Finishing a few off

Dissapointingly, no parcels arrived today from the Far East, so ive had no new bits to get excited over. I decided instead to finally get a couple of projects boxed up and completed.

First up was the little Chinese 40m Pixie. In the finest tradition of QRP minimalist radios, this got built into an Altoids tin

because of the clearances needed for the sockets, it wasnt possible to have the lid open as it originally did, so this has been removed and the 'hinges' flattened down, it now just clips on. There is space when open to slot a 9v PP3 battery in the tin to power the radio.

Next, was the 40m Sudden-2 kit from Kanga that I helped Sam build a couple of years ago! I had been looking for a suitable box for it. The case selected is a re-purposed Tvonics Freeview Set Top Box case.

The front has a sort of wave shape, but I think it looks quite groovey. I havent bothered to cover the back over, so theres still lots of cut-outs for SCART connectors etc, but some of the other holes have been pressed into service for the power and antenna connectors.

 The only problem was finding some knobs for it! I have a box full of knobs, but couldnt make up a matching set! Either they were of a type that will not secure to the shafts of the controls used in the kit, or they were missing their grub screws. Just where the heck have all my grub screws gone?
Coverage is about 7.05 - 7.15MHz. Sensitivity seems low, -75dBm ish for a decent sound, so will have to check that out. But, I think it looks alright

Other than that, the only other stuff done today has been more of the laser comms circuit mock up. The top section of the breadboard is the 555 timer sawtooth 40kHz generator. Below is where I have started to mock up the 741 op-amp based microphone amp.

The module beside them is a DDS module. When I finally work the pin-out out, this and an LCD module will be mocked up with a PIC chip to create a DDS VFO. I really should get that LCD sorted!

Old and New

Today has been a bit of old, and a bit of new, as far as radio work goes. I slept in very late, and eventually pottered into the workshop. First up, I decided to finally take a look inside this

 

 I salvaged a couple of these that were being junked, because the cases are nice aluminium extrusions, a new panel each end and they will make great project cases. Inside, theres a few nice bits, a bargraph LED block, some SIL resistor packs in sockets etc. Nice to see Zilog Z80 series chips again! The PCBs, once ive had any bits useful to me, will probably go in the 50p a go bucket at Finningley Rally.

Something else that ive been meaning to get around to doing is testing this MSF clock receiver

This was salvaged from the skip many months ago, probably years now, and its original case re-used as the housing of my Dekatron Spinner! I finally decided to actually power it up a few days ago and see if it worked, which it does! Next step then is to see if I can get it interfaced to something that can decode the time from it. It has only a +ve and -Ve connection - the signal pulses are output by pulling the supply line low. Im going to see about using a PIC to decode it, but Sam has also agreed that a Raspberry Pi might be the best way for him to learn programming, so ive given him a challenge to interface it to his Raspberry Pi (when I get him one)

 Also in the old list, Some time ago I got an old discone antenna from an ex-colleague. It had been up on a chimney for many years. The elements are bent, the feed open circuit, and very badly corroded and tarnished. Today I dismantled the feed section, and using a wire brush wheel on my drill press, removed the rust and corrosion.

 Now, with a new nut on the top, the feedpoint connections are all good again. I need to find a blind 'dome' nut and a suitable spring washer to suit, and I still have the 'cone' elements, which are aluminium tube, to straighten. My thought is to mount it on the workshop roof to give me a usable test antenna.

On the subject of antennas, I built the 4:1 balun today needed for the Cobweb antenna. This was a kit from Les at Amtools. I need to find a suitable box to mount it in now

The plastic case for the component tester also arrived today from China, so that is now built into its own box with three crocodile clip leads coming out of it. I managed somehow to mess up the measurements for the holes in the case for the LCD contrast adjust and the DC input, so these dont line up. I also couldnt find a button that would operate the power switch, so thats been removed and a SPST toggle switch mounted instead. At least now thats a nice convenient little test box, not an exposed PCB.

I also got around to testing my 80m ARDF beacon transmitter! The ATU is working correctly, but the NiCd battery pack went flat very quick, so I need to charge it up properly and redo the test.

