Great thanks you .does the sds100 decode weaker signals better than SDR's like the RTL-SDR ?
No - remember with an RTL-SDR you (software such as SDRTrunk) controls the gain, which you can crank up.
You can't with the Uniden SDS100/200.
These Uniden radios really aren't that sensitive in comparison to older Uniden radios and other receivers. They were designed to mitigate multipath interference caused by simulcast sites and they do that fairly well. But have such wide front ends that they are particularly susceptible to RFI. In fact, that is what the waterfall feature is for. To see if anything is transmitting at a freq close to your target freq.