Hacker News Reader

Hacker News

Comment by jhallenworld | Hacker News Reader

Parent Full thread

jhallenworld

W6LG made a lightbulb dipole and got 750 miles with FT8:

https://www.youtube.com/watch?v=XSy271C07b4

FT8 is really something. I built a cobweb antenna and got Japan from Massachusetts on my new IC-7300:

https://photos.app.goo.gl/ciefcobDkiTrawsB9

So here's a funny thing: FT8 was written by a Nobel laureate in Fortran!

View on HN

Funny thing is, a light bulb is a decent dummy load for an antenna tuner. I rigged one up to test out an Icom AH-4 at the ham store.

Can anyone simulate this light bulb setup in HFSS or another antenna simulation software? I'm always on the lookout for comparisons on weird cases like this for the simulation code I've written. If I can find material property data on custard as easily as for tungsten (watch the temperature dependence!) I might give that a shot next.

You really don’t need to simulate it. It will just be a electrically small magnetic loop with a large real resistance. Any antenna text book should have it, with gain proportional to frequency.

Of course the nonlinearity of the filament will change things slightly, but it will converge down to a fixed impedance.

I suppose a bit more context would be explanatory. My real interest is not the free-space performance of the antenna, but the eventual installed performance. In the video describing the setup he says "I talked with a couple of engineers, and some other guys, and we've come to the conclusion that if I put 100 watts into it, it might radiate a milliwatt. And not all that well." I'm not sure if they were thinking of it as a magnetic loop antenna the way you described or coming up with the numbers some other way. But then at the end mentions, "I'm gonna set it on the top part of that air conditioner and put it right in the window." How much of his success is a result of sticking the antenna on what may be effectively a (admittedly electrically small compared to 20m) metal box? That's what I think is interesting to simulate.

Reply on news.ycombinator.com