I was going to order a REM-800b from Universal but the way the page loaded on my phone wouldn't allow me to. I "googled" that number and found a page at AirSpy.US that offered it for $19 95 + $9.00 for Priority mail shipping, a combined cost that appeared unbeatable, so I ordered one. Today, I received an email that it shipped. BTW, several sources reveal that is an Alinco antenna. I ordered the BNC version as the SMA version appears to be the wrong version for a BCD436HP, but I'm going to use mine on a TRX-1.My 436 stock antenna seems fine and I'm not keen on using any antenna on a handheld, with any kind of adapter.
The one listed at ScannerMaster and Universal are both Remtronix. However, Remtronix is the U.S. distributor for Alinco. Remtronix was set up by the U.S. staff of the now defunct GRE. GRE originally made that antenna, sold under license to Radio Shack as their "800 MHz" antenna. Now that GRE is no longer around, Remtronix distributes the antenna. While I have not seen one labeled that way, I suppose that some might be labeled as Alinco, since Remtronix is the distributor.
The SMA version would work on the 436HP, as well as earlier handheld models such as the 396XT or 396T. However, the 436HP ships with an SMA to BNC adapter, so the BNC version would work as well. I use the BNC version, with the adapter on the scanners that need it, since I have multiple scanners, some with BNC antenna connections, others SMA. Using the adapter on the 436HP, among others, I can switch any of my collection of antennas among any of my handheld scanners. While there is a slight loss of signal when using an adapter, it's so small as to be a non-factor on sensitivity. Plus, using the adapter, I eliminate wear or damage to the scanner's SMA connection. If the adapter becomes worn, not mounting the antenna securely, I can easily swap out the adapter. Much easier, and less expensive, than having to replace the SMA on the scanner itself.
I've tried this antenna on my TRX-1, with unsatisfactory results. But that is because I'm near a major highway junction, surrounded by a literal forest of cell towers. That tends to overload the GRE/ now Whistler design scanners and causes them, at times, to be less sensitive.