The only other thing done today was to mock up on breadboard the 40kHz sawtooth generator circuit that will form part of the PWM modulator for the laser communications unit. This is only a simple 555 timer circuit and was very quick to get up and running, although my old oscilloscope took some time to become stable and not do silly things whilst displaying the waveform. I cant mock up any more of the circuit, as im still waiting on the comparitor ICs. 

My last chicken, Talullah, died a few days ago. She was very daft, more like a dog than a hen, and would follow me about. She was particularly fond of getting into the workshop and falling asleep on the bench

Hanging on the telephones

Actually, despite the title, the telephones in question here are somewhat before the era of Blondie!

The vintage high impedance headphones I purchased arrived today. They are in surprisingly good condition considering their age, and the repair mentioned in the sale listing is actually quite well done. Theres no fabric on the headband, but the fabric covered cord is in good nick. They are marked BTH BBC.

So far, I have tested these using a meter on the resistance ranges, the small current causing them to crackle - and I can hear that crackle in both 'receivers'. I cant read the resistance though, I suspect because my meter is rubbish! But, I can hear noises from them, which is what they are supposed to do.

Next trick is to get some audio into them, but I want to protect them from excessive DC (the winding wire is very thin!) so will rig up a small audio transformer to feed them.

Im hoping they will work nicely with the Pixie transceiver. I'll see about that tomorrow.

Frog complete, ready to test

 Carrying on with the Chinese 'Frog Sounds' CW transceiver build. Finding a bit more spare time, the next stage was to fit the capacitors

With these installed, I moved onto the semiconductors, and the rest of the parts.

 At this stage it was all but complete. The only parts not installed being L4 and L5. Ive left a little clearance above the PCB for the crystals, which I would normally install flush to prevent microphony, but the solder pads on the component side of the board looked a bit wider than the insulation around the pins, so I didnt want to risk them shorting out.

L4 and L5 proved to be a little more problematic. The paperwork that came with the unit states that these are 1uH and 22uH, but neglects to say how many turns, and which is which core! Thanks to members of the G-QRP club, and in particular Andy Cutland, I found out they are 11t on the ferrite toroid for L4 and 16t on the T37-2 toroid for L5.

A word of warning for those of you building one of these and used to the easy life of the western coil winder - the wire supplied is NOT self fluxing! I had to scrape of the enamel which is a delicate job. But, the coils are now wound and installed. All that remains is to test the unit.

As usual, it seems, with these Chinese Kits, Ive a lot of 'spare' parts left over! Lots of extra resistors, ceramic capacitors, probably three extra lots of the electrolytics! Plus the odd diode and a 2N7000 MOSFET. I notice its never the NE602s the put extra of in!

 Back to the subject of LASERs! -

I have on order a pack of ten 1mW 650nm Red laser modules. Well, I now also have a project for them! Im going to knock up a simple voice transmission link with them. Using a 555 timer and some op-amps and comparitors, it seems i should be able to use PWM (Pulse Width Modulation) at 40kHz, to create an amplitude modulated laser voice link.

My green laser pen that fell to bits I dismantled. Unfortunately, although the big brass block acts as a heatsink, this makes it hard to solder a wire to, and in doing so I over heated the module. The laser chip is fine - but I melted the plastic lens in the laser diode housing! It still works, but the beam is a tad divergent now!

Frivilous Purchases - Frikkin' LASERS!

I really shouldnt buy electronic items as a way to keep alert during night shifts!

A new 'violet' laser pointer, plus a pack of TEN 650nm laser diode modules...

I have NO need for them! But, ive been watching them for months and finally couldnt resist!

Less frivilous, ive also purchased, a pair of vintage high impedance headphones, for use with crystal sets and the little pixie type minimalist radios, and various items for finishing off other projects.

I dont intend to buy anything online tonight, as ive to go to finally collect a sextant in the morning. But I will be ordering out - probably a big filthy, dirty kebab!

