build a dual band ground plane

[ka3jjz]

Looking over some antenna articles to put on our wiki while at lunch, I found this...

Build a dual band ground plane

Unfortunately I can't connect to this right now, as it's timing out on me...but it looks like a dandy project for those folks that want a quick and dirty antenna to throw up in the attic or similar for just about any app. I don't believe the article had the formula as it's about cutting the antenna for 144 and 440 Mhz...but the pix are outstanding.

If I could get the correct formula for inches/centimeters instead of feet, I could very easily toss together an Excel spreadsheet for the various lengths, change it to a HTML or Wiki table and put in on the Discussions tab for the Antennas page. Quarter wave figures are used so widely in many different antenna applications (and some filtering applications, too) that a table like this ought to be downright indispensible - unless something like that already exists somewhere (in which case I'll simply add a link to the page....)

Comments? 73s Mike

 

[Al42]

Simplify it. The radials can be 1/4 wave on the lowest frequency of interest. (The important thing is the minimum size - ground can be anywhere from 1/2 wave diameter to 8,000 miles diameter [the actual Earth ground].)

Each vertical element is 1/4 wave on whatever frequency you need reception. I won't insult you by telling you how to calculate that.

 

[kb2vxa]

Hi guys,

One more time, let's build a groundplane. Forget all that complicated crap, follow the basic instructions but use 5 19" lengths of 1/16" diameter non fluxed brazing rod. You don't need to drill out anything, it's a perfect fit. Just put a little right angle bend in the ends of the radials so they go into the four screw holes in the flange and stick out at a 90 degree angle. No problem mounting when you file off the excess solder on the connector side of the flange, make it flat and it sits atop a 1 1/4" diameter mast nicely, just shove the coax up through it and the weight holds it in place. Just tape over the PL-259 from flange to about 2" down the coax and put a blob of silicone rubber over the insulator to keep moisture out. Yes, it's dual band, 1/4 wave on VHF and 3/4 wave on UHF plus has sufficient band width to receive well from 120 to 500MHz.

Hey, I'm not a snake oil salesman, hams are forbidden by law to have a commercial pecuniary interest in such matters. If you want oil from a snake the store is in Washington, you'll recognize it by the big white dome.

Oh Al, have you ever buried an antenna to work ground wave?

 

[Al42]

Oh Al, have you ever buried an antenna to work ground wave?

I'm reading this at work, so I have to try to not laugh out loud. You're not helping.

 

[kb2vxa]

Al stop laughing, the Navy did it at several locations for transmitting ELF to submarines. The miles long antenna in Michegan was featured in an episode of The X Files.

That "ground wave antenna" was one of the many jokes some friends and I played on CBers. You may resume laughing but do it quietly...
HIT THE BOSS KEY, HERE HE COMES!