Double Bazooka Antenna Question

[WA2SQQ]

I just built a double bazooka for 40m out of some RG-8X. The antenna works great. At about 6 ft off the ground the antenna was @ 1.3:1 SWR across the entire 40m band.

When I put up the antenna @ 40 ft, both of the band edges are up to 1.6:1 and the center is at 1.2:1. One thing I should mention is that when the antenna got hoisted, I coiled up about 9 turns of coax @ 9” diameter right at the feed point.

I saw two articles that mentioned that the double bazooka does not require a choke or balun. My question is, could the coax choke be responsible for the SWR changes? The changes are not especially critical, but I'm wondering what caused the change.

[w4bfs]

Q of the antenna went up as it went up .... this is normal and a good sign .... I don't think the air choke has a dog in the fight

[WA2SQQ]

OK, that's reassuring!

[w8khk]

If you have access to the ARRL periodicals archive, take a look at the technical correspondence on pages 29 and 30 of QST for September 1976.  This article addresses the apparent bandwidth of the coaxial dipole and explains the reasons for the lower indicated SWR. 

file:///C:/Users/Owner/Downloads/QST_Sep_1976_p29-30.pdf


Further detail is available on page 46 of Ham Radio, August 1976 issue.   Hope this helps.....

[Opcom]

I just built a double bazooka for 40m out of some RG-8X. The antenna works great. At about 6 ft off the ground the antenna was @ 1.3:1 SWR across the entire 40m band.

When I put up the antenna @ 40 ft, both of the band edges are up to 1.6:1 and the center is at 1.2:1. One thing I should mention is that when the antenna got hoisted, I coiled up about 9 turns of coax @ 9” diameter right at the feed point.

I saw two articles that mentioned that the double bazooka does not require a choke or balun. My question is, could the coax choke be responsible for the SWR changes? The changes are not especially critical, but I'm wondering what caused the change.

do you have a picture of this? I would like to see how it is made.

[WA2SQQ]

Here is the version I built. It really works great.
Had a G5RV that worked equally poor on most bands. Did a live comparison with a guy in Germany.
Running 100W, the G5RV was S7 - the double bazooka (with no tuner) was S9+.
The ambient noise level was also about 1 s unit lower. I did not expect it to be this good.

Got an idea to build one for 17M and use it as the driven element for a 2 or 3 element yagi. Its nice not to need a tuner for the entire 40M band.

http://www.k3dav.com/buildadoublebazookaant.htm

Read the referenced QST article - despite the authors debate with the design the end result is that its working great and its definitely more broadband that a traditional dipole - and I don't need to use any tuners! Over the years I've built many antennas that worked great. If my decisions were based on modeling the antenna, I would have probably not built half of them. If it works, and you are happy than it's the best antenna for you (until it comes down in a storm) in which case it was not large enough!