Friday, 26 February 2016

Another dissapointing ebay purchase

Well, seems im not having much luck this past few weeks!

This time its a Clansman coaxial downlead. Now, normally I would of course make my own up, but since this was available and i'd a few bob from sales, I decided to go for it, since as well as being authentic, it has the proper strain relief tie at the antenna end, something thats not easy to do on a homemade cable.

I made a 'best offer' which was accepted, and the cable came today, so far all very good. But, I dont accept goods until tested, so it was straight onto the analyser and dummy load, expecting to see a 50ohm, zero reactance, 1:1 match across the board.

Nope. VSWR 8:1 or higher, everywhere. Not good!

A check of continuity showed the center conductor open circuit, and the retaining nut on the straight BNC suspiciously loose.

It turns out its dry joint and hence has separated from the pin. Center to braid measured at this point, with the test load still on the other end, should have read 50 ohm 1:1 VSWR...

...but it STILL read open circuit!

Inspection of the right angle BNC revealed why - The cable has been pulled back, not only pulling the contact out from the center pin, making the center conductor open circuit, but pulling the dielectric clear of the fixed insulators. It was basically a toss up if this end read open or short!

So, on the whole im not very happy. I dont have time to mess about with such an item, so have plumped straight away to open a defective item case. Its also not worth sending back, as the cost in my time and fuel, plus postage, would equal the cost of the cable. And besides, its repairable. So i'd prefer a refund. Now, I dont want to be a total git, and im sure there was nothing untoward on the sellers part, but it was sold as in 'good used' condition, which in a cable I take to mean a bit scuffed and tarnished but electrically sound, it is a cable after all! Perhaps the seller couldnt test it, I guess not many sellers, even those regularly dealing in Clansman kit, have access to the sort of RF test gear I do! And im happy to repair it, so i'd be happy with a partial refund as a token recognition of the problem. I really dont like having to leave poor feedback for a small seller (the Far East merchants though are another matter!)

Just have to wait and see how this goes.

Some of the parts ordered from the Far East also came today - they will be getting tested later!

Monday, 22 February 2016

FM1100 repairs

Whilst testing the PRC-351 a few days back, I discovered that my faithful old FM1100 for 4m was having a few issues with bad wiring. Both the audio leads from the speaker connector block were frayed. As I inspected them, one of the audio wire pulled out of the radios main connector!

Ive now had time to strip back the connectors, and with a heck of a lot of jiggling and prodding removed the terminals. Its not possible to open up the crimping on these as they were very well done at the Philips factory, and without any spares, I will have to solder new connections to them in order to rebuild the system.

Saturday, 20 February 2016

Somewhat Dissapointed

Last friday, I took a punt on a 'spares or repair' Clansman PRC-320, which is to act as test bed and learning resource for developing the VFO controller. This was ordered for a not inconsiderable sum from a supplier I have used in the past and had no problems with.

Sadly, despite being supposedly on a 24h courier service, which meant it should have been with me tuesday at the latest, it is now over seven days and no sign of it at all. I had it shipped to my work address as well, which is manned 24/7 so no excuse at all for parcel companies to claim no one was in!

Not only has this set me back on the development timeline, but im also not entirely happy with the communications ive had from the supplier so far, having requested courier tracking numbers and not yet received them.

I appreciate that things do go awry in shipping, and so will not 'name and shame' at this juncture. However there is only so far I am prepared to go before lodging into the formal resolution processes. IF I havent received the radio by the end of today, then I will have to start that process.

Had this been a two quid device from the Far East with free shipping, i'd probably let it slide. But this is an expensive item, with expensive shipping, and only had to travel from York to Huddersfield!

Monday, 15 February 2016

Theremin build - As far as it goes for now!

Well, after storming ahead with it, ive now reached a point where I can go no further

The reason for this is simply that the remaining parts all need to be ordered in. They will probably be several weeks, as they make their way across the planet from the factories of the Far East.

Mk2 Theremin Build

Originally, about a year ago, I was commissioned to build a Theremin for a colleague. He paid me sufficient funds to obtain the necessary electronic components, and away I went to build a version of the Moog Etherwave.

Which wouldnt work. I can see now the likely reason, which is that the originally specified and now very hard to obtain inductors will have different self resonances than the more modern devices I used.

