Archive for the 'amateur radio' Category

Published by W7CF David on 20 Sep 2010

Toying with embedded systems

after almost 2 years of deafening silence on this blog, it’s time to post again… ouch.

Lately, I’ve been experimenting with embedded systems, probably an attempt to reconnect with my hardware roots from my electrical engineering past. I’ve stumbled over a exciting computer-on-module in form of the Overo series from gumstix. It’s also a great opportunity to refresh my rather rusty Unix/Linux knowhow. In the limit, I intend to port and install Android on this amazing piece of hardware.

I’m collecting my experiments in a wiki (using dokuwiki), mainly so that I have a way to retrace my own steps: Gumstix Overo with Android

So far, I’ve managed to install a host system with Linux, I have enlisted in the Android source repository and have started to adapt and compile the boot loaders for the Overo system. The first success: I’m able to boot the OMAP3 processor from the SD card into the u-boot bootloader prompt, using binaries built from x-loader and u-boot sources.

Next step is to get a basic Android kernel (which is actually an adapted Linux kernel) into at least terminal mode.

Published by W7CF David on 01 Nov 2008

W7CF moving to new QTH, so QRT for now

back in September my XYL Lisa and I bid for a new home with 2.5 acres of space, a bright quilt studio for her, a large woodworking shop for me and surrounded with plenty of 80-110ft high antenna supports. Last week our purchase finally closed.

I’ve been off the air for the past 6-8 weeks already (missing dear contests like Salmon Run CalQP, NAQP, CQ WW DX RTTY, etc), as we were too busy getting our old place spiffed up and updated and get it ready to put it on the market.

Yesterday, I disconnected and packed my radios, antenna and feedlines. Once the dust of our move settles, maybe in 2-3 weeks, I can think again about getting an antenna up and be QRV again

Published by W7CF David on 04 Jul 2008

What is contesting?

this is  a question I do get asked by friends and coworkers when I mention that I’ll be spending my weekend in front of a radio…. Admittedly, to make sense of such an intention, one has to experience the music and rhythm of the contest exchanges, especially in CW.
BTW: last weekend (FieldDay 2008 with RTKCC, MicroHams and RedmondARES), I sat next to Alan AC2K for almost an hour just listening in how he search&pounced the band and made plenty of contacts. He didn’t even bother using precanned CW sequences, all code was live keying with his Begali single-lever key. Ok, now I know why I need to further practice my code speed 🙂

Here’s a YouTube video that explains and conveys the contest rhythm quite nicely:

Published by W7CF David on 24 Jun 2008

ARRL VHF contest June 14th

This was my first attempt at both contesting outside of HF and away from my QTH: packed up my FT-817 up to TIger Mtn (CN97) to participate for a good hour in the VHF contest, namely on 6m. RX was great, helps to have an antenna more than 2700ft high 🙂 But reaching more remote stations, TX with QRP level is quite limiting unfortunately.

Published by W7CF David on 08 Apr 2008

Radio on the Trail

Fascinating concept: Being on a trail for several weeks or even months and also get to “play radio” on a daily basis 🙂 Even more compelling is the idea of doing radio with as little weight and volume as possible, as every ounce needs to get carried on your back.

Two well-known fellow hams (none of them I know personally) are on a trail this spring/summer:

Bruce N7RR is getting ready to traverse the Pacific Crest Trail, according to his blog.

Steve KD1JV, the designer of fame for the ATS3 radio,  is also out on the Appalachian Trail, see his trail journal.

I seem to have a genetic predisposition to be attracted to such long distance trails: Over the past 2-3 years, my Dad made it his retirement mission to hike all of Switzerland‘s national border, from one boundary stone to the next.
Note to myself: I’ve seens his photos and paper travel books from the parts he has already completed, fascinating!. I need to convince (and help) him to post his journal on a web site….

If I only dared putting aside the necessary time from work and wife, that would be a very tempting adventure for myself indeed, How about hiking Pacific Northwest Trail or Continental Divide Trail?

Published by W7CF David on 11 Feb 2008

Debugging my antenna

Several weeks ago, in the ARRL RTTY Roundup, I noticed a weird effect when sending in rapid succession: over several seconds, the SWR at my radio ramped up to ~3:1, consequently my transceiver folded back its output power. After maybe 20-30 seconds of rest, everything resumed to normal again.

On first hunch, this looks much like a thermal issue, something is heating up and cools off to revert to normal. On to debugging my antenna system. A quick test with a dummy load hooked directly to the transceiver showed no problem with either PA nor power supply.

Rain, work (and skiing, I admit) kept me from looking closer at the outside antenna components; besides, with lighter load cycles e.g. in CW, no repro. But this weekend, there was yet another RTTY contest, CQ WPX RTTY.

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Published by W7CF David on 30 Jan 2008

WordPress is amazingly efficient to setup

So I got my new callsign W7CF assign today at ~1am (well, that’s when I found out after consulting FCC’s ULS database).

Before work, I reserved and bought a new domain Tonight, after work I spent roughly one hour creating a new WordPress installation, moved my content from my previous blog hosted on and searched and tweaked a theme for my new site.

That is efficient, and the one hour I did spend on all of it was actually concentrated purely on the content and deciding what colors etc; not twiddling with the software! That’s how it should be: be able to concentrate on solving the problem, not satisfying housekeeping of software and tools.

Published by W7CF David on 29 Jan 2008

f(W7DIT) = W7CF

Eureka! The FCC ran its lottery, err, its nightly application processing tonight: It’s official, W7DIT is no longer, welcome W7CF.

 This is exciting, I do love the CW sound & rythm of the new call