My SDS100 appears to be approximately equal or slightly better in the VHF High band than my 436HP, no problem receiving NOAA in the house on either unit and even my dedicated weather radios have a hard time in the house.
Maybe there was a bad batch or problem with a run of the SDS100 units?
If I have time, I may try to test and compare the 2 radios with a variable attenuator on an off air signals and also on a signal generator.
I'd be very interested in your results if you do run a test using a SG for the signal.
With my SDS, any moderately strong VHF signals can and do wipe out the front end in my SDS when it is receiving a VHF P25 control or voice channel. Our statewide sites make use of many unused paging frequencies in the 152 MHz segment. When a paging transmitter comes on the air that is also in the 152 swath of the band, it wipes out my P25 control or voice channel totally.
I can replicate this using my SG by setting it about 1 MHz away from the tuned frequency on the SDS. Hook a rubber duck VHF antenna to the SG output and start raising its output power. I start seeing the RSSI value change on the SDS display at -7 dBm output from the SG. Oh, I'm using a rooftop discone for a receive antenna on my SDS so the SG's signal must go through my ceiling and to my discone maybe 15 to 20 feet above my ceiling.
As I crank the SG higher than -7 dBm, the SDS starts being swamped by the SG's signal. Eventually, the SDS loses its lock and any reception of the control channel or any voice channel on a frequency near 152 MHz.
I did some tests the other night and found that a -7 dBm SG output will start to affect the SDS reception when the SG's frequency is near 7 MHz or less away from the tuned frequency of the SDS.
This explains the short signal loss I see when monitoring the statewide system and the paging sites are not transmitting, it's the nearby EOC which still uses some VHF frequencies in the 154 and 155 MHz ranges for public safety and some fire tone out use.
I also tested VHF analog on the SDS using the same SG settings. Tune a nearby or somewhat distant NOAA station and set the SG to output near the 162 MHz range and it does not seem to desense the SDS front end. Even with the SG cranked to +14 dBm output I can still hear the NOAA signals, both nearby and the two distant stations.
So the issue I see with my SDS in at least the VHF band seems to really only be a problem when the SDS is set to a digital mode. I've only tested it with P25 signals but I suspect it will behave poorly in the other digital modes as well.
When I did the analog tests above with the NOAA signals, I did see the SDS RSSI value change as the SG increased in output level but at no time did its front end go into desense.
I don't know if you can replicate my findings as you may not have any digital signals in the VHF high band to test with but it's definitely a big problem here. My SDS is totally deaf to P25 signals when other relatively strong signals are on the air within about 6 MHz from the tuned frequency of the SDS. My x36HP and older x96XT models continue receiving the VHF digital signals without any problems. They are not even affected by the nearby paging signals using the same 152 MHz segment that my P25 signals are using!
As far as overall sensitivity in the VHF band, my SDS seems to be about the same as my older Uniden's when testing Analog performance.
I've not tested the UHF range yet.
