BCD996XT awesome scanner but....

[Boatanchor]

I am the proud owner of several scanners including the PSR-600, the BCD396XT and the BCD996XT.
My favorite, by far is the BCD996XT.

However, there are a few small things about the Uniden scanners that need attention in future models or firmware upgrades.

Firstly, the PL/CTCSS squelch. Why is it so damned slow to close after the PL tone disappears?
The Uniden scanners have a much more sensitive PL/CTCSS decoder than the GRE scanners.
I have confirmed that the Uniden scanners will decode PL tones at ridiculously low signal levels. So low in fact that you cannot hear any voice audio for the background hiss. My 996XT will decode PL tones reliable down to -122dBm or less, whereas the PSR600 has trouble reliably decoding at much stronger/quieter signals. The problem is that the Uniden scanners don't mute immediately the PL tone drops, so you get subjected to annoying squelch bursts on many conventional channels that run short (<500mS) 'quiet' tails. The whole idea of a 'quiet tail' on a repeater is to mute the receivers audio prior to dropping the transmitter. This eliminates the squelch burst on receivers when the signal drops.
The Uniden scanners fail miserably at this because the PL/CTCSS takes so long to close and in many cases doesn't mute at all before the noise squelch closes.

To GRE's credit, the PSR600 allow users to reduce the PL/CTCSS mute response to only 100-200 mS, which is great.

Secondly, why is there no PL/CTCSS filtering (300Hz High Pass filter) on the received audio when operating in FM + PL/CTCSS mode? Many services operate high PL tones (>200Hz) to reduce tone decoding times and presently the Uniden (and PSR600) scanners feed this annoying hum straight through to the audio amps and the speaker. How hard would it be to incorporate a simple 300Hz HPF, that gets switched into the audio path when a channel is identified with PL/CTCSS in 'search' or preset tone mode?

Incidentally there are so many things I love about the Uniden Scanners..

The IFX feature is absolutely awesome and has allowed me to listen to frequencies on my base discone that are simply overloaded by interference on the GRE scanners. Amazing!

The Alpha display's are so much better than the GRE scanners.

Receive performance is excellent on all bands and is at least 2dBm better on all bands than the PSR600, while FM rejection from nearby, high powered broadcast stations is actually much better on the Uniden than the GRE despite the Uniden's actually tuning the FM bands.

 

[W6KRU]

Yes, the squelch tail on my 396XT is awful compared to my PSR-500.

 

[SquierStrat]

I agree 1000 percent on the ctcss/ dcs issues all.uniden scanners seem to have. This issue, and whats even more annoying to me is how it will ALWAYS miss the first half second of a transmission with tones enabled. I disable tones and leave EVERYTHING else the same and the problem disappears... I firmly believe that if uniden scanners incorporated the same ctcss/dcs tone settings the psr 500 has (4 different parameters) this problem would be solved.

 

[captclint]

Just throwing this out there in case others want to comment. I have 346xt, and I have not noticed ANY of these problems except maybe the weak signal ctcss/ dcs decode. I use tones on almost all channels due to adjacent channel and other agencies with same freq. Quite a few are analog repeaters. I seem to recall(could be wrong), the 346xt was released slightly after 996xt/396xt, so could it be that they improved this?

 

[northzone]

I have both the GRE (Radioshack) and Uniden models. I agree with the comments but the bottom line I think is that the GRE decodes P25 digital 100% better than the Uniden. Side by side there is no comparison, the GRE sounds so much better.

 

[Mojaveflyer]

Uniden 996XT

I have a GRE PSR-600 I use in the car and a Uniden 396T I use for aircraft outside of the car. I'm seriously thinking about getting a 996XT for the car around town and use the PSR-600 for road trips. The 600 is great away from town but in town the intermod is driving me nuts! Since I mostly monitor aircraft and railroads very little had PL tones t keep the 'noise' out.

