Automotive Wiring Is A Pain In The Arse!

 Given a normal bit of desk or rack mounted 12v powered equipment, fitting a simple fused changeover relay would take me around 5min, and that includes working out the wiring route and tying it into the loom.

Exactly the same task, but on my car? Well, after 2 hours I'd found somewhere to mount the relay, and got the control wire through the bulkhead! and thats with the wire running parallel with the already routed bloody thick high current cable for the transceiver!

The purpose of this relay is to kill power to the transceiver when the ignition is off. As it currently stands, I can easily leave the radio on without noticing, with the result that I go to set off for work after 4-5 days off, and the battery is flat!

So, a 30A relay and a suitable tap into the switched supplies is needed. A few quid. But far more hassle! First of course, I had to find a suitable switched supply! The dashcams are fed from the switched feed to the wiper motor controller, which being an 'add-a-circuit' type piggy-back fuse holder connection, actually covers up several fuse positions! Luckily, Ive found that F44, a 3A feed to the cars audio system, is accessible. An extra 100mA or so on this wont hurt, and it keeps all the audio/comms systems on the same main circuits.

Then, where to mount the relay? This needs to be close to the battery, but of course cannot be on it! The nearest available secure place I could find was a hole on the corner of the EMU housing! Turns out the aluminium housing of the EMU is floating! Neither grounded nor as best I can determine isolated! Luckily the mounting bracket of the relay is isolated, but it means a longer wire run from the relay coil to ground at the battery negative terminal.

So with this selected, the tedious and trying task of getting a guide rod through the bulkhead rubber gasket was next. The rod in question being a 1.5mm stainless steel antenna rod. Thin and flexible to do the job, but none the less a real pain when single manned. Without an assistant, it was a case of push a few centimeters, climb out the footwell, into the engine bay, look but mostly feel for the end of the rod, and repeat, until such a time as I could finally grip and pull the rod far enough to attach the wire, without damaging anything else close by - cables, hoses etc! With the single 5A wire (blue) taped to the end of the rod, and an ample estimated length payed out from the spool, came the nerve wracking task of pulling the rod back though the bulkhead into the footwell beside the fusebox, hopefully without losing the end! Well, it took considerably more force than expected to get the bulge of the joint through!

So now, I have the relay fitted in place, hand tight, the control wire fed through, crimped and connected to one side of the relay coil. The ground connection wire is crimped and connected to the other side of the relay coil, has the eyelet crimp attached, but it tied up and taped ready to be attached to the battery negative terminal later. The fusebox end of the control wire is unterminated, and the positive high current connections are currently a loop of 30A wire crimped and attached to both of the relay contacts! This is because A - I dont have the bloody 'add-a-circuit' fuse module to complete the control connection, and B - Ive run out of bloody butt-joint crimps to complete the high current wiring with!

And so the circuit will stay in this state, as will the passenger side footwell and seat, which are littered with tubs of crimps, fuses, wire, tools etc, as well as the temporarily removed, but still full, glovebox itself, until such a time as I can get to my automotive parts supplier. Which could be hours, might be days.

And all this came about because im stuck in the house awaiting a delivery, and I also had a blown brake light to replace!

Conditional Alignment

 Gawd, that sounds like some form of sexual psychoanalytic technique! But, its actually a way to fix buggered binoculars!

Binoculars, like other optical systems, have a number of parameters that have to be in tip top alignment  for them to work properly. Some, such as chromatic aberation, coma, etc, are inherent to the glass itself and can only be solved by buying the best. But others are a physical alignment issue. In particular - collimation.

Ive come this because I decided to give away one of my pairs of 10x50 binos. Back-yard astronomy is a great and relatively simple hobby to get into for a youngster, but many people make the mistake of jumping straight to a telescope and are disappointed when the images they see are nothing remotely like what the press tell us they should be. Sorry, but nothing you can buy at amateur level is going to give you views like what are published in magazines and on the web from the Hubble space telescope or the myriad of astrophotographs created by allowing software to 'stack' hundred upon hundreds of long time exposures! Buy the biggest possible mirror in your budget, lets say thats a 8" dobsonian - and Andromeda will still be a vague fuzzy oblong! Sorry, thats how it is! Combined with the tiny field of view which makes actually finding the thing you want to see difficult in the first place, and its no wonder so many give up!

