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I understand a vacuum cap is very expensive. Is it necessary? Will an open air cap function in the same way?

Actually, The ddrr antenna can be made with materials that I have at my disposal. I figure 3/4 of 7/8 inch soft copper tubing should resonate quite well. The antenna will only be 4 inches above the roof of my truck. That is the height it is designed to operate above ground plane. It will be...

Im looking into building an 11 meter ddrr antenna for my mobile. I curently have a 102 inch whip that works great for local transmissions. The ddrr loks like a simple and cheap build. However, I have had someone suggest a vacume veriable capacitor for tuning the antenna. Is this necessary? I...

You know, Im not sure what the original length was. I acquired 2 of these. They came off some old junk pick up trucks.

Yes you do need the spring to make the 102" length. I was unable to get an acceptable SWR with this dual inverted v setup. Didn't want to cut down my whips so I aborted this mission. Put the radio back in my truck with the 102" antenna and have a flat SWR. Will work on a base setup at another time.

Holy crap! Thanks for the link. Lots of technical Information that i have yet to make sece of. I did see that antenna height can be fairly low for best performance. I did manage to get antenna up. The way it is on the ball mounts it can easily be changed to any configuration. V, horizontal...

1m guessing 20 to 25 feet maybe 30. Peak of roof on a ranch home and another 10 feet up from there. Dual use but more for dx. I live way out in the stix and not many cbers around.

Or use both in inverted v configuration?

Thoughts breing here. I came across 2 102 inch whips adjustable ball and spring mounts. Plan on putting one if not both on the roof of my house. Wich would be the best set up? Use both in a dipole configuration? Or use one and make some sort of ground plane for it? Could the tv antenna be used...

Build took about 30 minutes. Used 3/4 pex pipe and rg58 coax. I put 9 turns in it as advised. Radio traffic really slow on a tuesday night in rural nw Mo. I have managed to pull in a call sign in the 155mhz range. Eager to get mounted on the roof of the house. Just heard traffic at 42mhz. Think...

Ok thank you very much. I am excited to get home and build this. Shouldnt take more than about 10 minutes. Lol.

I listen to everybody here. that's why Im here. To learn.

I see when converted to inches the antenna he is building is almost exact length for 155 mhz. However toward the bottom of the page it shows a table for choke adjustment at different freq. 155 MHz with 25mm choke diameter says 5 turns. Confused!

yes and adjust the choke to 5 turns rather than 9? Or does that even matter for receive? This is all new to me.

thisis what i meant to copy in last post.

http://www.n7qvc.com/copper-cactus-dual-band-super-j-pole-antenna-project/ wow.this is amazingly simple. Do you think built for the 440 mhz range would recieve 150 mhz in same fashion as vise versa? The antenna would be a third of the size.

http://www.n7qvc.com/copper-cactus-dual-band-super-j-pole-antenna-project/

ok sounds easier than a discone. Where can I find instructions for the build?

this is the home brew section, right? looking now how to home brew a discone fore desired frequencies. thanks for educating on SO-239