Question on simulcasts for the DC area

[danesgs]

There are a number of counties with listings on RRDB for frequencies as "simulcast". Most of these are in the 851-852 region for Montgomery and Fairfax county. When they are being sent out are they digital P25 Phase 1 or what. I put these into a scanner but rarely hear anything. I know here in loudoun the FD uses 46.380 analog simulcasting their phase 2 stuff and Montgomery county uses 153.950 and 154.160 analog the same way. Are the other frequencies just deprecated and not used but kept around for something else? Also Metro here uses the 496 band P25 Phase 1 but occasionally you hear talk on one of those as analog but not very often.

 

[jonwienke]

In general, the analog freqs in the DC area are just rebroadcasts of specific digital talkgroups on various trunked systems, and are used only as backup or patch to old legacy equipment being phased out. If you have a scanner designed for simulcast, monitoring the trunked systems is a better bet than the analog stuff. Metro and other systems have simulcast sites, and if your scanner isn't designed for that, your reception may be spotty.

 

[marksmith]

If you have a radio designed for simulcast reception, the majority of activity is on those trunked talkgroups. Generally, scanners do lousy trying to receive simulcast transmissions because they involve simultaneous transmissions from multiple sites, which cancel out reception.

The stuff on vhf are not simulcast, but simply patched transmissions on legacy frequencies.

Radios such as Uniden SDS100 or SDS200 are made to handle simulcast reception when a,regular scanner, even with a very strong signal, will not be able to receive because it is not able to handle transmissions from multiple transmission sites simultaneously.

 

[danesgs]

Got it. Thanks

 

[maus92]

I don't quite understand the OP's question, but there are two meanings of "simulcast" wrt the counties he mentions. First, jurisdictions typically "simulcast" dispatch operations both on legacy VHF frequencies and a dispatch talkgroup on their 800Mhz trunked radio systems. They may also have the ability to "patch" together another VHF frequency to another operational TG if needed. The result is conversations are heard on both the VHF freq and the 800 TG at the same time, hence "simulcasting." The term "simulcast" is also used when defining a type of transmit site configuration typically used in wide area radio systems. In the simplest of terms, "simulcast" in this context means multiple radio tower sites transmitting the same conversation using the same frequency.

Both Fairfax and Montgomery Counties have very busy dispatch operations, so if you have programmed your receiver properly, you will hear a lot of traffic - if you are in range of the signal.

 

[maus92]

Dupe.