796.8250

[737mech]

This is something new to me, during a search from 794-800 I found this. It sounds like a SNACC repeater, all kinds of voice traffic from many users. I can't find it in the database?
Does anyone have info on this?

I'm also getting NHP voice transmissions on 794.559375 this is also not in the database.

 

[TOUGHLIFE]

Metro PD has been known to patch a given LVMPD channel to a channel from some other agency like NHP. This might simply be a test. Nothing unusual.

 

[dougr1252]

Is that with the PSR-500? The GRE radios are known to have image issues. 850-860 stuff is also heard around 79x.xx. If you have time, you might try to find the same traffic on 8xx frequencies with one of your other radios at the same time. I'd be interested to know if you can verify this, and we can add it to the Wiki for these radios.

 

[dougr1252]

OK, too much time on my hands. For 796.8250, try 867.7250. Anything?

 

[737mech]

Images?

OK, too much time on my hands. For 796.8250, try 867.7250. Anything?

Not sure what a "image issue" is but yes the traffic is the same as the snacc trunked system and for the other freq the same as NHP from the NV Shared System.

 

[dougr1252]

It's just a quirk of receivers. Signals on frequency A can also show up on Frequency B, even though they're not supposed to. So the signals on 796.xx are not really on those frequencies. Receivers from different manufacturers will usually have different image responses, so you can use 2 different receivers to check each other.

 

[br0adband]

If you know anything about music, specifically the concept of harmonics, an "image" in radio frequency terms means almost the same thing: if you transmit on a specific frequency, because of how receivers work they can pick up an "image" or a ghost of sorts of that signal at another frequency depending on the IF stage (Intermediate Frequency) of the receiver. Here's a wiki page that can explain some concepts:

http://en.wikipedia.org/wiki/Intermediate_frequency

I'm sure a radio engineer around here can explain it with far more technical terms, suffice to say one aspect of receivers - image rejection - means it'll reject those images better and you don't get quite so much interference when listening.

 

[Thunderknight]

Plus 796.xx is the wrong part of the band for base stations. On 700, the bases transmit low (760s, 770s) and the mobiles transmit high (790s, 800s). It's the reverse of 800 MHz...this way dual band portables and mobiles have their transmitter frequency bands adjacent to each other.