SDS100/SDS200: Scanner seems deaf on VHF High

[Ubbe]

It makes sense that Uniden have listened to the complaints about bad analog VHF reception and probably reduced the sensitivity in that band to make it more resistant to overload. As there have been less complaint in digital mode, and it is also more difficult to detect by a user, they could have left the digital mode sensitivity as it was.

One test to show if that is true are to note the signal strenght on the same frequency when switching between analog and digital mode.

/Ubbe

 

[tampatracker]

It makes sense that Uniden have listened to the complaints about bad analog VHF reception and probably reduced the sensitivity in that band to make it more resistant to overload. As there have been less complaint in digital mode, and it is also more difficult to detect by a user, they could have left the digital mode sensitivity as it was.

One test to show if that is true are to note the signal strenght on the same frequency when switching between analog and digital mode.

/Ubbe

Please excuse my relative inexperience on that subject, but do you mean to make sure all of my VHF channels that I want to listen to are switched to analog only in the selection menu?

 

[SCPD]

VHF/UHF

I ordered and rec'd my SDS100 with the smaller battery the very last week before the big battery units were shipped. My vhf/uhf receive is on par or the same as my 536 and any other analog scanner I own. I must have really lucked out with my radio as I have had zero - zippo - problems with it. I have run it thru the tests and jumped it thru the hoops and very satisfied with the performance. On a rooftop antenna (Diamond discone) I can hear vhf paging 30 miles away, in Preble County. Nothing negative to report from me. I feel for the folks who have problems with their SDS100. That must be very frustrating. I hope they either get their radios repaired, or hope it is fixed by fw update, or they get a replacement scanner in good working order. (or, if applicable, figure out what they are doing wrong i.e., their settings, programming, etc)


JD
kf4anc

Yes but does 136-174mhz and 440-450mhz frequencies seem to come in with -90- or worse or have you seen higher numbers?

 

[SCPD]

digital/analog/all

Please excuse my relative inexperience on that subject, but do you mean to make sure all of my VHF channels that I want to listen to are switched to analog only in the selection menu?

If you go into sentinel you have a mode column that you can use to select (digital/analog or all) transmissions the same thing can be done with edit channel.
The SDS-100 works better (gets a signal quicker) if you have it on the correct mode for your area.
If its Analog, make it analog .
I find mine gets more calls or "hits" with it on analog and no pl or dcs. (most of my area is analog)

 

[TailGator911]

Yes but does 136-174mhz and 440-450mhz frequencies seem to come in with -90- or worse or have you seen higher numbers?

I hear vhf/uhf on the SDS100 about the same (sometimes better) than my 536 and 1065. No complaints, and if I am hearing things loud and clear I rarely look at the numbers.

 

[SCPD]

so

I hear vhf/uhf on the SDS100 about the same (sometimes better) than my 536 and 1065. No complaints, and if I am hearing things loud and clear I rarely look at the numbers.

The TRX-1 blows this scanner out of the water on UHF, (sensitivity wise)
When a UV-82 Baofeng picks up better on VHF/UHF than a $649 scanner something is wrong.
I am 10 miles from NYC and I can not hear Manhattan Dispatch -103dbm if I hold the radio right.
Yes I have tried other antennas.Even the $20 scanner Pro-2010 Realistic(20 channels) I got a hamfest gets 476.5625 very
very well with the back of the set antenna.
I'm sorry you feel differently.

 

[TailGator911]

I'm sorry you feel differently.

Not really that I 'feel differently', I just stated facts. Nothing to apologize for man. My facts to report are that the SDS100 works great for me and no complaints whatsoever. My experience is much different than yours. There is no debate here, and no need to be sorry for me feeling 'differently'. If anything, I should be saying I'm sorry that you have a problematic SDS100. That sucks. I hope you get it straightened out with Uniden, good luck with that.

JD
kf4anc

 

[SCPD]

But are you using it for VHF/UHF 136-174 and 400-512mhz purposes?
For me it works great on 700 and 800mhz don't get me wrong.
The fact I called them and got blown off and then I posted a log file with no response baffles me about Uniden.

 

[kruser]

The R836 TV tuner chip in the SDS is designed for 6-8MHz bandwidth TV signals, it has a pretty poor in band third order intercept point but it improves out of band although its still not great.

If you try and listen to signals and have strong signals within the tracking filter bandwidth you are likely to suffer blocking or sensitivity loss, the only option then is to reduce the gain or add attenuation, the same as you have to do on an rtl dongle.

The inband iip3 has a quoted range of -7 to -14dBm, out of band it improves with a range of 0dBm to +8dBm.

Its not a high performance RF design, these chips are found in $20 TV tuners where signals are normally moderate strength you don't have close in interfering signals to worry about.

Thanks for this info. I know I've read this before but could not find it again plus I think your post has more detail.

The specs you posted seem to agree with what I see in my own testing as far as the design bandwidth of the tuner chip and how it corresponds with how far away I can tune the SG before I no longer see an issue with the SDS. And yes, it does have a poor ip3 value, both in and out of band!

This pretty much confirms my suspicions that the tuner chip used in the SDS is most likely responsible for the problems I see. Not sure if it is the reason others are seeing poor performance in the V/UHF bands but it is likely.

 

[ckqualls]

Haven't monitored Vhf yet, but noticed that Dallas PD on 460mhz is awful. 700/800MHz is great. In the city DPD is scratchy but monitoring, while in the city, my suburb PD on a P25 system 30 miles away is crystal clear.