996XT on VHF - Blech & Notes
I spent this evening carefully comparing what the 996XT does on 150-162 MHz VHF bands compared to what the exact channel allocations actually are frequency-wise.
The 996XT uses a semi-preset, built-in band plan to configure what we'll call it's "channel steps" across it's spectrum coverage. These can be modified by the user through both external software and the menu system.
There are 31 segments to this band plan.
This band plan effects user entered "custom search" as well as entering frequencies into memory channels manually. The radio's service search appears to be a set of separately configured individual channels using unique step sizes and those appear fairly accurate.
And most of the above band plan is pretty accurate and effective for most band segments. But there is (to me) a HUGE problem with VHF.
Even if you change the default band plan for the 150.8000-161.9950 segment from 5 KHz to 7.5 KHz you still won't be getting accurate "channelization" for many, many of the channels and services using VHF.
Why? Because the VHF band isn't this simple. There are several "breaks" in this band. These are caused mostly by small "guard bands" surrounding retained wide band FM channels and other breaks between the service allocations on VHF. VHF simply isn't this simple. If you start out the band at 150.800 (it actually starts at 150.7750) and start generating channels by simply adding on 7.5 KHz steps you'll end up well off the actual channel frequencies in many, many cases.
I thought I had discovered a work-around via software. Using some accurate data sources I generated a database including some 707 accurate VHF channel / service allocations. Earlier, I had observed that when using Butel's ARC XT software that if you simply pasted columns of numeric data (not "paste frequencies", just "paste") that the software didn't round off the entries to (incorrect) values. So I generated such a system and loaded it into the radio.
Egads! The radio is still over the place on VHF. With the radio's band plan switched to 7.5 KHz steps on VHF the memories which actually got loaded are a big mess. Some the radio rounded off the entry to what it thinks is the nearest VHF channel step (wrong!). On about half of the others it simply got programmed with 000.0000 for a frequency - not so good!
Now I know what the more casual hobbyist will say; "well, it's only 2.5 KHz off and the radio's functionality will be fine, everything will work and you'll hear everything just fine".
No, no you will not! Especially when its this far off. Issues;
#1. You'll simply miss altogether many, many bona fide allocated service channels. Dozens of them.
#2. For narrow band operations 2.5 Khz is significantly off-frequency. You'll catch a lot of static, erratic CTCSS/DPL receive and greatly reduced sensitivity. You'll also have more problems with adjacent channel interference.
#3. For beginners this causes a lot of confusion and frustration when trying to enter 7.5 KHz step VHF channels. "Why isn't the radio taking my entry?".
#4. For more advanced users this causes A LOT of trouble when programming the radio using software.
I don't know, but to me this a HUGE issue. Making it worse is that when you do manage to get a 7.5 Khz step VHF channel accurately programmed the 996XT is a STELLAR performer on VHF. Great sensitivity, selectivity, intermod resistance and filter shaping. What an enormous waste of a great receiver, all due to rotten planning and research.
Why am I being so hard on Uniden on this matter? Because it's been around for years and years, since VHF went to 7.5 Khz steps. Uniden blew it on the 780XLT and has continued to blow it on nearly every radio they've come out with since. GRE got it almost exactly right starting with the Pro-97 and continues to do so with every radio they've come out with.
To me, this is a real mess, especially with this otherwise high quality and very expensive radio. The cure will apparently require a firmware flash for a new band plan organization. They need more VHF chunks, accurately configured on VHF.
I had started this post with the goal of posting an all inclusive listing of right / wrong / error / missing VHF channels on the 996XT. When I reached a dozen problems before I got a quarter of the way through 151 MHz I stopped. Trust me, the 996XT as its shipping from the factory or as it can be adjusted by the user has some major, major problems in the VHF band.
I hope Uniden gets with the program and fixes this major fault with the radio. Other than this problem, its a pretty nice radio.
Happy Scanning! - Ted
Earlier observations...
Well I finally bit the bullet and bought a 996XT. Overall, very, very happy with
it. I have it hooked to a professional comm speaker and the digital decode on
Starcomm actually sounds better than the Starcomm radio we have at work - and
that is on the problematic North Cook and Lake Counties simulcast sites. Most
impressive. Tracking on SC21 is also excellent, I've yet to see it drop or
garble a transmission which the system itself wasn't garbling. Dare I say it?