Any thoughts from 996XT users about how the 996XT does on frequencies without PL tones, like the aircraft and railroad bands?

 

[garys]

I can tell you that the PSR 600/Pro 197 get beat up on 800 Mhz in urban areas. The 996XT is much better on 800 for both sensitivity and selectivity.

I don't know that the Unidens would be any better on VHF in high intermod areas, but the little non tone VHF I've heard suggests not.

I don't even notice the squelch thing that the OP complains about, or if I do it's so minor that I don't think it out weighs the other features.

The GRE/RS scanners do decode P25 much better, but I'd only really care if I lived in an all or mostly digital area. Unidens are much better than they used to be, but still have a way to go in that regard.

 

[Boatanchor]

I have a GRE PSR-600 I use in the car and a Uniden 396T I use for aircraft outside of the car. I'm seriously thinking about getting a 996XT for the car around town and use the PSR-600 for road trips. The 600 is great away from town but in town the intermod is driving me nuts! Since I mostly monitor aircraft and railroads very little had PL tones t keep the 'noise' out.

Any thoughts from 996XT users about how the 996XT does on frequencies without PL tones, like the aircraft and railroad bands?

Get the BCD996XT if you can afford it!

It has a more sensitive receiver than the PSR600 on ALL bands, but particularly on the 108-136Mhz band.
The 996XT has better front end filtering than the PSR600.
The 996XT covers more bands, with more available memories without being confined to awkward Virtual Scanner Memory (GRE term).
The 996XT has the IFX feature - Invaluable !!
The 996XT has a much larger, clearer display.
The 996XT has free (& excellent) 'Freescan' PC software.
The 996XT has more audio power output power (if you like it loud!).
The 996XT permits GPS/location based scanning if required.
The 996XT can be operated with the RH96 remote control head (still available) if you are short on install space.

But, on the other hand,
The PSR600 has a faster, more user configurable (although much less sensitive) PL/CTCSS FM squelch system.
Some argue that the PSR600 has better P25 audio - Although I dispute this. I don't really notice any difference between the PSR600 and the 996XT (latest firmware) on P25.

I have a feeling that once you experience the 996XT, your PSR600 might be destined for a new owner

 

[DaveNF2G]

I am keeping both my PSR-600 and my 996XT because the GRE scanners do one thing the Unidens cannot. I can detect the mode and squelch tone/code simultaneously on any signal with the GRE, and I can set a frequency to watch in TUNE mode in as much time as it takes to punch in the digits.

 

[Avery93]

I agree, the current Uniden scanners pretty much fail at anything related to CTCSS and DCS.

The main problem is that it just takes way too long for them to decode the tone and open squelch when you have a tone set on a channel. Longer than any professional radio I own, and much longer than GRE scanners. Unidens answer to this in the past is that the user must have the channels modulation set wrong (NFM when it should be FM, or vice-versa), however, at least in my case, this is simply not the problem.

Another major problem is that Unidens require CTCSS/DCS decode after a priority sample before audio will unmute. This means when you have priority scan on, and are scanning NON-priority channels that have CTCSS enabled, the scanner must decode the tone on the non-priority channels before the audio will unmute after every priority sample. See this thread for more info.

As the OP pointed out, these scanners really need high pass filters. I was receiving a distant repeater last night that was transmitting a 250.3 Hz tone. With my 996XT I could barely hear the voice traffic because the tone was so loud, however with my Icom F5021 I could hear the voice just fine with a little bit of hum/buzz in the background.

And as Dave pointed out, the digital Unidens are incapable of decoding CTCSS/DCS and P25 NAC on the same channel or in search mode. You can either set it to search for CTCSS/DCS on analog and block all digital transmissions, or search for NACs on digital and block all analog transmissions; but not listen to both at the same time and decode tones and NACs. This is something GREs can do without problem.

