Antenna Tuner, It Works

Well, the saying goes, 3rd time lucky. In my case it is 4th time, well 4th version of the design and 3rd time I have had boards made for this. The good thing is, it works this time. There are not masses of strays floating about anymore. They are just about all eliminated. You can see by the gain plot that its nice and linear with 0.5db loss from 1 to 30mhz. That is good enough for me. The losses are actually a little less than that, because i did not calibrate out the cable losses, but lets call it good enough for the kinds of girls I go out with.

Now its just a matter of rewriting the software to account for the changes I made and then putting it to use. Next version will have the capacitace switchable from low Z to high Z and there will be an SWR bridge and probably auto tuning. For now, i will finish this off and put it to use with some other home brew bits I have here.


2m Slim Jim Antenna

A long time ago now I built a slim jim for 2m and 70cm using the design calculator found here: anyway all i had to check it was a cheap SWR meter and it kind of looked ok and worked ok. So today after putting it back in the air so I can use it, i figured that I should chuck it on the VNA and see what is really going on. Well, it looks rather ugly that is for sure but it actually works well enough and its not very high off the ground either. Maybe 4 meters. But i can open a bunch of local repeaters ok from the Gold Coast to Noosa and that is good enough for me.



A New Linked Dipole

So for the longest time I have been using a Sotabeams linked dipole. Its been broken and repaired a number of times, but its getting to the end of its life. The links are more rust than metal, the centre has been broken and repaired a number of times and replaced, the coax and antenna wire has nicks in their sheaths. So rather than repair it or replace it, I decided it was time to build a new one from scratch. I have assembled the parts, RG316 coax, teflon wire and a sotabeams winder kit and parts. Will make it for 20, 40 and 80.


Tri-Band Trapped Vertical

Got a new antenna up. Trapped vertical for 20, 15 and 10m. Seems to be getting out better than the station master did by some and some more.

Just a quick install of the radials for testing before the storm arrives.

Still needs some pruning on the radials to bring it into resonance. Particularly on 10m


Never been spotted in Peru before and EU this early is not something I could manage either. I think im putting out a lot more signal than before.


Vertical Antenna For 20m

I do not have a lot of space for antennas. So i have to get creative when possible to be able to work the bands of interest for me at this time, 40 and 20m. I have a low slung dipole for 40m in the tiny space called our backyard. Which leaves doing something for 20m.

I have had this old station master CB antenna sitting in my workshop for a while that i planned to use on 15 or 10m. Well, nothing much is doing on either of those bands other than some E’s so i have reconfigured the station master into a 20m 1/4 wave.

Its about 4.5m to the base of the antenna and the 5m of radiator on top of that and 4 radials to bring the feed impedance up to 50 ohms.

The fact that the 2:1 bandwidth is 2mhz kind of tells me that i have made a high quality dummy load. I am still unconvinced that its not a dummy load even though it does radiate.

This is the FT8 map from today. It certainly hears better than the portable dipole and reports are about the same so it is doing something.

Not to be outdone, reverse beacon reports similar reports around the pacific region. The jury is still out and I might still yet pull it all apart and start again to see if i can get that swr bandwidth narrower. For now, its what I will be using on 20m.


Station Master CB antenna on 20m

I have had this antenna sitting under the work bench in the garage for some time. My initial plans were to use it on 15m by making it a little longer and going to town to get it close to a 50 ohm match and hope like hell it worked ok.

So, being the bottom of the cycle and not much doing on 15m at all and that i can tune the 40m dipole up on 15m and it will work ok, and 10m is pretty much a bust, I figured i would turn this thing into a 1/4 wave on 20m.

After a bunch of false starts and I want to smash this with an axe moments 🙂 I got to doing what was needed to make it kind of work. First part was to bypass the tuning coil as it is not needed, its about 5.2m long, a bit on the long side i know, but without going at it with a hacksaw it was not not becoming shorter LOL.


Put it on the vna and it looks kind of ugly. But We can fix that I hope.


A couple of radials later and its starting to look more like what it should. 2:1 swr across the whole 20m band. When i can be bothered to add another 2 radials that should come down even more.

Fired up FT8 and it seems to be working as good as the dipole. I dont think its any better, but it is certainly not worse. That gives me 20m at home now in a more permanent way until I can be bothered to buy a tri bander.


Sotabeams Linked Dipole 20m SWR

I had need to throw up the sotabeams 20m dipole here at home while I am operating as VI4LWF a special event call sign for the Armistice Day celebrations. I wondered why the autotuner went bonkers when i keyed up for the first time and so i thought i should take a look at it on the VNA, well it looks little on the long side to me, especially when operating up around 14.310 where most VKFF activators congregate. Its not bad, it just could be better.


Antenna is Done

So i got the dipole up now in its final position. The coax is now clamped to the mast so there is no flapping about in the breeze. The ends are up at their finished height. All up we have 7.6m apex and about 3m at the ends. Seems to be working ok, rx is certainly up.


SWR is as good as it is going to get and much broader banded than the old shortened dipole.

Photo bombed by Buster the Boxer. This is some fancy engenerding going on here. There is a 6ft star dropper 2ft in the ground right up the masts clacker providing the main support, the 2nd star dropper is screwed to the retaining wall and some big automotive clamps tying the 2 together. No idea what the safe working limit on all these things are LOL, but it did not move much during the big storm we had go thought last night. So i think it should be ok.