But it shouldnt be like this. The night sky is amazing - even if all you can see are the brighter navigational starts from a light polluted city. Its the way people are introduced to it that makes all the difference! Dont go out and buy a telescope! Go out, and buy - a planisphere! Or a simple, beginners level star atlas. Then - simply go out, and look up!

Of course, just looking denies you some of the more easily found wonders. But a pair of binoculars will reveal a plethora of amazing sights. Even for me, the sheer background of the starfield when using a pair of simple binos to look into the Milky Way is astonishing.

So when a work mate mentioned their daughter was interested in the night sky and wanted a telescope, I asked if they had any binos. With the answer being no, I decided my spare pair would perhaps give the young person a much better start into the hobby.

Now, This left me with my ancient Miranda 10x50s, that I bought when I was about Sams age, and still at school, and the cheap Bressers of Sams. This is when, in deciding to check them over, I found that Sams had been sat beside a bottle of aftershave, and all the rubber had gone sticky! I also found that the collimation was so far out that there may as well have been two of everything! So, how to fix?

Well, the sticky rubber was solved by rubbing a load of talc into it! Its not perfect, but pretty much the best I can do without the impossibility of replacing the rubber parts.

The collimation is something that I dont have the equipment to do fully, but it is relatively simple to do what is called 'conditional alignment', this is where the collimation is corrected, for the specific interpupilary distance in use. In other words, it fixes it for anyone whos eyes are the same distance apart. This is done by very carefully adjusting the prism adjustment screws hidden just under the rubber covers! I have done a 'rough and ready' job on these, entirely by trial and error with them focused on a pylon some 10 miles away. A more accurate alignment could be done using specialist Bahtinov masks, which are a form of grating, but I cant be bothered with the expense or difficulty in making my own, for a cheap pair of binos.

Anyway, these are the pair Tom was using up on the hill, and he assures me the images were sharp and not doubled, so it seems to be good enough for now.

The Sky At Night

 is, generally, cloudy. Sods law really. With my interest in most things waning, i find myself coming back to what has long fascinated me - the night sky. Despite a rigorous scientific background and a moderately deep understanding of the heavens, im still able, perhaps more so simply because i understand them so well and dont have to resort of mindless fantasy fiction (otherwise known as 'religion'), to be amazed by what can be seen.

To this end then, I decided now was a good time to improve my astronomy capabilities. Having decided on a budget and considered long and hard as to what kind of instrument I wanted to go for - do I go for the greater light gathering of a big Dobsonian mounted reflector, or the easier aiming of a slightly smaller set of optics on an equatorial mount, etc - I made a choice. Only to find it out of stock, in all variations, everywhere!

It seems, which people unable to go out and about as they used to due to the pandemic, that people are choosing to try out the more solitary pastime of amateur astronomy, and the shops are simply running out of stock! Such strange knock-on effects are starting to become apparent in many widely diverse activities, such as the famous flour shortage as everyone took to home baking!

So the telescope has not yet been upgraded, but I did manage to get my 2nd choice instrument. I had made a selection of the Celestron Skymaster 20x80 binoculars. These were a great price from my preferred supplier. Now, im going to briefly mention these and my recent experience. This is simply a statement of my experience and I dont wish it to be taken as anything but. My preferred supplier is Rother Valley Optics. When i dealt with them before in the shop i found them very helpful, and being a great price and a 'local' indepenant supplier wished to use them again. Having to do so online though, I found my enquiry regarding suitability, which included a very basic 'beginners' question, to be answered rather briefly, with none of the personal insight I would have expected from a friendly amateur astronomer. Also, my order for the binoculars was subsequently cancelled and refunded with no more than a note to 'check stock levels next time', no query as to whether I wished to hold on back-order until the stock came in. All in all I was somewhat disappointed by the experience. I do appreciate that these are difficult times, but as they say "civility cost nothing, young man!"

