jeffm77
Member
So, if i send my 436 in to uniden and tell them i got reception issues on uhf, will they fix it? I mean, it's their problem, they should fix it.
BCD436HP/BCD536HP: UHF Reception Issues due to Noise from Battery Compartment
- Thread starter bearcat
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Not likely send in with other issues like failure of light etc.
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Bob132
Member
Does anyone know if the .01uF capacitor that fixes the reception problem on the BCD436HP is polarity sensitive and if so, how to determine which end is negative and which end is positive ?
Thank's in advance,
Bob
Thank's in advance,
Bob
Poonwart
Member
They are not polarity sensitive. In fact, neither the cap nor the board are marked for polarity.
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Bob132
Member
FOLLOW UP:
Well . . . $89.95, and approximately three weeks later, my BCD436HP has come back from the Uniden repair shop in Roanoke, TX.
The clock battery issue seems to have been fixed, and the LCD display appears to be emitting a more "neutral" white color than the previous slightly bluish tone it had before.
In my repair request form, I complained about the radio's sensitivity issues and asked them to "replace a circuit board with a missing capacitor." The form that came back with the radio indicated "control board modification repair complete. F12J." I placed a follow-up call to a Uniden customer service representative who checked with the repair tech that did the work, and I was subsequently advised that "F12J is the capacitor."
I haven't yet noticed any significant improvement in the radio's sensitivity resulting from the installation of the "control board" and/or capacitor, but I'll keep testing. I'd mothballed the radio for a long time because of its lack of sensitivity to weak signals here in northern New Mexico, so it's been difficult for me to remember how well it generally behaved before I sent it in for repairs.
I know this is all about suppressing internally generated noise, and not the radio's actual rf sensitivity, but for the sake of brevity, I've chosen to use the word "sensitivity" to describe my problem with the 436.
I'll keep working with the radio and post a follow-up at some point.
Thanks for listening . . .
-Johnnie
Sensitivity is the ability of a receiver to detect any given signal and can be impacted by lot's of things. If the receiver signal-to-noise is low enough it can adversely affect sensitivity, so using the term sensitivity of a radio affected by some interfering noise/signal is appropriate. If the receiver cannot detect a signal of any particular level for whatever the reason, it's sensitivity is impacted. You would be correct to use the term "sensitivity". The C1 issue does affect sensitivity, just not as a part of the RF signal path, but by causing the signal-to-noise ratio to be decreased to a level that affects the resulting sensitivity of the receiver.
From reading about this issue, it seems that before the source of the RF noise was identified people discovered insulating the battery compartment helped. Maybe try wrapping some aluminum foil around the bottom of the radio while listening with earphones and see if there is any improvement. Try finding a UHF signal that transmits constantly like a control channel of a trunked system.
Good luck.
From reading about this issue, it seems that before the source of the RF noise was identified people discovered insulating the battery compartment helped. Maybe try wrapping some aluminum foil around the bottom of the radio while listening with earphones and see if there is any improvement. Try finding a UHF signal that transmits constantly like a control channel of a trunked system.
Good luck.
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Hello again.
After a week of informal, unscientific testing following installation of the F12J capacitor/control board, I must report that my BCD4356HP's reception of VHF-hi and UHF signals has improved . . . at least, when compared to its previous performance.
The 436's overall performance now seems comparable to my trusty old BCD396XT in terms of sensitivity. Having said that however, neither radio is as sensitive as my TRX-1, which serves me extremely well here in a generally weak-signal listening environment in rural northern New Mexico. I suspect that the TRX-1's extra sensitivity may become a liability in an urban, strong-signal environment, but that comparison will have to wait until the next time I'm in a big city with extra time on my hands.
I will continue to listen carefully to my 436 and conduct an extended side-by-side comparison with the 396, but I think it's safe to recommend that anyone experiencing sensitivity problems with his/her 436 should consider sending it back to Uniden to be fixed . . . if indeed it's missing the famous F12J capacitor. Those of you who are already doing your monitoring in strong-signal environments and who are happy with your 436 will probably not notice any significant improvement following the F12J surgery.
I hope this is useful information for someone out there.
Thanks for listening!
-Johnnie
I understood from reading this forum that C1 referred to the capacitor, but the service repair report that came back with the radio only referenced the F12J repair, so I called Uniden to make certain they'd done something about the missing capacitor. The customer service rep said the repair technician told him that F12J referred to the capacitor installation.
Semantics aside, I have noticed a slight improvement in my 2013-vintage 436.
Just out of curiosity, why in the world do you think Uniden would make a batch of F12J boards without the missing capacitor?
k3fs
Member
Why in the world is Uniden so silent about it?
When there is a problem, admit it as soon as possible.
Customers are not stupid. Ignoring or denying a legitimate problem is not the way to handle it.
When there is a problem, admit it as soon as possible.
Customers are not stupid. Ignoring or denying a legitimate problem is not the way to handle it.
Thays the million dollar question Uniden America has never even admitted that this is a issue. Although it would seem they do since they put the capacitor on the newer boards. Uniden customer support has been lacking a bit all around. Don't get me wrong I love the 436 I think it's a great radio I would just like to see Uniden to get it to work advertised.
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I'm guessing that officially acknowledging the problem would open up a can of potentially expensive liability worms.
A lot of people are happy with their 436's performance without the capacitor, so I suspect the Uniden budget/business office spent some time with their legal counsel counterparts and decided to fix the problem only if and as they encountered customers who were unhappy with their scanners' sensitivity. It's a relatively minor performance problem for some of us, not a safety issue for which the automobile industry routinely issues recalls in order to steer clear of multi-million-dollar lawsuits. I'd also guess that Uniden may be taking a minor financial loss on every unit that's returned to their repair contractor for the $80 control board/capacitor fix.
As a matter of credibility and customer relations, this has been a bit of disaster for Uniden, and I suspect that UPman and the marketing people have been spanked more than once for too quickly pushing a product out the door that wasn't ready for prime time exposure to a bunch of demanding and technically savvy customers.
I would really hate to see Uniden abandon the scanner market because of this issue. In my opinion, they've generally played a lead role in product development that's given us trunked radio system tracking, dynamic memory, and digital monitoring capabilities.
It's been a lessons-learned experience for all of us. I, for one, don't intend to buy another flagship scanner from Uniden until it's been thoroughly test-driven by all the demanding, technically savvy people who contribute to this forum. In fact, I don't intend to buy another scanner until one is developed that can handle Linear Simulcast Modulation.
My two cents . . .
-Johnnie
Thanks, jonwienke.
I understand that three versions of the control board have been produced. The relatively minor, but interesting, detail I don't understand is why they'd bother to redesign and distribute a board that had connections for a capacitor . . . but no capacitor. Oh well . . .
Happy monitoring!
-Johnnie
Has anyone compared the newest board, that has the cap installed, to the original board that does not have the pads for the cap? Would maybe like to add a cap with short wires but don't have a newer board to trace where the pads would connect to.
milcom_chaser
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Tracing anything is difficult because the board is 6 layers, and only traces on the top and bottom layers are visible.
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