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APX8000 vs. APX7000 Weak P25 Rx

Covering the following Subscriber devices: APX1000/1500, APX3000, APX4000/4500, APX6000, APX6000XE, APX6500, APX7000, APX7000XE, APX7000L, APX7500, and APX8000.

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a1emt
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APX8000 vs. APX7000 Weak P25 Rx

Postby a1emt » Fri Jul 20, 2018 7:36 am

Hi gang,

I just put an APX8000XE portable in service and I am noticing that my APX7000 U/800 seems to do a lot better on receiving a distant 800 MHz P25 simulcast system. The 7000 is solid decode, but the 8000 has noticeable periods of garbling and robotic voices. Just had an alignment done on the 8000 to be sure and all came back as "Pass".

Somewhat disappointed, as the 8000 is supposed to be the 'cats meow'.... I'm guessing this is the tradeoff of having a tri-band receiver. Anyone else noted this in the field?

THX

Jim

n1gtl
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What radios do you own?: XPR5550, XPR7550e

Re: APX8000 vs. APX7000 Weak P25 Rx

Postby n1gtl » Fri Jul 20, 2018 9:29 am

Set to CQPSK for simulcast on one and C4FM on the other maybe?

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a1emt
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Re: APX8000 vs. APX7000 Weak P25 Rx

Postby a1emt » Fri Jul 20, 2018 10:23 am

Yep, that was my thought as well. But it is set correctly to CQPSK. Very weird.

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thomsoningreen
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Re: APX8000 vs. APX7000 Weak P25 Rx

Postby thomsoningreen » Wed Jul 25, 2018 8:01 am

If you have an MOL account the latest firmware notes talk about
Abstract Intermittent distorted RX audio during priority scan from analog Updates
This is the only note I saw due to firmware updates what they fix. May need to look at this as well if your running older firmware.
Network Communications Integrator (NC)
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a1emt
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Re: APX8000 vs. APX7000 Weak P25 Rx

Postby a1emt » Thu Jul 26, 2018 5:51 am

Thanks for the tip on the firmware! Hadn't seen that one, I'll take a look.

Jim

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a1emt
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Re: APX8000 vs. APX7000 Weak P25 Rx

Postby a1emt » Thu Jul 26, 2018 9:22 pm

Thanks for the suggestion on looking at the firmware release notes!

I noted several abstracts on "Garbled audio" and one mentioned the "Concurrent Rx Enable" feature. After closely observing the behavior of my 8000 using the Multi-System scan list, CQPSK P25 audio was garbling, even in strong signal strength locations. The distortion was not noted on analog or single site (C4FM) P25.

After un-checking the "Concurrent Rx Enable" feature, it seems to have completely solved the issue. Apparently, even though it is designed for analog simplex personalities it affects trunking personalities as well.

Faith restored in the APX8000!

MattSR
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Re: APX8000 vs. APX7000 Weak P25 Rx

Postby MattSR » Sun Jul 29, 2018 3:28 pm

What is the "Concurrent Rx Enable" feature intended for?

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a1emt
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Re: APX8000 vs. APX7000 Weak P25 Rx

Postby a1emt » Sun Jul 29, 2018 6:42 pm

From what I'm reading, it seems to be intended for analog simplex channels where units may unintentionally attempt to transmit at the same time, like a fire ground tactical channel. Supposed to enhance the chances that the radio will unmute and hear at least one of the radios instead of remaining muted. Seems to have unintended consequences in other modes however.

Here's the info from the help file:
Radio Wide, Audio Options)

Enables the radio to remain unmuted even when multiple transmissions occur at the same time and on the same channel. This is only true when operating on analog Direct / Talkaround channels. These simultaneous transmissions are only heard when their received signal strengths are relatively strong and equal. This feature applies on a radio-wide basis.

The audio from these concurrent transmissions is mostly unintelligible. Receiving simultaneous transmissions is sometimes needed when managing on-scene incidents where it may be very important to receive all communications. For example, having this feature enabled may be crucial to incident management where analog-only communications are used, chaotic conditions are expected, and any received transmission is better than no transmission at all.


Enabling this feature will cause some weak signals that are normally received by the radio to remain muted; therefore, it is only recommended to enable this feature if the ability to receive concurrent transmissions has been identified as necessary.


For radio models containing firmware prior to version R12.00.00, this feature is applicable only to 25kHz channels (see also the Tx Deviation / Channel Spacing field). For radio models with R12.00.00 firmware or later, this field applies to both 12.5 kHz and 25 kHz channels.


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