Homemade balun SWR scan 1-60 MHz 20180415

Homemade balun SWR scan 10 meter band 20180415

Homemade balun SWR scan 20 meter band 20180415

So I removed the old balun and installed the one I made. Removing the old one wasn't easy: the Fritzel balun has a cover over the SO239 connector which makes the heavy duty connector I used very hard to unscrew. So I had to break bits of that cover to get the needed access. And the connector ended with a lot more scratches from my attempts to get access to it.

But now the balun is replaced, and measured. And it looks like some things have changed now causing the antenna to be 'mistuned'.

Update: Just some measurements and thinking: adding the big common mode choke in the mix makes the combination show better SWR curves (still not what I want) but with the frequency with the best SWR still too low. This suggests (to me) two things: I need more windings on the ferrite core and less extra wire length from the core to the connectors. Time for a rebuild.

I finally decided where to put the holes in the case for the dipole ends of the balun. This took some serious pondering!

I made those holes, put screws through them and wound the ferrite core with enamelled copper wire. To guess the needed length of wire I first wound it with packing rope, made a small knot at the point where it was enough and unwound the rope to measure the length I used and took a bit longer wire.

Using sanding paper I removed the enamel isolation from the ends of the wires and used soldering tin on it.

Other parts of this project:

• Building my own balun, part 1: idea and parts needed
• Building my own balun, part 2: measuring the 'old' balun
• Building my own balun, part 3: First work on the case
• Building my own balun, part 5: First tests of the result

As planned I participated in the EA RTTY Contest edition 2018.

I had most of the time to play radio on Sunday so I decided to participate in the SO20DX (single operator 20 meter band outside Spain) category. I did make two contacts on the 40 meter band when I thought I wasn't going to find any new station the 20 meter band but I returned. And found more stations on the 20 meter band.

Interference pattern on the 20 meter band

Radio propagation was ok, best DX were some Asiatic Russia stations and a US station in Illinois. The local noise was bad and there were some new sources of interference active. The pattern as in the image (links to full view of the 2.5 kHz waterfall) which is very stable in frequency and has a tendency to stop and start, and at the stop the carriers move together. Also a more 'rattling' noise which sounded like an electrical problem.

In the end I made 81 contacts in total, 79 on the 20 meter band.

Apr  6 23:41:16 greenblatt sshd[25116]: Invalid user squid from 139.99.122.129
Apr  7 01:44:09 greenblatt sshd[3495]: Invalid user squid from 110.10.189.108
Apr  7 08:21:37 greenblatt sshd[7106]: Invalid user squid from 118.24.100.11

I'm glad you read my newsitem about keeping squid running.

Another new country that should not be too hard to get in the log but did not happen until today: South Africa. ZS6ZA was active on 40 meter FT8 and received my answers.

I considered stopping using squid when upgrading to the new homeserver but I have now changed that decision: I need to keep it running for applications that want to do http connections to IPv6-only systems but can't handle those. There are some old scripts running that need it but it's also the way to fix the problem I noticed with linuxcounter.

In looking at a problem with the linuxcounter script I noticed I am now passing the 25 years with Linux mark. I first saw it in the beginning of 1993 when part of my internship happened at the 'expa' lab (if I recall correctly) of Hogeschool Utrecht with SLS Linux.

Anyway, still using Linux a lot. It's been an interesting 25 years!

After my participation in the EA PSK63 Contest 2018 I plan to have the radio active in the upcoming weekend for the EA RTTY Contest.

The first work on the balun case was placing the SO239 socket. This included drilling a hole in the case of the right size and at the right position. Figuring out where to put it was mostly influenced by the fact that the ferrite core has to be placed inside the case and I wanted the SO239 socket, the ferrite core and the output terminals not all jammed together. So the SO239 socket was not going to be in the center. For this my new caliper was a useful tool and I measured the inside size and the wanted location of the socket. And I figured out I could drill a 16mm hole and the SO239 socket would fit inside while leaving enough room for the mounting flange.

Holes were drilled and things worked out fine, so the SO239 socket is now mounted. After checking the future location I realized I will have to mount the balun with the SO239 socket facing downwards because the antenna cable is quite heavy. This has to be taken into account with the next steps.

Other parts of this project:

• Building my own balun, part 1: idea and parts needed
• Building my own balun, part 2: measuring the 'old' balun
• Building my own balun, part 4: Deciding on where to put dipole ends and finishing it
• Building my own balun, part 5: First tests of the result

Fritzel balun SWR scan 1-60 MHz 20180325

Fritzel balun SWR scan 10 meter band 20180325

Fritzel balun SWR scan 20 meter band 20180325

Since I want to replace a balun that has been up there for ages I want to be able to compare the two. So I used the antenna analyzer to get graphs of the SWR over the whole possible range (1-60 MHz) and on the amateur bands it was built for: the 10 meter band and the 20 meter band.

There was a very interesting difference with the earlier results on the 10 meter band when I first tested the SARK100 antenna analyzer from Linux. The 10 meter band dipole probably moved a bit or something else changed.

I have now tried FT8 on the 2 meter band several times. One time I received a message via FT8 to try it on the 70cm band too but I haven't figured out the right frequency on that band yet.

DX contacts have been made into England, France and Germany. Furthest 2 meter contact at the moment is 323 kilometers. From the doppler shift I see the most probably reason for these distances is aircraft scatter, which means I'm using big metal reflectors in the sky to bounce my signal, without even paying for an airplane ticket.

I'm looking forward to 'E-skip' and other phenomena that can make 2 meter radio signals reach larger distances. I wonder what that will bring me.

The different radio bands also have quite different properties. The HF bands below 30 MHz have ionospheric refraction which lets the signal return to earth in far away places. The VHF bands (30-300 MHz) are usually only line of sight, signals usually will not get beyond the horizon.

Recently I saw mention of the FT8 mode on the 2 meter band. Specifically here: Essex 2M Activity Day Update - Essex Ham and VHF FT8 - M1AVV.

This inspired me to give it a try myself. It took a bit of searching to find the right frequency for FT8 on 2 meter. I found out it's 144.178 MHz so I started trying there and soon made my first contacts with Dutch amateurs at reasonable distances. But from time to time I saw signals from further away than was possible, for example England and France. My best guess is that aircrafts reflect the signals. I also saw doppler shift in signals which confirms aircraft reflections.

After a few tries I was able to make my first contacts at nice distances in the Netherlands.