Originally Posted by Sybex7254
When will UpMan and Uniden finally acknowledge that the firmware did not correctly fix the LSM issue as it did for the HP-1 and BCD386XT, and a fix is forthcoming?
For myself, the LSM firmware fix did nothing obvious for the P25 systems I monitor on the HP-1, 396XT or 996XT.
What little it did do, it was equal for me on all the models that they released the firmware for. I've read the posts here and it does seem that more complaints are noted for the 996 over the 396. Maybe there is a reason for that like maybe there are more 996XT's out there than there are 396XT's. Or as was mentioned, something is amiss with your 996. Don't really have an answer. I have also seen posts stating the new firmware did help many with the 996XT. Another thing to keep in mind, as with many forums, only the bad is posted and those that did see an improvement never come back and report it. That's always been a problem not just here but also for review sites. People like to lodge their negative complaints but those same people will never log in and provide any positive reviews or comments. That's just the nature of the internet and many people in general. If there were a way to get people to post the positives like they do the negatives, things would be a lot different in my opinion.
Originally Posted by Sybex7254
I shouldn’t have to disconnect my external antenna in order to hear a system less than 2 miles from me.
Actually disconnecting an antenna for a system that close is not uncommon at all. The proper way is to turn on attenuation or use an indoor antenna or an external with less gain like a 1/4 wave antenna if you have an outdoor antenna with gain in the first place. A discone offers no gain. It is more like a 1/4 wave antenna. Not sure what you use for an external antenna. A Yagi aimed away from the system can also have the same effect as switching to an indoor antenna. For desense issues, all you need to do is reduce the offending signal just enough to where the AGC circuit in the receiver can handle the high power signal. If the receiver sees too much signal, the AGC circuit just turns down the sensitivity as low as it can go which can almost be like shutting the receiver off. When that happens, you receive nothing. The offending signal does not even need to be in the same band you are trying to receive.
Read up on desense. That will explain why using an indoor antenna for really close systems may work better than an outdoor antenna.
Scanners are very prone to desense due to their wideband front ends and often, poor filtering.
GRE's in particular are horrible and suffer from desense more than any scanner I've ever owned which is between 75 and 100 over the past 40+ years.
Our highway department cannot communicate truck to truck when they are gang plowing the interstates if they are using the repeater. And that is pure analog. The high power mobile in one truck will cause the receiver to desense in the other truck and then the other truck cannot hear the person trying to call him. They must either back away a few hundred feet or switch to a simplex or direct channel. So desense problems do not just affect scanners, it can also affect commercial two way radios. Scanners in general are much more prone to desense issues though.
For GRE scanners. I cannot use an external antenna (without external filters) with any of the digital models here on VHF due to desense from several nearby VHF paging transmitters. I have two options for the GRE's, one is to use a Notch filter tuned to the paging transmitters frequency range or the 152 MHz band specifically. The other option... use an indoor antenna which weakens the signal from the paging sites enough that the front end can cope with the paging signals and allow other frequencies to be heard. I opted for the notch filter as I do enjoy weak signal hunting and an indoor antenna is no good for that.
GRE's current crop of digital scanners do not work worth a darn in an urban area with lots of high level RF signals such as my area. That includes the PSR-500, 600 and 800 as well as the radioshack clones of the same models. GRE has very poor filtering or bandpass filters for the VHF range. Then the 700/800 MHz range is very easy to overload on the GRE's due to all the high level RF in my area from business systems, cell sites etc.
I rarely use my GRE's for the above reasons. They do work fine if I travel away from all the RF noise like when I go to our country property.
In general, the Uniden models will handle high power RF that may even be out of band way better than the GRE's do. If you live in a rural area, the GRE's usually do a good job but FM Broadcast can still wipe them out in the VHF range. A lot of users have found that a simple FM Trap works wonders for the GRE models. The same trap is not normally needed for the Unidens unless you have an FM broadcaster in your backyard!
Your 996 sounds like it may be suffering from desense or multipath (or both) if unhooking the outdoor antenna helps. Then there is multipath distortion which has no magic fix all that will work for everyone. By unhooking your antenna, it is very possible that a signal from another simulcast transmitter is reduced to the point the 996 no longer hears that signal which will often clean up multipath distortion and give you good decode rates from a simulcast system. Some (myself included) have good luck using a yagi antenna aimed at just one tower of a simulcast system. That does not work for everyone though.
