Insulated element support for ultralight VHF/UHF Yagi-Uda beams

Once upon a time, 10 years ago, I used to build VHF beams for high mountain contesting that could be carried in the backpack. My best result was a 5 element Yagi of DK7ZB design whose boom was a telescopic fiberglass fishing pole, elements attached with clothes pegs.

The system could not grow, though: longer poles have larger diameter, while there are no large clothes pegs.

I had built a 4 metre long aluminium square boom cut in two sections, that is OK for backpack transportation where there is no vegetation around. I broke it before the first contest.

Fast forward 6-7 years and I still haven't found a solution to the larger clothes pegs. But while hanging around "special offers" from Chinese online retailers I came across this product: Adhesive cable ties in packs of 6. I couldn't pass on them at the incredible price of 0.8€/pack, including shipping. Their original purpose is to keep cables (like USB) from falling off (behind) furniture.

But their base size matches my aluminium boom (6 or 8 mm per side) and the cable hole is perpendicular to the longest side: do you see a better, lightweight and cheap alternative to large clothes pegs?

The clip sitting on my old boom.

8 mm element into the clip.

The hole diameter is about 7.5 mm. An 8 mm dia. element fits perfectly with the right friction. A 6 mm dia. element needs to be embossed at the junction point with some rubber pipe.

While I could stick them to the fishing rod once fully extended, I will rebuild the Yagi beam with a square boom and element supports already in place.

Side view of the element inserted into the support.

Too bad I got only one color!

biNixie Clock current consumption

The biNixie Clock deserves a box with an antique look. But the technology inside remains modern, so why not use a rechargeable battery supply?

Without any optimization, at 12 Vdc the biNixie Clock drains 82 mA with two digits ON and 65 mA in stand-by. This means a normal battery pack or 2000 mAh would last between 20 and 30 hours. I have to identify how much current each module drains so that I can plan the power supply and the box size accordingly.

I would like to keep it running off a 3S LiPO pack!

Vacuum Flourescent Display from a Toshiba VCR

On the wave of my recently born passion for neon/vacuum displays I remembered I had a VFD (Vacuum Fluorescent Display) sitting in the "might come handy" box.

The board was removed from a Toshiba VCR and it was the front panel circuitry. Under the display there is a Toshiba TMP47C1670 chip. It is a pretty complex device, probably programmable like a recent microcontroller, plus it can drive VFD natively.

How to light it up? Two things helped tracing down connections: the TMP47C1670 (partial) datasheet and a DVM.

With DVM in continuity test mode I looked for the filament. Incidentally they are the outermost pins. The datasheet provided hints on which pins drove grids (output pin called Gn) and which were for anodes. With the help of DVM I mapped IC pins with display terminals.

That was it. I fed the filament with about 4Vdc from a battery. Then my 12V PSU ground went to one side of the filament and +V to grid and anodes. Moving around grid and anode touch points I could lit all segments:

This experiment was fun and rewarding. I learned a bit more about VFD technology. Unfortunately the display has too many pre-shaped symbols that make it unattractive for reuse. It is offered free + shipping to a good home (with a documented project).

biNixie clock - preview video

I have finally produced a working firmware for my own implementation of a two-digit clock using two Burroughs B5092 Nixie tubes from late 1960's. The biNixie Clock. It uses

• an Arduino clone,
• a lumos.sk high-voltage PSU,
• K155DI BCD decoders and
• a DS1307 RTC for timekeeping.

It works from 12Vdc. Each tube anode has an independent variable resistor to set luminosity.

I need to complete the circuit and firmware with a couple of (hidden) buttons to set the time and a proper wooden housing.

I will release the Arduino firmware after tiding up the code.

Friedrichshafen 2015 - What I bought

This is mainly a log for my future self of what I bought at Friedrichshafen HAM fair 2015:

• WW2 headset with PTT (1€).
• Bencher BY-2 paddle.
• A pair of Hama gamepad USB controllers.
• Diamond HF-20FX 20m mobile antenna.
• Burroughs Nixie sockets (priced between 50c and 3€ each).
• Russian VFD 7-segment IV-3 (1€ each).
• Russian VFD 7-segment IV-6 (1€ each).
• Russian VFD IV-1 (1€ each).
• Nixie driver chips K155DI (equivalent of 74141, 1€ each).
• Blank spiral mic cord (6 wires, 1€).

B5094 Nixie now fully operational

The B5094 Nixie was tickling me: why only two symbols light up? Why others don't? I asked around and the hint was to increase the voltage supply (as well as the current limiting resistor).

Worth a try. My PSU module reaches 186 V: not enough to light up other symbols. Then I added in series a 12 V battery pack for a total of 198 V and ... all 3+3 symbols said "Hello!".

The series resistor was increased to 47k that is probably still too low. I need to measure the working current of that specific Nixie and make sure I do not exceed the 3.5 mA stated in the datasheet.

The need for an increased voltage is a sign that the tube is "tired". The 4th B5092 doesn't fire with 198 V. I may try to go higher but that's not too easy to achieve with batteries, or keep it as a souvenir.

Friedrichshafen 2015 - What I have not bought

These are my regrets. Objects I have not bought at "Ham Radio 2015" in Friedrichshafen but I should have.

A Fluke 8050 bench multimeter (~50 €).

A Heathkit G-1 signal generator. Found under a table. Looked nice.

A strange 1960's telephone loudspeaker (1 €).

A metal box with three flanged N sockets (probably 1 €!).

An empty metal box with handle (probably 1 €1).


There were other interesting things too, mainly stuff older than me. Either too expensive for a home ornament or too big to transport in a already fully packed car.

1000 km round-trip

Walk for seven hours.
Smell of bakelite.
Dusty hands.
Smell of dusty bakelite.
Curious objects.
Negotiate.
An horizontal Tower of Babel.
Refrain from compulsive shopping.
Smell of not-so-healthy food.
Beer.
Airships.
Look for old-time friends.
Regrets (I should have bought that, that and that!).
One thousand kilometres round-trip.

That was my first visit at the largest European HAM fair in Friedrichshafen 2015.

I joined a local group of HAMs which included the person that about 30 years ago introduced me into the world of CB.