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  #41 (permalink)  
Old 08-13-2017, 3:27 PM
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With C1 installed, the 436 has excellent performance on UHF analog and digital.
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Uniden scanner internal GPS installations--making mobile scanning work the way it always should have.
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  #42 (permalink)  
Old 08-13-2017, 4:32 PM
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Originally Posted by jonwienke View Post
With C1 installed, the 436 has excellent performance on UHF analog and digital.
I'm a little unclear on this C1. Internal electronics are beyond my grasp at this point. I've been on the fence about buying a 436 due to the UHF issue since that is what my police and fire are on.

Does the 436 come with the C1 normally? How would you know if you didn't have it? Who installs it?
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  #43 (permalink)  
Old 08-13-2017, 5:06 PM
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Newer scanners have it installed at the factory. Scanners 1-2 years old may or may not have it. Scanners more than 2 years old generally don't.

If your scanner doesn't have it installed at the factory, I do it for an additional $5 when I install an internal GPS, unless you have an older scanner (2+ years) that doesn't have the soldering pads for it.
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  #44 (permalink)  
Old 08-13-2017, 5:07 PM
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Originally Posted by Mojomanny View Post
I recently took advantage of the $325 Amazon pricing and purchased a BCD436HP.

I updated the firmware and database, have loaded a Favorites List with some of my local channels.

At this point I am terribly underwhelmed by the reception performance of the 436. My local police and fire reception is perhaps 40% of the quality of the 396. It is static filled and hard to listen to. There is an occasional clear comm on some freqs, but they are few and far between.

I have verified the frequencies and settings are identical for both scanners, and that attenuator is off on both (that was my first thoguht).

I have also tried swapping the antenna's between the two radios (which seem to be the same antenna) with no change in performance.

I am suspecting a loose or bad connection between the antenna and the board.

Any thoughts if I am missing something or if I need to send it to Uniden for a service?

Thanks in advance for your input, insight and advice.
From what I'm understanding, from having read many threads about 436HP reception, this radio was designed for the future, digital. I did not see whether you indicated whether your bad reception was digital or analog.

My 436HP performs incredibly well on P25 conventional digital. In fact, I would go so far to say, "outstanding." However, on analog conventional, it does not compare to my PSR 500 digital or other analogs I own.

On P25 trunking, Phase I and II, reception depends on numerous factors, including the dreaded, linear simulcast distortion. I don't know if the FCC will ever phase out analog LE transmissions.

For now, I would not trade my two 436HP radios for nothing else.
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  #45 (permalink)  
Old 08-13-2017, 5:10 PM
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Originally Posted by jonwienke View Post
I have had the opportunity to test numerous 436 scanners against other Uniden models while doing internal GPS mods, and my testing indicates that when working properly, the 436 will match or beat the RF performance of mobile models.

Using separate antennas is never a valid methodology. Even if the antennas are exactly the same, the path from transmitter to receiver never will be. Use a single antenna and a splitter for a valid test, and of course make sure attenuation is off.

It is possible your 436 is missing C1 and is emitting mostly-UHF ststic from the battery compartment. This can interfere with reception when using the stock antenna, but has no effect when using an external antenna connected with a length of coax, and minimal effect when using an antenna like the Diamond RH77CA connected via the factory SMA-to-BNC adapter (using the adapter gets the antenna far enough from the noise that it doesn't interfere). Tune a SDR or another radio to an unused freq in the 400MHz range, set modulation to AM, turn the squelch all the way down, and put the antenna by the 436 battery compartment. If C1 is missing, vou will see or hear a significant increase in noise--a SDR will show about 15dB increase in the noise floor when the antenna is within a few inches of the battery compartment.

When I install an internal GPS, I install C1 if it is missing, and the UHF static from the battery compartment goes away. C1 has been missing in about 50% of the scanners I've modded--Uniden made some changes and newer boards have it and older ones do not.

Do a comparison with both scanners connected to the same external antenna with a splitter. If the 436 still has trouble, it may be defective. If that fixes the disparity in RF performance, then your 436 may be missing C1, and using any antenna other than the factory ducky (particularly ones with BNC connectors like the Diamond RH77CA) will make the disparity go away.
Thanks for this information. I am getting ready to send my first 436HP in for the clock repair. I will have them check this out when they fix the loose antenna jack.
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  #46 (permalink)  
Old 08-13-2017, 5:16 PM
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Sending in your 436 for the clock repair makes sense. But if the antenna connector is loose, you can tighten it yourself if you can find a pair of needlenose pliers or a spanner with tips that fit in the slots in the metal ring around the SMA connector. It's actually a special nut that holds the connector in place.
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  #47 (permalink)  
Old 08-13-2017, 6:30 PM
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Quote:
Originally Posted by jonwienke View Post
Newer scanners have it installed at the factory. Scanners 1-2 years old may or may not have it. Scanners more than 2 years old generally don't.

