Hum Fix

[Ed6698]

I have not owned a new Uniden scanner in a long time. I finally decided I wanted a base scanner capable of good P25 simulcast performance, been using a Unication G4 with the Trunking Free Scan FW with good results. I stayed away from the Uniden SDS200 due to some of the complaints of the hum issue lottery. I purchased the SDS200 from Bearcat Warehouse last week and everything seemed good, I could hear a little hum from the unit with the internal speaker, but nothing totally bothersome. However I always use external speakers on my base scanners. Once I hooked up the external speaker the hum was terrible, tried multiple different speakers, that hum was totally unacceptable. I researched a while back on the hum fix before even buying it, plus I always used to be handy with electronics back when I was younger. I took it apart today following all the stuff I have read on here in the past few days. I did the @StaticDischarge fix and now the SDS200 sounds great on the external speaker, no more hum at all. If I could not have done the repair I would have probably returned it. So thanks to all on here that posted all the good information including the photos for opening the radio up and the actual fix that works. I really do like this SDS200.

 

[jtwalker]

Maybe a Ground Loop Noise Isolator would help with external speaker.

 

[Ed6698]

Maybe a Ground Loop Noise Isolator would help with external speaker.

I personally do not know if one of those would work, as the hum is also on internal speaker, in a totally quiet room I could hear it from the internal speaker, but with speaker on bottom it kind of masks it. Take a look at the sticky at top of forum for hum fix and search around, this has been going on since release of SDS200, but not on every single radio I believe. I even left the mitigation part in radio that Uniden uses to supposedly limit the problem. I am impressed with the SDS 200 now without the hum noise, I can sit in a totally quiet room and not be bothered by the hum.

 

[eaf1956]

The mitigation part is useless after the fix.

 

[jtwalker]

So I recommended the ground loop isolator because I have no hum on my internal speaker on sds200, but I do have a hum or buzz when using a hardwired, amplified external speaker. The isolator resolves this for me.

try it, don’t try it ...

 

[Ed6698]

So I recommended the ground loop isolator because I have no hum on my internal speaker on sds200, but I do have a hum or buzz when using a hardwired, amplified external speaker. The isolator resolves this for me.

try it, don’t try it ...

Thanks for tip, but with the @StaticDischarge fix posted in the sticky at top of forum, that actually fixes the problem, the ground loop isolator is not even needed at all, I was hearing the hum with a unamplified external speaker, I could just imagine how bad it would have been with a amplified speaker. My Whistler WS1095 does not need a ground loop isolator and it has a external speaker also and has no hum or background noise at all with same speaker.

 

[Stecomp]

Glad the fix worked for you. I have 2 and they both had the issue. The first one was a day 1 release that went back to Uniden on day 2 with the hum and pop at end of transmission. After nearly a month in for repair, Upman advised me they had used it for a test bed resulting in the development of the mitigation part. The part took care of most of the hum but still had a little pop as has also been discussed here quite a bit.

As this was going to be used in a dedicated scanner rack with an external speaker I was still not too happy with the pop. Fortunately around this time someone on here talked about the Ground Loop Noise Isolator above and that took care of any noise and pop.

Second scanner was an open box purchased earlier last year with a slight hum and pop. I did the Staticdischarge fix and the hum was taken care of, but the pop was still there at a lower level. I tried the Isolator with a Uniden unpowered speaker but for some reason still had the pop unlike the first unit. It was then suggested to use a Inline Volume Control adapter with the speaker and that took care of the pop but in adjusting the adapter I had to turn volume up on scanner but no big deal.

 

[Ubbe]

It was then suggested to use a Inline Volume Control adapter with the speaker and that took care of the pop but in adjusting the adapter I had to turn volume up on scanner but no big deal.

The "hum" and pops are independent of the volume setting, so if you manage to reduce the sound volume from the speaker, using a ground loop isolator that are designed for high ohm applications, it will reduce the total volume so the "hum" or pops are not heard, but you have to raise the scanner volume to compensate for the loss of audio level.

The same if you use external speakers. A non effecient one will give less power and the "hum" are not heard and with amplified speakers you have to adjust the speakers own volume down to a level where the "hum" isn't heard and then increase the scanners volume.

/Ubbe

 

[Ed6698]

I know one thing for sure that after doing the hum fix the audio is fantastic, even listening to scanner with wired earbuds is great. After not having a Uniden for so long I am really impressed with this SDS200 so far. I worked with Sentinal for week or so before getting the scanner so I have myself a nice list of favorites. The SDS200 is a nice addition to my small collection of radios