One would tend to think it still would have an affect with an ext antenna. Cant a signal even further away fall prey to the noise?
BCD436HP/BCD536HP: UHF Reception Issues due to Noise from Battery Compartment
- Thread starter bearcat
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One would tend to think it still would have an affect with an ext antenna. Cant a signal even further away fall prey to the noise?
troymail
Silent Key
Not if the noise is being "locally generated" by the radio.
From what I see, the 436 has problems decoding/processing DMR that is "noisy" -- When I search, I hear lots of digital noise that is DMR but the radio plays it as analog (but I'm sure it's DMR). It's it's not clear enough the radio won't decode it - and just a little noise that appears to be getting generated by the radio appears to crush reception decoding without the shielding and/or use of an antenna that isn't near the radio itself.
One would still think that that little bit of noise could have the same effect on a distant system that might have decoded better (even tho its far away) without that noise generated by the radio..
k3fs
Member
The noise source is generated by the radio. An antenna mounted on the radio picks up enough of the noise for it to affect reception. It has been shown that moving the antenna just a foot away from the radio using shielded coax improves reception and decreases the amount of noise received.
It is good to see one company actively working with their consumers to trouble shoot a problem. They walk the walk. Another does not follow their own rules of conduct, which is frustrating.
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.
It is good to see one company actively working with their consumers to trouble shoot a problem. They walk the walk. Another does not follow their own rules of conduct, which is frustrating.
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.
No not duct tape. It has to be some sort of RF shielding tape. You can review this thread near the start to see some options. In a nut shell here is what works.
RF/EMI spray with a piece of aluminum shielding tape over the foam
Aluminum shielding tape over the inside of the door going over the foam
Copper shielding tape over the inside of the door going over the foam, about 6 layers.
These are in the order of best to worst, but that could be splitting hairs a bit. They all work to some degree.
W8RMH
Feed Provider Since 2012
I thought I would give this a try. I bought < $4 of copper EMI tape on eBay and low and behold I am receiving things I never even received before, and with 5 bars too. DMR, UHF, and even P25 is better.
902
Member
No. Not the dollar-a-roll silver plastic with some fibers and adhesive on the other side. That won't do anything. The very thin metal foil with adhesive and usually a paper backing under the adhesive kind of duct tape, yes. Then there's mylar tape with some kind of metalization. I don't think anyone's tried that.
Something like this:
https://www.amazon.com/Aluminum-Foi...1474898022&sr=1-8&keywords=aluminum+foil+tape
Not this:
https://jet.com/product/detail/05a0...15&gclid=CNGtys6Xrc8CFRDWNwod3o0DaQ&gclsrc=ds
(No endorsement of either website, product, or purchasing method, you can get these in just about any locality from a bunch of places. Just used them to illustrate my reply.)
For what it's worth, I recently went on a trip where there were discrete UHF users, as well as UHF trunked systems. I did the "magic" tape job on the battery door and I thought my 436 worked reasonably well in those parts of the country with the stock antenna on it.
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Wow. Six layers! It's a good thing I bought three feet of the gold foil EMI/RF stuff.
Six layers on top of the foam pad is going to make the battery door be a bit tight
to close. But my tape should be here tomorrow so I'll try it.
Thanks.
teknishun
JamesO
Member
I have been on the sideline watching this.
A few questions/ideas, not sure all of these options are possible or worth trying.
1.Can the batteries be removed and the scanner be used with external power as a test?
2. Can a battery pack be used remotely with wire connected to the battery tabs as a test?
3. Has anyone thought/used conductive foam on the battery door?
a. There are different types of conductive foam, there is the black anti static foam that must be partially conductive that is used for things like DIP micro chips. Something like this - https://www.amazon.com/Desco-High-D...id=1474972533&sr=8-3&keywords=conductive+foam
b. Thee is also RF conductive/shielding foam as well. More expensive and my be more useful at higher frequencies. Something like this - http://www.mouser.com/ProductDetail...XHtCQjYQssHU7d4dtk8vHF6tNP1KRHuJkMaAgDn8P8HAQ
4.Has anyone considered/used any ferrite beads on the battery terminal wires leading back into the scanner?
