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The Uniden Tavern - For general chit-chat and non-technical discussion specific to Uniden and does not fall within the above forum topics. This is not the forum to get technical advice from.

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Old 05-13-2018, 6:09 PM
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Default BCD325P2 vs BCD436HP Close Call

I didn't want to put this in the Uniden Technical forum because I'm sure many people will let me know how my testing is flawed and useless.

Anyway, made a 285 mile trip last week and had both the 325 and 436 on the same antenna setup (800 3dB antenna and a dual-band 150/460 antenna into a Comet diplexer into a Stridsberg MCA204M, using identical jumpers) searching the same range (460-465) with CC DND activated.

On VHF (air and LMR) it was pretty much a dead heat, with both radios either getting the CC hit at the same time or within milliseconds of each other, UHF was completely different. The 436 would hardly ever get the same CC hits as the 325, it would remain silent most of the time.

On the return trip I swapped the jumpers and had the same results (436 was usually silent on UHF).

Interestingly, with the UHF limit search they would both receive the same weak signals.
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Old 05-13-2018, 6:50 PM
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Does your 436 lack the infamous capacitor?��
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Old 05-13-2018, 6:54 PM
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Originally Posted by ur20v View Post
Does your 436 lack the infamous capacitor?��
Yes it does. But you'd think that would show up on a limit search as well, plus I'm using external antennas.
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Old 05-13-2018, 8:05 PM
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IMO it's probably related to C1 missing. The frequency counter chip used for Close Call may be near the noise source on the board. My 436 doesn't have a noticeable difference in close call sensitivity between UHF and VHF, but it has C1 installed.
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Old 05-15-2018, 11:37 AM
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Originally Posted by jonwienke View Post
IMO it's probably related to C1 missing. The frequency counter chip used for Close Call may be near the noise source on the board. My 436 doesn't have a noticeable difference in close call sensitivity between UHF and VHF, but it has C1 installed.
+1 .
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Old 05-15-2018, 2:40 PM
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Originally Posted by jonwienke View Post
IMO it's probably related to C1 missing. The frequency counter chip used for Close Call may be near the noise source on the board. My 436 doesn't have a noticeable difference in close call sensitivity between UHF and VHF, but it has C1 installed.
Could be, but I guess I'll never know unless Uniden admits this is an issue and agrees to install it for free.

And if this is it all the people saying to just use an external antenna or just a SMA-to-BNC adapter (for a radio mounted antenna) to minimize the impact need to add the caveat that CC on UHF will still be almost useless.
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Old 05-15-2018, 3:27 PM
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Installing the capacitor takes about 10 minutes if you have one and some SMD soldering skills.
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Old 05-15-2018, 3:38 PM
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Installing the capacitor takes about 10 minutes if you have one and some SMD soldering skills.
So I'm expected to correct Uniden's design flaw?
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Old 05-15-2018, 3:39 PM
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Could be, but I guess I'll never know unless Uniden admits this is an issue and agrees to install it for free.

And if this is it all the people saying to just use an external antenna or just a SMA-to-BNC adapter (for a radio mounted antenna) to minimize the impact need to add the caveat that CC on UHF will still be almost useless.
Send it to John...
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Old 05-15-2018, 3:42 PM
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Send it to John...
I didn't know he did Uniden warranty work. That's good info to have.
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Old 05-15-2018, 4:25 PM
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I install C1, usually while I have the scanner apart already doing GPS or battery mods. But I am not a Uniden authorized warranty repair provider.
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Old 05-15-2018, 9:39 PM
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Could be, but I guess I'll never know unless Uniden admits this is an issue and agrees to install it for free.

And if this is it all the people saying to just use an external antenna or just a SMA-to-BNC adapter (for a radio mounted antenna) to minimize the impact need to add the caveat that CC on UHF will still be almost useless.
My 436 was repaired early in the campaign and was missing C1. I sent it in describing poor receive in the 450mhz range. They billed my credit card when the unit was received. It was repaired with the comment F12J complete. They refunded my credit card and paid return shipping. I thought that was great. The original repair was January 2016. This repair was April 2018.
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Old 05-15-2018, 10:16 PM
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I keep forgetting I live very close to Jon Wienke, well, both Jon Wienkes, actually... one of these days I'll head over yonder and have the one Jon install C1 and the other Jon show me how to make a custom hearing protection device for my 191... eh, never mind.
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Old 05-15-2018, 10:43 PM
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Quote:
Originally Posted by KevinC View Post
I didn't want to put this in the Uniden Technical forum because I'm sure many people will let me know how my testing is flawed and useless.

Anyway, made a 285 mile trip last week and had both the 325 and 436 on the same antenna setup (800 3dB antenna and a dual-band 150/460 antenna into a Comet diplexer into a Stridsberg MCA204M, using identical jumpers) searching the same range (460-465) with CC DND activated.

On VHF (air and LMR) it was pretty much a dead heat, with both radios either getting the CC hit at the same time or within milliseconds of each other, UHF was completely different. The 436 would hardly ever get the same CC hits as the 325, it would remain silent most of the time.

On the return trip I swapped the jumpers and had the same results (436 was usually silent on UHF).

Interestingly, with the UHF limit search they would both receive the same weak signals.
Thanks for posting your observations. I will run my own tests between a BCD436HP, BCD396XT, and BC125AT in VHF/UHF analog transmissions, and between the two digital scanners on digital P25.
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Old 05-16-2018, 9:29 AM
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Originally Posted by jonwienke View Post
IMO it's probably related to C1 missing. The frequency counter chip used for Close Call may be near the noise source on the board. My 436 doesn't have a noticeable difference in close call sensitivity between UHF and VHF, but it has C1 installed.
How can I tell if I am missing C1 without opening the radio? When I send the radio in for the RTC problem.
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Old 05-16-2018, 9:32 AM
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If your radio has the RTC or display issues, it definitely doesn't have C1, because that version of the board doesn't have the pads to install C1.
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Old 05-16-2018, 9:37 AM
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Originally Posted by jonwienke View Post
If your radio has the RTC or display issues, it definitely doesn't have C1, because that version of the board doesn't have the pads to install C1.
So far after I turn them in for RTC over a year ago I had no problems with display or RTC problems.
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Old 05-16-2018, 9:45 AM
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If you have had the RTC repair done, your scanner probably has C1, unless the repair was done in the first few months of the repair campaign.
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Old 05-16-2018, 9:54 AM
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If you have had the RTC repair done, your scanner probably has C1, unless the repair was done in the first few months of the repair campaign.
Okay thanks. I think I done that the first week or second week when they had the repair campaign. I do still have use to the cooper tape on the door on the 436.
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Old 05-26-2018, 3:17 PM
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Wasn't really sure how to test CC on the bench, so I just put the radios in CC only and injected a signal until it triggered. I played with the signal levels until it would trigger consistently every time I turned the generator off and on.

I had about a 8-10 dB difference in the UHF range between the 325 and 436, other bands were within a couple of dB of each other.

I haven't done bench work in about 20 years and the eyes aren't what they used to be, but I got out the temp controlled solder station, cleaned the tip, soaked up the sponge, found the proper cap in my SMD project box and had at it.

In the UHF range the difference between the 325 and 436 now seems to be within a couple of dB of each other (just like the other bands). I'll have to try it on the road next week to see how it performs in the field.

Posts like this are completely false as using an external antenna made no difference on CC...

https://forums.radioreference.com/un...ml#post2745026

It's also a shame I had to do this myself instead of Uniden publicly admiting they omitted the cap on the RTC issue replacement boards.
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