These RC connectors. Do you have to allow for them when cutting and measuring the dipole lengths as they will be put on after you’ve measured the swr and cut the dipole several times. Surely the clips make the wire longer? Or is it too small to notice?
Thanks
Anthony
Well yes, the wire lengths for the links will affect the tuning. For a 20m dipole, every 1cm of wire moves the frequency about 10kHz near 14.0MHz. As you go up in frequency the length for 10kHz change gets less. So the tail will have an effect but is marginal and you can include the tails in the calculations.
A good way to learn about these things to is to get some scrap wire and something like an MFJ259 antenna analyser, or better one that draws graphs. Make a dipole, string it up in the garden and measure it. Then play with adding/removing wire and see what happens.
When you calculate the wire lengths without adding in factors such as the link length you will usually find there is additional length present, hence it is often resonant lower down in frequency.
I usually wrap a few turns round the “eye” of the spacer and turn it back on itself creating a knot. If you do this you can easily adjust the wire length and wrap the additional wire around the eye without having to cut and re solder the croc clip, assuming your using small gauge wire. This make the dipole easier to tune and setup.
There is also little point in trying to obtain exact resonant matches in terms of the frequency of interest as it does vary from summit to summit.
Dipoles are not my favorite HF antenna system for SOTA, they are great for multiple band usage, but in terms of set up speed a vertical is much quicker to setup and use.
Jonathan
You can get the correct length just using an SWR meter, but the problem is that you can do this only within the permitted frequencies, Good for fine tuning only I guess. I wouldn’t be without my RigExpert that I bought s/h. Quick and easy tuning.
Here is my ultra light (and cheap) solution for linked dipole
Wire is the spare from a norcal doublet, mechanical link is done with fishing swivels and rf connetor is a SMA.
The connectors are simple breadboard jumpers.
Obviously this is not a waterproof solution but I already used the antenna in pictures for some activation including two under rain and it still have no “rust signs”.
My two cents
73 de IZ3GME Marco
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