Instead, my order was re-placed through Amazon, with Carmarthen Cameras. This cost me £8 more, but at least they had stock! Having no direct contact with the store, I can only report on the fact that they arrived quickly, and the packaging while not substantial was adequate.

Now, these binos are not pocket eyeglasses! They are huge! Ideally they should be mounted on a tripod, but my only spare one is a lightweight one for the SLR and rather flimsy. Nevertheless, myself and Tom took a stroll up the local hill yesterday to test them out. My main concern was ensuring that they were properly collimated, the slightest error in collimation and they would be on their way back to the shop! Much testing on very distant objects and I can say, at least within the limits of my own horrendously myopic and astigmatic vision, that the collimation is good. The arm strain as a result of hand holding them for an hour not so good! A couple of targets proved remarkable for testing these, one was a lucky chance of a hot air balloon over York, which to the naked eye was just noticeable as a dark balloon shape, in Toms 10x50s as a dark blue balloon, and in these as a dark blue balloon with a yellow and blue checkered top section! The other was a pair of aircraft warning lights (this of course was mid-afternoon) somewhere in Leeds city center. Not even the building they were on was visible in the 10x50s!

On the night these arrived the sky was clear and I did have a chance to play for a few minutes before it clouded over. Its been overcast since! But the main joy of the trip up the hill yesterday was teaching Tom how to use binoculars! With the light weight cheapo Bresser 10x50s that i'd just repaired (so far out of collimation that there was literally two of every object! and the rubber sticky from alcohol degradation that needed talc rubbing in), I spent some time to teach Tom properly how to set them up, starting with Interpupilary distance, followed by eye relief, and dioptre setting, then focusing. I think the excited shouts and comments can be taken as confirmation that he enjoyed the experience!

One thing ive realised though, is that I dont have anything I can comfortably sit/lay out in the garden on to observe! Im hoping that with it now being autumn, cheap sunloungers might be on discount somewhere!

No Enthusiasm

 Ive not posted on here for quite some time. What with the Covid-19 lock-downs, the unprecidented and unbelievable scene of the control of the nations radio and TV being effected by dispersed engineer-operators working from home (myself included - I carried out one of the initial tests of the system), the travel restrictions, the cancellation of fairs, rallies, and other events, and then the sheer confusion and inconvenience of returning to working from the office....

...I just cant be bothered!

This is true, I seem to have lost all enthusiasm for not just radio and electronics, but pretty much everything other than reading and taking long baths. (this is itself is nothing unusual - ive lost interest many times before, however those times have usually coincided with life events, for instance losing interest in radio during the years I serviced public safety radio systems) The only odd thing is that this time, the loss of enthusiasm is making me anxious.

I still have many projects on the go, but I just cant bring myself to get on with any of them. I do recognise that this is a detrimental aspect of my mental health, although im rather glad that it isnt manifesting itself in the form of panic attacks! Oddly, as a result of working from home using telephony headsets and with without people close by, my telephobia has actually improved. I seem somewhat more confident and able to use the phone with less hesitation and worry, even, I feel, to perhaps having a bit of time out portable with a nice bit of HF combat net radio!

Of course, much of my current state may be attributed to the drugs im using to control other symptoms. These include some rather potent controlled substances, plus a few 'special' molecules, and are helping me overcome the insomnia, and settling down the Willis-Ekbom. Unfortunately they are also allowing me to observe and analyze life from a 3rd person perspective.

I do feel that I need to get back into some level of radio though. Not from the shack though I feel, but perhaps portable, a little SOTA maybe. Little by little myself and Bob M1BBV have managed to find slots to get a little walking in, so a few SOTA activations may be on the horizon. If nothing else, I need to get out and have some time in the wild open countryside.

I just need the motivation and inspiration to get started!

There will be more interesting posts eventually, I assure you (whoever you are, although I doubt I have many 'followers') but for now, like almost everything in life, its a case of keeping distance, and waiting.

