Digital Hotspot

I started collecting stuff to put together a digital radio tinkering platform a while ago. MMDVM is a digital modem impelemntation by Jonathan Naylor G4KLX that runs on the Arduino Due and other 32-bit ARM platforms, not only does it do DMR, it also does Icom’s DSTAR and Yaesu’s C4FM. I’ve been nagged by some users of GB3NM to put a C4FM facility on there so maybe this could be the start of that implementation, who knows?…

Hucknall Rolls-Royce ARC hosted a talk by Jonathan on Friday 2nd June which I attended – well worth the trip, excellent presentation! So now I feel a bit more confident about how it all fits together maybe I can make some progress.

I ordered a ZUM interface board from Bruce VE2GZI via the MMDVM website back in March, and apart from plugging it into the board no progress until today. After chatting with Dominic G7NPW he suggested it was possible to build a hotspot with only one radio so let’s see what I can get working so far (no radio at this point).

At this point I don’t have a decent radio to set up the RF side, athough I try getting it to work with Yaesu radios that have a 9600baud data connection (FT-817ND, FT-8900 might work).

Well so far I’ve managed to get it connected to the Brandmeister network. Dominic recommended a Rasperry Pi image that has a pre-configured hotspot, Pi-Star. I’ll investigate this just as soon as I find where I left my Pi Zero and spare SD cards…

5MHz Archives – [ukfivemegs]

I’ve just been catching up with emails and I noticed that there was a post by the current list owner of the [ukfivemegs] Yahoo group to close the list and concerns around a recent Yahoo! security breach.

I’m not sure whether this means closing (and deleting) or closing and converting to an archived group. Either way it would be sad to lose this valuable resource which goes back to the poineering days of the Uk 5MHz experiment. If the group is closed (archived) then I feel that the messages should at least be made public so they can be indexed by the search engines.

I’ve checked my own email archive and mine goes back to 2004. The group appears to have been created in August 2002 by Tim G4VXE so I wonder if anybody reading this has anything archived from the period 2002 – 2004?

73s Nick G4IRX

A Tale of Two Radios

KG-UV6D with antennas

KG-UV6D with antennas

I’ve recently bought a couple of Wouxun KG-UV6D handies. The first because it covers the UK 70MHz (4 metre) band, the second one because it was a bargain (£49) as I was so impressed with the first.

What did surprise me was the differences between the two models. I’ll put that down to “continuous improvement” by Wouxun. I’d already noted that the 4m version was different to the one reviewed in this article.

Clearly the 4m/2m version is the earlier of the two. This has a lower capacity battery and the SMA-J (male connector on the radio body.

4M - SMA male antenna connector.

4M – SMA male antenna connector.

4M - lower capacity 1300mAh battery

4M – lower capacity 1300mAh battery

The 2m/70cm version – probably the most common one out there – has the higher capacity battery and the SMA female connector on the radio body. This is the same connector as used on the later KG-UV8D and KG-UV9D radios and a lot of the Japanese Yaecomwood brands.

2m/70cm radio - SMA male antenna connector.

2m/70cm radio – SMA male antenna connector.

2m/70cm higher capacity 1700mAh battery.

2m/70cm higher capacity 1700mAh battery.

Both seem to perform extremely well on receive, they don’t seem to suffer the overload problems of the cheaper Baofeng sets. Looking at the schematics and service manuals posted elesewhere on-line I can see these sets use dual conversion receivers with proper filtering at the first and second IFs. They also have a built-in FM broadcast band tuner.

On transmit the 4m/2m radio was a little disappointing producing 4w on 4m and 5w on 2m. Realistically this wouldn’t be noticed unless the signal was marginal.

Programming can be done from the keyboard or with Wouxun’s own software. This software is a bit picky for me because (a) you need the specific version depending on what bands your radio has (b) It doesn’t run on Windows 8.1 so it needs to be installed on a W7 PC. Fortunately there are two alternatives;  KG-UV Commander – which again doesn’t work for me on W8.1, or the Chirp project which supports these radios and some. Chirp has versions for Linux and Mac OSX.

