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 -

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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.