BCD436HP reception pales compared to BCD396XT

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Mojomanny

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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.
 
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pdfdems286

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I think the best suited thing I can say about the vhf/uhf reception of the bcd436hp <according to numerous report's> is that it is sub par with other uniden scanner's. I have fence sat on wanting one, since they were announced. With that being said, I think at this point I will stick with my bcd325p2/bcd396xt combo. Note - I am not Uniden bashing here. I did purchase a bcd436hp, and it arrived doa. Thing's happen for a reason.
 

jonwienke

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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.
 

mancow

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I've still never seen a definitive answer as to exactly where in the circuit C1 connects. I not talking about a blank spot on a board but electrically. I would like to see it drawn in a schematic but apparently that's too much to ask from uniden.
 

SteveSimpkin

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If Uniden had just done their job the first time, it would have alleviated the problem.
The history of product development is also a history of defects in design that were missed by the engineers and testers. In many cases a large amount of money was spend and a great deal of oversight and testing was performed but design defects were missed, sometimes with disastrous effects.
I have no doubt the BCD436HP met its sensitivity goals when connected directly to a signal generator. It passed FCC Part 15 emissions testing. It probably appeared to pass field tests without problems. The nature of this issue often makes it difficult to observe and some customers have not been able to duplicate the problem at all.

You can fault Uniden for a number of issues and the way they may handle the after effects but I can't find fault with them missing this particular problem during testing.
 

jonwienke

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I've still never seen a definitive answer as to exactly where in the circuit C1 connects.
It connects to one of the voltage converter/regulator ICs that takes battery voltage (which can vary between 3.1V and 4.5V) and outputs a constant voltage. The switching design is efficient, but generates RF noise if the capacitor isn't connected to it.
 

Nasby

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Uniden defintely dropped the ball on the 436. It has never really measured up to its lofty, inflated advertising.

It is rife with defects and unfinished features.

That being said, it is for sure one of the best receiving units for 700/800 digital systems which is what the majority of scanner users want to hear.
 

mtindor

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Mine was as deaf as a post on UHF. I saw a post on here about adding copper tape to the inside of the battery cover. Reception went from 0% to 100%.
Same here. I'm sure C1 is the real fix. But I have bad eyes, fat fingers, and the jitters. Copper take resolved any issue I had, and I think the BCD436HP has the best sensitivity-selectivity balance. I have / have had scanners with the GRE guts -- plenty sensitive, but plenty of overload and imaging.

Copper tape was cheap. Forgot what I paid for it, but I kept the spool around for use on other things. I'm sure some day I'll find something else that benefits from it.

Mike
 

KD4UXQ

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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.
I recently bought my BCD436HP on sale from Amazon. The serial number is one of the latest made. I had read some users having reception issues, especially on UHF. I did a side-by-side comparison between the BCD436HP and my BCD396XT using the same after-market antenna. The RS 800 MHZ antenna which performs very well on pretty much anything VHF Air and above. Better than the stock antenna on VHF Air and above.

I have not compared VHF low on a suitable antenna, but did compare VHF Air, VHF HI, UHF and 700/800MHz. My BCD436HP is somewhat less sensitive than the BCD396XT on VHF Air, VHF HI and UHF. I will likely put both on a signal generator the next time I have access to one. The sensitivity specs for the 436 are in the manual, but so far I can't find them for the 396 for comparison. There is not enough difference to even consider the BCD436HP to be overall less sensitive, and actually it is less prone to interference from strong nearby signals. I could not tell any difference in performance with trunked systems between the two, except the BCD436HP decodes P25 better, but signal level wise they compare. And it actually performs better overall on VHF Air because I get less interference from the leaky cable TV system nearby, and the audio band pass seems lower in frequency and clearer.

If I was as concerned about mine as you are with yours, I think I would try and exchange it with Amazon or send it to Uniden for checkout/repair. I think I likely got a good copy.
 

KD4UXQ

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Thanks, UPMan!

The published receiver specs between the 2 are pretty much the same. I wondered if they were. Published specs usually indicate even if not explicitly stated, the worst case limit. It seems that my BCD396XT is a bit more sensitive than published on UHF if the BCD436HP is within the limit. I no longer have regular access to test equipment for checking receivers. I need to buy me a used signal generator off eBay, but a good choice is still expensive for no more than I need one for any of my amateur radio gear.
 

Mojomanny

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Repair, Tape or Return

Paul / Upman -

I see the specs. I can tell you on an external antenna the UHF Public Safety is dramatically improved.

Do you recommend I send it in for repair, I install some copper tape or I exchange it for a new radio and hope for better reception?
 

mancow

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It connects to one of the voltage converter/regulator ICs that takes battery voltage (which can vary between 3.1V and 4.5V) and outputs a constant voltage. The switching design is efficient, but generates RF noise if the capacitor isn't connected to it.
Can you identify which one?

Is it a .01 cap?
 

jonwienke

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Someone else traced the connection, but I don't remember which IC it went to.The front circuit board is a 6-layer sandwich, so following traces visually is impossible when they are in layers 2-5.

A .01&#956;F cap works great.
 

rwier

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I see a whole lot of "agenda" going on with these kind of threads. Instead of a thread title "BCD436HP reception pales compared to BCD396XT", I would prefer the NO-AGENDA "My BCD436HP reception pales compared to My BCD396XT". All of my scanners are near perfect equals, and I am up against the "notorious" RWC monster TRS, lol.
 

jonwienke

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I've done comparison testing between 11 436s and 2 996P2s, connected to an outdoor antenna and a splitter to ensure signal levels are equal to each radio, as part of the GPS mods I've done. All of the 436s have had C1 installed except one--it didn't have the pads. So IMO I'm in a better position than most to comment on unit variations in Uniden scanner RF performance.
 
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