SDS100: Built In Pre-Amp

Status
Not open for further replies.

xusmarine1979

Active Member
Joined
Mar 17, 2005
Messages
1,458
Location
Louisville, Ohio
All,


For about a week now I've noticed a great reduction in the signals that my radio receives. But it's not the same symptoms as when I had the csj issues last year. It still decodes and receives just fine, just a weaker signal.

Anyway, I attempted to see if it was the connector and all seems fine on that end. There was no change to the signal.

So I started doing some reading and read about the pre-amp that is installed in the radio and it sounds like it has possibly burned out. Other than reducing the signal a bit, should I have any concerns? To be honest, I seem to get a cleaner signal on Ohio's MARCS which is simulcast in my county anyway. I really haven't gone into any buildings or anything to see how much it will affect there, and I can place a 2M antenna on the radio and listen to NOAA without messing with the filters or IFX. And it's not as strong as using the attenuator. But anyway, I just wanted to see if anyone else has had this and if there would be any kind of benefit to not using the built in pre-amp.
 

IndyScan

Always Connected...
Premium Subscriber
Joined
Dec 19, 2002
Messages
154
Location
Fishers, IN
I'm experiencing a similar issue with my SDS100 acting a little hard of hearing all of a sudden. When I'm at home I use my 100 in the same location. I noticed several of the P25 systems I had been scanning were actively searching for the control channel. When I moved a little closer to the window on the other side of the room the scanner would lock on & when I returned to by desk it stayed connected with 75-100% RSSI signal (and low errors). Kept working until I toggled the FL off/on then it would just search for the control Chans again.

Attenuator is not on, location is correct (range 0.0) & I have no lockouts/avoids. Literally nothing has changed in the radio for 3-weeks other than toggling off/on FL's.

Remtronics antenna is what I was using. Connected up a SpectrumForce on a pizza pan for a ground plane and it helps some, but the Remtronics worked perfectly before.

It's acting like it's not hearing the CC's but I can see it pause and attempt to decode. D-Error is always less than 50.

Systems in question:
--ISP Dist-51 Pendleton Tower
--ISP Dist-52 ISP Post Tower
--Indianapolis System 2 (Indy PD)

Tower for this one is a mile form my house so it obviously works, even without an antenna.
--Indianapolis System 3 (Hamilton County Sim).
 

xusmarine1979

Active Member
Joined
Mar 17, 2005
Messages
1,458
Location
Louisville, Ohio
Yup, same here. Same antenna as well. I haven't tried more distant sites but I do work within about 1,000 feet from one of the neighboring county's site and sitting outside of the office in direct line of site was able to pick up my county before, but a bit choppy at best. Now it comes in perfectly clear. So I know the signal is reduced, also by listening to NOAA with the Remtronics antenna but I don't listen to much of anything else at the same time. I may take a drive this weekend to see the difference while on the road.
 

RBMTS

WA Database Admin
Database Admin
Joined
Apr 28, 2002
Messages
1,033
Location
Somewhere out there
One thing to remember - trees and foliage can be a slight disruption to receiving RF. This is obviously most prevalent during the spring and summer months. During the late fall and winter months my SDS was indicating an error rate of around -60 on a local system. Now with the trees and foliage fully bloomed, the error rate is in the high -70's to low -80s. I find that my radios always become a bit noiser during the summertime. Winter months when trees are bare - much better. You might be experiencing the same thing.
 

SteveSimpkin

Member
Premium Subscriber
Joined
Apr 13, 2009
Messages
910
Location
Lancaster, CA
It is possible that an interfering signal is triggering the automatic gain control to reduce the input gain on the SDS tuner chip. Try changing the Global filter option (Normal, Inverted, off) while listening to one of these problem sites.
 

IndyScan

Always Connected...
Premium Subscriber
Joined
Dec 19, 2002
Messages
154
Location
Fishers, IN
I'm playing with that tonight. It's just weird that I went from solid copy to unable to lock onto the CC overnight on more than one system. I'm in north suburban Indianapolis. Not a lot of RF out here compared to downtown. Hopefully xusmarine1979 has some success with this as well!
 

xusmarine1979

Active Member
Joined
Mar 17, 2005
Messages
1,458
Location
Louisville, Ohio
Yeah I've exhausted all possibilities. I used this radio daily and know it well. It happens on all bands, and there isn't much rf in my small town either. I've read some other forums where folks have mentioned the pre-amp going out and this most certainly sounds like it. But honestly I can live without it if that's the case. The radio seems to perform better in the areas that do have the high rf, but I just haven't tried on the weaker stuff yet. I've never been so intrigued of the 30 years I've been in this hobby lol.
 

n1chu

Member
Premium Subscriber
Joined
Oct 18, 2002
Messages
999
Location
Farmington, Connecticut
As previously stated, global filtering (along with other filtering options) should be turned off first. Since these filtering options are susceptible to geographic locations (where your filter settings may differ than others), the scanner may work well with a certain filter setting only to change when you move... in some cases from one room to another, never mind leaving your house! It would be nice to have a buddy with the same radio try your SD card in his radio to compare.
 

xusmarine1979

Active Member
Joined
Mar 17, 2005
Messages
1,458
Location
Louisville, Ohio
As previously stated, global filtering (along with other filtering options) should be turned off first. Since these filtering options are susceptible to geographic locations (where your filter settings may differ than others), the scanner may work well with a certain filter setting only to change when you move... in some cases from one room to another, never mind leaving your house! It would be nice to have a buddy with the same radio try your SD card in his radio to compare.
As previously stated I also use the radio at work in the neighboring county, about 25 miles from home. And again it's on all bands, VHF (NOAA), UHF and the 700/800Mhz for MARCS. I'd say I've spent nearly 1,000 hours of testing the different filters along with ifx since they came out with the filters. In fact, I even created a thread not too long ago about the filters to understand them a bit more clearly.

I've actually been debating on purchasing a second one myself and was thinking about the SD card.

But the best example that I can compare is if we drive our car everyday, we know its typical behavior. You'll rarely see me without the radio, and I am pretty familiar with it's normal behavior. So if something becomes out of character, like an odd noise or the car performing abnormally, it's certainly noticeable. I know the RSSI isn't always a factor, but I've noticed about a 15db decrease on everything that I do monitor. I don't think it's foliage, because it only started last weekend, and we're well into July. But the decrease isn't as noticeable when I previously used the attenuator, but just to be sure I have ensured that it's not on anything at all.

Otherwise the radio does seem to function just fine, the signals just seem to be a bit weaker.
 

IndyScan

Always Connected...
Premium Subscriber
Joined
Dec 19, 2002
Messages
154
Location
Fishers, IN
Hey @xusmarine1979 How often do you turn your scanner off? I got tired of messing with the filters last night and turned it off for the night & just turned it back on after coming home form work.

Performance has noticeably improved after it sat. I had been running the 100 for weeks at a time off a laptop (connected to ProScan) as I was identifying units on my local system. It was pretty warm around the metal antenna band as you know it gets.

I'm scanning one of the systems I was having problems with & logging the history in ProScan (including signal strength). I'll be curious if it starts getting worse the longer it's running.

Just throwing it out there.
 

xusmarine1979

Active Member
Joined
Mar 17, 2005
Messages
1,458
Location
Louisville, Ohio
Oh I turn it off at night and here and there. Yeah it sure does get warm but I definitely ensure for it to rest. Since it's still performing pretty well, I'm just trying to avoid sending it in because I'm sure it'll take a while for it to return.
 
Status
Not open for further replies.
Top