he seems to believe that the old ISP mobile radios were actually built better 30+ years ago and went a bit farther (range wise) than they do today. These old times talk about monitoring District 5 (Joliet) when the covered La Salle County, aparently w/o a remote receive site.

 

[scannerbum]

What I can hear .

I monitor ISP Dist 9 . Before I got my new antenna this week ( RS 20 - 176 ) , I could hear dispatch and maybe mobiles if they were like at the end of my block. With this new antenna about 20 feet off the ground I can now hear mobiles about 10 miles away.
However this new antenna does not seem to work well my new PRO 2055 , so right now
I am using it on my cheap BC 350 C .

 

[ewink]

District 10 has remote sites at Champaign, Danville, Strasburg and Decatur. This allows them to select the closest transmitter for the car involved. They also use voting receivers, where multiple receivers are connected to a central voter (by microwave or phone line) and the voter selects the best quality audio to send to the console.

This allows ISP to cover such a large area without needing a 2 mile tall tower or a million watts of power.

I had always wondered how that worked. You have no idea who I am, but you have just became my favorite person on the internet.