RX vertical
Update 27/09/2021
I have removed the transformer!
Doesn't seem to be necessary after the measurement at my home.
20/09/2021
ON4PQ Lieven had given me info a while back about a simple RX vertical for 160m monoband.
DL8LAS also has one and PA5MW. (Clicking on their call will take you to their website.)
I don't know who made this RX first and I didn't find the time to look it up.
When I gave a PowerPoint presentation about RX systems at my club a while back, I came into contact with ON4PQ.
That is the advantage if you give a presentation, you come into contact with other amateurs who are also loving the low bands.
After a while we got in touch on Facebook and he talked about this RX vertical.
Now that I am building some RX systems, I wanted to see what such 1 vertical could do and I started with my own version.
I contacted ON4PQ again, he still had the necessary cores lying around and I drove to his house to pick them up.
I would like to thank him again for the hospitality and for the cores I received from him.
You see hams that help each other still exist.
Building the system
You can see how PA5MW has made it on his site.
If you click on his call you will come to his site and it is vertical at the end of his page.
You need a core (FT114-61) on which you make a winding or about 50 with magnetic wire.
Why 50 turns? it's easier to take turns off than to make them.
Every time you make/remove a winding you can adjust the resonance frequency.
As you can see, the core with the turns how many there were exactly, I didn't count I just filled the core.
You also need an impedance transformer.
I should have measured my impedance first without that adjustment.
Here I just followed ON4PQ's advice, 5 turns on one side and 4 turns on the other. I used magnetic wire again.
With these windings you should go from about 100 Ohms to around 50 Ohms.
You can simply measure this.
Take a 100 Ohm resistor and solder it to the side where you have 5 turns. If you have a VNA then you have an advantage because you connect the side of the 4 windings to the VNA and then you will see that you arrive at approximately 50 Ohms.
Unfortunately I forgot to take a screenshot of what you should see on the VNA.
If I ever change it I'll post it below.
My waterproof box, As you can see I have adjusted a few things.
I plugged in a relay so I can switch the vertical to ground when not in use or when I'm transmitting.
It is also to prevent that my TX antenna and RX antennas can influence each other. (re-radiating)
To be able to see from my shack if the system is getting 12v I plugged in a LED so that I can see it burning from my shack.
There is also a fuse in it, you never know what could happen.
The 12vdc is on the side, the box was too small to fit them from underneath.
This makes no difference to the system.
I don't think I need to explain how the vertical is made. I do work with aluminum tubes and not with copper wire.
I had them from another project and I needed my fiberglass mast for the FO0AAA RX antenna.
The length of the vertical doesn't matter that much.
ON4PQ's is made around 6m mine is around 7m not because I wanted to go longer but that was the length I had and didn't feel like cutting it shorter.
My ground is just the mounting pipe where the antenna is attached on. On the site of PA5MW you will read that he also uses some radials, but I haven't done this (yet) and I don't think it will make a big difference. (If you have poor conductive ground, this might be worth considering.)
As I expected I was way too low in frequency to adjust this just remove some windings until you finally end up where you want to use the antenna.
As you can see, this is easy to adjust to your needs.
The future will show whether this system will work well.
What I also did is using 2 common mode chokes, 1at the feed point of the antenna and 1 on the RX coax switch at the shack.
DL8LAS uses a Hiz preamp more info about his system on his site.
In a few weeks I will put my 9 RX circle array back and I hope to have the coax loop and the FO0AAA Delta RX loop operational by then.
We then have 4 types of RX systems, which makes the comparison a little easier.
Received some nice DX yesterday evening on FT8 on 160 m
Farthest DX was Japan.
I don't think it's a miracle antenna, but this can be a good solution for many if space is limited.
I suspect it will be between the coax loop and the FO0AAA.
The FO0AAA will be better because it is directional (low angle of reception).
The Coax loop is also directional, but the reception angle is much higher.
I don't think I should make a comparison with the 9 RX circle, it doesn't seem easy to outclass that one.
We shall see....
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