Building the Frog Sounds v.3

 This little kit arrived a few days ago all the way from China. It is a 40m CW Transceiver, based around the NE602 plus a few other bits, and is supposedly capable to kicking out up to 3W.

All came reasonably well packed, although as usual the instructions are machine translated from the Chinese and next to useless! Most of it can be worked out easily enough, although two toroids that need to be wound have no turns information!

 Here it is next to my previous little Chinese transceiver kit, the Pixie. This one also has the odd quirk that the sockets all fit with a couple of degrees angle to them! Here its just mocked up -

All the resistors are 5-stripe types, which I hate trying to read, so ran the ohmeter over them all! They are as usual all vertical mounted. They are all fitted in this photo, and theres a lot extra left over! I suspect they are so cheap that so long as the minimum number are included they dont care how many more you get! All spares for me I suppose.

And, finally for today, with the lower profile sockets, IC sockets, and fixed inductors installed

There does seem to be some debate as to whether this is the same as a '49-er' kit, Ive no idea myself, never having built nor seen a '49-er' before!

Ive also just ordered a plastic case for the component tester I built some time ago - this is easier and probably cheaper than trying to fabricate one!

I also couldnt resist ordering a AM/FM broadcast portable radio kit! This is an old 1980's style analogue tuning radio which I fully expect to perform to its price! But hey, it'll be a bit of fun to build when it gets here.

I must get around to boxing up the Pixie and the SurfPI as well

Modernizing Hand-held Battery Chargers

Many of us have an old handie, usually for 2m, that we love. One thats served us well over the years and whos features and ergonomics suit us. For me that device is the Alinco DJ-F1E.


Over the years ive had many handhelds. My first was an Alinco KT-22, a copy of a venerable Icom design and set to frequency using thumbwheel switches. This unit was stolen off my belt outside Doncaster market. It was a big chunky beast, and whilst outside a B&Q store was once asked by a fellow if he could 'borrow my phone' - this was back in the days of TACS analogue mobile phones!

This was followed, after some playing about with a UHF Icom mobile at the start of the UK 'novice' era, with an Icom dual bander, W-21A I think? Not a great radio and this eventually passed on to my protege Bob M1BBV. I then got an Alinco DJ-S1E off of Martin Lynch's stall at Drayton rally one year.

I loved the S1, but it had one drawback - no DTMF! It also had very few memories. But both were upgradable. In time, I added the keypad and the memory unit. I then sold it.

Now, after owning and selling several, im on my third F1E. The F1 differs from the S1 in that it comes with the keypad. Ive since upgraded it with the addition of the CTCSS/DTMF codec and the memory module.

But this brings us back to the big problem - batteries. Over the years, the NiCd packs wear out and fail. Battery technology advances, and when you come to re-cell the pack (quite easy on these) you can no longer get the same capacity cells. Usually not a problem, as the bigger cells just need a little longer to charge. The Alinco stock slow charger is 70mA, although mine runs at 80mA.

This is fine if you've re-celled with say 800mah, over the original 600mah. But, I found  a deal with a fellow SOTA activator for 2500mah (2.5A!!!) Hybrid NiMH tagged cells. The stock charger would take over 50h to charge these, and risks serious damage from overcharging.

So whats the answer? No stock charger for this handheld could cope, and are all very expensive. No 'intelligent' consumer charger can be used as they are tagged cells in a pack, not loose cells.

I then came across a little known aspect of the rather bizarre sport of 'Airsoft'...

For those not familiar with this, Airsoft is an odd activity in which realistic looking plastic guns are used to shoot 6mm plastic balls at people. This is a game enjoyed by people, seemingly all boys, dressed in excessive amounts of surplus kit, using illegal comms in no particular correct manner, all of whom seem to be either built wider than they are tall and with a prediliction for  cake and chips, or overtly macho of the type invariably seen on Ripon station waiting for the train home on the evening of the first day of basic training, or more commonly - at the end of the first day of selection weekend. All strive to cultivate a 1000yd stare and rarely extend their visual range beyond a couple of feet. They pop up all over technical, ammunition and forces forums asking deeply involved questions that they could answer from a copy of 'Soldier', or making comments in threads which demonstrate their complete lack of service/understanding/IQ.

