Monday, 6 July 2015

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

Thursday, 25 June 2015

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!

Sunday, 10 May 2015

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

Thursday, 23 April 2015

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 -

JustGiving - Sponsor me now!

Saturday, 18 April 2015

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!

Friday, 17 April 2015

FT-290R-mk1 Battery Compartment repairs

 If im going to use my venerable 'Electic Handbag' for SSB comms during our Lyke Wake Walk, then I need it to be working on its internal batteries.

Unfortunately, the battery holders are corroded. So I need to replace them.

Incidentally, If you enjoy this blog, please take a look at the link beside for our Lyke Wake Walk blog, in support of MAG. And then please click this link and donate!

JustGiving - Sponsor me now!

The terminals of the original battery holders have corroded badly in places, with one of the positive terminals completely falling apart.

The old holders are just held in place on the carrier with a sticky tape. Once removed, the new ones can be fitted

The new ones are very slightly longer, but I dont think it will be a problem, perhaps a bit of filing might be needed. One modification that is needed to them is to reroute the wires so they pass out the holder lower down, in order that they match with the holes in the metal carrier. Luckily there are slots in the holders where I can do this.

Monday, 13 April 2015

Inside Cheap ebay PP3 Batteries

Well I think this should serve as a warning to anyone looking to obtain bargain rechargeable PP3s!

I took a punt on a pair of these on ebay from a Honk Kong seller. Now, I buy a lot of stuff that way from the far east, and on the whole its good kit, but there are rogues out there and conterfeit stuff does turn up. These batteries are in that league!

Marked as 'BTY' 300mAh 9v Ni-MH batteries, when these arrived I thought they were amazingly light. Suspiciously light in fact! They weigh in at just 25g, whereas an alkaline PP3 weighs 35g!

So I decided to open one up and see what was in it.

At first glance it looks quite good, but the giveaway is in the spec of the cells!

The are NiCd's! So, these so called 300mAh NiMH batteries are not even the right chemistry!

Also, they are '60K' series cells - rated 18mAh!

So, quite clearly fraudulent on many levels! I dont know yet whether I will raise a case with ebay over these, but maybe think twice if your considering buying these.

A night in the cells

Yesterday I visited, for the first time, the Norbreck rally in Blackpool, taking the family along so they could have a day out riding trams and on the beach. I took a shopping list of just a few items I required,

Well I didnt get any of them! And the rain and wind meant that the kids never got on the beach, nor did I, and I was looking forward to a bit of metal detecting.

I did however meet a number of the other SOTA activators, and got, finally, some replacement cells for the EBP-16N 7.2v pack for my Alinco handheld. These are 2500mAhr 1.2v NiMH 'hybrid' cells, a substantial improvement in capacity from the packs original 700mAhr rating!

Re-celling battery packs is not something I enjoy, its hard work, awkward, and fiddly.

Above is the open pack, showing its innards and the card tubes that held the old cells. These new cells are either a fraction wider, or the tubes have shrunk, either way they wouldnt go back on and have been discarded after I checked there were no places the cells could short out. Most fiddly was getting the bimetal resettable fuse to fit correctly at the top of the pack.

And this is the finished pack beside my venerable Alinco DJ-F1E, the mainstay of my SOTA operations. It isnt pretty, but the tape can be removed to repair the pack much more easily than if I glued the pack back together!

Planning the SOTA side of the Lyke Wake Walk ( Why not support us? ) I also discovered that the terminals of the battery holders in my FT-290mk1 are corroded. So next job, when the new ones arrive, is to replace the holders within the Electric Handbag to hold the 8x C size 4000mAhr NiMH cells.

Saturday, 11 April 2015

Lyke Wake Walk 2015 - June 28th

Ok, so now a blatant plug for my charity!

As well as radio, Im an avid hill walker. I am also a staunch opponent of the use of indiscriminate weapons, such as antipersonnel landmines and cluster munitions. Therefore I support the charity MAG (Mines Advisory Group) who provide landmine and unexploded ordnance clearance, weapons disposal and education and awareness.

You can read more about the work of MAG here -

At the end of June, myself and Bob M1BBV will be walking the long distance path of the Lyke Wake Walk, a 40mile challenge walk with 5,000ft of ascent across the North Yorks Moors, in under 24h. Oh, and well throw in a couple of SOTA activations on 2m as well! Details of the walk can be found here -

As well as becoming confirmed 'Dirgers', we hope to raise lots of money for MAG. This is where you, the reader of my blog, can help!

If you've enjoyed reading my musings on here, please support myself and Bob on our challenge! You can donate via our JustGiving webpage -

And, so you know who your supporting, here we are! -

Me, Martin G7MRV

 Bob M1BBV

Please help us out with whatever you can!

Saturday, 4 April 2015

PI and Pixie

A week or so ago I ordered, off ebay and from China, a kit for a 40m Pixie transceiver. This was a tad over £3 including postage! I cant source the parts for that, let alone etch a PCB. This kit came with all the parts and a proper through hole plated, conformal coated and silk screened board! Could it be any good for that price?

Well, heres the kit before assembly

The instructions were no more than a components list, circuit diagram and board layout, but hey, what else do you need? All the connectors were supplied, BNC, 3.5mm jacks, and a DC socket for the power. The crystal is on 7.023MHz, which is a bit unusual for a QRP job, but I can soon change that if needed from stock.

I proceeded with assembly starting as you should with the resistors

The next photo shows the board with all the passives and the diodes fitted. All the parts were there, in fact I had several ceramic capacitors extra!

The completed board, the two transistors being the last parts fitted. The only oddities I noticed were that the sockets all fitted on with a very slight angle, clearly a slight error in laying out the artwork for the boards onto the processing machine, but also that all the tracks were on the 'component' side! This could be some technique for minimising instability, although I suspect someone forgot to invert the artwork!

Once populated, I tagged a PP3 clip onto the board, attached the antenna connector to my QRP power meter (rated 2W fsd) and with a spare jack plug shorted the key contacts

Thats around 600mW by my reconing! Not a bad output for a couple of small signal NPNs. With the Pixie connected to my doublet via the ATU, and a crystal earpiece, several CW transmissions can be heard. Theres no side-tone, but I think this will prove to be a fun little rig.

Ive also found time today to do some more work on the Surf PI metal detector. Ive added all the controls, and started testing. The coil I had produced is, it seems, far too low inductance. The unit just wouldnt behave with it. So, I quickly threw together a new coil of 8 inch or so diameter from enameled copper wire, stuck it with masking tape on the end of a fibreglass rod to get it clear of any metal, and connected it up. Its performance was poor, but at least I could detect a coin with it at about 6 inch. On measuring it showed to be too high an inductance at 410uH. A few turns off and I have a 27t, 310uH 2.4ohm coil for testing.

 The buzzer that comes with the kit is ok, but ive swapped it for a small 1.25 inch loudspeaker, which is a little less harsh in tone. The offset control zeroed fine, and the pulse waveform looks roughly how it should on the oscilloscope. The Delay control doesnt seem to have much effect though, I suspect because the coil isnt properly damped. The next step is to rig an adjustable damping resistance, and properly match the coil and damping resistor.

Ultimately, instead of the damping resistor thats included on board, I will fit the matched resistors into the coils themselves. That makes it possible to change coil for different sizes and purposes, such as a huge coil for really deep searching, or a tiddly little coil for pinpointing.