All posts by Gareth Blades

Motorola MC Micro Audio Connector

I have designed a 3D printable audio adaptor for the Motorola MC Micro radio. The design cab be downloaded on Thingiverse here :-

The design consists of 3 parts. The first is a grip which wedges between the internals of a 9 pin d-sub plug and the chassis of the radio. This isn’t strictly necessary but does help to avoid the plug vibrating loose. The internals of different plugs might vary so this grip might not always work but the design is made available in Tinkercad to tweak if required. I tried making a plug which would go all the way around but the minimum thickness of plastic most printers use is 0.4mm and there was insufficient space for this to work.
The second is a plate which holds the phono socket while making it easy to access the nut to do it up tight.
Finally there is a simple spacer piece to stop the end of the phono socket touching the d-sub contacts. This part is 20mm long and can simply be scaled to a different height when printing to compensate for a phono socket which has a much greater or shorter required depth.
All designs can be customised in Tinkercad :-

Parts Required :-
1* 9 pin d-sub plug
2* M3 * 30mm screws
1* phono socket

You will need to remove the metal surround from the d-sub plug. You might be able to snip it away using some cutters but I used a dremel type device with a small cutting disc to chop through it at the top and then peeled it back using a pair of pliers. If you do this please wear safety glasses as these small discs can shatter very easily if they catch and the sharp pieces can go flying off at quite a speed.

Step 1 is to push in the d-sub plug and then push in the grip behind it.

Next take the phono socket and solder wires to it and the solder ring. Make sure you do this before fitting as the heat will very easily melt the plastic.
Fit the phono socket. The plastic tends to deform a little under constant pressure so even with a spring washer it might loosen a bit after a while so I would suggest adding some silicone to fix everything in place and help stop the socket from rotating.

Feed the wires through the spacer and solder them onto the d-sub plug onto the speaker contacts.

Screw everything together and fit a phono plug onto the end of the speaker wires and it’s ready to test.

Motorola mc micro power connector

I have designed a 3D printable plug for the Motorola MC Micro radio. The design cab be downloaded on Thingiverse here :-

The design has a few close tolerance parts to ensure the pins fit well in the connector. Depending on the printer the holes may need to be enlarged or made a little smaller. The plug itself is not a snug fit inside the socket and relies on the connectors to provide the friction to hold it in place so there is a little room to enlarge or shrink it before printing but I have also made the tinkercad project accessible if anyone wishes to modify the design themselves :-

The crimps used inside the plug are Molex 5.08mm commonly used in PC power cables as in the photo below. So you can either buy a lead and remove the pins from it or purchase the crimps separately but these can be fiddly to assemble if you don’t have a crimping tool.

I bought the crimps on ebay and crimped them myself as I didn’t want to have to join the wires. I got them from

Selecting the correct cable for the plugs is quite critical. In order to be able to have the crimps grip and hold the insulation properly you will want cable with an outside diameter of between 1.9 and 2.5mm. That is quite small considering the radio can draw in the region of 8-9A. In that size range you could get something like which has a cross sectional area of 0.44mm. At 8A you are going to get a voltage drop in the power cable of 0.6V per meter (reference which is going to become significant at longer distances.
This is one of the reasons that you can see in the final photo that I chose to make an adaptor lead. The length of the adaptor is kept relatively short in order to minimise the voltage drop along the thinner cable.

The first step is to check that the pin crimp fits snugly. It is not quite round and in one direction it will be a loose fit and in the other it will be tighter. This orientation gives the best fit.

There could up to around 8-9A going through the contact when transmitting so it needs to be a good tight fit. It is probably a reasonable contact but of you flatten the end just a fraction it will be a lot better. Flatten in he orientation shown below so the naturally wider part becomes a little wider.

Next crimp the connectors. Start with the pin you have just squashed and crimp the ground wire to it. I had a crimping tool and found the ‘AWG 18-22’ setting worked well as you can see in the above photo. You could use a pair of pliers but it would be difficult to get the crimp as neat and small enough to fit in the back of the plug and you would probably want to add some solder.