Anyway, rather than persevere with this design, I noticed a much easier to align version in one of the copies of Everyday & Practical Electronics that Steve G7TAO has given me. So, having found a supplier for the necessary IF transformers, and obtained a PCB from the publisher, im now well on the way with this build

A few other parts I dont have in stock, so have to order in, including very annoyingly a 7809 9v regulator, which I was sure I would have had! Most parts I have either as new stock or salvage. Some I can even salvage from the abortive Etherwave build. It is now effectively costing me money to complete the project, but in a way I dont mind, as id very much like to see not only a completed working machine, but also Daz's attempts to play it! And of course, I did promise to build him a working Theremin!

Clansman PRC-351 Antenna Connector

The Clansman PRC-351 VHF manpack is designed to be used with a 1.2m whip antenna, for which it has a special multi-angle antenna connector. Unfortunately, on my set, this is badly worn, such that the antenna will not stay up in position, but can overcome the position indents under its own weight and fall down.

It occurred to me that it might be possible to repair this internally, so today I removed it from the radio to open it up and take a look.

The above photo shows the dismantled antenna connector. The main boss uses a pair of plastic inserts that are pressed into the notches on the body by a semicircular spring clip. These inserts were worn almost flat on the face towards the body.

Turning them around and reinserting them, at first glance it looks like it will be a good repair. Next job was to brush out all the dirt, dust and powdered plastic insert!

With the connector cleaned, I reassembled it, and replaced it in position on the radio. A further task for the future will be to either replace or repair the antenna contact in the radio which is rather loose.  Reassembling the connector was a simple reversal process, making sure not to loose the little O ring or the two washers. If I was going for a full CES rebuild, then I would have followed the old soldiers adage of 'always grease your ring' when replacing the two O ring seals.

Sadly, after refitting the connector to the radio, it was found that the antenna will still drop from position if knocked or shaken too much. It is tighter than it was, but not sufficient to use the whip antenna with the radio on the back. Luckily, PTSNorfolk stock these connectors, so ive ordered a couple of replacements.

Two packages have just arrived, which despite their small size seemed to give the postman trouble getting through the letter box! One is the PCB for the EPE Theremin, which im building on behalf of a work colleague. The other is an Arduino Uno board, and a 'getting started' book, courtesy of Steve G7TAO, for Sam to use to learn more programming techniques. As Sam has a friend over to play today, im going to have a bit of a read!

Sunday, 14 February 2016

Clansman PRC-351 modifications

This morning I decided the -351 VHF manpack needed its first on-air testing under controlled conditions. So, with me operating the FM1100, I kitted Sam out with the radio. But, I also insisted he looked the part, so stuck my 95 pattern smock and my beret on him! Its always worth, as a parent, acquiring a good set of  embarrassing 'ransom' photos!

So with Sam on the -351, and me on the FM1100, we compared performance in both W (whisper) and L (Loud) modes.

In L mode the Tx from the Clansman is too low, and the Rx audio too high. In W the Tx mod is perfect, but the audio in the headphones is too low. It seems to be a good amateur set, a bit of modification will be required, to 'cross over' these settings such that at least one of them has good audio out and good Tx mod. This should really be quite easy, perhaps just a case of adjusting the deviation and the audio levels.

Thursday, 11 February 2016

Yaesu FT-290Rmk1 fault found

 Well, after all the testing, it turns out to be a common 'stock' fault, albeit showing itself in an unusual guise.
The external power socket on these is notorious for its internal switch contacts sticking and causing the external power to be fed onto the internal batteries. But in this instance, the contacts were shorting out the internal batteries when the set was switched on. Im not sure how exactly, but 'exercising' the contacts (by plugging the external power lead in and waggling it about) has solved the problem. It remains to be decided whether or not i'll replace the socket.

So, here she is, complete with leatherette carry case and shoulder strap, and rubber duck antenna -

Another FT-290Rmk1

Many thanks to my old friend and colleague Steve G7TAO, who has donated to me his Mk1 Yaesu FT-290.

Not only does this radio have a few of the ancillary items mine doesnt, it also doesnt have the USB carrier balance fault mine has! allowing me to get back on 2m SSB whilst mine is 'in the shop'. But it does have one odd issue

The radio works perfectly on external power, but not on batteries. On batteries, switching the set on shorts the pack, but also the pack never reads above 10v! This is despite the batteries being perfectly fine used in my set! Whats more odd, is that after briefly switching on and then off, I can watch, on my meter, the voltage work its way back up slowly! The power input socket seems to be good. Im starting to suspect something strange like one of the protection diodes is at fault.

