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I have been having some problems with my virgin media broadband connection over the last few days and it looks like the whole thing has finally fallen over completely. This means that MB7UBP is not gating to the internet until I can fix this!
Hopefully it will be back on soon
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One interesting thing to come out of the discussion with M0RXW was his work with the omnima embedded controller for APRS. I have blogged before about using APRS4R running on an Asus router flashed with Openwrt here at MB7UBP to reduce the cost and environmental impact of the Igate and this has been running for about 2 years now. Whilst APRS4R works many folks, including me, find it a bit clunky to use. Furthermore the Asus routers are now out of production so the aprs4r development team are looking at other hardware platforms.
In the meantime Reuben, M0RXW, has got Openwrt and APRX running on the Omnima (which with box and programming cable costs about £50 or $75). The flashing process looks a bit more involved and there is no GUI for settings, but these are both problems for me with APRS4R so I am not worried about that. How long will I be able to hold out before I splash the cash to play with one? I suspect it won’t be long….. I have been on holiday for a week, so had to turn of the MB7UBP APRS I-gate to meet the shut down terms of its licence. M3SXA provides such good coverage of North London that I am not sure it was missed too much.
I used aprs.fi to look at my track after driving home (up the M20 from the Channel Tunnel and round the M25). I was surprised to see that there were some serious problems with the paths. This was backed up when a Kent I-gate owner, M0RXW enquired on the aprsig email list to solve the problem. |he group came up with an interesting solution – it seems that Alan, G3RJI’s new bi-directional I-gate, MB7UUE, is translating local internet packets to RF. I have no problem with this (*if* it is limited to very local packets) but, Alan has a great location and a high gain antenna giving him a large RF footprint and therefore high channel occupancy. This meant that timing of packets was being disrupted as the I-gate had to wait for a free slot on the air to TX a packet queued from the internet. As we have reasonable I-gate density around the perimeter of London the overall effect was to cause my position to jump around on the map. For example Time 1; M0BPQ-9 heard by M0RXW and gated to the internet at position X. Time 1: The channel at MB7UUE is busy so the position X received via the internet packet is stored until the freq is clear Time 2: M0BPQ-9 Heard by M0RXW and at position Y and gated to the internet Time 2: Channel clears at MB7UUE and the stored packets (including M0BPQ-9’s the out of date position X) are sent to RF Time 3: The MB7UUE packets are gated back to the internet by M0RXW. The overall effect on the internet map is the M0BPQ-9 travels from X to Y and then back again! What is there to learn form this? The main issue is to set your “ignore dupes received with n seconds” setting at the correct level if you are gating Internet to RF. Perhaps this needs to be longer for Internet sourced spots than it is for ones generated on RF? Secondly, perhaps I beacon too frequently when mobile? I will revisit my smart beacon settings to look at this. This is certainly not a criticism of Alan and his efforts to get more activity back onto RF (which I applaud), but an interesting example of the pitfalls faced by this system. I am happy to report that once Alan realised what was going on the resolved the problem quickly, so well done that man. I finally got my act together and sorted out the gear for Steve M3SXA to run an APRS I-gate from his QTH in North West London so I popped over there at the weekend and helped him get everything set up. For once things went smoothly and Steve is now gating items from all over west London and even to the southern stretch of the M25, which is a real step forwards in coverage. The plots from aprs.fi below look great, the darker red the square the more packet have been received from it:  Steve’s station runs a tri-band collinear on the chimney which has about 3db more gain than the antenna at MB7UBP, so I am wondering whether I should change things around here to get better coverage..... or maybe I have loaned out one of my best radios!
The MB7UBP I-gate continues to give good service using APRS4R, but I always knew that my location would limit my coverage quite dramatically due to rising ground to the North east and South west. I spent a little time using the DB0ANF web server to analyse my actual coverage and the picture shows that I really don’t cover west London at all.  A few minutes more using Radio Mobile shows exactly which bits I don’t cover - West London really is a blank spot!  But looking on the APRS.fi site, there are several stations who are regularly active only via the internet in this area, but not RF. I decided to write to one of those, M3SXA, asking him if he would consider becoming active as an RX only I-gate. A full two way gate would be preferable, but as a foundation licence holder Steve is unable to hold an NoV so working on the “something is better than nothing” basis this would be a real step forwards. Steve got back to me straight away and said yes – what a nice bloke! I am very grateful to Steve for offering his location for the good of the wider amateur community. Steve has a nice radio set up, most of which will be wasted on APRS. I have therefore agreed to loan him a TNC, PMR set and PSU to get things going. Radio Mobile suggests that coverage will be a real improvement!  I’d better get on with sorting all the bits out…..
I have been running an IGate in North London for some time, with the call sign MB7UBP using APRS4R running under OpenWRT on an Asus router. All has been fine and the system has needed little attention, until this weekend when the gate stopped reporting to the Internet.
I have logged into APRS4R and everything is running OK, but I couldn’t get the router to ping the WWW. I run a wired LAN to my radio shack (loft!) and the cables were firmly seated at both my ADSL router and the APRS box. This had stumped me for a while, until I realised that I was forced to cheat when wiring the APRS LAN cable. During installation I didn’t have a long enough cable to do the whole lot in a single run, so I made up two shorter cables, connected with a female back to back joiner. This joiner happens to be quite close to the main electrical switch to the shack and it seems that I managed to dislodge one Ethernet cable when I reached across to throw the switch on my way out. Doh! Anyhow, all is now fixed and I am back on the air. That has taken me three days to work out, so my apologies to users who may have missed some functionality. The only good news is that the system was still active on RF and other local gates such as 2E0RNT and M0XDC probably picked up traffic for me in, albeit with an extra hop inserted. Still very busy with work at the moment, but I was trying to get my APRS digi up an running at home again to see if I can fill in some of the holes left by the demise of GB2GP. I shot off after VHF FD for two weeks on holiday in France. The first week was split between the North (near Calais) and a city break in Toulouse. The second week we had a gite near Pau and a hire car so I threw in my FT-60E, Opentracker+, puck GPS and a ¼ wave mini mag mount to see if things worked out there. Again a big gap between posts. |
AuthorA few notes on recent radio activity by Steve, M0BPQ. Archives
December 2020
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