SDS200 Front end overload again

nr2d

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Dec 28, 2003
Messages
450
Location
Laurel Springs, NJ
#1
I had a problem receiving my local state police, Motorola 860 MHz conventional trunking system on my BCD536HP. I rectified the problem by turning on the
internal attenuator. I was able to identify the problem as most likely 2 very close cell towers. If I connected
the scanner to an inside antenna with out the attenuator on I received the state police fine. Once I turned
on the attenuator on and went back to an external antenna I had no problem.

Well I have the same problem on the SDS200. The only problem now is that even with the internal attenuator on I still can't receive the local state police. I tired
and inside antenna whip antenna and I had just minor luck receiving some transmissions. So again it looks like the SDS200 like the BCD536HP is susceptible to
close channel/adjacent channel interference.
 
Joined
May 11, 2007
Messages
2,018
Location
Evansville, IN
#2
I had a problem receiving my local state police, Motorola 860 MHz conventional trunking system on my BCD536HP. I rectified the problem by turning on the
internal attenuator. I was able to identify the problem as most likely 2 very close cell towers. If I connected
the scanner to an inside antenna with out the attenuator on I received the state police fine. Once I turned
on the attenuator on and went back to an external antenna I had no problem.

Well I have the same problem on the SDS200. The only problem now is that even with the internal attenuator on I still can't receive the local state police. I tired
and inside antenna whip antenna and I had just minor luck receiving some transmissions. So again it looks like the SDS200 like the BCD536HP is susceptible to
close channel/adjacent channel interference.
Try using the new filters.
 

Ubbe

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Sep 8, 2006
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Stockholm, Sweden
#5
Are these filter RF or audio?
They are RF filters, although there are some of us who wish Uniden would let us have user settings for bass-treble-loudness to adapt to the different acustics in rooms and vehicles. It's like having a car stereo and home stereo without any tone controls. The only way now to improve sound quality are to try different speakers to find one that suits the room and the scanners audio profile. Each user has its own unique acustic enviroment, just as users have unique RF enviroments that force us to use different antennas, different filters that do not correspond to a neighbours setup.

/Ubbe
 

epilab

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Location
Mass
#6
Have the same issue here. All on conventional 400 meg systems. Breaks random system frequencies. Any ideas as to which RF filter to apply and should it be for each of the conventional channels. No Issues on Motorola smart zones in the 800mg range

I am considering just return for credit and await for improvement before return credit time come to the end. Not happy about that
 

weathermedic

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#8
Not much luck experimenting with the filters. I've had some luck with the signal overload on the NYPD conventional 470 mhz frequencies by using the channel selectable attenuator function. Keeps most of the transmissions from getting cut out by the interference, but I can still hear the intermod somewhat while the frequency is in use. Works ok for nearby signals, but division frequencies from some of the more distant borough precinct locations are completely killed with the attenuator on. Have to use my trusty 15X to listen to those. I am using a discone rooftop on top of a 2 story house.
 

epilab

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#10
I hope if uniden monitors some of the issues that are being seen, a fix happens before returns start
 

epilab

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#11
Well. Spent the day trying all the different filters. Can’t reduce the front end overload
I throwing in the towel
Not looking forward returning a potential great product
 

epilab

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#12
Well. Spent the day trying all the different filters. Can’t reduce the front end overload
I throwing in the towel
Not looking forward returning a potential great product
Talked Uniden customer support
My call was first with a front end overload problem. And unknown solution at this time
 

ka3jjz

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Bowie, Md.
#13
What antenna are you using? In heavy RF situations, it's some times true - though counter intuitive, I agree - that a smaller antenna needs to be used. Have you determined what it is that is overloading you? If it's something specific, like a pager, for example , there are filters that can handle this.

Overloading is a tough nut to crack, and frankly consumer grade scanners are not the best at handling this. Mike
 

epilab

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#14
One kind sounds like telemetry burst other are audio bursts the telemetry is the loudest and the issues on conventional sites
 

KR7CQ

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Phoenix
#15
Question for those who may be able to answer: Does the SDS-200 display VHF / UHF intermod problems not seen on other top-end base scanners, when hooked up to the same outdoor antenna? That would be a 100% deal-breaker.
 
Joined
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Location
Stockholm, Sweden
#16
SDR chips do not have the best RF performance needed to let them be used in a high end scanner without problems popping up in a thougher RF enviroment. Upman ones stated that if you do not suffer from simulcast issues you're probably better off with a BCD436 than a SDS100. Probably the same will apply to BCD536/SDS200.

/Ubbe
 
Joined
Dec 28, 2003
Messages
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Location
Laurel Springs, NJ
#17
KR7CQ, from my testing I see the adjacent channel/co-location in my 536HP. By switching on the internal attenuator on the 536HP solved the problem. Using the same antennas, external on my tower and inside my radio room sitting in a window Even with the internal attenuator on in the SDS-200 I can't eliminate the problem.

I have 2 cell phone towers with about 1800' of my location. On my 536HP I tried both antennas and I found the problem when I decided to try my Homepatrol-2 on the same frequencies/systems with the antenna that came with the scanner. With the HP-2 sitting on my desk I had no problem receiving the system. So that's what led me to trying the internal attenuator on the 536HP. This worked.

The SDS-200 is set-up the same as the 536HP in regards to the RF settings but with out luck. I was able to receive inter. transmissions with the telescoping antenna attached to the SDS-200 but not with very much reliability. I even tried an external 3dB attenuator on the SDS-200 but again it droop the desired signals down too low for reliable reception. When I get back to work I'm going to try the SDS-200 on 1 of my discone antennas. I don't have any cell sites with in 1 mile of my location at work. So I'll see what happens then.

Now the SDS-200 performs as good as the 536HP on my counties 700 MHz P.25 system with 1 small minor problem. When receiving a conventional FM transmission I hear "crackling" on the received signal but the TDMA P.25 Phase II audio is for the most part clear maybe a bit better than my 536HP.
 
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CQ

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Exosphere
#19
Question for those who may be able to answer: Does the SDS-200 display VHF / UHF intermod problems not seen on other top-end base scanners, when hooked up to the same outdoor antenna? That would be a 100% deal-breaker.
SDS200 is a champ so far. Only radio with intermod issues was a TRX-2, of all my radios in the last 20 years at this location.
 

sparklehorse

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Portland, Oregon
#20
<snip> I have 2 cell phone towers with about 1800' of my location. On my 536HP I tried both antennas and I found the problem when I decided to try my Homepatrol-2 on the same frequencies/systems with the antenna that came with the scanner. With the HP-2 sitting on my desk I had no problem receiving the system. So that's what led me to trying the internal attenuator on the 536HP. This worked. <snip>

One thing you could try is a cheap cell phone Yagi:

https://www.amazon.com/XHTECH-824-9...1549934949&sr=8-46&keywords=cell+yagi+antenna

You might be able to null out your cell tower interference while boosting your p25 system performance. I’ve used these to help deal with simulcast distortion on my local p25 system with my BCD536 and had good luck. It may take some experimenting with direction, etc. It took me a while to find a sweet spot. If it doesn’t help you’re not out much.

.
 
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