BCD436HP/BCD536HP: Poor sensitivity in the VHF high bands.

[meridiangold]

Still learning how the 436hp works. I've noticed my 436 is pretty deaf in the 155 to 170 Mhz range. I'm comparing it to my RS Pro528, which has awesome sensitivity with just it's rubber ducky. I've connected the 436 to two different antennas in my loft with poor results on the 436 but awesome results with the pro528. Of course reception improves noticeably on my 436 when mobile and a different 2m whip like the one in my loft. I modified the loft antenna by adding a substantial ground plane, sort of. I'm going to trim that one more specifically for the range I mentioned. A proper outdoor antenna will happen when winter passes. I did crank the AGC/DGC settings with no improvement. My squelch sits at two. The air band works awesome as does a lot of the UHF band(s). Has the 436 been shown to exhibit this behavior? I wonder if UNIDEN knows this and might work out the algorithm in a future update. I'm not exactly in a signal dense area, but the Pro528 outshines the 436 hugely.

 

[mshumeyk]

Uniden's main selling point for the 436hp was reception of P25 Phase 2 trunked systems. A second point was the memory containing the US frequency database along with computer programming and software updates. Sensitivity took a hit. Unfortunately, the 436 is subject to problems with simulcast distortion in locations where several towers are in range. The SDS100 does not have the same problems with simulcast distortion but has even less sensitivity than the 436hp, especially on VHF low and high band. For VHF and UHF analog my Uniden 396XT and BCD 325P2 do far better than the SDS100 and 436HP. Yes, you would think that when you pay the price of an SDS 100 or 436HP reception of analog signals would at least match that of earlier scanners, but alas, that is not the case. With Uniden there is no single "superscanner" that excels in all aspects. For optimal reception of everything you want to monitor you often need to use several scanners side by side.

 

[737mech]

I recently picked up a BCD436HP and I'm using a Diamond SRH320A. Works great on VHF and UHF. Not sure your location or specific VHF you can't get but check into antennas and settings as well. Service types/Modulation/Priority Modes/ etc' all that can screw up your scanning experience with the BCD436HP.

 

[meridiangold]

I purposely avoided the SDS100/200 series after reading the 436 performs better than the SDS on conventional vhf FM. I live very rural, with an abundance of conventional traffic, and need to go urban for reliable P25 and it's derivatives, and I don't travel expansively very often. Conventional simplex and a few repeaters is my main diet. I bet Uniden could tweak the reception with some manner of dual squelch software component. mshumec is correct about the bandwidth sensitivity. My 436 behaves much better at around 140-150MHZ, and again above 160-170Mhz. If the SRH320A has better specs, I'll replace my attic whip and my mobile whip, IF they can handle some serious winter elements. My plan is to look for a base antenna with some gain in the right ranges too. I've tried numerous scanner configs to little or no benefit save for the AGC settings. I hope Uniden reads these forums and the potential of the 436hp. Think of the children!

 

[737mech]

There are many posts about "My old scanner worked but my new scanner doesn't" I just want to remind you to check all coax connections and adapters. Maybe replace the feed coax for LMR-400? There are many base antennas that can dial in closer to your range needed. Personally I use the DPDProductions LP for base but no longer available. However the Omni X is a great antenna and available. Some here have mixed results but in your situation I think it would solve the problem. Outside and higher would be best.

 

[bearcatrp]

I hope Uniden reads these forums and the potential of the 436hp. Think of the children!

. Unidont only thinks about their wallet. Notice how many updates have come out for these expensive radios? Not many. The latest radios have potential but unidont left us to fend for ourselves. With little competition, unidont sits back selling their current line of radios without backing up their product to make them better. My 436 is a pretty good radio but could be better IF they would update it. Wanted a SDS 100 but way to many issues. My SDS200 seems to be fairly good. Knock on wood, no issue so far.