If your scanner doesn't have it installed at the factory, I do it for an additional $5 when I install an internal GPS, unless you have an older scanner (2+ years) that doesn't have the soldering pads for it.
Are we able to tell which are the newer ones through the serial number?
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  #48 (permalink)  
Old 08-13-2017, 9:08 PM
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Originally Posted by Ensnared View Post
From what I'm understanding, from having read many threads about 436HP reception, this radio was designed for the future, digital. I did not see whether you indicated whether your bad reception was digital or analog.
This is a misconception. Reception is the same for a frequency, regardless of whether digital or analog. The difference with digital is that it sounds perfect until the S/N ratio is too low for the bits to be accurately decoded, and then the audio quality suddenly changes from perfect to a total mess. The only way you can meaningfully compare performance is to test at the ragged edge of fringe reception. Anything else is going to give digital an apparent advantage.
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  #49 (permalink)  
Old 08-13-2017, 9:13 PM
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The digit after the Z indicates the year of manufacture. If it's a 7, that indicates a 2017 vintage and it will likely have C1 installed If it's a 6 or a 5, maybe, maybe not. If it's a 4 or lower, not likely. I log the serial numbers of the scanners I mod, and track whether they need C1 installed or not. As I get more data, I can be more specific.
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  #50 (permalink)  
Old 08-14-2017, 10:50 AM
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Quote:
Originally Posted by jonwienke View Post
The digit after the Z indicates the year of manufacture. If it's a 7, that indicates a 2017 vintage and it will likely have C1 installed If it's a 6 or a 5, maybe, maybe not. If it's a 4 or lower, not likely. I log the serial numbers of the scanners I mod, and track whether they need C1 installed or not. As I get more data, I can be more specific.
Hi Jon,

I'm sure I recall the discussion about what value capacitor to use, but its a really long thread. I'm curious as to the specific capacitor type/value that you use when you add C1 to the BCD436HP. Could you provide that info to me? I'd like to grab some off of ebay/amazon to fix my own scanner.

Thanks

mike
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  #51 (permalink)  
Old 08-14-2017, 11:00 AM
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.01 microfarad is what I've been using, and it has worked on every scanner I've modded so far.
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Old 08-14-2017, 11:21 AM
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Have you modded any without the pads?
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  #53 (permalink)  
Old 08-14-2017, 11:43 AM
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No, tracing connections on the front PCB is nearly impossible--it's a 6-layer sandwich. Also, the boards without the C1 pads are the ones with the clock and display problems, so IMO it would be preferable to utilize Uniden's repair campaign to get a new board, and then think about adding C1 (if the new board doesn't already have it) and/or doing other mods.
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Old 08-14-2017, 9:31 PM
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Quote:
Originally Posted by jonwienke View Post
.01 microfarad is what I've been using, and it has worked on every scanner I've modded so far.
Thank you, Jon.

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Old 08-15-2017, 5:42 AM
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Quote:
Originally Posted by jonwienke View Post
Sending in your 436 for the clock repair makes sense. But if the antenna connector is loose, you can tighten it yourself if you can find a pair of needlenose pliers or a spanner with tips that fit in the slots in the metal ring around the SMA connector. It's actually a special nut that holds the connector in place.
Thanks, can an idiot reach it? I am that idiot. If it is on the inside, I don't know if I am capable of fixing it.
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  #56 (permalink)  
Old 08-15-2017, 6:34 AM
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Take the antenna off and look at the metal ring around the sma connector. It is a nut that you turn by engaging the slots in the top surface with a tool.
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  #57 (permalink)  
Old 08-17-2017, 10:29 AM
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Take the antenna off and look at the metal ring around the sma connector. It is a nut that you turn by engaging the slots in the top surface with a tool.
I have been reading about this tightening of the SMA; however, after opening up the back of my 436HP, I quickly closed the case and left it alone.

I removed the antenna and adapter. Then I saw two slots. I am assuming these are the two slots you mentioned. I am going to find an X-tool to tighten this if I am correct.

I suppose the tightening will be clockwise, right?
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  #58 (permalink)  
Old 08-17-2017, 11:39 AM
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Yes on the slots in the ring around the SMA connector, and yes on clockwise to tighten.

Be firm, but gentle.
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  #59 (permalink)  
Old 08-17-2017, 4:54 PM
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I'm wondering if I should have not returned my "deaf" 436HP as it was likely the cap issue. But, regardless, Uniden should be ashamed for shipping a product with such a glaring flaw and taking more than a year to apparently quietly fix it. I'm also a Whistler/Grecom guy and have to admit the whole Uniden experience and user interface seemed rather foreign and ill conceived. But I know devoted Uniden guys say the same thing about Whistler.

Back to the OP's situation I think it's fairly clear at least some 436HP's have UHF reception issues and he may have had one of them. I also stand by my statement the TRX 1/2 are not that difficult to learn and program and have several advantages over anything Uniden makes.

Unfortunately there's no one standout scanner or receiver that does most everything well. Uniden and Whistler are both mass market brands that offer everything from radar detectors to probably toaster ovens next so I guess we shouldn't expect too much. It's no surprise they get a lot wrong. What's sad is even the dedicated companies like Icom, AOR, Yaesu, Kenwood, Winradio, etc. don't have better offerings for monitoring digital traffic.
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