Icom ID-5100 digital crossband operation

[gMan1971]

Hi there,
So, I've searched all over the internet for a definitive answer on this matter, but it seems, like most interweb these days, results are inconclusive, so I figured I'd ask here.

This document seems one of the best sources that indicate the ID-5100 can do it, but not sure what the differences are between the 5100 and the 5100A (region?)

https://www.dcara.net/library/ID-5100_DStar_Crossband_Repeating.pdf

Based on that information, and other little tidbits I've read, seems like the ID-5100 is one of the very few radios that can do Digital C4FM crossband operation.

I know that being a ham radio it will suffer from issues due to the wider open front end, etc, but I already have preselectors/cavities to deal with that...

Has anyone done this?

Thanks in advance.

G.

 

[Jim1348]

Some things come to mind, so far.

There is a Facebook group devoted to the Icom ID-5100. It might be worth looking around there, joining and posting that question. https://www.facebook.com/groups/498988960228934

I could have sworn that Death-Star is actually GMSK, not C4FM.

https://www.dcara.net/library/ID-5100_DStar_Crossband_Repeating.pdf

 

[gMan1971]

Some things come to mind, so far.

There is a Facebook group devoted to the Icom ID-5100. It might be worth looking around there, joining and posting that question. https://www.facebook.com/groups/498988960228934

I could have sworn that Death-Star is actually GMSK, not C4FM.

https://www.dcara.net/library/ID-5100_DStar_Crossband_Repeating.pdf

Well, thanks!!

Read the FB ground, and it certainly looks like, if placed in both 25k FM crossband, it will pass any digital C4FM modulation... so, I might pick one up, give it a spin. I am absolutely shocked nobody has done this for commercial application, for a delivery van fleet having a small SL7550 for the driver and a van repeater to contact the warehouse... for any of the C4FM digital modes, DMR, P25, et. alll...

G,

 

[Astro Spectra]

DSTAR is GMSK. Two level fsk, C4FM is four level fsk.

If the frequency response of the coupling mechanism is flat enough and the squelch opens it might repeat modes other than analog FM. YMMV.

Why would people not do this on commercial bands? The ID-5100 is a ham rig and is not approved for Part 90 usage.

 

[gMan1971]

@Astro Spectra

Well, I am just exploring all options here. And yes, thank you for pointing out its not a Part90 radio... but then again, Motorola and most radio manufacturers are just too limited with single band operation, and forcing the users into repeater-duplex operation when there is a frequency split for DMR. The only exception for this single band commercial situation is the APX lineup, but even those APX flagships seemingly lack any digital crossband functionality. In addition to that, there is the cost factor, and the fact that installing APX8500 multiband radios on food delivery vans seems totally overkill, especially when the radio itself might be more expensive than the van its installed on.

So far I've managed to build some sort of UHF->VHF DV DMR bridge with a pair of CDM750s, using a 10k pot, Data PTT, etc with a homebrew cable, but the BER is quite high on the other side, which is the reason why I am exploring every possible alternative.

Thanks.

G.

 

[sarguy1941]

What is the end goal ? You can grab a UHF XPR on ebay for under $1000 every day. Drop the repeater on the warehouse and give the guy an HT in the van. If this is a business part 90 or cell phones...

 

[gMan1971]

Hi,
So, the end goal is to have the driver carry a low power SL7550, which talks to the van, and the van uses an UHF to VHF bridge to send things far away , and the warehouse will have a VHF to UHF bridge with a few SL7550 on each office, so the people in the building can talk to the drivers.

This is how the setup that was in place worked, and worked very well, it was easy to maintain but it was FM... so.


G.

 

[MTS2000DES]

I'm intrigued. I have a 5100A (at Icom now in Washington, left side RX is out due to a broken speaker jack). They're blaming COVID but what else is new. Would love to try this idea of P25 repeating. I have a VHF Quantar and plenty of UHF P25 portables to play with. Icom is claiming "COVID-19" and a "tech has my radio" and to "give them a couple of weeks"...

