Monday, April 21, 2014

Slinky dipole for 40m on balcony

My 10m wide balcony works fairly well for 20m but I wanted to try 40m. Good news, Australian Geographic stores carry very nice metal slinky's for $10 each so today I made up a balun and strung up two slinky's as a dipole.

A question: should the turns go the same way on both sides or should they be opposite? I have them in the same direction but it's not working very well.

With the slinky's extended to fill the available space I get a very good match but a little high in frequency for 40m.

This is an astonishingly good SWR and impedance for any antenna in my all-metal balcony, much better than what I get with the simple 20m dipole.

I can tune up on reasonable 40m frequencies, such as 7.146, with the Emtronic EAT-300 tuner but presumably co-ax losses are quite high.

As usual, I'm using about 10m of RG-174 thin coax to get from the balun, in through a window, to the transmitting position.

The windows here have soft rubber like seals and the thin coax will happily go through a closed window without much damaging compression.

Signal reception on 40m is disappointing, I've heard a few nets this afternoon but my CQ calls on 7.2 have gone unanswered so far.

It's a fine looking antenna but I don't think I should leave it out over night for fear of it blowing overboard and clobbering someone - leading to the breaking of another by-law no doubt.

This morning I had a pre-arranged contact with Stephen, VK2BLQ, who could certainly hear me OK, although no where near as strongly as you'd expect given our close proximity.

Sunday, April 20, 2014

Using a PC headset mic with a KX3

The KX3 is a radio with convenient standard looking connectors, either 2.5mm or 3.5mm sockets. Elecraft mentioned that many low cost PC headset mics can be used in the four conductor mic socket but I found for my Logitech unit a small adapter cable had to be constructed.

The wiring is as follows:

I used a standard 3.5mm, three conductor inline socket and a 4.5mm four conductor plug which Jaycar carries in store. Doing it this way means I could leave the Mic PTT switching turned on, but I use the transmit switch (XMIT) on the lower front of the rig for control. Here's how it looks:

When I first tried this, mic gain was way too low, but I noticed that Elecraft had a firmware update I hadn't applied that offered increased microphone gain.  "SUPPORT FOR HEIL HC-6 MIC ELEMENTS: Mic gain can now be set as much as 20 dB higher to support these low-sensitivity elements."

On air reports from Mal, VK2BMS and Stephen, VK2BLQ suggest that the audio from the $15 headset is a little lacking in bass compared to the normal microphone but this can be adjusted if required. The headset is very light and comfortable but probably not robust enough for field use.

Incidentally, I accidentally interrupted the firmware update process and this left the KX4 in a mode where it displayed "MCU LD" on the display with the red TX light flashing. I wrote to Elecraft customer support and Howard replied within minutes with the procedure to get past this. (I won't reproduce it here as I guess it might change over time).

Thursday, April 17, 2014

Ham radio story on ABC Open

Stephen, VK2BLQ spotted this story on ABC News24 the other day. A great piece from ABC Open.

Brenton: Ham Radio from Micah Barnes Photography on Vimeo.

How I lost weight

When I returned from Hong Kong in 2002 I was 82kg, today I'm fairly stable at around 71kg. My work is sedentary and losing weight is a struggle.

I hate depriving myself at every meal as you do in a traditional diet. Last year I got a Fitbit and did 10,000 steps a day - which did work to some extent. Certainly the computerised feedback on activity is a great thing with a huge future.

In December I read Michael Mosely's "Fast Diet" book. It's very simple, you just don't eat at all (or a tiny bit only) a day or two a week. My target is Monday and Thursday but often social events rule out one of those.

The other days are normal but here's the weird thing - after not eating for a day, I can't eat as much as normal. I guess the stomach shrinks a bit from not being filled every day.

For me it's been easy, I got used to not eating quite easily and it showed me how much of the time I just eat because it's time to eat. This may not work for you, but it's worth a try if you have a few extra kilos to shed.

Sorry for the off topic post, we now resume regular transmissions.

Monday, April 14, 2014

Antenna experiments curtailed in the flat

It's the down side of living in a unit. My squid pole antenna support off the balcony is virtually invisible from the ground, but not it seems to the resident one floor above. Today I received a polite but firm note.

I've only been leaving it up over weekends but unfortunately that needs to stop for a while. Here's the new more "stealthy" arrangement.

Unfortunately, due to all the metal in the balcony, the SWR is quite high. I can tune it down to about 3:1 but that's as good as it gets.

Friday, April 04, 2014

Home made low cost keyboard tray

I'm finding typing on the dining table gives me sore shoulders so overnight I had an idea. Two $9 F-clamps and a plank and I have a nifty adjustable keyboard tray.

No doubt this is elaborate procrastination but it seems like a simple solution.

Saturday, March 29, 2014

ARNSW Home Brew Group - Smart phone and tablet apps for Ham Radio

Today at the ARNSW Home Brew group, a different kind of meeting. We turned to a survey of applications for Ham Radio that run on popular tablets and smart phone. Convener, Peter, VK2EMU rigged up an impressive camera on a tripod to project devices on to the big screen.

Peter showed a number of apps that generate audio tones, including sweeps, white and grey noise for measuring frequency response. We announced our plans to bring a tone source for an RF generator to iOS. I showed some phone apps including Morse and PSK31 decoding, antenna calculation and naturally I plugged my own free app for watching WSPR spots called WSPR Watch.

There was some home brew electronics on display with another great project from Stephen, VK2BLQ, showing a Drew Diamond design with the addition of a PIC based frequency counter.

The meeting did decline into a bit of an Android vs iOS discussion and we ended up discussing the demise of support for Windows XP and what that might mean for those who cling to it. I mentioned that people who see an iPad or iPhone as being out of reach should consider an iPod Touch as these start at AU$249 and run all the same software as an iPhone.

A huge turn out today, perhaps due to the weather, all kinds of interesting transport was on display, this one with space for your gun.

Today was also the last meeting with John, VK2ASU in attendance before he heads north to his new QTH. John has been a generous contributor to the group, net coordinator of the Home Brew nets over many years and super helpful to us newbies - we will miss you mate.

Sunday, March 16, 2014

iOS icon resizer script

Goodness, iOS 6 & 7 needs a lot of different icon sizes for a universal app. I wish Apple would support SVG. Here's my little script to resize a large icon down. It requires Imagemagick.

# Usage: bigicon.png
# You need to brew install imagemagick
filename=$(basename "$1")
echo "resizing ${filename}..."
echo "filename = $filename"
for size in 29 40 50 57 58 72 76 80 100 114 120 144 152
    echo "$filename$size.png"
    convert {$1} -resize $sizex$size $filename$size.png

This is a note to myself really.