Tag Archives: Antenna

4-Element Home-Brew Folded Dipole Yagi Dimensions

I’ve┬árecently “made” a 4-element Yagi in software for my YouTube channel which should give a great match to 50 ohms.

If you’re into MMANA software modeling, here’s the file:

NOTE: This is a ZIP file because my Content Management System doesn’t like files ending in MMA. By all means have your Virus Scanner check this Zip file. There is only one file inside this ZIP. Just the MMANA file.

Tuning a vertical antenna with the ocean tide

cornwall qthHere’s a new one that you wouldn’t read in the books.

I’m seriously hammering the 40m band here in Cornwall and have tuned the vertical antenna so that the whole of 40m SSB is almost 1:1 swr, certainly from 7.05 through to 7.1Mhz. Over the last few days though, I’ve noticed that the tuning might change over a few hours to give me some serious SWR headaches. Enough to force me at one point to fold back the top of the element by 70cms.

It took me a while to track down what was happening but it turns out that when the tide is in, the vertical is effectively closer to the salt water ground and requires to be shorter than when the tide has been out for a while, long enough for the salt water to drain out the sand and reduce the salt water table by probably 15 to 20 feet or so.

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