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Rx issues, mostly one radio...

Posted: Tue Jul 31, 2018 2:20 am
by W8DEX
I have a "jumbospot" (duplex MMDVM HS Hat) and 2 radios: a Baofeng RD-5R and an Ailunce HD1 GPS.
I am having a hard time getting the hotspot to receive from the Ailunce HD1, while it seems to be working 90% of the time with the RD-5R.

The Ailunce is a better radio (???) but I get about 5-10% success when trying to tx to the hotspot.
Even the RD-5R sometimes misses but I get in about 90% of the time on first key press.

I made sure to put in the Rx/Tx offsets from the sticker, I don't know what else to do or to look for.
Pi-star and MMDVM fw are all up-to-date.
fw on the radios are up-to-date
Tx/Rx freq are 5Mhz apart (447/442)

Also sometimes when I try to key in with the Ailunce I get both slots on the hotspot keyed in (????) very strange.

I have tested calling the radios to each other in simplex and they seem to work as expected 100% all the time.

Please help if you can!

Chris, W8DEX

Re: Rx issues, mostly one radio...

Posted: Wed Aug 01, 2018 11:58 am
by W8DEX
No suggestions?

Re: Rx issues, mostly one radio...

Posted: Wed Aug 01, 2018 12:05 pm
The JumboSPOT isn't a dual hotspot. If you really have a JumboSPOT, try setting your Controller Mode to Simplex.

Re: Rx issues, mostly one radio...

Posted: Wed Aug 01, 2018 11:07 pm
by W8DEX
KE0FHS wrote: Wed Aug 01, 2018 12:05 pm The JumboSPOT isn't a dual hotspot.
Well one can always make mistakes but just to make sure I got the name right I went and looked: ... m570.l1313

Yep, it's called Jumbospot, at least this one and it has 2 antennas and it has been working as a repeater since I bought it.

But I have tried simplex too and I get the same result.

I guess no help is coming.

Re: Rx issues, mostly one radio...

Posted: Wed Aug 01, 2018 11:34 pm
Well, you didn't make a mistake ... but the seller did. Probably the seller is someone who doesn't know what they're selling or else they're trying to leverage the JumboSPOT name. That's actually an MMDVM_HS_Hat_Duplex board (probably a clone). And that leads to your next troubleshooting steps: Does the board have the correct firmware and is the correct modem type selected in Pi-Star? If both of those are correct, then you may need to adjust the RXOffset in the Expert Editor or you may have a defective board. Good luck!

Re: Rx issues, mostly one radio...

Posted: Wed Aug 01, 2018 11:44 pm
by W8DEX
Check, check, check. Gotcha.

Still wondering why it would work with one radio and not another.
I wish some DMR experts would hang around here.

My suspicion is on modulation. Maybe the two radios have some emission differences that the hotspot is sensitive to.
Or maybe they have different DMR standards?? Here is where some of those hobby geniuses could help figure it out....

Oh well, CQ,CQ,CQ big radio and DMR experts....

Re: Rx issues, mostly one radio...

Posted: Wed Aug 01, 2018 11:54 pm
It's definitely possible the two radios will need different RXOffsets to function optimally. Worth playing around with anyway.

One issue with clone boards is that they sometimes use lower quality or even defective chips. Re: the JumboSPOT, I've read about issues with the oscillators and the TXCO chips.

Anyway, I'm going to bow out and make room for the geniuses to step in! :)

Re: Rx issues, mostly one radio...

Posted: Thu Aug 02, 2018 12:37 pm
by G8SEZ
Suggest that you look for any frequency adjustments in the CPS for the 2 radios, for instance with the Tytera radios there is a frequency offset with settings low, medium, high and it's available in each channel definition and appears to default to low. I think this means that the radio will have all frequencies offset a little in one direction. Try changing it to medium on the channel you use for hotspot access.

Re: Rx issues, mostly one radio...

Posted: Sat Aug 04, 2018 10:24 pm
by n0xlf
That's not a TX offset. Stolen from the SharkRF forums:

From Connect Systems: "Selects the Reference Frequency used when receiving on the current channel. The reference frequency can be shifted to allow the radio to operate on channel frequencies that would otherwise be blocked by internally generated spurious signals. Internally generated spurious signals would appear as silent carriers on certain channel frequencies. Shifting the reference frequency allows these permanent signal carrier to be shifted to unused frequencies so that the desired channel frequencies can still be used.This is a channel-wide feature."

Re: Rx issues, mostly one radio...

Posted: Mon Aug 06, 2018 1:15 pm
by W8DEX
Well, I think I might have found the culprit.

While looking for a tx offset setting, I found out the Ailunce HD1 does not have one, but it has a "repeater mode" setting.
In other words, for some reasons, the channel programmed for communication for a repeater must be set in "repeater mode".

I used to set the channel to "simplex" to communicate with the hotspot, but the one I have is a repeater as set up.
Once I changed the mode everything seems to be working fine. At least I get almost 100% coms now while transmitting with the Ailunce HD1 to the hotspot.

This might sound like a "duh" moment, but it is not.
The RD-5R does not have this settings of this kind at all. It is virtually always transmitting in the same mode, either radio-to-radio or radio-to repeater.

I am no DMR expert so I am not sure what technical difference is between "simplex mode" and "repeater mode", but it does make a difference to the hotspot, so it must be something to do to DMR specific modulation.

The "repeater mode" does not set the radio to be a repeater, just to be clear. It sets the radio to communicate with repeaters.

I find this interesting and I am wondering if other radios (TYT, Motorola, Hytera, etc.) are more like the RD-5R (one tx/rx mode) or like the Ailunce HD1 (3 different modes: simplex, repeater and dual slot).