Yesterday i finished the installation of my personal DXSpider node. DXSpider is one of the various software packages out there to build cluster nodes. Apparently DXSpider is the most commonly used, so i went for that.
My mini-server sitting in his dark corner in development mode
I have a spare Asus EeePC 701 netbook which i am using as mini-server for the cluster. The EeePC contains an Intel Celeron 900MHz running at 600MHz, 512Mb of memory and 4Gb SSD drive. The netbook is running Ubuntu Server 12.04, so you can definitely say that it’s a mini-server.
DXSpider is almost 100% based on Perl, so i thought that this would be enough to run the cluster.
Also since it’s a small laptop and has no moving parts it doesn’t make any sound. My living room is my datacenter and i don’t want to watch TV with the buzzing noise fans and disks around me.
The node is running the cluster over telnet, AX25 and packet and has the web interface configured as well.
Now let’s see if can get some spots in and out.
Cluster node in operational state
As you know, antennas are a critical part of any HAM radio setup. Where i live we are not allowed to build any decent size antenna because of the view. Yes, they are that picky here. So i’m always struggling and fiddling with either mobile antennas or wire antennas.
This time i built a wire dipole out of scrap material i had lying around.This antenna is very wide banded and is useful on any band between 40 and 6 meters. Here is what i did:
First the feed line.
I took a bunch of normal loudspeaker twin-wire and connected one end to my MFJ 941-E antenna tuner. This tuner has connections for ladder lines and has a 4:1 balun integrated. My speaker wire is my ladder line with very little spacing between the elements.
At the end of the feed line i connected a choke balun (thanks, Mark PA5MW for winding and sending it) and created two hookup “eye” pieces to clip the radials in. These “eye” pieces are just a piece of wire in the form of a circle which i completely soldered to give it structure.
As you can see i hooked everything up with regular connector block electricians use.
On my terrace i fixed two hooks on the outside wall to fix the end of the radials. The radials themselves are the same speaker wire i used for the feed line.
Of course there are two issues i have to deal with. One it isolation of the radials from ground. That’s why the tie-wrap is there.
The other issue i wanted to deal with is the tensioning of the radials so they remain sort of straight. I used simple springs to hook up the wires. Now i am able to define the tension with the tie-wrap without having to change the length of the radials and therefor changing the resonance frequency.
The other end of the radial created a sort of “hook” so i can clip the wires into the “eyes”
So this is what the antenna looks like now. The center under the gutter, the radials spread out to the farthest points of the terrace wall.
SWR of the antenna is 3:1 on 8 MHz, 1,1:1 on 11.500 MHz, 1,5:1 on 18,400 MHz and 1:1 on 27,555 MHz. That, BTW, is just a coincidence…
I don’t know how effective the antenna is, but i have made contacts on 20, 17, 15, 12 and 10m with stations inside and outside of Europe, so for me this antenna works. Sort of.