 

[meridiangold]

There are many posts about "My old scanner worked but my new scanner doesn't" I just want to remind you to check all coax connections and adapters. Maybe replace the feed coax for LMR-400? There are many base antennas that can dial in closer to your range needed. Personally I use the DPDProductions LP for base but no longer available. However the Omni X is a great antenna and available. Some here have mixed results but in your situation I think it would solve the problem. Outside and higher would be best...

Yeah, this very much. I've got a small treasure of LMR stored for the day an OD antenna comes to reality. The same with high quality Amphenol connectors. Ham radio has me ruined. My loft is due a visit also.

 

[meridiangold]

. Unidont only thinks about their wallet. Notice how many updates have come out for these expensive radios? Not many. The latest radios have potential but unidont left us to fend for ourselves. With little competition, unidont sits back selling their current line of radios without backing up their product to make them better. My 436 is a pretty good radio but could be better IF they would update it. Wanted a SDS 100 but way to many issues. My SDS200 seems to be fairly good. Knock on wood, no issue so far.

IIRC Uniden has been like this for years. I bought my 436 used, so no warranty. At some point I'm gonna' want to crack that creature open and try some vile things with the interior heh heh. I've seen some interesting hacks floating the net. Add a DIY butt ugly antenna and embarrass my wife. Uniden reminds me of the old HTC phone manufacturer. Sad.

 

[spongella]

I would look at the sensitivity specifications for each model. Check the op manuals for that and compare. Also sensitivity specs can be different depending on the mode and frequency.

 

[Ubbe]

... poor results on the 436 but awesome results with the pro528. Of course reception improves noticeably on my 436 when mobile and a different 2m whip like the one in my loft.

Most receivers starts to gradually lose sensitivity when a signal are received that can pass thru the bandpass filters and when it goes higher and higher in strength. When the signal reach a certain level it will start to create intermodulation where you hear signals on frequencies they do not belong to. But long before that you have lost receive sensitivity.

Every scanner user that have external antennas should have a variable 0-20dB $20 attenuator inline with the coax and while monitoring a weak signal adjust to more attenuation to see if reception improves. If that are the case it will need more notch filters and the cheapest one are FM broadcast, that could be a very powerful signals that makes it pass any bandpass filter in the scanner but VHF are probably the most affected band. Or keep the attenuator at the level where the scanner works best.

/Ubbe

 

[meridiangold]

I would look at the sensitivity specifications for each model. Check the op manuals for that and compare. Also sensitivity specs can be different depending on the mode and frequency.

I know specs can vary wildly depending on the frequency. The specs on the 436 are actually decent, from an actual engineering aspect. It seems to me Uniden derived the specs from a best case, signal rich environment. This is the norm in such endeavors. I wish Uniden had tweaked it's design algorithm and programming for better flex. It's a decent product for it's price.

 

[meridiangold]

Most receivers starts to gradually lose sensitivity when a signal are received that can pass thru the bandpass filters and when it goes higher and higher in strength. When the signal reach a certain level it will start to create intermodulation where you hear signals on frequencies they do not belong to. But long before that you have lost receive sensitivity.

Every scanner user that have external antennas should have a variable 0-20dB $20 attenuator inline with the coax and while monitoring a weak signal adjust to more attenuation to see if reception improves. If that are the case it will need more notch filters and the cheapest one are FM broadcast, that could be a very powerful signals that makes it pass any bandpass filter in the scanner but VHF are probably the most affected band. Or keep the attenuator at the level where the scanner works best.

/Ubbe

Yes. I've experienced this in mobile use of the scanner, especially at around 160Mhz. This is where Uniiden could have designed it attenuator setting to be less restrictive with better user settings. Maybe Uniden needs to invest in new hearing aids...lol

 

[kb3isq]

I remember back a couple years there was a problem with the 436 on UHF and putting a piece of copper tape on the battery cover helped. I don't remember it helping on VHF though.

 

[buddrousa]

If you have overload problems you would a hate a Whistler TRX Scanner as my 22 plus Unidens 536's 996P2's 15 and 15x's all receive the same on a shared antenna system.
Also in my car a 200 436 325P2 and a TRX-1 all share the same antenna system and my 436 will receive a 155.000 at almost 40 air miles.
It sounds like you need a better antenna or the inside of the scanner has seen a CB Radio Magic Screwdriver already.

