Raspberry Pi as an OpenVPN server

Many of us work inside fire walled networks where virtually all ports are blocked and web traffic goes through an annoying proxy server. A VPN connection makes your computer appear to be on another network and these issues go away.

Another big reason to operate through a VPN is if you are on someone else's network, perhaps a cafe Wifi service, and are (rightly) concerned about your traffic being snooped.

There are commercial VPN services available but I've recently set up a raspberry pi as a server and it works really well sitting on my home internet connection.

OpenVPN requires a single port, either TCP or UDP, between client and server.

Installation is well documented in several places, but I referred to the excellent instructions on Remi Bergsma's Blog.

I made two changes:

• Used tcp rather than udp as for some reason I couldn't connect via udp - update the setting in /etc/openvpn/server.conf
• Enabled nat on the pi as I was unable to set a static route on my home router - an Apple Airport extreme.

The command to enable nat on the pi is:

iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE

I added that to /etc/rc.local so it will be re-applied on each boot.

Finally I forwarded the TCP port I want to use to connect from my home router to the Raspberry Pi. My home internet connection occasionally changes public IP address so if that becomes a problem I might use a dynamic DNS service to keep track of it.

Client

I use MacOS mostly and I'm using the Viscosity client which has a 30 trial period (which I'm still in) and then costs just US$9 which is very reasonable.

Digital data transmission tests on Radio Australia

Please be advised of the second Radio Australia HF test using the digital text modes MFSK and FLARQ.  Freeware fldigi will handle these automatically - see http://voaradiogram.net/   and http://www.w1hkj.com/

The text will contain text and images from Radio Australia's web site as well as contact details for sending responses. Note 2150 UT Sunday is Monday morning 0750 EST in Melbourne etc.

All dates/times are in UT, all frequencies in kHz
Saturday/Sunday 8/9 June 2013

0850-0857 UT on

 7410 (PNG & south-west Pacific)


11945 (south Pacific, NZ, central America, Europe)

1230-1237 UT on

 6080 (PNG, west Pacific, Philippines, Japan),  new freq for MFSK

 9580 (central Pacific, NAM)

12065 (central Pacific, NAM)

2150-2157 UT on

11695 (south-east Asia, Europe)  new freq for MFSK

21740  (central Pacific, NAm)   new freq for MFSK

with 40s of RA tuning signal (Waltzing Matilda) at the start of each session.

Extremely poor reception here this morning of 11695. I could barely detect that there was a station there and only a few words were decoded.

Update

The tests have been a success and reports are coming in from around the globe. The Voice of America's Dr Kim Elliot, reports on his reception in Northern Virginia where despite poor audio reception, the digital text message was perfect.

Knobless Wonder 40m SSB QRP circuit from VK3YE

Peter, VK3YE, recently showed me a new home brew fixed frequency single sideband rig he dubbed the "knobless wonder". I think this is a great group project where the fact that it's fixed frequency is an advantage in encouraging contacts between builders.

He's given permission for the circuit to be published here (click to enlarge).

I highly recommend Peter's walkthrough video complete with a series of contacts on the actual rig.




Thanks Peter!

Tune in to "Download this show" tonight

If you are near a radio this evening, tune in to ABC Radio National where I join host Marc Fennel and co-guest Claire Porter (from news.com.au) to chat about human technology matches and mis-matches.

Can't tune in? guess what, you can download this show or subscribe to the podcast by searching for it in your podcast app or iTunes.

Always a pleasure to join Marc and other guests on my beloved Radio National.

Tablet friendly M65 Jacket - as seen on TV

You don't get much fashion advice on this blog, until now. If the M65 field jacket seems familiar, it's because Robert De Niro wore one in Taxi Driver, Al Pacino wore one in Serpico, Sylvester Stallone wore one in multiple movies and Arnold Schwarzenegger wore a decorated one in Terminator. And that's just the start, check Wikipedia for about 40 references.

Introduced into the US military in 1965 to replace the M51 which replaced the M43 (you can figure the years).

The exterior is poly cotton mix, there is a 100% cotton lining and a further, buttoned on detachable inner warm layer. The instructions warn not to dry it on a stove, so I guess that was a problem.

What's amazing is that in 1965 they correctly predicted the dimensions of the now popular seven inch tablets and a Nexus 7 fits nicely in the side pockets. Great forethought there. Available at army disposals stores globally.

First test with cheap $5 AD9850 DDS board and Arduino

News of the availability of very low cost AD9850 DDS boards from China via eBay has swept the home brew radio community in recent weeks. These chips alone were quite expensive and the surface mount soldering was a challenge.

Now the chip, mounted on a nice carrier board, with 125MHz crystal, is available for a very reasonable price. Here's mine sweeping a few frequencies near 10MHz:


The Arduino code I used is from NR80 which in turn is based on code from Andrew Smallbone.

I simply powered mine from the 5V on the Arduino and it seems to work just fine.

Our plan is to make a little crystal replacement board for QRP purposes with a multi-position switch to select the frequency.

Purchased a blank Arduino shield board and have now mounted the DDS board nicely for future software development.

Melbourne meetup with homebrew legend VK3YE

While in Melbourne for the fabulous "One More Thing" conference this weekend I had the pleasure of breakfast with ham radio home brew legend Peter Parker, VK3YE.

Gracious with his time, Peter brought along a number of recent projects including the famous "Beach 40" and a new fixed frequency SSB transceiver he dubbed the "knobless wonder" that has been recently completed.

Peter works in the public transport industry, (may I say how impressed I am with the Melbourne MyKi system), his knowledge of the network is impressive.

We talked of many things including cross-overs between amateur radio and public transport including Tony Sanderson, VK3AML, and the videos made by Dave VK3ASE of the Glenhuntly station crossing.

Peter is a self-taught radio electronics engineer who is performing a great service to all would-be home brew designers.

Here's some previews of the "Knobless Wonder":

Nice crystal filter array there.

Here's the popular Beach 40:

Thanks Peter for your time and generousity. Keep up the great work!

Update

Thanks to Bill of Soldersmoke for the mention.

Good news: Peter has updated the Knobless Wonder circuit and published a video here:



The circuit is here.

A wonderful One more thing conference

Really enjoyed "One more thing" again this year in Melbourne and at the pub afterwards ran in to Luke Anear who pulled out a Google Glass device much to my amazement.

I put on the Google Glass headset and found the display incredibly clear. Despite the noisy pub environment, even with a band playing the speech recognition worked very well.

After returning to Sydney I introduced Luke to Marc Fennel who followed up with a great video story about Glass on SBS2's The Feed.