In fact, it seems they cannot be trusted to know what size and voltage battery their gun takes!

Now this leads to a great opportunity! Their battery chargers are cheap, intellegent, automatic. Fitted with a generic model plug, they connect to any NiCd or NiMH pack between 4-10 cells, automatically set the voltage and use deltaV monitoring to asses state of charge and turn off point. At just about £12 inc. postage, I opted for a VapexTech VTE500P. Sold as an Airsoft charger (or, oddly, a model charger for a couple of quid more!), it came with a short adapter cable from the normal model connector to a mini version, which I decided to sacrifice, as I have no need for it, to provide the connections to the Alinco charger.

The idea was simple - remove the power pack and cable from the Alinco charger stand, and replace it with the adapter cable. This done, the next step was to bridge over the current limit resistor in the housing that allowed the stand to be used with the different voltage packs, as this is now done by the new charger. Simples.

Now, the charger will sense for itself whether the pack is the 12v 800mah, or the 8.4v 2500mah. And instead of 50h and the risk of serious overcharging, it will handle the big capacity pack in around 5h, and the little one in about 2h!

And, just in time for the big walk!

Pack Antennas

One of the problems that need resolving for the Lyke Wake and GB0MAG, is the antennas. We need something that will give good performance, increased range, but also have no impediment to access to our packs, or any risk of snagging on anything, or causing any obstruction to either us or any other walkers. It also must have the absolute minimu of weight!

As the radio to be used is a handheld, this will be secured on one of the chest straps of my pack. The radios own rubber ducky antenna would be far from ideal. Directly mounted better antennas such as my Super-rod-2, would be wildly inconvenient, in fact, bordering on dangerous! So, what is needed is an antenna solution that mounts to our Bergens, high enough to give a good 'field of view', but effectively out of the way.

What looked promising was this W6JJZ 2m Bicycle Antenna - a variation on the J-pole. So, I set about building one

The first thing I had to do though, was find out what the velocity factor was of the coax I intended to use! Luckily, this is something that can be done with my antenna analyser. I did find it a bit tricky at first, until I remembered to add the series 50 ohm resistor!

With the velocity factor found, about 0.66, the next tricky part was the matching stub. Unlike a standard J-pole or Slim Jim antenna, this design turns the matching section away from the bottom of the antenna, and out to the side, forming the section from a coax stub. Fabricating this proved a bit tricky

The lot once built was taped to a couple of top sections of telescopic fibreglass tube, and tuned up. The short required in the stub was created during testing by pushing a dressmaking pin through it to short the inner and outer. It was found that this short is the primary adjustment, and is quite crucial, a few mm either way equating to a MHz or more! Final fina adjustment was made by trimming the radiating element.

The photo below shows the first build, ANT1, attached as for field use to my Bergen. Tests on this one, which has the tuning stub sticking out at right angles, showed 1.5:1 SWR points at 144.6 and 146.6MHz, with 1:1 and indeed resonance (X=0) occuring once adjusted in the FM portion of the band, just where needed. On-air tests showed a 7- S-point improvement over the radios own rubber duck antenna at the same height.

A second build, ANT2, was tried. This was specifically constructed to remove the various joints in the first version, and to run the stub parallel to the feedline, meaning there would be nothing sticking out (the stub is only an inch and a half long anyway!)

This second build proved more difficult to tame than the first. The parallel stub seems responsible for greater body capacity interactions, probably as a result of common-mode currents. A pair of TDK snap-on ferrites solved this, but made the match more critical. On-air performance was the same as with ANT1.

The bottom of the fibreglass mast has a dowel  inserted and secured with filler. This engages with the eyelet tag at the base of the pack to secure the mast.

