New SDS200 - poor VHF and UHF sensitivity

[RocketNJ]

I have a new SDS200 which has poor VHF and UHF sensitivity.
Tomorrow I will test with an Aeroflex 3920 service monitor.

Using the included telescopic antenna and comparing to a Uniden 396XT with rubber duck antenna.

Recception on weather channels 162.400 and 162.500. Receiving on 396XT slightly noisy and zero receive on SDS200. Tried different filters and IFX with no difference.

Next tuned in Jersey City, NJ P25 phase 1 system.

396XT received fine. SDS200 would not lock on control channel. (470.2625 MHz control channel.)

700 MHz reception seems OK.

 

[Ravenfalls]

Update firmware & see which filters work best for you. For VHF & UHF 'Wide Normal' good starting spot.

 

[RocketNJ]

using Tax Day firmware. Tested with every possible filter and also filter off.
Will be interested in results of sensitivity test using the service monitor tomorrow.

Compared to the old 396XT it is VERY poor RX sensitivity.
The 396 ran circles around the SDS200 on VHF conventional and also the P25 phase 1 system (470 MHz range control channel It is a C4FM system.

The SDS200 does well on UHF linear simulcast systems though.

Dave

 

[KR7CQ]

It's primarily an LSM scanner. Analog is secondary in its mission. It will never be first choice for serious analog work in high RF areas like mine. I'm just thrilled to have a scanner that does LSM after years of cut outs and fiddling with yagis or using a pager in situations where I want a scanner. I'll take whatever it can do on analog as a bonus.

 

[ansky]

Next tuned in Jersey City, NJ P25 phase 1 system.

396XT received fine. SDS200 would not lock on control channel. (470.2625 MHz control channel.)

.

I'm about 10 miles out in West Orange and I get the Jersey City TRS loud and clear with a small indoor antenna. My SDS200 performs fine on digital systems in general. However I do have major intermod problems with UHF analog in the 460-480 MHz range. As an example, Newark PD on 460.50 constantly bleeds into Jersey City Fireground on 460.60. The IFX setting does not help at all. I also get a ton of intermod on the NYPD frequencies.

 

[KR7CQ]

I'm about 10 miles out in West Orange and I get the Jersey City TRS loud and clear with a small indoor antenna. My SDS200 performs fine on digital systems in general. However I do have major intermod problems with UHF analog in the 460-480 MHz range. As an example, Newark PD on 460.50 constantly bleeds into Jersey City Fireground on 460.60. The IFX setting does not help at all. I also get a ton of intermod on the NYPD frequencies.

This mirrors my experience with that frequency range in the Phoenix area. Spot on. I have not found any combination of attenuation, filtering, or the use of IFX that will get me where I need to be. I keep a BCT15X next to my SDS200 on the same multicoupler for my primary UHF scanner, and the old PRO-2006 sits in the same cabinet when I want to really work weaker signal stuff. The SDS200 combined with rooftop antenna does great things on LSM overall and earned a permanent place in my main scanner cabinet within a few days of testing so I love it, but UHF in high RF areas is probably its weakest area, followed by air band.

 

[KC1UA]

When conditions are right I find the SDS200 to receive on a par with other scanners. The key words are "when conditions are right"....which as mentioned in a high RF environment are problematic.

It is frustrating but more often than not thus far I have found a solution for the problem. It will never be my first choice for DX'ing as I have other receivers for such things, but for $700 I hope it will become at least in the ballpark of prior models. Only time will tell, but when there are a ton of reports indicating that updated firmware has reduced sensitivity I hold out hope for a "fix" at least in that regard.

Ironically the receivers I use for DX'ing are Airspy SDR's in conjunction with SDR# software. They are under $200 and ironically do not in my case anyway suffer 1/100th of the interference/intermod/adjacent channel rejection my SDR200 does, using the same antenna at the same time through a Stridsberg Multicoupler. An example of this: I have a weaker 800 MHz conventional analog police frequency of 855.2375, with a strong local at 855.2125. If I hold on 855.2375 with the SDS200 and 855.2125 transmits the .2375 signal is seriously attenuated. The Airspy of course displays the adjacent signal on the spectrum display of SDR#, but other than the visual you'd not even know it was present. Yes, I'm running NFM on the 200. Hopefully such issues can be perhaps minimized over time.

 

[Ubbe]

If I hold on 855.2375 with the SDS200 and 855.2125 transmits the .2375 signal is seriously attenuated.