Put the pin in first and then the socket. When pushing in the socket connector make sure it is orientated so that the pin naturally likes to twist into the correct orientation in order to make inserting the plug easier.

When the socket is inserted it will push in most of the way and them seem to stop in the position shown below. There are small barbs on the socket and you can grip the cable just behind the metal and then push it the rest of the way in and it will be a good tight fit.

That’s it pretty much assembled. When removing the plug the pin will tend to try to pull out of the socket. This isn’t a problem but you can add a bit of glue or put on some heat shrink (the stuff with adhesive if you have it)

Finally I prefer to have the plug almost a permanent fitting so I made it into a short adapter lead with a XT30 connector at the other end so if I wan’t to disconnect the radio I can just unplug the XT30 instead.



The RSGB has basic information on using repeaters here:-

Accessing repeaters is detailed here:-

Table 1 below shows the closest repeaters to where the club meets. If you live elsewhere you can go to and enter your postcode to find out your grid location. Then go to and enter your grid location and click on [km] to filter by distance.

There is a useful app called ‘RepeaterBook’ for Android and Apple devices which uses your location and shows the nearest repeaters to you of the selected type.

One thing which has caught me out is that new repeaters are required to support CTCSS however they often also support the 1750Hz tone burst. When CTCSS is used to access them then they are also required to output CTCSS. The mistake that I made was configuring the radio with the CTCSS tone for send/receive. I was missing some transmissions and the radio was indicating a CTCSS mismatch. This might have just been the the regular beacon they transmit but it might have been someone talking which used the tone burst to access. Switching my Yaesu from ‘T SQL’ to ‘T ENC’ resolved this issue.

Table 1
List of UK repeaters closest to IO91nk which is the grid containing the Woodford Park Leisure Centre.

GB3TU433.2250434.8250AIO91PS38017TRING HERTS77.0Hz
GB3SN145.7250145.1250AIO91LC38197ALTON HANTS71.9Hz
GB3BV433.0250434.6250AFIO91SR43041HEMEL HEMPSTEAD82.5Hz

Logging & QSL

I use for looking up callsigns as it seems very popular and it is nice to see a bit of information about the person you are speaking to in addition to being an additional check you have recorded their callsign correctly.
If you sign up you should be able to get someone else to add your callsign to the database. If that doesn’t seem to work or you prefer you can go onto their forum and provide basic information and someone there will add it for you. It took a couple of days for someone to update my callsign so that it was associated with myself correctly. Once it is all setup you can update some information about yourself and use the online logbook.
If you prefer windows software then I have played with ‘log4om’ which seems pretty good. If you want it to automatically post to then you need to subscribe to at least the xml logbook package which is around $30/year. Personally I just use but if you are using HF and have a link to the computer so log4of can read the radio settings and are making a few contacts then I can certainly see the benefit in it.

Although using the logbook you can request confirmation you don’t get any form of QSL card. The RSGB offers a bureau service ( but a lot of people seem to use an electronic version like Basic access is free but you can pay for various additions such as bronze membership which enables you to upload your own custom card design plus additional benefits.

Tom M0LTE Suggested
“You mention logging, which reminded me – for anyone interested in logging, might I also suggest Cloudlog, a modern web app fit for this decade, which has just been launched as an inexpensive subscription service (previously your only option was to install it on a webserver of your own – you can still do that for free but it’s hardly worth the hassle for £4/month).”

Other Links

There are various web based SDR’s that you can use to listen on different bands at various points around the world. is a very good list and the Farnham one can be accessed at is a system where you can use a PC or an app on a mobile phone to link to other Echolink devices. You do need to upload your Ofcom certificate to get the account validated but I found this was very quick. Other devices can be other users, groups or even repeaters.


Gareth M7GRB