 

[meridiangold]

I remember back a couple years there was a problem with the 436 on UHF and putting a piece of copper tape on the battery cover helped. I don't remember it helping on VHF though.

Yes. I asked the seller about said defects(?). I was informed my unit is a 2021 model, and apparently this mod wasn't necessary. Will I check to ensure? Yes, eventually. My region, is slowly evolving into UHF territory with trunking systems becoming more available in rural areas. I might even try said mod for fun today. Beats shovelling.

 

[meridiangold]

If you have overload problems you would a hate a Whistler TRX Scanner as my 22 plus Unidens 536's 996P2's 15 and 15x's all receive the same on a shared antenna system.
Also in my car a 200 436 325P2 and a TRX-1 all share the same antenna system and my 436 will receive a 155.000 at almost 40 air miles.
It sounds like you need a better antenna or the inside of the scanner has seen a CB Radio Magic Screwdriver already.

I absolutely need better antennas for both mobile and base. My location sure doesn't help, as I'm surrounded by lofty hills and living at sea level. When I'm mobile, and travel at about 700 feet ASL the world of scanning opens up abruptly. Incidentally, one of the very first things I did upon receipt of my unit was check the case screws for tampering. It seemed in good order, but I'm no CSI aficionado. I'm convinced I'm feeding my unit a poor diet of radio waves. Gain is in my future.

 

[donc13]

And you have answered your own question. The higher the frequency in VHF the more "line of sight" is required. Literally, if you stretched a string line from the transmitter antenna to your receiver antenna, it doesn't take a whole lot of earth in the way to greatly attenuate the signal.

That's why the old VHF TV towers are located as high as they can be.

 

[meridiangold]

And you have answered your own question. The higher the frequency in VHF the more "line of sight" is required. Literally, if you stretched a string line from the transmitter antenna to your receiver antenna, it doesn't take a whole lot of earth in the way to greatly attenuate the signal.

That's why the old VHF TV towers are located as high as they can be.

Yes. I guess I was hoping for that one tidbit of advice that was maybe exclusive to the 436. I've seen how crafty some folks in the forum can be. I've received good advice on my post. Besides my 436 and RS528 pretty much the entirety of my scanning is mobile using an Icom V8000 and my trusty IC91a ht, and almost always mobile. Both worked tremendously because it's just in the design and build. A properly mounted antenna designed for better gain is the only answer. I wish it was christmas.

 

[Ensnared]

Still learning how the 436hp works. I've noticed my 436 is pretty deaf in the 155 to 170 Mhz range. I'm comparing it to my RS Pro528, which has awesome sensitivity with just it's rubber ducky. I've connected the 436 to two different antennas in my loft with poor results on the 436 but awesome results with the pro528. Of course reception improves noticeably on my 436 when mobile and a different 2m whip like the one in my loft. I modified the loft antenna by adding a substantial ground plane, sort of. I'm going to trim that one more specifically for the range I mentioned. A proper outdoor antenna will happen when winter passes. I did crank the AGC/DGC settings with no improvement. My squelch sits at two. The air band works awesome as does a lot of the UHF band(s). Has the 436 been shown to exhibit this behavior? I wonder if UNIDEN knows this and might work out the algorithm in a future update. I'm not exactly in a signal dense area, but the Pro528 outshines the 436 hugely.

I would concur with you if you are making reference to VHF analog frequencies; however, based on my experiences, VHF digital works incredibly well, across many different terrains and environments.

 

[donc13]

Digital is better than analog for receiving as digital has checksums and is simply the equivalent of on/off or high/low.

That's why modern communications are moving to digital because it is easier to decode. Think back to 2009 when US TV switched from NTSC to ATSC and pretty much no more "snow", ghosts or static.

But the electromagnetic characteristics of the frequency didn't change. It still gets blocked by the ground, just the information that can get through from a digital signal can be decoded better.