The receiver chip in SDS scanners have an automatic gain control that reduce the gain if it sees a powerful signal even several channels away. It's an internal function in the chip that cannot be disabled by any external commands to the chip. It is what it is. If it didn't reduce the gain it would be even worse in the intermod department. The chip is designed primarely for wideband signals and the RF signal strenght detector that the AGC uses have a too wide filter to be able to sort out one single NFM channel from the adjacent ones. But as the front end also have a wide band filter it wouldn't help anyhow and would still give a desense of the monitored signal due to overload and also increase the intermod problem.
The only function in the scanner that could possible make a difference for this problem, if the monitored signal are strong enough, are the attenuator, not filter settings or IFX.

/Ubbe

 

[KC1UA]

That is great info. Thanks Ubbe.

I am beginning to think that for non-DX'ing general scanning with the 200, less is more. I'm using a side mounted off of a tower Antennacraft Scantenna ST-2 via a 4 port Stridsberg Multicoupler which likely "helps" just a hair in the signal department anyway. Maybe a lower antenna will do the trick...

Unfortunately I have an impending monsoon (not really but it's going to rain like hell) this weekend. I have some ideas for relocating one or more of said antennae and seeing how or if things change. I've tried just a back of set and it's not happy either, probably because of my own RF antenna farm AKA computers, televisions, and other electronics. Once I don't have to use a rowboat to get to the tower to climb to the roof I'll make some moves and see what transpires.

I tried attenuation also but that served to completely finish the job and eliminate the .2375 signal altogether. As stated "it is what it is". It is just far more noticeable with this scanner than with anything else I've ever used, and again the nature of this beast, I guess.

 

[RocketNJ]

I did tests and the direct receiver sensitivity was quite good using the Aeroflex service monitor. I decided to do some over the air testing using a UHF base unity gain antenna I had laying around in my office vs the telescopic whip fully collapsed (closer to a 1/4 wave on UHF.

Watching the receive signal level (in dBm) on the front display I loaded our P25 LSM phase 1 system.

With the antenna included with the scanner the control channel was bouncing between -73 and -78 dBm.

I switched to the unity gain with 20 feet of 1/4" Superflex cable with antenna propped up in corner.
Control channel was between -56 and -62 dBm. Over a 15 dB improvement!

Bottom line is the included collapsible antenna is bad unless you can receive the system fairly strong.

It appears the 396XT has better matching to the rubber duck antenna on VHF and UHF than the SDS200 with the included antenna.

Time to look at purchasing a discone……...

 

[Ubbe]

Maybe a lower antenna will do the trick...

You should always use the best antenna and position possible and then use a $20 variable attenuator in front of the Stridsberg and adjust the attenuation level to best possible reception. If some scanners connected to the Stridsberg can handle stronger signals then set the variable attenuator between Stridsberg and the scanner that can't handle the strong signal and adjust until problems go away, or are acceptable and do not annoy enough to be a problem. In most cases this is all that's needed. Other times you'll also need external filters and a FM broadcast trap filter are always helpful, it it's of good quality and doesn't attenuate other frequencies too much.
https://www.amazon.com/Broadcast-FM-Block-Filter-88/dp/B01LE9LRPM

/Ubbe

 

[devicelab]

It's primarily an LSM scanner. Analog is secondary in its mission.

If this is the case then I want a FULL refund -- now!

 

[KR7CQ]

If this is the case then I want a FULL refund -- now!

Then hopefully you purchased from a source with a good return policy, in which case you are all set. If I had purchased my SDS's thinking they were going to be analog workhorses I would have returned them as well. A $145 BCT15X fits that bill, and as a result I have a few of them along with many other scanners that shine on VHF / UHF analog. But short of my Unication G4, the SDS's are my only valid LSM solution, and unlike the G4, the only way to scan multiple LSM systems at the same time.

It all comes down to each individual and their individual situation. The SDS is not "the dream", the one device that performs like professional gear on every band, with every protocol, with LSM, with AM, with SSB, 25-1300 MHz, with everything. There will likely never be such a device as it would only be needed by hobbyists and there aren't enough willing to pay the thousands that it would cost for each unit. It is what it is.

 

[KC1UA]

You should always use the best antenna and position possible and then use a $20 variable attenuator in front of the Stridsberg and adjust the attenuation level to best possible reception. If some scanners connected to the Stridsberg can handle stronger signals then set the variable attenuator between Stridsberg and the scanner that can't handle the strong signal and adjust until problems go away, or are acceptable and do not annoy enough to be a problem. In most cases this is all that's needed. Other times you'll also need external filters and a FM broadcast trap filter are always helpful, it it's of good quality and doesn't attenuate other frequencies too much.
https://www.amazon.com/Broadcast-FM-Block-Filter-88/dp/B01LE9LRPM

/Ubbe

I always have used the best antenna because I've never seen the issues I see with this scanner, although there are assuredly some high RF environment issues that plague me overall. That said a variable attenuator would have to be unique to the cable run to the SDS200. I'd give it a whirl to be certain. I also use Par Electronics filters in front of the Stridsberg. One is a FM broadcast band filter that croaks 88-108 MHz. The other is for a specific 152 MHz frequency that has an excessively dirty paging signal on it. The reduction in interference with these two devices alone is worth their price. I couldn't live without them. Well I could live, but my radio hobby would suck!

