IC-746 - a problem that wasn't!

Well, my heart sank yesterday as I connected up to the 2m slimjim atop my roof and tried to send FT8 with the new ICOM IC-746.

Nothing happened!

I tried to work through everything, but got nowhere.  The data transmission works perfectly on all bands except 144MHz - the very band I'd bought the 746 for!  If I manually pressed 'Transmit' on the front panel, the data went out just fine.  So it seemed to be a TX-trigger issue of some sort.

I could find no help on the internet, and so resorted to asking for help from ICOM in the UK.

Outstanding help from Icom.

I've specifically written this blogpost to highlight to others the incredible fact that ICOM actually phoned me back within 30 minutes of sending an enquiry to their servicing team.  How many companies bother to answer at all these days, let alone so quickly?

A very friendly technician told me it was simply a case of having a different transmit trigger line for VHF (the so-called 'HSEND' for HF, and 'VSEND' for VHF). 

With just one simple, free support callback for a second-hand rig, ICOM have shown themselves to be a rig maker worth taking very seriously in my next new purchase.  Take note, other makers!

Three others who must be thanked for kindly helping me when they might reasonably have just turned their eyes skyward at another fool asking for assistance were:

• Technofix, providers of just about any data/CAT cable you can imagine

• Neil, owner of low noise data interfaces and accessories at ZLP Electronics

• Sam Hayward at UK ham radio outlet, Radioworld

UPDATE:

I eventually found some useful information online, courtesy of N5KBP, Marty Duplissey.  My colleague PE4BAS rightly says there is pinout information in the manual (p.72), but I wanted to triple-check I wouldn't get it all wrong and damage the rig.  One thing to remember is that, when looking at the pinout diagrams, you are looking at the socket as it appears at the rear of the rig, not the plug you are trying to wire!

Here's what N5KBP kindly submitted, which may help others in future (or help me remember when I do it again!)

'All the audio goes through ACC1 regardless of band. Pin 4 is audio from computer to radio, Pin 5 is audio from radio to computer, pin 2 is ground and pin 3 is ground to transmit on HF. On ACC2 the only pin you will use is pin 6 for VHF ground to transmit.  All you need to do is to wire pin 6 on ACC2 in parallel with pin 3 on ACC1.   On my setup I built the ACC1 8 pin connection then just ran a single wire from pin 3 on it out to pin 6 on a 7 pin din plug for the ACC2 to enable transmit for VHF.  Basically get it going on HF then add the wire to ACC2 to enable VHF transmit.'

It turns out that it's quite difficult to solder another wire onto pin 3.  You need very thin gauge wire, first of all.  I found it a bit easier, although not ideal, to cut into the cable some way from the DIN connector, and take a tap from it.  Having not yet received my 7-pin DIN plug from E-bay, I couldn't wait and just fashioned a 'pin' from 1mm copper wire.

It got me going.  I replaced the wire with a proper DIN plug later.

This is my schematic for the connections:

Et, voila!  Works a dream!

First 24hr reception reports, with a fair few QSOs, too!

VHF/UHF Switch Problem.

I had a rare listen to 2m and 70cm FM last evening.  Here in North Wales, there is essentially zero 2m activity, even on repeaters, and those few who remain operational are generally not worth having a QSO with.

I noticed that, as I turned the antenna switch to its end-stop, the signal on 2m suddenly increased - by about 4 'S' points.  How strange!

On opening the VHF/UHF switch, I was firstly surprised to see how little I had received for the quite large amount of money paid for it! 

As you can see, it's just a shim of brass moving between the outputs!

How much did I pay for this?

Clearly, there's not an awful lot that can go wrong with such a simple switch.  Because more pressure on the switch brought about the improved signal, I thought this was probably corrosion on the brass metal knife.

After applying some metal polish with a ear-cleaning stick, it was obvious that there was quite a lot of surface corrosion to be cleaned away.  If you do this cleaning, please make sure you remove all traces of the metal polish, because if you don't, when it dries, it forms a non-conductive powder.

Quite a lot of surface corrosion on that kife switch!

After this simple treatment, the fluctuating signal problem had disappeared and full strength reception was restored!

New phenomenon found?

Over the past few months, I've been quietly gathering evidence on a strange radio phenomenon I've noticed in the local area.

Regular readers will know the QTH is based on an old copper mine.  This sounds fantastic - and it is - for radio.  But it's dissolved iron that is probably responsible for the world beating ground characteristics to be found here, because it is by far the most common element.

Bacteria (actually, Archaea, as separate Kingdom) eat away at iron bound with sulphur, producing sulphuric acid.  I've measured pH as low as 1 on the mountain.  At pH of below around 5 or so, iron is in the Fe2+ state, and is dissolved (handy to know if you ever have a rust stain on the bath - just put some acid toilet cleaner on it!)  At above pH 5, the iron stops being soluble, and becomes the more familiar Fe3+ in the form of a 'floc' that smothers the river bed.

Afon Goch, near Amlwch.  The pH remains low enough, even at 1km or so from source, to keep most of the iron in solution.

So as well as having a very high level of mineralisation, there is also highly acidic conditions.  Thinking about it today, I realise that sounds a bit like a battery!  I must think about that a bit more.

But the strange thing I've found is that, at a very precise and repeatable location, commercial FM radio suffers 'crosstalk' for a moment.  Now, crosstalk is not uncommon, and we are located relatively high up, in line-of-sight to many Irish Sea areas.

Acid drainage from Parys runs under the road below the white cursor (you can see vents to the surface in a line running roughly centre to upper right corner)

But this kind of crosstalk occurs only when I move in a car over an underground, highly acidic mine drainage stream - appropriately known as 'afon goch' (red river).  The interference only happens momentarily - just a second or so, exactly as the stream passes underneath me.  Afon Goch, incidentally, is the largest single source of heavy metal pollution into the Irish Sea.

It could be a coincidence, and that it's geography, rather than the river that is responsible.  That's why I've been testing it many times.  Stratified atmospheric conditions do not seem to be responsible, as it occurs under windy and calm weather alike, and regardless of season.  And it doesn't happen anywhere else!

Well, that's something to think about some more.  Perhaps the acid drainage produces some kind of earth current?  Metal detectorists know very well about the crazy effects of mineralised ground which, looking at some online data this morning, tells me is due to a modified magnetic field (which is pretty obvious, really, given it's not only metal but iron in the ground).