No go on the 5V SLAB

Well, the SLAB that was reading 5V has definitely had it! Initially, it looked good, and I was able to transfer it to my Accucel charger. But then, the voltage started to drop, even on charge.  It was always unlikely that this one would recover.

The one reading 10V, I was much more conservative with the water (about 2ml per cell), and have left this on the slower charger. Its still only taking a very low current, just a handful of mA, but this is steadily increasing.

So, who knows?

Refurbishing dead SLABs?

I use quite a few 12V 7Ah Sealed Lead Acid batteries (SLABs), which I normally obtain as surplus due to routine replacement in UPS equipment. Recently, this source hasn't been available due to the pandemic, and I find myself with one usable battery and two dead ones.

The two dead ones are reading 5V and 10V. Shaking the one reading 5V, it audibly rattled! Clearly, it wasnt as wet in there as it should be!

So, I thought i'd try and refurbish it! The lid of these is lightly glued on, and it was fairly easy to prise it of using a sharp chisel. Under the lid, the cells are closed off using pushed on rubber caps. These easily lifted off, revealing the plates of the cells, all but dry!

As it happens, I had a bottle of de-ionised water on the shelf in the workshop. Using a syringe, ive refilled the cells up to the top, and then gently sucked the excess out of the filler holes. This proved to be a rather messy job, so a roll of paper towel was kept handy to mop up any spills and splashes.

With each cell refilled, the caps replaced, and the lid put loosely back on, it was time to try it on the charger. For this, I am using my 'semi-intelligent' SLAB charger, and monitoring the current into the battery using a multi-meter. This showed the current rapidly ramping up! Ive left it for now as the current was passing 60mA and climbing. A check of the battery voltage showed it to have risen to well over 7V at this point.

Whether the battery will recover enough to be useful, who knows. Its certainly worth a try.

Now, one thing to note - I have added more water to this first test battery than required. There is a reason for this - I dont know yet how easily the glass matting absorbs the water. It may be that it takes several hours to do so. Supposedly, the correct amount of water is just enough for the matting to appear wet.  I will top up the second battery more slowly and observe.

The first battery had dropped to about 6.5V over the 7h since I stopped charging. On restarting the charge, the current input was up at 400mA and rising. The charger can supply 1.5A. As it is now daytime and I can keep an eye on it, I will allow it to charge during the rest of the day and see how it does. For safety, it is in a plastic box and covered with paper towels.

Off-Grid BOINC research computer proof of concept

Quite some time ago, after a mobile phone upgrade, I hard wired a Buck converter module to the battery terminals of a Samsung Galaxy S7, removed the SIM card, and left it crunching numbers as part of the BOINC project, sat in the corner of the shack powered by the main station PSU. In its steady operating state with no display lit, it consumes about 130mA, which is probably less than the operating current consumed by the big linear PSU powering it!

My plan has always been that my main BOINC contribution should be independent of mains supply, so, after a slight debacle involving a fraudulent sale on ebay of a 100W solar panel with 30A charge controller, which when tested was shown to be a 20W panel and the controller hardly built for 10A, I have a solar panel and charge controller with which to set up a proof of concept... and half my money refunded!

The concept is simple. The BOINC phone and its Buck converter connect to the charge controller load terminals, a 12V 7Ah SLAB to the battery terminals, and the 20W panel to, well, the panel terminals of course! Unfortunately, the only battery of this size I have remaining in an operational state is the one used to power the under stairs lighting! This has been borrowed temporarily. It will be replaced for the time being with a 25Ah beast that just happens to be doing nothing.

The whole lot is in a position where it will receive a decent amount of south facing sun through the day - on my eldest boys windowsill! He wont mind - its already covered in IT and computer parts!

Some tests on the phone showed a peak current at start up of about 450mA, and a steady operational current (computing but display off) of about 130mA. This with a fully charged and 100% capacity 7Ah battery should last several days. At full sun output, the 20W panel should be capable of charging a 7Ah battery in around 5h. So in theory, this set-up should be able to operate 24/7. Of course, this battery is not new and far from peak condition!

