In a simulcast system, you have multiple transmit towers (sub-sites), all transmitting
exactly the same radio traffic, as the
same time, using the same frequency.
The problem, for the scanner, is that all these sub-sites are at various distances from you, so the signals arrive at your location out of sync. For scanners other than the Uniden SDS series scanners, these signals, out of sync, can basically "confuse" the scanner enough to make it impossible for it to give you clear audio. In some cases, simulcast may mean that you hear nothing. At other times, what you hear is garbled audio instead of a clear transmission. Simulcast is
extremely location specific. Sometimes, even moving your scanner a foot or two, you can find a "sweet spot" where it might work.
A more complete description of Simulcast, along with a few things you might try, are in this Wiki page:
Simulcast digital distortion - The RadioReference Wiki
Remember that when dealing with simulcast, a "better" antenna (one that provides a stronger signal) may make things worse.
Click on the site's name on the TxWARN page. That will bring up a map showing the location of these various transmit towers. Here's what pulls up for the Montgomery County Simulcast site:
View attachment 145904
Depending on exactly where you are, you see the various towers at at varying distances from your specific location. So, the transmisisons, arriving at your scanner, but not all at the exact same time, are enough to cause problems. The SDS series Uniden scanners can handle simulcast. The Unication pagers can also deal with it, but you are limited to (I think) 64 talkgroups groups & only one site at a time. If
everything you wanted to hear was on the exact same simulcast site, and you had 64 (or less) talkgroups of interest, it would work. You can program additional sites, as well as more sets of talkgroups, but only can monitor a single site, and a single set of talkgroups, at any one time.
You can use an SDR dongle, along with downloaded software, and use your PC, which can monitor what you want. But that's not something portable that you can carry with you. I don't have a Unication pager; the other radio that also works is the Blue Tail receiver. That's programmed with a PC, and does not have a display (unless that's changed recently) See
this page. (I don't own that either, but I've seen a number of comments that it does work.)