It took me several months of experimentation before I found a solution that worked well.
For my VHF desense issues, it was as easy as notch filtering the high power paging band which I was lucky and it was only the 152 MHz paging band. I do have paging transmitters in the 158 MHz band also but they are far enough away to not cause desense issues on all but the GRE's. I do need 158 MHz notch filters for the GRE's if I monitor any VHF systems but I don't monitor VHF often with the GRE's so I leave that filter out.
For the 700/800 MHz systems that are simulcast systems, I use a 12 element yagi on a rotor so I can aim for the system I feel like monitoring at the time. Lucky for me, a lot of those systems are not simulcast so I don't experience much multipath unless I'm also getting a reflection off a nearby building. Reflections are just as much a cause of P25 decode errors as are simulcast signals arriving at your antenna a few milliseconds apart. They can both cause your decode rate to drop way off. Reflections can occur on simulcast and single site systems and are usually harder issues to fix than what Uniden is attempting to do with firmware.
Then you try and receive those signals with a typical scanner that usually has very poor front end filtering, you will end up with poor results on digital systems.
For one 800 MHz P25 system here, none of my GRE's will decode the system at all unless I throw in some serious attenuation before the radio. I must attenuate that system to the point there is almost no signal at all.
Once I do that, the GRE's will decode that system just fine.
For the same system, I need no attenuation at all for any of the Uniden's.
I blame a lot of that on the need for the 12 element yagi and the overly sensitive front end in the GRE models. My building is wrapped with steel mesh so an outdoor antenna is a must here for the distant systems.
So unhooking your outdoor antenna for a very nearby system is often a solution that will work for many yet many do not try it because it seems backwards. As you found though, it does help at least on your 996.
I've known several people that found using just a paperclip for receiving nearby 800 MHz P25 sites solved their reception problems. I don't know if their problems were due to desense, multipath or simple overload but the trick worked.
Then of course when they want to monitor distant systems, they must hookup the real antenna again.
That is a pain but not much you can do about it with the wideband receive all front ends in today's scanners.
A scanner that can cope with most of the above problems would probably cost in excess of 10 grand after the manufacturer adds in all the proper bandpass filters. There would never be a market for it other than government users and super die hard hobbiests so I doubt you will ever see such a beast. The closest you will find that can handle high RF levels like found in many large urban areas are the professional grade receivers like the top of the line Icom's and the like. And they do not even do P25 or follow a trunked system. There is a P25 module for the Icom R1500 and R2500 radios but they don't offer the same performance as the R9000 or R9500 for example. And even those radios could be prone to multipath issues as can a commercial radio.
Monitor a P25 system long enough and you will hear the users or the dispatcher complaining of digital issues on occasion. And those users are using high cost top of the line radios. So multipath issues do affect even the pro commercial radios and systems but not as bad as a typical scanner.
I wish Uniden could fix the problem with firmware alone but there are just too many variables that come into play. Each users receive site is different from the next user so I don't see much hope in a firmware release fixing this problem for everyone. It may help some but may degrade others as seems to be the case from reading the posts here.
They almost need a firmware with a switch that the user can toggle the LSM fix on and off on the fly to see which method gives them the best decode rate. That would not be a positive test though as simple things like changes in the weather can cause a huge change in P25 decode rates. It would be much faster for making comparison tests over loading older or newer firmware which can take several minutes in which time external conditions could change. Those external condition changes could make testing different firmwares invalid considering the time it takes to load different FW versions. I'm not sure they could add a soft switch into a menu setting that would allow the end user to quickly compare which is better but it would be a neat idea if it could be done.
The older 396 and 996T models do allow a per system mode change that kind of allows the end user to quickly change settings for a P25 site.
That manual mode does seem to work much better on most systems over the fixed auto mode that the XT series use. The XT series do allow for some control of the P25 settings but it is radio wide and not per system like it is for the T models. Plus you must turn the XT off and hold keys down to even get to the hidden menu.
I know one thing for certain, my T models work much better on simulcast P25 systems than my XT series ever have.
Why they don't re-enable the T's manual mode in the XT's is beyond me but perhaps there is some hardware limitation in the XT models that prevents the old T manual mode.