Is the sensitivity for the P25RX-II better than the P25RX? I ask this because there is an 800 mHz P25 Phase 1 system somewhat near me that has a marginal to poor signal in my area. I installed a yagi in my attic pointed towards the system's nearest-to-me tower and my Unication G5 now gets a very usable signal from this system. If I plug the yagi into my P25RX I still get no signal. I was quite surprised and disappointed by this. Similarly, a neighboring county's 700 mHz P25 Phase II system (somewhat in the same direction) comes in quite well on my G5 with the yagi, but not so much on the P25RX. Has anybody else compared reception on a G4/G5 vs a P25RX? Any thoughts? Thanks.
P25RX Sensitivity
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goldmyne99
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I can not answer the question about the G4/G5 compared to the P25RX. In can say that my P25RX has no issues decoding distant 700 MHz and 800 MHz P1 and P2 systems down to -121 dBm daily with the supplied whip antenna from btt.
FreqNout
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My thoughts as a Wireless Engineer, anecdotal comparing any number of receivers has limited value. Local RF conditions would not be valid for all locations.
That being said, I just reviewed the G4/G5 tech specs on their web site. Sensitivity is listed as -116 dBm in their brochure.
I have not ‘measured‘ my P25RX‘s sensitivity. My anecdotal observation agrees with @goldmyne99 of good decodes below -120 dBm. ymmv.
FreqNout
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The P25RX-II design has added improved blocking performance filtering to reduce the large out of band sigs.
I'm in a 3 level townhouse using radios indoors on either of the upper 2 levels. Phase 1 signal levels with the P25RX or the RX-II become unstable after 5 miles (I have both). The Unication G5 is useable up to about 25 miles. Since I'm 2.25 miles from the nearest simulcast tower, I don't have signal issues indoors. The first thing I wonder when I see a post from someone who can't receive something (regardless of radio) -- what's their distance from their location to whatever they're trying to monitor. I'm located in roughly the center of a 3 county triangle. No problem hearing anything.
There's a new Phase II P25 system at the university 33 miles SW of me. I can receive that one with a G5 indoors if I stand in one of the upper floor west facing windows. None of my other radios (Uniden, Whistler or Bluetail) can receive that system from here.
Some of my friends with Bluetail Tech radios have improved their reception by improvising various antennas with more gain than the little helix antenna that comes with the radios or by using a preamp.
FreqNout
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Your observations are valid at your location. For me, I have no issues with perfect decodes 25-30 miles from my p25rx on btt shipped antennas. Local RF conditions will vary greatly due to terrain, foliage, rfi, etc.
Back to the OP question of the P25RX-II vs. P25RX sensitivity. The P25RX-II design would have better 'selectivity' with the improvements in out of band filtering that @btt has posted in previous threads. Ymmv based on the local RF conditions.
The P25RX-II sensitivity is better at the lower VHF frequencies when compared to the P25RX. This is due to the filter cutoff rolling off sooner. Other than that, they are very similar. The internal device noise floor is very low and doesn't cause any issues with reception. As @FreqNout pointed out, the receivers don't have any issues with decoding voice at very low levels when the SNR is there. I am able to decode well between -117 and -120 dBm quite often. As many of you probably know, the key to good sensitivity is a combination of low-loss before the first LNA, the gain of the LNA, and the noise figure of the LNA. Both models have good specs and low internal noise floors. Some users here have reported receiving P25 systems from 100 miles away with a yagi. (for those comparing distance). As someone pointed out, the P25RX has some issues with being blocked by some nearby cell phone towers. I do not believe this is an issue with the P25RX-II.
OK all, thanks for the responses. For comparison, the P25 Phase 1 system (which is the system I cannot get at all on my P25RX) on my G5 has an RSSI of -105 dBm. On the P25RX it is -130 dBm. (Using the same antenna for both - my attic mounted yagi.) Not sure where it leaves me besides having to use the G5 for this system. Though I am puzzled (and somewhat disappointed) with the difference in RSSI. 
goldmyne99
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Has your P25RX performance/rssi changed recently with any other systems? There could be a hardware failure (i.e. sma connection inside the P25RX, etc.)
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What frequency are you trying to receive when it doesn't work? Something is definitely not right if you are seeing a reading that is 25 dB different from your G5. Feel free to email and arrange to send it in to have it checked.
goldmyne99
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The -130 dBm reading you are seeing on a known active CC is very odd.
I did a few tests. I only get a -130 dBm reading when I connect a 50 ohm termination to my sma port. On multiple known "clear" 850 frequencies I am seeing readings between -121 to -126 dBm (the noise floor **). I do hope you find the root cause, as Todd mentioned something is not right.
** (the noise floor values in btconfig agree with measured Spec Analyzer values.)
I did a few tests. I only get a -130 dBm reading when I connect a 50 ohm termination to my sma port. On multiple known "clear" 850 frequencies I am seeing readings between -121 to -126 dBm (the noise floor **). I do hope you find the root cause, as Todd mentioned something is not right.
** (the noise floor values in btconfig agree with measured Spec Analyzer values.)
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