Power level, CTCSS and narrow/wide band can be programmed on a per-channel basis. This is excellent compared to my older Kenwood and Yaesu radios where the power and bandwidth is a global setting.

Speaker/Mic pinout is the standard Kenwood 2.5mm/3.5mm connector as used by Baoefeng and others. This also accommodates the programming cable.

Good value – definately. I’ll report any further oberservations after using them out and about.

Baofeng UV-3R Programming


A proper lash-up! Baofeng UV-3R programming interface.

I picked up a Baofeng UV-3R (mkII) to play around with. £20 delivered to my door! It should be useful for the transmitter side of a 2m or 70cm APRS tracker.

The programming cable isn’t the standard 3.5/2.5 Kenwood combo normally used by Baofeng, it uses a 4-pole 3.5mm jack for the speaker/mic or programming cable. I used a CP2102 USB serial interface that I keep for these kind of jobs and a spare Nokia phone AV cable which just happened to have the correct jack plug termination.

Finding the UV-3R software was slightly more challenging as it isn’t available on Baofeng’s website. I managed to find it on  I can also use CHIRP but for some reason it helps to program first with the manufacturer’s software otherwise memories get corrupted and displayed as 666.666.

This radio seems to perform well apart from the annoyance with the volume control. The default function of the rotary control selects the frequency (or memory) and you need to press the VOL key to adjust. Apparently there were second harminic issues with early sets so I’ll be taking a look on test equipment to see how clean it is.

Direwolf Pi

Direwolf Screenshot

Direwolf Screenshot

I am now evaluating Direwolf for HF packet reception on 10.1476MHz. It’s running on a Rasperry Pi 2 with the cheapo Cmedia sound card and the performance looks extremely good. I just need to figure out why I’m getting broken pipe errors though.

I haven’t yet decided whether to run it as stand-alone igate or use it as a TNC in conjunction with Xastir as it provides either AGWPE or KISS type interfaces to external programs.

Update 13th May – I reduced the number of parallel modems from 7 to 3 and this seems to have cured the broken pipe errors. I’m now gating received traffic to APRS-IS using the built-in client. Traffic reported can be seen on

AR7030 Power Supply Fail

After sixteen years of reliable operation, the model 952452 power supply for my AOR 7030 receiver finally died.

I was tuning around listening to CW and datamodes stations that sounded like they all had raspy notes. A quick check on the PSU voltage with a voltmeter revealed it was sitting at 17v whereas it should be 15v. Substituting the PSU with another (AOR) 15v power supply cleaned up the raspy signals again so I decided to investigate if it was repairable.

AR7030 PSU disassembly

Continue reading

Multimode APRS – V2

aprsis32_multimode_v2 aprsis32_multimode_v2

I’ve made some changes to the Multimode setup to give it more flexibility.

The main feature is that I’ve added the SV1AGW Packet Engine – AGWPE. This is an extremely flexible program that allows me to share the SCS Tracker (or any other TNC) over  a tcp/ip connection. I just needed to change the APRSIS32 port configuration from a KISS serial port to a second AGWPE port and configure AGWPE itself to allow connections on 8001/tcp. (8000/tcp is already in use by UZ7HO SounddModem).

This now allows me to run an AX25 monitor program (such as UZ7HO’s  EasyTerm) so I can trace activity on the RPR channel.

Developing things further, AGWPE and UZ7HO_SM accept multiple tcp connections and therefore multipe applications can share a single TNC (unfortunately Messenger doesn’t yet). I can now make connections from other hosts on my network, for example I have Xastir running on a Rasperyy Pi connecting to AGWPE. I’m now considering running just the TNC/modem radio interfaces on the shack PC and the APRS applications can live elsewhere!



Multimode APRS RX Setup

Click for full size

System Diagram


Download aprsis32_multimode system diagram – PDF.

