FlightAware Discussions

What's wrong with 5/8?

I was reading about VERTICAL antennas and groundplanes, and came upon this GRAPH, showing a 5/8 antenna
has significantly MORE signal than a 1/4wavelength vertical.
At 1090 MHZ, that’s NOT a difficult thing to do.
http://part15.us/files.p15/ant2.gif

It’s 2.9 dB of gain if you do it right. The radiation pattern of the 5/8 favors the horizon more than the 1/4 wave. For transmitting use (such as in the VHF/UHF ham bands and business bands) a matching network is needed with the 5/8 as the feed impedance isn’t close to 50 Ohms.

Asking a bunch of hams which is better, a 1/4 wave or a 5/8 is a good way to start a riot (sorry, “spirited discussion”)…

bob k6rtm

Since we’re not talking about a lot of copper, I’d just thought I’d throw that out for anyone interested in experimenting.
And since the improvement is likely to be subtle, I’m sure there’ll be some debate. That’s another reason I ended up with
Multi-Pis, to compare antennas.
Would a groundplane help a collinear???

Nice thing about a 5/8 wave antenna is that if it doesn’t work, you can always cut it down (ground plane/spider, that is). It’s so much easier to remove than add on. :smiley:

I made a 5/8 wave spider and it didn’t work so well. 1/4 wave has been best for me. This is my latest model. It’s a hybrid cantenna (credit @abcd567). It works great. The whip is 69 mm and the “leaves” are 69 mm total length.

Only watching this antenna, makes me to look for a pack of band aids already! :laughing:

Seriously, did you cut yourself with it, before it was completely mounted? I would have for sure!

I made the cuts with scissors and, believe it or not, the edges of the “leaves” are not deadly sharp. I never even felt a scratch while handling it. I suppose if you rubbed the edge with any pressure you might get cut. If you make one like this you could sand the edges or put some clear tape over them if you wanted to.

I think adding airline logos to the leaves would be interesting – you could probably convince some that it improves reception, increasing affinity or some b*s like that… If nothing else would make it more an obj d’art…

bob k6rtm

I made this logo conetenna in January. The cone has a 45 degree slope and length of 69 mm, same as the whip.

ars longa vita brevis :slight_smile:

:smiley: :smiley: :smiley: :mrgreen: