BCD996XT: Bring your 3/996XT into the 21st century :)

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Boatanchor

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Alternative heading - Supercharge your x96XT scanner :)

Firstly, let me state that I love the x96XT scanners.

Despite being a few years old now, the XT scanners still have some unique features that were not included in the newer models. It seems a shame then to 'upgrade' when there is little really wrong with the older units - As long as you don't need phase 11 (& simulcast improvement?) capability of course :)

The one thing that 'did' annoy me somewhat about the x96XT design, was the relatively poor weak signal NFM, AM and P25 receive performance compared to 'real' ($1000 plus) radios and even the older PSR600, in some cases.

This is a problem for me because it has reached the point where 90% of the analogue and P25 comms that I want to listen to are NFM. Standard FM (+-5Khz deviation) is almost a thing of the past now, as virtually all Government and Commercial services adopt the newer Narrowband channels to comply with new government mandates or to reduce spectrum tax in those countries that charge fees based on the spectrum/bandwidth used.

Now, before people pipe up and say "Hey, the x96XT does NFM!, It is an option in the menu for each channel/system that you program in."
Well, the above statement is sort of right, but mostly wrong.

Yes, the option is there to program NFM. However, when you select NFM in the x96XT menu, all you are doing is telling the scanner to add a little extra audio processing to lift the audio level up a little to compensate for the much lower deviation. The scanner is not switching in any narrower filters or changing anything in the RF chain.

The crux of the problem..

The x96XT scanners (unlike the newer x36HP and even the venerable old PSR-5/600 and RS equivalents that both have an FM and a 'real' NFM final IF filter) have only one final IF filter. This 450Khz ceramic filter was chosen as a compromise to pass AM, FM, P25 and NFM. As there is only one filter present, the filter had to have a bandwdth wide enough to pass the widest possible modulation. In this case, standard FM.

The problem is, that the standard 450Khz ceramic filter in the x96XT scanner has a bandwidth that is far too wide for NFM, P25 and even AM. Yes it will work, but adjacent channel rejection and signal to noise ratio will suffer on the narrow modes under weaker signal conditions.

So, what can be done?

Actually, it's relatively simple - Replace the 450Khz final IF filter!

Firstly though, let me state that while I have modded my 996XT, I have not done this mod on a 396XT - Yet!
I see no reason why it couldn't be done, I just haven't had the time to pull the little 396XT apart yet :)

The original Murata '50E' ceramic filter in the 996XT is not that hard to replace.
Although it is a surface mount device, it can be un-soldered with a fine tipped soldering iron - Carefully!. Ideally, though a SMD rework hot air gun makes the job a quick and simple process.

I chose to replace the stock Murata '50E' filter with a Murata '50G' (+-4.5Khz or 9Khz total BW) filter of the same specification and size.

After replacing the stock IF filter, I have noticed the following characteristics:

* NFM - Weak signals are much, much quieter (less noise, pops & clicks), less adjacent channel interference & improved reception on crowded trunking networks. - BIG improvement!

* AM - Massive improvement in AM aircraft and 27Mhz reception. Less noise, improved weak signal performance etc. (The original filter bandwidth is/was twice as wide as necessary for AM voice reception). Again, BIG improvement!

* P25 - Remember that most P25 modulation is already Narrowband. Replacing the 450Khz IF filter improves weak signal P25 reception and adjacent channel interference for the same reasons it improves NFM performance. If you live in an area where trunking channels are crammed together in narrow portions of the band and you have very strong channels right next to weaker distant channels, this mod is for you!
My 996XT scanner will now decode distant P25 voice at levels so low that the PSR-600 doesn't even know a P25 signal is present (on the same base antenna).

* Standard FM - While the replacement 455kHz IF filter, in theory at least, is a little too narrow for standard (+-5Khz) FM, in practice I haven't noticed any signs of distortion or any signal degradation at all after installing the narrow filter. I have several FM channels programmed into my scan banks including 2M/70CM channels and the odd commercial channel, but I've not noticed any drop in performance on these channels regardless of whether they are very strong or very weak. It is conceivable that there may be very slight audio distortion on voice peaks, if the FM signal is very weak and the deviation of the transmitted signal is right up to or exceeds the +-5Khz level. In most cases though, typical FM signals tend to deviate closer to +-4.5kHz, so you may never even experience this phenomenon.

Overall, I would suggest that if you want optimum performance from your X96XT scanner, this mod is very worthwhile..

Edit -- Oh, one thing I forgot to mention.. After replacing the IF filter, you will still need to select 'NFM' for those channels/systems that use NFM.
As mentioned previously, selecting NFM won't actually change anything in the RF/IF/Demodulation stages, but it will boost the audio level up to the same level as FM, AM and demodulated P25. Of course, you still have the option to adjust the audio gain on a per channel basis as well, if you need to fine tune the levels a little.

Important! If you are not confident in pulling your radio apart, you don't want to void any remaining warranty or you are not comfortable messing with SMD components (even big ones) - Do not attempt!
 
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Boatanchor

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Although I haven't confirmed this, since I don't own one, I suspect that the BCD15X scanner has a similarly designed IF section.

If so, It is highly likely that the 15X scanner would benefit from this mod too.

Maybe someone could PM a close-up photo of the discriminator/final IF section of the 15X so that I can confirm.
 

mrkelso

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Good read. I would never attempt this mod as my hands shake to much.
 

LIScanner101

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Wow, this is a GREAT thread! I was a tech for years and fortunately I'm still relatively good at soldering small areas so I might actually give this a try!!!

Thanks OP!!
 

dave111c

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Radio Mod....

Listen ,we should'nt have to do all this work to get a radio to sound better....we spend good money for our uniden radio's......they I have good engineers designing these radio's (I thought).....they should know this filter from the start of designing these newer radios.....

Just like the Home Patrol.....In my opinion poor ergonomics....poor reception........
 

wtp

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outside the box

how many people would send their radio to uniden for this service is the question .
i am as cheap as they come and i would.
yes, i would like a quality radio.
and as long as they also did the usual service (i have a cracked 6 button) this would be great !
so ,yes, i would pay extra to have this done by the pros !
 

kruser

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Listen ,we should'nt have to do all this work to get a radio to sound better....we spend good money for our uniden radio's......they I have good engineers designing these radio's (I thought).....they should know this filter from the start of designing these newer radios.....

Just like the Home Patrol.....In my opinion poor ergonomics....poor reception........
I think you will find that all makes and models that have a so called NFM mode do not really reduce the bandwidth.
Someone else had a similar thread comparing Uniden's audio filter method with whatever GRE did. I don't recall that threads OP but it was found that GRE also did not truly reduce the bandwidth for narrowband systems. Something tells me they only reduced one side of the filter leaving the other side open and subject to co-channel interference. Another words, GRE only did it half way better than Uniden did. I don't know if that changed with the PSR-800 but it was true with the older 500 and 600 models as well as the radioshack clones.

Boatanchors suggestion does work though. I've been doing the same with crystal scanners ever since narrowband became a reality. Sometimes I'd do the 455 kHz stage and other times I'd swap out the 10.7 MHz IF filters for narrower filters. For 10.7 MHz IF models, it is easy to find narrow filters. For the old Electra crystal scanners, I never did find a source of narrower 10.8 MHz IF filters as Electra used a 10.8 MHz IF. The Electra's were filtered with a narrow 455 Khz filter instead when it was possible.
The mod also helped the old crystal scanners eliminate (or reduce)intermod mixing issues that the old single conversion models were known for.

It was much easier with the old crystal scanners as everything was thru hole design. Now with today's SMD components, one must have proper tools and good removal and soldering skills as has been pointed out.

The mod is sound though and does improve reception pretty much exactly as Boatanchor explained it.

It will also work with the older T series 396 and 996 models. I don't recall if the RF board component placement was the same in the "T's" as the XT models but the part is pretty easy to ID.
Maybe someone can take a decent closeup picture showing the filter. My camera is poor for closeups.

Boatanchor, do you have a source link and part number for the Murata filter you ended up using?

I don't recall the 15X innards but I think the RF board was almost an exact match with the 3/996XT models. The main change there was in the logic board.
 
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kruser

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how many people would send their radio to uniden for this service is the question .
i am as cheap as they come and i would.
yes, i would like a quality radio.
and as long as they also did the usual service (i have a cracked 6 button) this would be great !
so ,yes, i would pay extra to have this done by the pros !
Something tells me that Uniden would never offer this service as it affects pretty much every scanner ever made.
Replacing that component could also require re-certification with the FCC although I doubt it would cause any unwanted emissions from the radio greater than what is already present. If anything, it may reduce spurious emissions.
 

pro92b

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I chose to replace the stock Murata '50E' filter with a Murata '50G' (+-4.5Khz or 9Khz total BW) filter of the same specification and size.
With the 50G filter does the radio have any trouble tracking EDACS standard systems?
 

Boatanchor

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Part required:

Further info..

The part required is Murata part CFWKA450KGFA-R0.
It can be purchased from various online suppliers in one off quantities.

Don't bother sending your radio in to Uniden. They will not modify your radio!
Mods like these are not endorsed by manufacturers. Uniden will not modify your radio away from the original spec/design..

Mods like this will likely void any factory warranty remaining on your unit!

This mod will improve AM, FMN and probably P25 phase 1 reception, It MAY degrade standard FM reception (although I have not noticed any performance degradation on FM systems I monitor).

If you have a discriminator tap fitted, this mod will also likely improve DMR and other digital mode reception.

Further comments to follow..
 

Boatanchor

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With the 50G filter does the radio have any trouble tracking EDACS standard systems?
Sorry, I can't advise about ADACS standard (FM). I don't have any EDACS services nearby to test.
If EDACS (Standard) runs high deviation levels on the data channel, and I'm talking about +-5Khz or more, you may experience degradation in decode performance. Many EDACS systems are narrowband now anyway, so this mod will not impact on such systems.

EDACS - The RadioReference Wiki

The other mode I cannot test is LTR.

If LTR runs wide (standard) FM it may be a problem.

Presumably though most LTR networks have been 'Narrowbanded' to comply with Government mandates.

Maybe someone out there can tell me/us what the narrowband status is of LTR.
 

ka3nxn

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I have an older 396T would this benefit from this mod? I have actually two 396's, one 796D, and one 996T. I am good at SMD soldering and would be willing to mod radios for folks. If this indeed does work. I just found eight of these filters on EBay for $10.00 and I ordered them. Cross your fingers.

Jaime-KA3NXN
 
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kellykeeton

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Listen ,we should'nt have to do all this work to get a radio to sound better....we spend good money for our uniden radio's......they I have good engineers designing these radio's (I thought).....they should know this filter from the start of designing these newer radios.....

Just like the Home Patrol.....In my opinion poor ergonomics....poor reception........
glad to see people make insane posts that they have no clue what your talking about complain and spewing negative garbage all over just like the x36 haters..

here is a photo of the 996T .. its gonna look the same for any unit.

CFWKA450KGFA-R0 -http://www.murata.com/products/catalog/pdf/p05e.pdf

you could also make a switch to run the original filter with the old to have increased bandwith

just a dpdt for the input and output pins, 2 pins are ground. then you can select 750khz or 450khz

lots of edits because I didnt see OP posted the part number
 

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Boatanchor

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glad to see people make insane posts that they have no clue what your talking about complain and spewing negative garbage all over just like the x36 haters..


the letter means nothing more then G=450khz E=750khz

possible part numbers (I cant find a 9khz total bandwidth part)
CFWKA450KGFA-R0
CFUGC455G


(this isnt for sure just from assuming what he means randomly reading the data sheets)

here is a photo of the 996T .. its gonna look the same for any unit.
The Murata filters are only labeled '50E' or '50G' or similar.
'50' represents the centre frequency (450Khz) and 'G' represents the filter bandwidth.

It is hard to find much technical info on the filters. Even the Murata website datasheets are a little vague as to the filter characteristics outside of the specified passband.

One of my posts above has the exact part number and as mentioned, they are available from somewhat surprising sources at very cheap prices :)

Providing you are not totally ham fisted and destroy your scanner during the modification process, you are not going to 'risk the farm' by doing this mod. If it doesn't work out for you, simply put the original filter back in..
 
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kellykeeton

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The Murata filters are only labeled '50E' or '50G' or similar.
'50' represents the centre frequency (450Khz) and 'G' represents the filter bandwidth.