I’ve been experimenting with APRS on 10MHz. Mainly reception at home and also some portable operation. After spending some time with UIview32, I changed over to APRSISCE/32 which I find more suitable for my needs.

For 300baud FSK packet I use the UZ7HO SoundModem. This uses a soundcard for TX and RX and emulates the AGW Packet Engine interface. It can be configured to use two audio frequencies simultaneously and has a waterfall display to aid tuning.

Chris G4HYG has just released version 3.29 of his APRS Messenger program. Not only does this interface with a standard TNC. It also supports sending and receiving APRS traffic over PSK, GMSK and MFSK16 modes. This makes use of the MMVARI engine which he has configured to run as multiple receivers. It will also connect the the UZ7HO SoundModem but presently this only works on receive. Stephen WA8LMF has also written some extensive notes on configuring APRS Messenger and using with UIview.

APRSISCE/32 is more flexible in this respect, so I configured an additional text port to connect to APRS Messenger port 8063. In this setup, APRS Messenger is used purely as a PSK/GMSK/MFSK16 receive decoder.

Finally I bought the SCS-Tracker TNC. After placing my order back in April, I had a few months to wait due to a re-design of the enclosure. This is configured to run in Robust Packet Mode and connects to the APRSISCE/32 host using KISS protocol over a USB serial connection.

Audio Frequency Settings

  • The receiver is set to 10147.30kHz USB dial frequency.
  • A PBT offset of +500Hz shifts the top end of the audio passband up to 3kHz.
  • The HF modems in APRS Messenger are set for 2400Hz.
  • The HF modem in UZ7HO SoundModem is set for 2000Hz.
  • The RPR modem in the SCS Tracker is set for 1500Hz.

Both APRS Messenger share the same sound card. Both applications should be set for a sampling frequency of 11025kHz and the SoundModem should be calibrated for best results.

APRSCE/32 Port Settings

  1. APRS-IS – Your normal APRS Internet connection (not shown in the diagram).
  2. KISS TNC – connected to SCS-Tracker TNC via USB.
  3. UZ7HO_SM – AGWPE connection to tcp/ip port 8000.
  4. APRS_MSGR – TEXT connection to tcp/ip port 8063.


10Mhz APRS seems quite active and I’m hearing a lot of traffic on RPR, probably more than on 300baud FSK. There isn’t much PSK/MFSK activity and I’m hoping to contribite to that mode with my portable setup.

See the system diagram above (click on it for full size or download the PDF!) to see how it all fits together.

Check the Digipeater Users list at DB0ANF.

5MHz Beacon Monitor Program

I’ve just discovered that the GB3RAL.EXE program, written by Peter G3PLX, is no longer available from . This is the software used to monitor the UK 5MHz beacons – GB3RAL, GB3WES and GB3ORK

After digging back through my emails, I found the most recent version that Peter sent me which supports  both conventional (mono) input and I-Q inputs for a SDR. This is the version I last had running with my Softrock receivers. As the documentation is in the now depreciated Windows .HLP format,  I’ve added the notes that Peter originally provided to the zip file in text format.

It should still run on any version of Windows from Windows 98 up to WIndows 8.1 (I must test this!). Just unzip the file into it’s own folder e.g. C:\beacons and run the program GB3RAL.EXE. If you’re installing on Windows Vista or later then don’t install under the program files folders as Windows will complain noisily! It can also be run on systems such as Linux and OSX using the Wine emulator.

It’s now available for download from here –



I’ve just started experimenting with WSPR – a weak signals digital mode, using the Icom IC703 and 5W to a 15m end-fed wire. I’d been transmitting on and off for around an hour, checking in the WSPRnet spots database to see how far away I was being copied.

Imagine my surprise when I saw this one.

2014-05-20 19:32 G4IRX 10.140155 -26 0 IO92jv 5 VK5MR PF96lh 16221 72

I double-checked VK5MR’s reported spots – he was hearing lots of EU and some Japanese traffic so I guess he must be operating from home! Now if only I could get that far on 10MHz APRS…