Boatanchor
Member
- Joined
- Jul 17, 2011
- Messages
- 991
We've heard anecdotal reports about questionable VHF performance on Uniden's 'Flagship' handheld scanner on this forum over the last nine months or so. I thought it was about time we finally nailed some sensitivity figures down and found out what is really going on here.
The following tests were conducted with a calibrated HP service monitor using a high quality RG-400 coax patch lead. The received audio was taken from the headphone socket in each case via the same audio line isolation transformer. All tests were conducted in NFM mode at 1.5Khz deviation. I should mention that my BCD396XT has had the 450Khz IF filter changed to the narrower 'G' version, which should closely mimic the filter characteristics in the BCD436HP in NFM mode. Regardless, the filter change in the BCD396XT would not impact greatly on the observed figures in these tests.
Caveat:
There are obviously slight variations in performance from model to model and even within the same batch of the same model.
The following results may have been impacted slightly by these variations. The results I obtained may be different to results others obtain.
Regardless, I am confident that in my case at least, there is a significant difference in sensitivity between my two units.
There are two fields in this test.
The first field measured sensitivity in dBm, the second in uV.
The dBm measurement is this case is more accurate, however the uV tests have been included so that you can compare the measured figures with Uniden's claimed specifications.
Comments and observations:
Firstly, it was immediately obvious that my BCD436HP does have some serious sensitivity 'deficiencies' on some bands. The 163Mhz, 420Mhz and 820Mhz bands were all 2-3dBm down in sensitivity compared to the older BCD396XT. Looking at the uV figures, my BCD436HP doesn't even meet Uniden's own specified 0.3uV level. This is very poor form IMHO.
During these tests, My BCD436HP only met the specified 0.3uV sensitivity on bands below 146Mhz.
It was interesting that the BCD436HP actually outperformed the BCD396XT on the 53Mhz (6M) band.
Another issue I have confirmed, is that the BCD436HP does in fact radiate some low level, broadband noise on the VHF bands. The noise is radiated from the vicinity of the LCD. I believe that the noise is likely produced by an internal CPU or associated system. This noise appears to degrade VHF reception slightly when using the supplied stubby antenna, or any other handheld antenna and results in weak signals not opening the squelch, even at it's lowest setting of 2..
So there you go.. For what it's worth, my results of sensitivity testing on my two Uniden scanners.
And, while these tests were conducted in NFM mode, sensitivity figures also effect weak signal digital performance too. Yes, the BCD436HP sounds great on P25, but the fact is that if you want optimum weak signal performance, it's pretty hard to beat the humble little BCD396XT.
As always, YMMV, but personally, I am a little disappointed in the RF performance of my BCD436HP.
The following tests were conducted with a calibrated HP service monitor using a high quality RG-400 coax patch lead. The received audio was taken from the headphone socket in each case via the same audio line isolation transformer. All tests were conducted in NFM mode at 1.5Khz deviation. I should mention that my BCD396XT has had the 450Khz IF filter changed to the narrower 'G' version, which should closely mimic the filter characteristics in the BCD436HP in NFM mode. Regardless, the filter change in the BCD396XT would not impact greatly on the observed figures in these tests.
Caveat:
There are obviously slight variations in performance from model to model and even within the same batch of the same model.
The following results may have been impacted slightly by these variations. The results I obtained may be different to results others obtain.
Regardless, I am confident that in my case at least, there is a significant difference in sensitivity between my two units.
There are two fields in this test.
The first field measured sensitivity in dBm, the second in uV.
The dBm measurement is this case is more accurate, however the uV tests have been included so that you can compare the measured figures with Uniden's claimed specifications.
Comments and observations:
Firstly, it was immediately obvious that my BCD436HP does have some serious sensitivity 'deficiencies' on some bands. The 163Mhz, 420Mhz and 820Mhz bands were all 2-3dBm down in sensitivity compared to the older BCD396XT. Looking at the uV figures, my BCD436HP doesn't even meet Uniden's own specified 0.3uV level. This is very poor form IMHO.
During these tests, My BCD436HP only met the specified 0.3uV sensitivity on bands below 146Mhz.
It was interesting that the BCD436HP actually outperformed the BCD396XT on the 53Mhz (6M) band.
Another issue I have confirmed, is that the BCD436HP does in fact radiate some low level, broadband noise on the VHF bands. The noise is radiated from the vicinity of the LCD. I believe that the noise is likely produced by an internal CPU or associated system. This noise appears to degrade VHF reception slightly when using the supplied stubby antenna, or any other handheld antenna and results in weak signals not opening the squelch, even at it's lowest setting of 2..
So there you go.. For what it's worth, my results of sensitivity testing on my two Uniden scanners.
And, while these tests were conducted in NFM mode, sensitivity figures also effect weak signal digital performance too. Yes, the BCD436HP sounds great on P25, but the fact is that if you want optimum weak signal performance, it's pretty hard to beat the humble little BCD396XT.
As always, YMMV, but personally, I am a little disappointed in the RF performance of my BCD436HP.
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