Tuesday, 2 February 2016

Mobile USB power

I have a dashcam DVR. Its mounted, as the law requires, behind the rear view mirror, at the passenger side, and not impinging on the area swept by the wipers too far. Its set to start recording automatically as soon as its powered, which up until today was when I pushed the USB adapter into the fag lighter socket. This arrangement is far from ideal, not least because the power cable just hangs about loose.

So today, I installed a 12v to 5v 3A USB power converter, using a clever little gizmo that allows you to add an extra fused connection into the vehicle fusebox by replacing a fuse with this device. I chose to pinch a connection from the front windscreen wiper supply, which I knew was an ignition switched circuit. This is a 20A mini blade fuse. So, pulling that fuse and installing it instead in the lower socket of the 'Add-a-circuit' fuseholder, a 5A mini blade fuse in the upper socket, and plugging the whole assembly into the original fuses place in the fusebox, and I had a 5A switched 12v supply.

The microUSB power cable to the cam was fed up and under the headliner behind the courtesy light, across to the passenger side door pillar, down inside the trim, and behind the glove box - which happens to be where the fusebox is. The DC converter blocks +ve wire was crimped to the new fuse units output wire, and the -ve, fitted with an eyelet crimp, bolted to the chassis metalwork.

Now, this power block came with a standard USB socket as its output connection. So, a section of the outer jacket of the cable was removed, exposing the two wire cores, to which the USB lead for the cam, now cut and with the cores bared back, was attached using two 'snap-in' insulation displacement connectors. I was a bit dubious that these would work with such thin wire, but on powering up all is well. The camera starts up when I start the ignition, and shuts down when I kill the engine.

The original USB connector - well, using a Stanley knife I cut out a slot in the plastic of the fascia between the glovebox and the central column of the dash, and now have a switched 5v USB port for charging my phone or Kindle!

Following on from yesterdays work on the Clansman LiPo battery, all that remains is to mark it up in such a way as to make it obvious its not a standard battery and must not be charged on a normal charger.

So, here it is swathed in masking tape ready for spraying. Whilst purchasing the automotive parts for the job discussed above, I also picked up a can of scarlet red spray paint. The top cover of the battery is going to be sprayed red, along with a one inch wide stripe right the way around the battery case.

Monday, 1 February 2016

Clansman Lithium Polymer battery conversion finished

With the Zippy 4000mAh 7s 28v Lithium Polymer battery, the charging port, the low voltage alarm module and the temperature sensor all already installed into the alloy case, all that was left for me to do today was pack the remaining space with foam, and attache the lid.

Rather than glue nuts to the inside of the lid, at the risk of them coming loose and at worst case shorting the battery, I used impact adhesive to secure a pair of softwood runners inside the alloy lid. Into these, through the fixing holes, ive put in eight small woodscrews. I would have preferred small domeheads to the countersink heads these have, but they will do.

All that remains now is to add the several bright red or yellow safety warnings! Its absolutely essential that this is not confused for a NiCd pack - if charged improperly, this is essentially a neatly packaged incendiary bomb! Charged properly and handled correctly, its a damn sight lighter to carry than the NiCd beside it in the picture!

The NiCd pack weighs 3.4kg. The LiPo pack weighs 1.12kg.

Put that into perspective when walking the hills with the PRC-320 - the weight difference is 2 1/3 liters more water!

Another slice of PI

Prompted to get off my arse and do some work by a fellow detectorists progress on his Surf PI, Ive spent some time today getting the project a little further on.

The first task was to piece and drill the holes for the controls, and to create the hole pattern for the speaker. One of the controls (the sensitivity) has a bit too long a shaft but i'll decide whether or not to cut that down at a later date. The loudspeaker is not yet secured, there will be a layer of mylar film between it and the holes. The speaker holes are all 2mm, which will help against most splashes.

With the batteries installed and the coil connected above. Ive used twin shielded loudspeaker cable, which I just happen to have lots of.Only one core is used, giving a spare should the cable be damaged. This extra length of 'floating' copper doesnt seem to have any detrimental effect.

The test bed setup is shown below. In this configuration it 'see's' a small jubilee clip at about six inches, and a small pair of long nose pliers at around 8inch. Oddly it doesnt detect at all a two inch long phosphor bronze heatsink retaining clip! Must remember to try that against the Ace 250!

The final photo here shows the unit fully boxed . The next job, once the speaker is secured, will be to build a shaft and mountings. Once thats done, I can decide on a coil housing and a final coil.