POCSAG from the Jumbospot

I finally got round to setting up an account with the DAPNET, which means my Jumbospot can now transmit POCSAG pager transmissions, I put the NooElec NESDR SMArt on my tablet and on the standardised pager frequency in the Amateur 70cm band and indeed the hotspot is genuinely transmitting.

I hope to try and get hold of a compatible pager and use this to its full potential, because it's retro tech and works well for what it is, and this service being part of the Amateur radio service is perfectly legal to decode, unlike commercial pager systems.

The hotspot is working as follows, when it is idle, the POCSAG transmissions can take place on the worldwide spot frequency of 439.9875MHz (or whatever frequency is set up for paging, though this one is the standard in most of the world), once the hotspot has done this is switches back to the hotspot frequency (in my case I use 438.800 as in the UK bandplan this is set aside for personal hotspots, though your country my differ), while a digital voice transmission is in progress or the hotspot is receiving a digital voice transmission it will not transmit any further POCSAG until the hotspot has returned to its standby state.

If you want to use the DAPNET yourself you need to go onto hampager.de, open a ticket to create an account (you will need to also submit your licence document as proof you are an Amateur radio operator), then you will need to open a ticket to register a transmitter, which will give you the auth code to put into the POCSAG settings on your hotspot, this does work with most Pi-Star based hotspots but not sure about others.

If you have a pager you'll need to obtain a RIC, open another ticket to do this.

I have Josh KI6NAZ from Ham Radio Crash Course to thank for me actually getting registered with DAPNET, one of his previous livestreams featured a pager in it (though the subject was the NanoVNA) and he has a video on the pager subject as well which is what motivated me to finally get on and do it, and though his channel is an American channel I highly recommend you check him out no matter where in the world you are.

there's more to come on this subject so do watch this space

73 de M0WNU/26CT730

Pager revisit

In June I posted about how POCSAG pagers were being used in Amateur radio and had been for some time by the Germans using the DAPNET, further investigation led me to discover that ETCC had been able to get Ofcom to issue NoVs for some POCSAG transmitters on the Amateur bands, specifically a spot frequency in 70cm, located in the south of England, I believe there are 4 of them all with callsigns MB7Pxx (where xx is two letters), and Pi-Star, as I posted about, can transmit POCSAG messages on the same spot frequency used worldwide (with some regulatory exceptions).

This is all part of a German system called DAPNET, the Decentralised Amateur Paging Network, and because I am a fan of older technology, as it has been proven to work hence one reason I enjoy Amateur radio as a lot of old radio gear is still in working order or has been restored to working order, pagers simply add another aspect to this, they are in very seldom use by commercial users now and only one paging network exists in the UK now, so us Amateurs can keep it alive, though we cannot use it commercially as that would be against the terms of the licence in every country and against the nature of Amateur radio in general.

Pagers have to be assigned a RIC to work, a radio identity code I believe, the system is, like a commercial pager system, one-way, so good for transmitting information on local clubs, nets, SOTA spots, or any other bit of information of interest to the Amateur radio community, the DAPNET has something called 'rubrics' which you can choose to receive information from.

Now I have my full licence I plan to play with this, though I need to put through a new DMR ID first as I believe a pager RIC would be derived from that (though pager RICs don't go up as far as DMR IDs from what I understand), though I plan to run an APRS igate which would require a NoV, running a pager gateway would require a second NoV which would be required to allow me to run both, as demand for pager use is lower than APRS-IS access then I don't have to worry for now.

73 de M0WNU

POCSAG in Amateur radio

The dreaded POCSAG (dreaded if you run cheap Chinese radios on 2-meters) has found it's way into Amateur radio, the Germans have been running it for years, in recent months I've seen an option for it in Pi-Star however up until a few days ago my Jumbospot would not be able to transmit it, however the board received a firmware upgrade and should now transmit it.

To receive it from the Jumbospot I'd need a pager though my RTL-SDR combined with PDW can do the same thing, however though I want to play with it I'm not sure what I could do with it or how it fits in Amateur radio however the Germans have it sorted, getting a used UK pager would not work  because the Jumbospot and the standardised frequency used are both in 70cm and UK pagers are set on 153MHz.

I am a fan of the older technology, pagers are no exception to this, even though I now know that poorly built 2-meter rigs (Chinese ones primarily) suffer badly from commercial installations of POCSAG and FLEX transmitters as these are so high powered and the radios alluded to have wide front ends, people may ask why I want to buy or even use a pager, however if it's in Amateur radio it would be free and I am pretty sure some kind of QSO can be done using them over the DAPNET.

Perhaps in the coming months I will play with this, after all it is there so why not.

73 de 2E0EIJ

Portable ops and pager intermod follow up

Today I went back to the old racecourse in Richmond and gave another go at portable operation there but this time using my KT-8900D, this radio suffered from the intermod issue as well but nowhere near as bad as the VV-898, as for me to hear it I had to open the squelch (which is shown in the video I took).

I managed one QSO, and almost got another one too but there was some confusion on S20 as to who was calling who, no matter, one was better than none at all.

This has drawn me to the conclusion that I must now build a notch filter (or spend US$90 or so on one pre made which I'd rather avoid), as my intent is to block out pagers I can use the pager frequencies and the RTL-SDR to tweak it and suppress the pager transmissions so they don't cause intermod.

Looking online there are some designs for these, some use a coil of wire and capacitors and screened enclosures, of course what I need is something that can basically work to TX on 2 and 70 without any issue so I will look at that of course, however the ultimate aim is to stop the pager noise dead in its tracks.

I will obviously test the final design with the worst offending radio, the VV-898, in the field at the old racecourse.

73 de 2E0EIJ

Portable ops... ruined by pagers

Yesterday I went out to do some portable ops on 2-meters (FM only considering my equipment though I could have done DMR had I took an adaptor with me for the Anytone which I did not do), I took my Leixen VV-898 as the radio simply because I could go as low as 5 watts (which is QRP in my opinion) if I wanted though I stuck with 10, however no matter what channel I went on in the FM simplex range or any of the repeaters, the radio was wiped out by intermod from pagers in the 155-158MHz range, and though pagers are not as common as they were because of the SMS facility on mobile phones, they are still in use as they work almost anywhere a mobile phone does not as they use high power transmissions from their base stations.

I will of course be doing a test with my QYT KT-8900D to see if it has better rejection of the paging traffic or not in the same location, and will also make a point to promote the hobby at that time and also the local club to try and get some more numbers there, after all it makes some sense.

I have a video of how the VV-898 was swamped by the pager noise in the pipeline, a short one but it gives you an idea of what the problem was, and I will do some footage of the KT-8900D when I go up next to the location to show if the KT-8900D is a better radio or not.

I am also looking at fitting a notch filter to the VV-898 to see if that helps get rid of the pager intermod as that seems to be the worst problem for it.

The pager issue itself will not go away, but there are means to help prevent it interfering with Amateur radio operations.

The video should appear on YouTube and here in the next day or two, and an update regarding if the KT-8900D is also suffering intermod from pagers will be posted as and when.

73 de 2E0EIJ

Edit: the video is live on YouTube and is also available here, comment on YouTube if you have one of these radios and have suffered the same intermod problems