If it operates without shutting down in the middle of the night using this battery, then I can have confidence in it operating well with a better 2nd hand unit, which I will have to scrounge up another time!

NAVTEX Antenna repair - bypassed

The bypassing is now in place. A 100nF cap from pin 1 to pin 11 of the mixer ICs pads (remember that the IC isnt there!), this effectively connects the secondary of L3 to the supply rail. Since this system uses a combined power/signal line, that should now be feeding the receiver. A temporary link takes the other side of the secondary to ground. One leg of a 680 ohm resistor has been lifted to isolate the DC from the secondary, and a final temporary link jumps the missing L4 secondary to re-establish the DC supply to the front end transistors.

With the NAVTEX receiver in spectrum test mode, I can now see 'noise' where-as before this was totally blank, unless I put a finger on the supply wire. I can get a peak to appear on the display if I crank up a 518kHz signal from the Marconi 2955 test set. This is air coupled from a whip antenna, and had to be cranked up to about -20dBm output, but moving the antenna and its feeder around near the whip does suggest that the pick-up is by the antenna and not via the feeder or any other means. So far so good, but the proof of course will be whether it actually receives a NAVTEX transmission!

I have the station reserve receiver tuned to 518kHz as well to compare. Sadly, at the time of writing, were in a quiet part of the transmission schedules!

NASA Active Dual Channel NAVTEX Antenna Repair

Despite what the title says, its unlikely this will ever be a dual channel antenna again!

For a start, the PIC 12C508 IC, which provides the switching control and the local oscillator for the channel conversion, is not working. Whether it is just physically damaged but the code can be read, will have to be discovered. Even if the code will read, chances are that its been protected and cannot be used.

The mixer IC MC1496 has also been removed from the board. I have no easy way of testing this, so have to assume for now that it is faulty. Ive removed it to prevent any damage from causing problems with the rest of the circuit.

And so we come to L4 (as I have designated it). This is the output tuned transformer. And its knackered! I had noticed some corrosion under it, as there was with the PIC and the previously rotted off crystal. On removing it from the board I found that the fine wires of the primary had completely corroded away.

This seems at first a major problem, but in reality probably not. The frequency its tuned to is known, 518kHz, and its series capacitance also known, 150pF, so its a simple matter to calculate the secondary inductance needed, which is 630uH. Replacing it is just a matter of finding a suitable 10mm can transformer with that impedance secondary and the same winding configuration.

But for now, I have the trouble of bypassing all this to try and get the direct 'pass-through' 518kHz channel working. All the transistors tested out OK off board on their DC parameters, so hopefully its just a case of getting the supply to them and the signal from them!

The secondary of L3 is the problem. This would normally feed the mixer inputs, but also has a DC level on it for one of those input pins. So, I need to isolate that DC level from the transformer, provide a DC block from the transformer to the output/supply wire to allow the signal out, and temporarily ground the other side of the winding. I 'think' that I can isolate the DC by lifting one leg of one of the 680 ohm resistors, and a 100nF cap should work for coupling the signal.

NAVTEX Active Antenna

Ive finally come back to the antenna for the NASA Target NAVTEX receiver.

Ive mapped out the circuit diagram, and can now start working out how to fix it.

My suspicion of the lack of 518kHz was with the transistors, but ive had them off the board today and tested, and they check out ok.

Now, I know the PIC oscillator is not working. The original crystal was corroded, so has been replaced by one close but not exactly right. I would have expected it to work but give perhaps slightly off frequencies. I suspect that at some time the antenna feed has been reverse polarised, and this has killed the chip. It might well have killed the MC1496 as well.

So, the plan now is to remove the MC1496 and the PIC 12C508 from the board, plus lift any associated components that might affect the signal path, and see if I can get it working just on 518kHz, by bypassing the conversion circuitry. Im also going to remove the transformers and test them off-board to ensure their windings are intact, as some corrosion/dirt can be seen under one of them. Testing them on board is pointless as the DC circuitry is routed through them/across their pins.

If I can get that working, then I can work on the conversion side another time.