Other than that, I think that Unidens are good scanners. Analog audio is better than GRE, they are less prone to overloading and decode P25 alright (except for my neighboring counties oddball VHF Midland P25 system). However the issues above have limited the use of my 996XT to monitoring aircraft and some local repeaters that are relatively interference free so I can run them in carrier squelch (no CTCSS), and limited my 346XT to decoding fire tone outs.

 

[SquierStrat]

The main problem is that it just takes way too long for them to decode the tone and open squelch when you have a tone set on a channel. Longer than any professional radio I own, and much longer than GRE scanners. Unidens answer to this in the past is that the user must have the channels modulation set wrong (NFM when it should be FM, or vice-versa), however, at least in my case, this is simply not the problem..

Yep. i 2nd that entire paragraph. What ive found helped a little tho; i used to have my p25 wait time set to 0 thinking this would help the most. One day i changed it to 100 and noticed a little bit of improvement. Its still nowhere near perfect, like the GREs tho

 

[Avery93]

Yep. i 2nd that entire paragraph. What ive found helped a little tho; i used to have my p25 wait time set to 0 thinking this would help the most. One day i changed it to 100 and noticed a little bit of improvement. Its still nowhere near perfect, like the GREs tho

The P25 wait time setting should have no effect on channels with CTCSS/DCS set, as they are automatically recognized by the scanner as analog only. P25 wait time should only come into play if you set the audio type on a channel to "All".

 

[Boatanchor]

All CTCSS tone decoders take a certain number of cycles before they decode correctly.
The lower the tone frequency, the longer the cycles are and therefore the longer the delay in decoding the tone. A channel operating with a tone of 67Hz will take much longer time to decode than a channel with a tone of 241.8Hz. This is why most network operators tend to prefer the higher tones as it reduces network 'key-up' times. Unfortunately though, the higher tones tend to be the ones heard if the receiver doesn't employ suitable high pass filtering (as appears to be the case in most scanners).

While it may only be a difference of 100-200mS, these delays can end up being significant, if multiple links are required.

A slow CTCSS decoder should activate in <250mS, even on a very low tone.

I will do some timing tests on the PSR600 and the Uniden to compare actual tone decoder performance, but I don't think the Uniden is really that slow to decode on a 'preset tone' channel (but they sure are slow to close once the tone is disabled). There may be other factors coming into play here.

I think the CTCSS 'Search feature' could well be quite slow and if the decoder is required to scan through all the tones before finding the correct one, this could explain the delays. If the tone search feature was activated on a Priority channel, this could slow things down considerable, although in theory you would expect the tone search function to only activate and slow the scanning process down, if the noise mute actually opened on the priority channel first.

Will look into this further..

 

[Avery93]

All CTCSS tone decoders take a certain number of cycles before they decode correctly.
The lower the tone frequency, the longer the cycles are and therefore the longer the delay in decoding the tone. A channel operating with a tone of 67Hz will take much longer to decode than a channel with a tone of 241.8Hz. This is why most network operators tend to prefer the higher tones as it reduces network 'key-up' times. Unfortunately though, the higher tones tend to be the ones heard if the receiver doesn't employ suitable high pass filtering (as appears to be the case in most scanners).

While it may only be a difference of 100-200mS, these delays can end up being significant, if multiple links are required.

A slow CTCSS decoder should activate in <250mS, even on a very low tone.

There was an interesting thread over on Batlabs where a member had precisely measured the delay of the PL decoder on several Motorola and GE radios. Unfortunately I can't find it now but if I remember correctly the delay was always between 180 and 200 milliseconds, and surprisingly there wasn't much difference between the lower frequency and higher frequency tones.

Reference the thread I linked earlier, If you take the priority sample times of my 996XT with CTCSS enabled on the non-priority channel (longest was 420ms), and remove the time it takes for the receiver to check the frequency during a priority sample (around 80ms), you can conclude that it takes the 996XT about 340 milliseconds to decode a CTCSS tone.

 

[Boatanchor]

Anyone out there know if there is a circuit diagram floating around for the 996XT?