All posts by j0n

Married, 4 radios, no cats or dogs, one stove!

DMR and Talkgroups in EI

Quite often I get asked about DMR Radio and how to program Talkgroups (TGs) and Timeslots (Slots).

First, what it a timeslot? Your transmitted signal is broken into 30ms digital packets. Each slot is 27.5ms of data, 2.5ms of a gap, the result being your transmitter switches on and off very rapidly. Doing this allows your signals to share the same channel at the same time as someone else. One on Time Slot 1 and one on Time Slot 2.

Group A are using Slot 1 while Group B are using Slot 2 simultaneously. They don’t interfere with, nor can the be heard by one another.

A DMR talkgroup is a method of organising radio traffic such that the the DMR users can choose to hear the same thing and not be bothered by other radio traffic on a DMR network.

Talkgroups can exist for many purposes. On the Brandmeister network World Wide is TG91, Jamboree on the Air (JOTA) is TG907, a link to the Southern Ireland Repeater Group voice network is on TG27240. Just about any group of DMR users could have a talkgroup assigned to them that they can all monitor and take part in, without having to talk to each other one by one.

Given the demand for Talkgroups however, and how quickly their use can fade, no one is all that keen on allocating a Talkgroup number for everything. A good way to start out is to use one persons DMR ID as the Talkgroup ID and try it out. If the special interest group is still running after 6 months or so, then everyone can be fairly confident that it won’t be waste to allocate an ID to it.

Now what does this mean regarding programming them? Well, based on the current guidelines, I have updated my own DMR page with an example of three different repeaters, and how a memory bank (Zone) could be programmed in line with the guidelines. If it still isn’t making sense to you. Drop me an email ( details on HamQTH and QRZ). 73

Geek vanity

I’ve been on an enforced go-slow recently and now that I’m more mobile I started looking for things to do. Several of my transceivers have the ability to add custom ‘bootup’ screens. So I thought how hard could it be?

Like most things, it is easy once you know how. K9WX figured it out already in short, use a 120×48 pixel, 1 bit bitmap, 120×48 created in Microsoft Paint.

The result isn’t very imaginative, but I get a chuckle out of it and that’s all that matters.

TH-D72

Southern Ireland Repeater Network

I was asked to do a presentation on the Southern Ireland Repeater Network for the Irish Radio Transmitters Society AGM weekend that should have taken place in April. Unfortunately, due to the ongoing pandemic, it didn’t happen. Currently, the repeater network is maintained by the Southern Ireland Repeater Group.

As the AGM was cancelled, I kicked the can down the road a bit, but finally last Monday evening I presented the slides to my local club (SEARG). Given it was originally supposed to be a presentation to a national audience, the slides are now available from here.

Predicted coverage map of the Southern Ireland analogue voice repeater network

Shack 2.0

So, several months later, house move complete and it is time to get a shack operational again.

I am a fan of keeping things running when the power goes out. From a Amateur Radio Communications perspective, I have had a 80Ah battery in the shack for over 10 years and I have been using a West Mountain Radio Super PWRgate PG40S and Rigrunner 4010S to power my radio equipment and to keep the battery charged. My current ‘desktop’ is based on a Intel NUC 7i7BNH these along with their LCD’s are running off an older APC Smart UPS 1500, which gives between one and two hours of run-time should the power go out.

While everything was in boxes, I purchased a West Mountain Radio EPIC PWRgate (I wonder what adjective will be used to describe the 4th Generation!) this device can charge Lead Acid, AGM/GEL and LiFePO4 Lithium battery types, and, what attracted me to it is that it has a built in Photovoltaic (PV) Charge Controller. Which removes the need for a dedicated Charge Controller.

Sometime during the move, the old AGM battery died (Ophelia was its final ‘performance’). New shack, new battery, a Trojan EverExceed ST-1280 was ordered from O’Connell Batteries in Cork and duly arrived.