5. Has anyone considered/used any small value (pF) capacitors on the battery wiring to attempt to decouple and RF to a ground path inside the scanner?
Just thought I would toss some of these ideas out as thinking points and someone may consider some of these other ideas.
A few questions/ideas, not sure all of these options are possible or worth trying.
1.Can the batteries be removed and the scanner be used with external power as a test?
2. Can a battery pack be used remotely with wire connected to the battery tabs as a test?
3. Has anyone thought/used conductive foam on the battery door?
a. There are different types of conductive foam, there is the black anti static foam that must be partially conductive that is used for things like DIP micro chips. Something like this - https://www.amazon.com/Desco-High-D...id=1474972533&sr=8-3&keywords=conductive+foam
b. Thee is also RF conductive/shielding foam as well. More expensive and my be more useful at higher frequencies. Something like this - http://www.mouser.com/ProductDetail...XHtCQjYQssHU7d4dtk8vHF6tNP1KRHuJkMaAgDn8P8HAQ
4.Has anyone considered/used any ferrite beads on the battery terminal wires leading back into the scanner?
5. Has anyone considered/used any small value (pF) capacitors on the battery wiring to attempt to decouple and RF to a ground path inside the scanner?
Just thought I would toss some of these ideas out as thinking points and someone may consider some of these other ideas.
fourthhorseman
Member
I can advise as to #4...The Batt Terminals are soldered directly to the PCB..
JamesO
Member
Thanks for confirming this. It just makes things a bit trickier to experiment with.
Might have to cut a circuit trace and use something like a ferrite bead with a lead inserted or looped through a few holes in the core.
Also what about one or more ferrite beads in series with the batter contacts on the buss side of the battery compartment?
I have not bothered to dig out my spectrum analyzer and make a sniffer cable to see what is going on. I need to wait until I send my 436HP in for the RTC clock battery replacement before I start any modifications.
Certainly all of your ideas have merit. Give them a try. With the surface mount boards there is really no wiring to play with, but if you can figure out something I am sure the folks on this list would love to hear about the results. I know I would. I think there is a component that could be added/removed that would eliminate the noise. I just have no idea what it would be. At this point the only solution I know of is using a shielded battery door. Keep us posted!
Make sure you look at some of the pictures at the beginning of this post. The copper I was gifted was very thin. The battery door fit fine. The foam will squish down as you apply more layers. We found a very weak constantly transmitting UHF RF link freq that the 436 could not hear. Then we applied the copper until we started hearing the signal. Actually at 8 layers the signal got worse. So we settled at 6 layers. If the tape you get is thicker then you may need less. You should try to find a UHF signal that you can hear on another radio that you cannot hear on the 436 and go from there. If you do not have another radio then getting it right gets a bit more tricky. As you are trying find signals that the 436 currently cannot hear. Good Luck
One point I forgot. You mentioned RF/EMI foam. I did try shielding just the foam and that did not work. I did try putting foam on the entire door and it did not work. Shielding the inside of the door going over the foam is the best results I have achieved. Hopefully you will find a new trick.
JamesO
Member
So I played around with my 436HP this morning, Note that I did not re-read this thread from the beginning so I may not have had the scanner set up as yours.
I have Rohde & Schwarz FSH6 spectrum analyzer with the Pre-Amp option. I set the spectrum analyzer up to 500 MHz center frequency and played around with many settings of the Resolution Bandwidth and Span. With the scanner on and scanning what ever I usually scan, I started sniffing round the batteries with and without the rear cover installed.
I was unable to pick up any spurious emissions as low as -105 dBm.
I would like get a better idea of a frequency or group of frequecies that you are having problems with. Is there a system from the RR Database I can easily download or enter into the scanner that would be a good "test" system to work with?
