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XPR 5350 back-to-back crossbang repeater

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Posts: 61
Joined: Thu Nov 06, 2014 9:53 am

XPR 5350 back-to-back crossbang repeater

Postby Wiregeek » Tue Dec 29, 2015 2:22 pm

Just got done bashing my skull against a pair of XPR 5350.

Original config was back-to-back through the accessory ports, crossing RX and TX audio, crossing PL Detect and PTT, everything set to active low, debounce off, life is good. Had some Pyramid external notch filters, filtering out the opposing radio's TX frequency. with ~70 db isolation from _each_ can, as well as planned physical isolation in the final deployment, I had a very slick little "VHF-VHF crossband repeater", or VHF Range Extender.

Got to the customer's site and I got no repeat in either direction. Got the meter out and fixed the cable (lost a pin during transit), and I got intermittent functionality for a few minutes... then nothing.

Popped the plastic off and threw a gentle hand torque on the case screws (as per CDM) with no change. got the meter on the pins and I'm seeing ~1.8v on the low side of PL Detect. Rebuilt the radio to radio cable using fresh connector bodies, pins, and wire. No change.

Brought the rf plate with me (both radios and the RF filters, all bolted to the same aluminum plate), and threw it back on the bench. Both radios sharing the same power input, I'm seeing anywhere between 1.1v and 1.9v on the PL Detect pins, there seems to be no rhyme or reason to it. My senior techs wondered why I hadn't used a RICK, so I pulled one and tried it. Took some time to do the research and find the appropriate pinouts... and I'm still not keying reliably.

Swapped out the 5350s for a pair of 4350s we had in a very similar setup (unidirectional VHF repeat with a Zetron controller, though), changed up the codeplug and swapped them into my RICK, and I'm 100% functional. Audio is solid. This setup won't so much as twitch.

What the blazes happened to those 5350s? Did I just get lemons, or did the poor things get shaken apart on the ~500 miles of bad road between the shop and the customer's location? (They did spend that time frame bolted to a plate bolted to a box sitting on the floor of a van, at the front of the cargo compartment).

I've already got a pair of new 5350s on order, so now I'm debating whether or not to get rid of the RICK and go back to the MRE1032 style cable.

Anyone have any thoughts?

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Re: XPR 5350 back-to-back crossband repeater

Postby RFguy » Wed Dec 30, 2015 9:58 am

It "should" work. I would try grounding the PTT though an milliamp meter and confirming what sort of current the PTT requires to transmit. I don't see any high current outputs on the 5350's (not that you should need it). They are just bipolar transistor output. I note the 5350's have 2 transistors in a package with a 47K resistor on the base to activate where the 4350's are a single transistor package with a 10K resistor.

It would appear the 4350 would sink more current than the 5350's.

You may have to throw in a transistor switch using a 3904 or a 2222.

The output should go down to 0.2 volts. It's either the one radio not able to sink enough current, or the other radio requiring too much current to sink.

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Re: XPR 5350 back-to-back crossbang repeater

Postby Wiregeek » Wed Dec 30, 2015 10:14 am

1.3 - 1.8v on the PL det line with the other end not connected to anything. No mAmp meter available for ~2 weeks.

HOWEVER, the 5350s are in a box headed back to Big Mo. New radios on the way.

still curious though.

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Re: XPR 5350 back-to-back crossbang repeater

Postby jackhackett » Thu Dec 31, 2015 1:20 pm

I don't have a 5350 service manual, but the EXT PTT circuit can't be much different that the 4350, which is a digital transistor with a 4.7K pullup to 5V on it's base. That should source around 1 mA. which the GPIO pins should be able to handle with no problem.

Not sure what could have happened.. some kind of transient maybe, lightning or power surge. Are the two radios on the same power supply? If not they may have gotten a voltage difference between them.

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Re: XPR 5350 back-to-back crossbang repeater

Postby Astro Spectra » Fri Jan 01, 2016 12:25 pm

So cross 'bang' wasn't a typo?

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Re: XPR 5350 back-to-back crossbang repeater

Postby Wiregeek » Sun Jan 03, 2016 3:55 pm

Cross Bang was a typo, but it was one of the perfect ones that has to be kept.

Both radios were on the same power supply at all times, and while I can't guarantee there weren't any transients, the bench power supply is about as trusted as they come (40 pound Motorola adjustable voltage/current unit. I check it about once a week against a Fluke 117).

The power supply in the box is built around four deep cycle 12v batteries...

I have to conclude transient or ESD, but there's no practical way to prove that at all.

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Re: XPR 5350 back-to-back crossbang repeater

Postby RF_Burns » Tue Jan 05, 2016 10:25 am

I haven't tried this with a 5350 yet, but I did have some issues with a CM200D in the same application. In the old days of M208/216/120 and GM300's etc Pin 8 was the default COR/PL detect Pin. With the CM200D however you can set Pin 8 for this function, but nothing happens. Checked 3 radios new in box with the same result. Programming Pin 14 though for PL detect works like a charm.

I'm not sure if its just the software version or the Engineers just like to waste your time to figure this out. As M always says "Works as designed"

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Re: XPR 5350 back-to-back crossbang repeater

Postby Wiregeek » Mon Jan 25, 2016 11:20 am

As a followup - we got two new XPR5350 in and I rebuilt the RF plate. Before I plugged the RICK in I metered the Digital I/O pins - 0.2v on the low side. much better than the 1.4-1.8v of the previous radios.

go figure, they worked great.

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