P25 voice sounds almost natural and not at all like some annoying, warbling
Nextel. I wouldn't say it sounds as good as well engineered analog FM channels,
but its at the point where you do start to appreciate the lack of any analog
static.
Very good sensitive and selective receiver. UHF sensitivity in the 460-465 Band
is slightly improved over the 996T, but is still just a tad lacking there. Its
very good but not super great there. It also seems slightly prone to FM
broadcast band interference in the lower end of the VHF aeronautical band, but
I'm at a very problematic location for that and the noise squelches out nicely.
I have found zero birdies or noise in the 225-400 Milair band. It seems
generally pretty "quiet" across the rest of its spectrum, as well. I'm still
searching it out for real birdies. I haven't brought it down into the city yet
to see how it stands up to real intermod, but I haven't experienced any pager or
taxicab noise yet from home.
Its very sensitive on VHF. From home I'm routinely copying base traffic from
Marengo, out past Kenosha, through Gary and out into Porter County, Indiana. An
impressive radio on VHF and the narrowband adjacent channel rejection on both
VHF and UHF is quite good. Not perfect, but that's the nature of the beast.
(see more recent negatives on its VHF configuration above)
I can find very few negatives for this radio, but here's a few:
-I think I've stumbled across a few minor software glitches, mostly in the
operating menu system. If you encounter something strange just repeat what ever
you are doing and it always seems to work on the 2nd try. Same for programming
complex trunked systems via software. I sometimes detect a glitch or two on the
initial program, but then it loads fine on the second attempt. Keep in mind this
is the initial firmware for this new radio and its minor stuff. I have to start
making notes...
-No printed manual. I hate this. This is a very complex radio with an
intimidating learning curve, it needs a manual. They give you Uniden's operator
help web page on a CD, its okay but it's not a real manual.
There are some new files available at:
SiteExport < UnidenMan4 < TWiki
-No programming cable or operating software on the disc that came with my radio.
The programming cable for my 396T works fine. A serial programming cable is
supposed to be included.
-The radio case needs some feet. Its sliding back on the shelf when I push the
radio's buttons. I'm going to get some stick-on non-skid feet for it.
-I'm starting to suspect Uniden didn't get every single one of the 7.5 KHz step
channel allocations in the VHF public safety band exactly right. Okay, I'm
finicky about this. It can be addressed by customizing the radio's built-in band
plan. (no it can't - see above)
-Delay and hold (new) settings are by group, not by channel. They work amazing
well, however.
I've tried Butel's ARC XT Pro software and it really rocks. The bandscope
feature is incredibly well implemented and lightning fast. Almost like having a
real spectrum analyzer. It's "limited" to 3200 channel steps (manual says 1600,
its wrong), though in practical application I find 800 a more efficient upper
limit. That is a nice chunk of spectrum. It has both peak and waterfall
displays. It can operate in span or custom limits modes and step sizes and modes
are user-adjustable. The display works best at around 1024x768 screen
resolution. Clicking on a peak snap tunes the radio to the found frequency. The
bandscope will cover 162-174 using 5 KHz steps in about 35 seconds. If you
happen to have a "real" high resolution display and mouse setup that will come
in handy. ARC XT will import files from their 996T and 396T software and it does
the radioreference imports, too. Its great software. It comms with the radio at
speeds up to 115200, which makes programming a lot faster than on my 396T.
On the 996XT you really have to sit down and start learning the key functions to
get the most out of the radio. The radio has 8 different operating modes and
most of the keys do something unique in each mode. Then there's function + key,
key hold, etc. This radio will keep me busy for months just learning it.
The multi-color display is a lot of fun. You can also use it as an alert (along
with the tones). In that mode it flashes a user selectable color at user
selectable fast or slow rate a few times before the display reverts back to the
color you selected for the group or channel.
The radio has a built in 6-tiered scan ordering system, in addition to a
(complex!) user priority system. If scan order is important to you I'd suggest
reviewing how it actually scans prior to programming as some of it involves
alphabeticals and system structure. Pretty cool! See:
BCD996XTScanMode < UnidenMan4 < TWiki
Happy Scanning! - Ted
