BCD996XT Slow compared to BCD396XT

[KF5OBS]

Hey,

I got a brand new BCD-996XT and after I made sure it has the current Firmware, I simply copied all my setting and Systems/Sites/Talkgroups from my BCD 396XT into the 996XT using Freescan. I am listening to the Arkansas AWIN system. I notice that the BCD996XT is a lot slower in reacting to an active TGID than the BCD396XT. Had anyone else noticed this? When I put the two scanners next to each other, I always catch the entire conversation with the BCD396XT and the 996XT joins a little bit later, sometimes missing important bits like the Callsign.

Both radios have the most current Firmware and are receiving the exact same RF level. How do I know the latter? Because I am used a splitter to create equal conditions for both antennas. I even went as far as switching the ports on the splitter and hooking the splitter up to my network analyzer. No difference. The signal levels show great on both scanners. If I hold on a TGID, both are similarly fast.

Also, I sometime hear some of the control channel "audio" after the end of the transmission. Did anyone else ever have this and has an idea how to fix it?

 

[ofd8001]

You might check the "hidden" P25 settings in both scanners and see if they are identical.

That would be my only thought. . .

 

[Boatanchor]

There appears to be an 'issue' with high noise floor levels in the x96XT series.
If you have the 996XT connected to an external antenna and there is significant levels of broadband noise around (typically, such noise will not break the squelch and will therefore not register on the 'S' meter), the scan and search rate will slow down to less than 50% of normal.

Just for interests sake, remove the antenna from your 996XT and see if the scan rate speeds up compared to your 396xt.

I should point out that high noise floors, typically occur on the VHF bands, so this would be the first place to look.

 

[KF5OBS]

There appears to be an 'issue' with high noise floor levels in the x96XT series.
If you have the 996XT connected to an external antenna and there is significant levels of broadband noise around (typically, such noise will not break the squelch and will therefore not register on the 'S' meter), the scan and search rate will slow down to less than 50% of normal.

Just for interests sake, remove the antenna from your 996XT and see if the scan rate speeds up compared to your 396xt.
.

Interestingly, this does actually work. I have better results with the included factory antenna. But no problem, I have a preamp and a bandpass filter in the mail, so if it's that, it should be resolved shortly on the external antenna.

 

[Boatanchor]

Interestingly, this does actually work. I have better results with the included factory antenna. But no problem, I have a preamp and a bandpass filter in the mail, so if it's that, it should be resolved shortly on the external antenna.

I doubt that the pre-amp will help as it will amplify the noise floor as well as the targeted signals, plus it will add a little noise of itself into the mix. The bandpass filter will help with out of band interference, but the x96XT series doesn't seem to be too affected by this anyway (unless you are unfortunate enough to live a few houses away from a cell tower, paging site or FM broadcast transmitter).

I haven't fully delved into this noise floor/scan speed issue but it appears that the cpu monitors the RSSI level (or more likely the noise detector output level) as the scanner is scanning/searching and if the noise is above a certain threshold, it slows the scan/search speed down A LOT!.
Presumably, this was done to improve weak signal detection under noisy conditions.

Anyway, it is a bit of a pain, particularly when you scan a lot of VHF channels that are more susceptible to high noise floor than the 800Mhz band.

Those of us that do run pre-amps and external antennas just seem to have to put up with slow scan speeds unfortunatly.
My PSR600 that is connected up to the same external antenna/pre-amp/splitter combo, is lightning fast to scan and search compared to the x96XT. But the PSR600 has other, worse problems of it's own.

 

[KF5OBS]

I doubt that the pre-amp will help as it will amplify the noise floor as well as the targeted signals, plus it will add a little noise of itself into the mix. The bandpass filter will help with out of band interference, but the x96XT series doesn't seem to be too affected by this anyway (unless you are unfortunate enough to live a few houses away from a cell tower, paging site or FM broadcast transmitter)..

We shall see what happens. the noise figure of the amplifier is a bit above 3 dB for the desired frequency range (Mini Circuits ZX60-2534M+). It's part of a bigger set-up. I have a few conventional 800 MHz frequencies and some remote P25 sites that I'd like to listen to. But they're in a different direction than the main sites for the city I live in. Therefore I have a Larsen 850 MHz Yagi pointed in their direction and use a wideband discone antenna for local. to combine the signals I am going to use a Mini Circuits ZN2PD-920+ splitter / combiner. The combiner itself has a 800 - 920 MHz bandpass characteristic. then the mix will go into the preamp and - just to make sure - through a VBFZ-925+ bandpass filter and then to the radio.

Once that is set up I'll hook it up to the Tektronix MDO4104B and see what the spectrum looks like.

I did hook it up to the stock antenna that comes with the 996XT. See attached pictures for reference. It's not many dB between the control channel (around 850 MHz) and broadcast radio but who knows, maybe that's the culprit! There's plenty of VHF and UHF signals with higher levels around, too.

 

[Boatanchor]

Tektronix MDO4104B

Nice peice of kit.

Just be aware that the noise floor levels I'm talking about are circa -120dBm (or around 0.25uV).
Usually, to display levels down around -120dBm on any kind of Spectrum Analyser or FFT requires very narrow display/sampling bandwidths and slow sweep speeds to obtain the required dynamic range. Slow sweep speeds don't depict random noise well at all.

Surprisingly, the most cost effective tool I've found so far for seeing/tracking down noise sources, is a FuncubeDonglePro+ SDR and a decent laptop. The FCDP+ can easily depict carriers down to -140dBm and has no problem showing broadband noise of only a few dB above the receivers own noise floor (which is very low) and this at 196Khz displayed bandwidth. Teamed up with a decent yagi, this combination makes a killer noise tracer/tracker.

 

[fourthhorseman]

You might check the "hidden" P25 settings in both scanners and see if they are identical.

That would be my only thought. . .

What are the Hidden P25 settings?..Ive had a 996 & 396 for 6mos+ and sing ARCXT-PRO..I dont think I have come across these..

Thanks!

 

[ofd8001]

To access the "hidden" stuff on the scanner, press and hold the HOLD button while powering on the scanner. The scanner display will cycle through the colors.

Then its Menu>Settings. You'll see P25 LP Filter, P25 Adjust Mode and P25 Adjust Level.

These things are accessible only on the scanner - ARC XT doesn't get you there.

Also when making changes, note what you started with in case you need to go back to the defaults.