All posts by James

Preconfigured Raspbian Buster Lite

Whenever I set up a Raspberry Pi, I go through the whole setup thing. Can’t remember what I did the previous time or how. So it’s the same tedious production each time. Most of the configuration is the same as the last time.

I now create a preconfigured version of the Raspbian versions I use. This way I only need to configure things specific to a particular use.

For the Raspbian Buster Lite image, I’ve done the following:

  • Wrote the stock image to SD card and configured it on a Pi 1 Model B Revision 2.0.
  • Did it on a 4GB card in case I want to put it on a small card later.
  • Configured sudo to ask for password for pi user (and other users if added).
  • Enabled SSH.
  • Set graphics memory to 16GB.
  • Disabled root login.
  • Disabled user pi SSH login.
  • Set SSH login grace period to 30s.
  • Set fixed IP address in dhcpcd.conf.
  • Installed ufw firewall and allowed SSH.
  • Updated the OS after everything was done.
  • I did not remove the pi user as, according to some articles, the pi user is required by some software. Don’t know which, but decided to not tempt fate.

    There is probably more that could be preconfigured, but some are sort of security sensitive and others will change from install to install.

    I’ve also run it on a Pi 2 and a Pi 3 – seemed OK.

    My Raspbian Buster Lite preconfigured image can be downloaded from here:

    The zip file includes:

  • The image
  • A file that describes how I got Raspbian onto the SD card.
  • A file that describes what I’ve configured and how. (this is available as a separated download).
  • Now I have no excuse to get my crowd/flock/bother/menagerie/gaggle (?) of Pi-s something to do!

    Rugged LDMOS devices

    These things seem to be insanely rugged, as specified in their datasheets. Watch these demos.

    This is BBI Amps from the US, one of those guys who like to build crazy high power CB amps. Love them or hate them, they are entertaining. And some of them build some beautiful looking amps. This guy builds all sorts of solid state- and valve amps. In this video (starting at 21:40) he is showing the ruggedness of his latest amp using the BLF188XR LDMOS FET.

    In this video (fun starts at 1:30), the ruggedness of a Freescale MRFE6VP61K25 is demonstrated. It would be interesting to know how much of this can be done before it starts degrading, if ever.

    TX/RX relay

    I was looking for a TX/RX relay that can work up to at least 100W and 6m.

    Looking at some construction projects and the relays they use, it looked like you can more or less get away with murder compared to what is required on higher frequencies.

    On one forum someone who builds linears professionally, claims they use JW1FSN-12V in linears up to several hundred watts. These are available off Ebay for around ¬£3 or ¬£4 so I thought I’d give it a go. Continue reading TX/RX relay

    Some audio

    I have some of my recorded audio files on another server. The idea was to put more on there, but there hasn’t been much opportunity.

    With the exception of the 2015 file, all of them were recorded in South Africa at Hartebeespoort near Pretoria  Рlocator KG34WG. The one recorded in 2015 was in the UK.

    File order is a mess. There is a plan, believe it or not.

    Interesting clip (in Afrikaans) is some hams doing musical tests on 80m (20101015_213134_3748L_musikale-frekwensie_.mp3). This is still legal in SA subject to some strict limitations. This particular group does this on LSB (some of them wideband) and do actually experiment with audio quality.

    Click here to feed your snap, crackle and pop addiction.

    Portable listening on 6m during 22 March 2016 UKAC

    The UK Activity Contests are held by the RSGB Contest Committee ( throughout the month on Tuesdays from 20h00-22h30 local time. First Tuesday of the month is 144MHz, second is 432MHz, third is 1.3GHz and the fourth Tuesday is 50MHz and 13cm to 3cm.

    I’ve always been interested in 6m, but have never done much about it. I bought a Yaesu FT690 a while ago with a whip antenna (Moonraker MR625) and PL259 magnetic mount for the car. On the evening of the 22nd on the spur of the moment I decided to drive out the Newlands Corner just outside Guildford and listen on 6m. This is at location IO91RF95.

    Continue reading Portable listening on 6m during 22 March 2016 UKAC