 

[gMan1971]

Awesome, in theory, it should repeat C4FM, and I've seen a couple of youtube videos, claiming so, but then again, no description on how they did it...

COVID... well, lol, lets not go there, right? hahhaa

Eagerly awaiting your results, thanks for being willing to try this.

G.

 

[MTS2000DES]

I can confirm that the 5100A deluxe will indeed cross band repeat P25 (C4FM) like a boss. I used an APX8000 on UHF set to the same NAC and bandwidth as my VHF Quantar. Set the VHF side to the Quantar's pair with NO PL/DPL (CSQ), and CSQ on the UHF side. It works beautifully and in both directions with no detectable BER or issues. Certainly adds to the usability of this radio. Aside I only paid $340 for mine back in December when R&L Electronics had them on sale. It's actually a very high quality piece of equipment, Japanese made.
Next steps will be to see how it handles NXDN. Theoretically, it should do this with no problem. Just need to dust off and charge up my NXDN portables and give it a go.

 

[gMan1971]

Thank you. So, it is safe to assume it will work with DMR... since DMR is C4FM as well.

Thanks.

G.

 

[xpr8300]

Great, something else for me to spend money on. Gee thanks!

 

[MTS2000DES]

DMR doesn't pass because it's TDMA from the subscriber. Otherwise, I've tested D-Star (obviously), P25, NXDN and YSF (DN mode). All pass without issue.

 

[gMan1971]

I see, so, did you had a chance to test DMR then?

 

[Wodie]

DMR need time slot sync signal generated by the repeater. It is not just to retransmit in->out. The same applies for P25 Phase 2. If you have a DMR radio, program a DMR channel with different Tx and Rx freq. And you will find out it will not Tx as it is waiting for the repeater sync signal. Take a look to the DMR Tier 2 standard and you will see.

 

[MTS2000DES]

DMR doesn't work, as was explained above, the TDMA rapid cycling won't activate the repeater. Every other digital mode works: P25 C4FM, D-Star, YSF, and NXDN (6.25 and 12.5). And yes, I tried DMR using an XPR7550e pair (one V and on U) and it wouldn't even activate the cross band.

 

[RadioSkaf]

DMR need time slot sync signal generated by the repeater. It is not just to retransmit in->out. The same applies for P25 Phase 2. If you have a DMR radio, program a DMR channel with different Tx and Rx freq. And you will find out it will not Tx as it is waiting for the repeater sync signal. Take a look to the DMR Tier 2 standard and you will see.

Sorry if it may sound like a dumb question (and it probably is) [I will have to take more deeper look at ETSI TS102-361 to be less dumb]

but if I understand your statement correctly, that means that split-frequency half-duplex (in "let's say, simplex, even if it is a misnomer" mode between two handhelds) which is not a problem in analog, is impossible in DMR ?

I do know that sync is needed and sync patterns differs between operating modes (as I understand, because of that you cannot listen to a repeater input [and output too when not in talkaround ?] in DMR simplex, contrary to analog too)...

But as DCDM is a thing on "real" (one frequency) simplex mode for sync, why can't it be "technically (maybe Firmware doable, similar to PoC||GTFO on the MD380)" possible on half duplex between handhelds ?

This is a purely technical/Curiosity question as it is quite useless/limited from a practical point of view... I never really played with esoteric configurations in DMR, I've only done bog standard programming...

I do also know that some cheap sh*t DMR CCR (thanks to a friend because I don't have any DMR CCR) will refuse to TX when RX & TX are differents and no repeaters are in range (Retevis RT3S), but some others cheap sh*t DMR CCR (Retevis RT84) will happily TX with differents RX & TX freqs and no repeaters in range...
I just assume they are so crappy they don't even respect basic CAI DMR Standard... Any thought on this ?

Thanks !