It is known that one of the issues of this design (the J-pole) is common-mode, due to the absense of a true ground return. The ferrites used on ANT2 act as a choke, preventing these from flowing. Its likely that the wide bandwidth of ANT1 is a result of the common-mode currents and the aparent lack of interaction due to the longer feedline length acting as a counterpoise. This would be a concern if the antenna was to be used in a more RF intense environment, or where RFI is an issue, such as built up areas. But these antennas are for remote field use. On-air performance, and in particular performance from mountain top and ridge line, if of much greater importance, and will be tested i na  couple of weeks on a SOTA.

Oh, and my LiPo batteries have eventually arrived! Ive also aquired a control box for the rotator, so I can now see if that is workable. If it is, It can go up and have the 6m beam on it, and perhaps also a 4m Moxon

On the slow boat from.... Sweden?

In order to power the Surf PI metal detector, I decided to follow the advice of another builder and purchase a set of Lithium Polymer batteries and charger, from a reliable* Far East online supplier. All seems reasonably well, apart from one small issue - it seems the customs in whichever part of the Far East these were due to ship from are going rather overboard in interpreting ICAO shipping regulations and wouldnt let these get on a plane!

So, I received an email stating that the tracking number had changed. Logging in, and finding a guide to interpreting the tracking numbers in order to go to the correct webpage to see the process, I find myself taken to the website of NordPost! It seems my batteries have been rerouted to be dispatched from Sweden of all places! I can only assume that a large shipping container full of these batteries made its slow way around to Scandinavia some time ago, and that my cells are even now making the steady journey across the North Sea!

To increase my frustration at the shipping delay, the battery holder for these cells of course did pass customs, and arrived today by airmail!

Onto Lyke Wake Walk preparations - After sorting the batteries in my FT-290R mk1, I found that the S-meter, was almost but not quite pegged on transmit on USB. Putting the rig onto the test set showed 2w output power with NO modulation! FM worked as expected, and LSB was also fine. Hmmm, looks like a case of bad carrier balance! Indeed it was, and a steady adjustment to VR1001 had the set back into spec. It was then I discovered that the PTT switch was intermittent as well. Some liberal Servisol (other switch contact cleaners are available...) and that was also fixed.

However, after weighing up the pro's and con's, quite literally, weve decided FM only is the way to go for the walk - the FT-290 weighs 2.5kg with batteries, the Alinco DJ-F1 - just 450g!

Please click the link to the right and take a look at our blog for the Lyke Wake Walk preparations, and please, feel free to sponsor myself and Bob M1BBV, by clicking here -

Drastic Modifications

It turns out that the couple of millimeters extra length of the new battery holders for the FT-290Rmk1 actually do matter! They didnt fit the carrier without bending it, which of course is out of the question, because then the carrier wouldnt fit back in the radio.

So I trawled the online suppliers looking for replacement replacement battery holders, two millimeters shorter. The only ones I could find were twice the price of the ones I had, and didnt look like they would survive a stiff breeze!

Faced with the possibility of a long protracted and expensive hunt for suitable battery holders, or even less likely - Yaesu originals! - I started to reason the problem out, like this...

The PLASTIC battery holders fit into a STEEL carrier.
The TERMINALS are at either end
The PLASTIC in the middle only keeps the batteries off the carrier

In other words - the  main body of the holders is just there as a guide and insulation for the batteries, it contains no electrical parts, and when installed in the carrier, has no mechanical value either. So, since the carrier provides all the mechanical support, whats to stop me simply cutting the holders in half, shaving off the extra length from the middle, and putting them back together within the carrier?

This is exactly what Ive done -

Clamping the holder in the workmate, I brutally amputated one end with a ripsaw. This took about a millimeter out, then, with the aid of side-cutters, I shaved another millimeter off one of the halves.

One relocated into the carrier frame, the cut is irrelevant. A little polystyrene Q-dope into the gaps and they are once again complete holders.

I also took the opportunity at the same time to replace the aging insulation tape between the carrier and the regulator PCB, with modern cloth based insulating tape.

I have yet to test the new holders, as im waiting until the dope is completely cured.

UPDATE - Carrier refitted and secured, NiMH 4000mAhr C cells installed, and lid replaced. Radio powering up and working on internal batteries. Job Jobbed!