It is hard to find much technical info on the filters. Even the Murata website datasheets are a little vague as to the filter characteristics outside of the specified passband.

One of my posts above has the exact part number and as mentioned, they are available from somewhat surprising sources at very cheap prices :)

Providing you are not totally ham fisted and destroy your scanner during the modification process, you are not going to 'risk the farm' by doing this mod. If it doesn't work out for you, simply put the original filter back in..

Yea I had hit reply before you posted but never hit send so was a little off time there haha - edited it clean up
 

kruser

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Yea I had hit reply before you posted but never hit send so was a little off time there haha - edited it clean up
Thanks for the innards pic of a T model. I figured they were essentially the same but it was not an easy task removing mine from its mount plus my good camera is at work that does nice closeup's.


And thanks to Boatanchor for posting the full part number you used!
As you noted, technical info is a tad confusing or missing even from Murata's site.
 

kruser

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you could also make a switch to run the original filter with the old to have increased bandwith

just a dpdt for the input and output pins, 2 pins are ground. then you can select 750khz or 450khz.
Being as Uniden does do some audio filtering trickery for NFM mode, I wonder just how hard it would be to grab that signal line and do some auto switching via relay so you could switch the wide filter back in circuit when FM is selected. Having no service manuals on these things would make it hard but not impossible. I'd guess some form of switching transistor would also be needed to handle the load of the relay coil.
There are several county PD mobiles here that are way off frequency. When I use an Icom R9000 in NFM mode, I cannot hear them. The R9000 does have proper narrow filters of course.
So this mod would need to be bypassed should I do it on any of my recent Unidens and wish to monitor the local county guys.
The county was granted an exemption of the narrowband rules so they remain wide until they get a new multi-site P25 system up and running.

It would be nice to do the mod without adding any external switches in order to switch the wide filter back inline.
Maybe some day I'll probe around and try and find a useable signal line that can be used to drive a relay depending on if the scanner(s) are set to FM or NFM mode.
 

pro106import

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It would be nice to do the mod without adding any external switches in order to switch the wide filter back inline.
Maybe some day I'll probe around and try and find a useable signal line that can be used to drive a relay depending on if the scanner(s) are set to FM or NFM mode.
That would work but I wonder if the scan speed would suffer dramatically do to the switching. There is a lag time involved there.

The ebay guy from Sweeden must be wondering what the heck is going on. 5 orders in the last 12 hours :p
May take a little more shipping time to get them in our hands from Sweeden. The problem with local places like Digi-Key is they sell by the reel (350 pieces in this case). To get single amounts they charge a "reel cutting fee", and after all of the other charges you end up paying 5 times as much for one piece.

Wonder where Paul is on all of this?
 

kruser

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That would work but I wonder if the scan speed would suffer dramatically do to the switching. There is a lag time involved there.

Wonder where Paul is on all of this?
I guess you are talking an increase in scan speed due to the relay switching? (I see you mentioned this already!)
I would probably not scan wide FM and NFM at the same time and in all honesty, I would probably be sitting on a wide channel in hold mode when using the old wide filter as there are only a handful of frequencies that have not narrowbanded here.
So using an internal circuit should not affect my scan speed at all but I could see how it may not switch as fast as the scanner scans. The scanner would have no way of knowing if the wide or narrow filter is inline though so scan speed should not be altered in any way.

I doubt Paul will comment on this as it is not a manufacturer sanctioned modification. It's pretty much all on the owner from this point forward should anyone choose to do the mod.
 

sodjan

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> The ebay guy from Sweeden must be wondering what the heck is going on. 5 orders in the last 12 hours

Right, I just told my wife about it... :) She and my son helps with the packing of eBay stuff.
I got a surplus batch (18 large cardboxes) with SMD parts from some company shutting down a site. What is left now is all the SMD inductors, mostly Coilcraft. I have an inventory as an PDF
available on my server if anyone is interested: http://jescab2.dyndns.org/pub_docs/ind.pdf.

For those that have purchased from my eBay offering, we'll ship on
Monday and they might be in the US before next weekend.

Best Regards,
Jan-Erik Söderholm

PS:
Feel free to through me out if this post feels offensive...
 
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