 

[Wodie]

When you program different Tx and Rx freq on a DMR radio, when you press PTT the radio send a Wakeup signal to the repeater and the radio wait for the repeater signal, which is a two free slots sync signal. Then your radio sync its Tx clock and Tx only during the time assigned for its time slot. The repeater will Rx such slot signal and place data on its two slot Tx signal. The Rx radio will receive both slots, but it will only process the selected Slot.
If a lets say third radio wants to Tx on the free Slot, when the user press PTT, it will sync with the repeater signal (which already have both slots) and sync its Tx clock to the selected (free) slot and start transmitting to the repeater. The repeater will mix both Rx Slots and Tx them.
That said, if a standards compliant radio wants to Tx to a repeater (which is the only reason to have different Tx and Rx freq.) it will try to wakeup the repeater and listen to it to sync its Tx clock and Tx its selected slot (if it is free). If there is no sync sygnal, the radio will not Tx.
When you go simplex (same Tx and Rx freq.) there is no need for sync signal (except for a Motorola TDMA simplex mode, where a radio is designated to do the time slot clock) and you are not able to use 2 time slots on the same frequency at the same time. Even the Tx radio only Tx on one slot, any other radio that “could”use the free slot, will not be able to sync, as in simplex, radios do not monitor sync signal as they do for repeater mode.
Any way, you can try with two DMR radios and your iCom, if you want to look closer to what is happening, get a spectrum analyzer, so you can see when radios Tx, how long and if it is fast enough, you will see the time slots each radio Tx. if you can reach a repeater it will be more illustrative.
If you want a cheap DMR repeater, take a look to Amateur MMDVM repeaters. You can build one with a Raspberry Pi, an MMDVM board and a pair of analog radios (search for compatible models) like Motorola GM 300 or Pro 3100. Honestly nothing compared to a Motorola DMR repeater, but you get something that “works”.

 

[KA1RBI]

DMR doesn't work, as was explained above, the TDMA rapid cycling won't activate the repeater. Every other digital mode works: P25 C4FM, D-Star, YSF, and NXDN (6.25 and 12.5). And yes, I tried DMR using an XPR7550e pair (one V and on U) and it wouldn't even activate the cross band.

If that is true, I doubt the radio is demodulating the signals into digital bits and then re-modulating the signal (i.e., I doubt it's doing regeneration)- although this is possible.

Sounds to me like it's simply repeating on an audio basis - or possibly not even that, it could be repeating on a single-signal IF basis. By the latter I mean that the signal is received, the IF is filtered to remove all other signals outside of the desired one, and repeated - all without any demodulation or re-modulation. According to the PDF linked above for the ID-5100,

1.Set both bands to FM mode. Do not use FM-Narrow or DV mode.

No reason why any cross-band repeating radio couldn't be used to do the same thing - as long as both RX and TX utilize circuitry that is linear and time-invariant (i.e., very low group delay) - something not usually done in ordinary radios since voice can tolerate certain types of non-linearities pretty well and it's more expensive to properly condition the (de)modulators.

Also, separately, yaesu should really, really, not have used the acronym "C4FM" to describe their modulation format as that acronym described a different, incompatible modulation format used in FDMA P25. P25 transmitters utilize a full Raised Cosine filter whereas yaesu transmitters utilize a Root Raised Cosine filter. P25 receivers utilize only a shaping filter whereas yaesu "c4fm" (sic) receivers contain a Root Raised Cosine filter that is matched to that in the transmitter.

DMR (base station) differs from DMR (mobile station) in that DMR base station transmits a full, 100% duty cycle signal, again using a paired Root Raised Cosine filter, one each at TX and RX. A digital RX that receives DMR (base station) is basically the same as one that receives yaesu "c4fm" (sic) with the exception that the specified deviation levels are slightly different. Finally, d-star is GMSK, not fsk and not c4fm.

73

Max

 

[MTS2000DES]

It is just operating as a "bent pipe" as you described. TDMA won't work because the simple COS/COR won't actuate as the inbound carrier isn't up long enough.