I am about a mile as the crow flies from a hill that is loaded with transmitters on all bands, pretty much, including FM broadcast. Sometimes I can sit in my driveway and receive UHF departments from a good distance away better than I hear them indoors using the BCD996XT mounted in it and a Larsen tri-band roof mounted NMO antenna! I also have 50' of tower side mounted to my house with a Comet GP-15 at the top (primarily used for DX'ing VHF and UHF bands), 3 Antennacraft Scantenna ST-2's side mounted off of the tower (one of which the SDS200 is using), and an Omni-X. At ground level I'm about 110' above sea level so the top of my tower is pretty much line of site to "the hill from hell". Thus the "less is more" consideration for the SDS200. Everything else, to include my Airspy SDR's, is much more forgiving.

But for $20 I will definitely seek out a variable attenuator for experimental purposes!

 

[KC1UA]

If this is the case then I want a FULL refund -- now!

Don't give up the ship yet. Even taking into consideration my environment as described above I have overcome many problems thus far with the combination of filters and IFX. I know I won't get them all but that said I've never used my #1 shack scanner for DX'ing anyway. I'm tweaking it to hear what I want it to and that's its job. As mentioned I do have some spare analog scanners on hand for "just such an emergency".

It has been somewhat of a frustrating experience but it can be overcome. With the many reports of reduced sensitivity during the last firmware updates I expect that will be resolved down the road, if it is in fact a problem. I do wonder if it is the environment because we are surely seeing that no two of these act quite alike!

 

[mule1075]

If this is the case then I want a FULL refund -- now!

I guess you did not do enough research it was said when the sds100 came out that if no simulcast issues you could probably stick with the x36hp series. The only one you should be mad at is yourself for not researching it better. As for a full refund take that up with who you bought it off of but it is highly unlikely that will happen. One upside is you can sell it yourself and probably get most of the money back you spent. But hey better research and you would not be in this conundrum.

 

[TailGator911]

Yes, I think we are realizing just how finicky these SDR scanners can be. There are so many variables to be aware of. Reception definitely depends on correct programming, adjusted settings, filter settings, antenna type and placement, location location location, and attention to detail. Not to mention patience, research, determination, and dedication. I can't stress that enough. I think some folks just threw their hands up and sent the scanner back, just as I did a couple few years ago with the 436, too much of a learning process. Don't give up! Once you get the SDS scanners tweaked just right, they fit like an old baseball glove.

JD
kf4anc

 

[garys]

I don't know if "finicky" is the word I'd use. I think it's important to remember that these are Software Defined Scanners. They aren't just scanners with a lot of firmware options. They can be adjusted and fine tuned to work in different areas and for different types of systems.

As I found out just yesterday, filter settings can have a dramatic effect on the reception users get. For me at least, turning the filters off has resulted in the best overall performance. There are a lot of analog UHF and VHF systems in my area, particularly UHF. There is some digital, including digital trunked systems. With the filters off, I get really good reception across the board.

I'll probably find some systems that will work better with other filter settings, however I haven't found one yet.

The only things that I would like to see added are per frequency filtering for conventional systems and a Global filter setting for multi site trunk systems. There is a large DMR network with sites in MA, RI, NH, and maybe ME. There are a total of 36 sites as of now and it would be very helpful to be able to set a Global filter for the entire network and then only have to adjust filter settings on any sites with problems.

I expect that we'll see more software options during the life of the SDS. At least I hope so.

OP, if you haven't, try different filter settings and see if any improve your reception.

 

[Wilrobnson]

It's primarily an LSM scanner. Analog is secondary in its mission. It will never be first choice for serious analog work in high RF areas like mine. I'm just thrilled to have a scanner that does LSM after years of cut outs and fiddling with yagis or using a pager in situations where I want a scanner. I'll take whatever it can do on analog as a bonus.

Too bad you're not a Uniden mouthpiece. That sounds like some good old fashioned false advertising.

 

[RocketNJ]

To finish this subject, my point is the included antenna is horrible on both VHF and UHF compared to a 396XT with included antenna. I would have expected better performance from the telescopic antenna.

Direct RX sensitivity using the service monitor is decent for a scanner and reception using an outdoor antenna is fine.