My time may be limited, but I will attempt to play around when I have time.
I also assume you have used different types of batteries? What are you running at the moment? I just has standard Eneloop cells in my radio at the time.
I have Rohde & Schwarz FSH6 spectrum analyzer with the Pre-Amp option. I set the spectrum analyzer up to 500 MHz center frequency and played around with many settings of the Resolution Bandwidth and Span. With the scanner on and scanning what ever I usually scan, I started sniffing round the batteries with and without the rear cover installed.
I was unable to pick up any spurious emissions as low as -105 dBm.
I would like get a better idea of a frequency or group of frequecies that you are having problems with. Is there a system from the RR Database I can easily download or enter into the scanner that would be a good "test" system to work with?
My time may be limited, but I will attempt to play around when I have time.
I also assume you have used different types of batteries? What are you running at the moment? I just has standard Eneloop cells in my radio at the time.
troymail
Silent Key
Unfortunately, there seem to be many variables - to include that some have reported not having this problem (some radios appear to be demonstrating the issue while others do not). Apparently, from what I recall, it doesn't seem to be tied to a specific manufacturing date (I could be wrong) which sounds to me to be more like either a random manufacturing issue or a component issue.
I mostly use Eneloops of various type and age as well. I was experiencing issues with Maryland systems (Baltimore/FleetTalk and Anne Arundel/Southwest are a few) that are on ~460 Mhz and ~495 Mhz.
Placing the copper foil under the foam pad didn't help me at all. However, as soon as I changed this to the foil over the foam, it made a huge difference.
As I do not have an SA. I used an Airspy SDR. I have to turn the gain up fairly high on the software to see the noise. I had the Spectrum Spy set to a center freq of 460 and a 200 mhz BW. The noise was very broad banded from like 250mhz to 550mhz. I was using a stubby 1 inch antenna on the end of the Airspy ant connector. Later on down the road I had access to an SA and I could not see the noise with it. My thought is I could not get enough gain to see it. Remember while the noise effects the radio on UHF receive, it would still be considered fairly low level. Measure the noise in the area of the positive side of the middle battery.
JamesO
Member
I am starting to wonder what is going on with the foam.
So it seems if the foil is put over the foam, you are basically somehow making a capacitor?
Maybe swapping the foam for some of the conductive foam that is use to store micro chip DIP in might be different or some other cheap foam.
Also wonder how a anti-static plastic back memory chips or other components are shipped in will help?
My spectrum analyzer has the Pre-amp option and I turned this on after searching without the Pre-amp on. Too much sensitivity will cause me to pick up local signals, but with the Pre-amp on and the piece of coax I was using as a sniffer cable, it was on the edge of acting like an antenna.
You also mentioned that the RSSI indicator has 1-2 bars in the 400-500 MHz band as I recall. This seems to be a clue to the problem radios? What happens to the RSSI indcitor if you do the following?
A. Remove the antenna?
B. Enable the attenuator in the radio?
C. Install a 50 Ohm terminator on the antenna jack?
I am just tossing out questions, ideas and thinking outside of the box.
So it seems if the foil is put over the foam, you are basically somehow making a capacitor?
Maybe swapping the foam for some of the conductive foam that is use to store micro chip DIP in might be different or some other cheap foam.
Also wonder how a anti-static plastic back memory chips or other components are shipped in will help?
My spectrum analyzer has the Pre-amp option and I turned this on after searching without the Pre-amp on. Too much sensitivity will cause me to pick up local signals, but with the Pre-amp on and the piece of coax I was using as a sniffer cable, it was on the edge of acting like an antenna.
You also mentioned that the RSSI indicator has 1-2 bars in the 400-500 MHz band as I recall. This seems to be a clue to the problem radios? What happens to the RSSI indcitor if you do the following?
A. Remove the antenna?
B. Enable the attenuator in the radio?
C. Install a 50 Ohm terminator on the antenna jack?
I am just tossing out questions, ideas and thinking outside of the box.
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