Plug-and-play? well not-exactly. After looking at the specs, the default ‘AGM’ setting in the Epic PWRgate needed some adjusting to avoid overcharging the battery. The battery specifications say 2.35 Volts per cell (for 12 hours), so the ‘Max charge voltage’ needed to be dropped from 14.4 to 14.1 volts, and the PSU set to 14.2. On Linux, the Epic PWRgate appears as /dev/ttyACM0, guessing I used 115200, N81, no handshaking and its console immediately popped up.

Battery:  1-Disable, 2-Gel, 3-AGM, 4-LiFePo4, 5-Other:    <3>: 3                
Reset to default values (Y,N):   (Y,N) <Y>? n                                   
Max charge voltage in Volts:    <14.10>:                                        
Max charge current in Amps:    <10.00>:                                         
Min charge current in Amps:    <1.00>:                                          
Trickle current in Amps:    <0.25>:                                             
Recharge voltage in Volts:    <13.49>:                                          
Max charge (minutes):    <720>:                                                 
Retry after abort (minutes):    <240>:                                          
Min supply voltage for charging in Volts:    <14.15>:                           

Once out of setup mode, it spits out readings about once per second. This includes what the state of the chargers is, the power supply voltage (PS), Battery voltage and charging current (Bat), Solar Panel voltage (Sol), Number of minutes in this charging state (Min)

 Trickle   PS=14.22V Bat=13.61V,  0.05A  Sol= 0.04V   Min=962  PWM=337  adc=6                                                    
 Trickle   PS=14.22V Bat=13.61V,  0.05A  Sol= 0.04V   Min=962  PWM=338  adc=6                                                    
 Trickle   PS=14.22V Bat=13.61V,  0.05A  Sol= 0.04V   Min=962  PWM=339  adc=6                                                    
 Trickle   PS=14.20V Bat=13.62V,  0.05A  Sol= 0.08V   Min=962  PWM=339  adc=6  

Hopefully the battery is as reliable and lasts as long as the last one!

EI7CDD DMR Repeater, Retevis RT8 and GPS functionality

Last week, I gave a short talk on DMR and Brandmeister at the South Eastern Amateur Radio Group club meeting. There were quite a few members present and there were plenty questions.  The full presentation is available from here, but what is new (since the IRTS AGM presentation) is this image taken from Xastir.

2018-04-29-DMR-GPS

This is a track formed by a numberof GPS position information beacons from my Retevis RT8 Radio, the data bursts are received at the EI7CDD DMR Repeater, and then forwarded to the worldwide APRS Internet Service backbone before appearing on the map.

What is interesting to me is that the RT8 was just thrown on the dash of a van, no special effort was made to optimise its position, the terrain is by no means flat, undulating would be the best description, and yet, the RT8 was still able to hit the EI7CDD repeater from up to 20k away.

EI7T at Ballinacourty Lighthouse

Late last year, it was suggested at a Tipperary Amateur Radio Group club meeting that we should do something ‘different’ in 2017.

The suggestion was made to Activate a Lighthouse for the International Lighthouse and Lightship weekend.  Given the lack of lighthouses in Tipperary, I made the suggestion that we use Ballinacourty Lighthouse.  I had assisted EI2GN with an activation there years before and my recollection was that it was quite accessible.

Due to work commitments, I was late down to the site so kudos to EI3ENB, EI2HI, EI4KN and EI5JF for getting everything set up.  I thoroughly enjoyed the operation before I had to head away again.

Andy, EI5JF, made a short film (and took some pictures) of the operation, which isn’t too bad considering the material he had to work with!

Certificate surprise!

I got an email from my better half this morning asking me what deliveries I was expecting as the postman had left a note.  I couldn’t think what it could be and quickly forgot about it.

Much to my surprise, this it was is was…

Shadow-beacon experiment
What a lovely certificate for my (fairly minimal) participation in the experiment.  In fairness the photograph taken with my phone does not do it justice.