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Under construction

Due to the problem with commenting I am reluctantly moving this blog to a new template. This will probably take a few days – especially as I will be going to hospital on Tuesday – because a lot of trial and error will be involved (more error than trial I dare say.)

Please bear with me while I make changes, try different graphics and so on. Normal service will be restored as soon as possible!

The final over

Less than three weeks ago I wrote of having a bit of a headache. Since then, a lot has happened. I went to hospital in Newcastle, where it was discovered that I have a brain tumour. I was going to write about all of that in a bit more detail but things didn’t turn out quite as I hoped they would.

Read the rest of this entry »

Off-air frequency standard

This is an unbuilt kit for an Off-Air Frequency Standard from Spectrum Communications. It is a crystal calibrator phase locked to BBC Radio 4 on 198kHz with an output of 2V peak to peak at 10MHz.

I got this with the intention of using it to frequency lock my Elecraft K3 using the KREF3 module. Regular readers may remember that last year I purchased a surplus Efratom LPRO-101 rubidium frequency standard to calibrate my radios. But a rubidium frequency standard has a finite life which will be used up very quickly if it is turned on all day to use as a real-time frequency reference. My intention is that the off-air frequency standard will run all day and keep my K3 as accurate as I need it to be.

I ordered the full kit from Spectrum. I was disappointed to find that what looked like a die cast box in the picture is actually a plastic box with a grey metallic finish. If I had realized it was not a die cast box I would probably have opted for the cheaper PCB kit and ordered one of the nice extruded aluminium alloy Hammond cases for the project. I hope it will be RF-proof enough to work in my shack environment where up to 100W may be used into indoor antennas.

The other disappointment was the rather home made looking PCB which does not have a silk screened component overlay. There is a printed layout in the instruction sheet but relating the component positions to the holes on the PCB is easier said than done. My initial thought was that I am not going to be able to build this. What I will have to do is draw the component overlay on to the PCB itself prior to construction. But it isn’t easy with my diminishing eyesight and need to use different strength lenses which makes switching between things at different distances a real trial. Having a silk screened PCB would just have made things a bit easier. I think my days of kit building are definitely numbered.

Kenwood TM-D710 firmware update

According to Bob Bruninga WB4APR, Kenwood announced an update to the TM-D710 firmware at Dayton. The changes are:

– INTERRUPT ALWAYS: always displays information about every packet received on screen for a few seconds, not just packets from new stations.

– INFINITE: extends the above to retain the information about the last heard packet on screen.

– MY PACKET: now displays the actual digi path used when your own packet is digipeated so you don’t just see that it was digipeated you can see which digipeater.

– TOP button: LIST display inserts new entries at the top so no need to scroll down.

– HEADING/UP: you can toggle the compass rose to North-UP or Heading
UP.

– PREVIEW of PHRASES: When selecting phrases you can see a preview of
first 9 bytes.

– READ/REPLY keys come up when a message is flashed on the front panel

– OVERLAYS: You can now select overlay characters on any symbol

– TOTAL hops can be set as low as 0 instead of 1.

– Auto-Powerup-Time set (if GPS is connected and is locked)

The update also contains some bug fixes. It does not include support for item-in-message or any other previously unsupported APRS features. 🙁

At this time the update is not yet available for download from Kenwood’s website.

No charge

The object on the left of the picture is a 9600mAh external back-up battery for MP3 players, mobile phones and other 5V devices. I bought it on eBay (where else?) for $55.99 including shipping with the intention of using it to power my HTC Touch Pro smartphone so that it could run all day using GPS and internet connected apps like the APRS client APRSISCE. Previously I hadn’t been able to make much use of such applications when out and about on foot because if I was away from a power supply for more than a couple of hours the end result was a dead battery and a phone that could not be used to make phone calls.

The product arrived after a couple of weeks wait rather poorly packed in a jiffy bag containing the battery back-up unit, a 5V USB charger with the usual two-prong fold-out mains plug, and a USB cable with coiled lead and interchangeable power connectors. There was no box, nor any instructions so I had to figure things out for myself. Clearly the DC IN port was meant for the charger, the USB socket marked DC OUT was the output and the slide switch next to it turned the output on and off. The four LEDs showed the battery state for a few seconds after the POWER button to the left of it was pressed, and the charging state whilst charging.

There was no cable for charging, so I presumed I had to use the USB lead supplied for output and one of the interchangeable connectors. One of them did fit, though not very well, poorly enough in fact that it pulled out of the socket if there was the slightest tension on the coiled cable.

I started charging the power pack. Two lights lit up on the charger and the charge status showed two of the four LEDs lit. Next time I looked at it all the LEDs were off. Surely the batteries could not have charged so quickly? Eventually I measured the output from the charger and found it was about 0.25V. Clearly the charger had failed.

I sent an email to the eBay seller who was anxious enough about the possibility of receiving negative feedback to immediately promise to send a replacement. Meanwhile I found that the charger which came with my HTC phone had a USB output so I charged the battery pack with that. With hindsight that was rather foolhardy and I ought to have attempted to measure the current drawn first, but I got away with it. Though rated at 1.0 Amp output the HTC charger got fairly warm, but eventually the charge level reached full and the charger got cold again so I assume that it finished charging and the pack was fully charged.

The charger that came with the battery pack is labelled as an “MP3 Power Supply” and the output is rated at: DC 200mA +/- 30mA. Even the 1500mAh battery in the little Baofeng radio takes more than 400mA on charge. I managed to find a cable that would enable me to charge the battery pack from my workbench variable metered power supply and even when the battery pack is only half discharged it is drawing a current of almost 800mA. So I think the charger supplied simply blew up! I’m just hoping the eBay seller will provide a more adequate charger as a replacement. Sure, I can use my existing HTC phone charger. It may even be more convenient than having separate chargers for the two devices. But it would be nice to receive what one paid for.

By the way, if you ever wondered what is inside those Chinese wall-wart power supplies, how come they are so light, here are some pictures of the innards of the one that failed.

The answer, it seems, is not much. Call me old fashioned, but I’m just a bit apprehensive about having just a handful of components between my equipment and the 230V mains!

It’s a pity that this problem has occurred because I would have liked to have been able to recommend this battery pack to other users of APRSISCE on Windows Mobile. My initial test on the workbench suggest that this battery pack is more than capable of powering the phone with GPS and mobile data connection active during a day’s outing. The battery pack itself seems well made and I would guess that it is probably supplied by its Chinese manufacturer in a nice box with instructions and an adequately rated charger. The trouble in this case would seem to be caused by a cheapskate eBay seller.

Elecraft KX3 demo video

A chance to see the new Elecraft KX3 demonstrated by N6KR at the QRP ARCI “Four Days In May” convention in Dayton 2011.

A K3 in your pocket

Even more Elecraft KX3 #hamradio #kx3 on TwitpicMore Elecraft KX3 #hamradio #kx3 on TwitpicElecraft K3 with paddles attached. #hamradio #kx3 on Twitpic

Jeff Davis KE9V was among the first to post pictures from Dayton of Elecraft’s latest announcement, a portable all mode HF to 50MHz transceiver – almost literally “a K3 in your pocket.”

   Weight: 1.5 lbs
   Size: 1.7×3.5×7.4″
   KX1 form-factor
   internal battery pack & charger
   internal wide-range ATU
   new adjustable, attached keyer paddle

…and a K3-like front panel, including the same LCD.

I want one!


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  • Matt W1MST, Managing Editor