The BAZOOKA Antenna

[sinus trouble]

Seasons Greetings Necks!

So the Bazooka also known as a coaxial sleeve antenna seems to be a cheap and simple antenna to experiment with?

Yet it is not as simple as it looks? I have built them in the past but never got them to perform as they should?

There is a lot of conflicting info on these? Such as, Is it centre fed or off centre? The central feed coax must have some kind of influence on the sleeve?

Some also claim that the antenna does not need a Balun due to the effect of the quarter wave sleeve?

I have posted an example below, If anyone could clear up some of these inconsistencies? Id like to hear your thoughts?

bazooka.gif

[radium98]

i found this in an italian forum ,from coaxial ,i dunno if it the same .

[sinus trouble]

Thank you Radium

That looks to me like some kind of Co-linear antenna? Which should have some decent gain as it consists of multiple stacked elements. (Like a bunch or array of antennas)

The Bazooka antenna is pretty much a single dipole minus the boom and can be mounted directly at the very top of the mast.

I am 99% sure that it is an off centre dipole due to the interaction of the feedline! I have some old URM67 coax here so i will make one and post the results!

[sinus trouble]

Just to add! These antenna DO work! I have cocked it up somehow? Which is not unusual!

These antenna are quite common but not always seen! Especially in 2.4Ghz gear on a smaller scale ofcourse!

[Albert H]

Look for the "Flowerpot Antenna" It's easier than the "simple" Bazooka to get going:

http://vk2zoi.com/articles/half-wave-flower-pot/

[XXL]

Does the flowerpot antenna have any advantage over a dipole ? Otherwise just another pointless reinvention of the wheel.

[XXL]

That choke looks like a nightmare to build without a proper antenna analyser aswell.

[sinus trouble]

Does the flowerpot antenna have any advantage over a dipole ? Otherwise just another pointless reinvention of the wheel.

No.... It is a dipole.

The advantages are;

It can be mounted at the top of the mast.

Cheaper than a conventional dipole (Boom, Centre and elements not required)

Possibly no need for a BALUN? (Bazooka, Not flowerpot)

It doesnt look like a dipole.

[sinus trouble]

That choke looks like a nightmare to build without a proper antenna analyser aswell.

Indeed XXL

The Flowerpot choke adds more complications.

Not just with tuning? But physical manipulation of the coax cable itself, Which is adequate with say RG58 etc..

Good luck trying to attempt this with RG213, LMR400 etc..

[Albert H]

I've built a couple of the stacked ⅝-wave "Flowerpots", using UR67 for the aerial. The balun isn't all that critical - it tunes quite broadly. It goes really well from a good site, and we built them inside big drainage pipes. They don't look like Band II aerials, and they cost nothing to build.

[XXL]

Yeh I don’t ever use a dipole because it’s just so bait and obvious. I use a jpole for end fed setups using copper pipes. I don’t have any equipment to 100% tune them but I always get a better performance out of them somehow. Maybe just luck.

[sinus trouble]

I would deffo like to give the Jpole a try someday XXL

Technically none of these antennas are 'End Fed' As the Jpole has the matching section, The 1/2 wave relies on stray capacitance via counterpoise, coax or through the matching circuit itself! Even the 5/8 uses the remaining 3/8 to achieve matching in the form of radials.

Whilst the dipole is 'Bait' we cannot deny that it is the most reliable antenna.

Because 'End Feds' are not balanced? They can work to an advantage! But they are an absolute pain to get right.

[sinus trouble]

UPDATE!

I began building a Bazooka today and it went better than expected? One of the biggest obstacles i encountered with RG58 in the past was rolling back the braid! It would tend to bunch and bind up into a complete mess!

This time i used URM67 (similar to RG213) and it worked perfect!

I will post some pics below, I would have took it outside for a test but its too bloody cold for all that business right now.

Anyways the pics aint too clear? But i taped it to the outside of a PVC pipe to allow adjustments to be made!
I also taped the frayed end of the braid which allows me to slide it up or down slightly!

PS ignore the colour of the braid, It has suffered a severe dose of the 'Black Death' due to the good old British weather!

[sinus trouble]

Bazooka01.png

[sinus trouble]

Bazooka02.png

[sinus trouble]

Bazooka03.png

[Polecat]

Nice and simple Sinus. Dangle it from a window and no-one would know.

[Rfdiva]

No fear Sinus havd built a B1 link .

[sinus trouble]

Nice and simple Sinus. Dangle it from a window and no-one would know.

Haha! Yeh deffo more stealth than a conventional dipole! I did take it outdoors for a quick test, The results were not great?

I suspect i didnt have it high enough above ground (1 Metre ish) and needs a bit more tweaking?

I have not thrown in the towel just yet! I am determined to get it working!

PS I used a 'Portable Rig' to do the test! One which you may recognise!

Portable Rig.png

[Polecat]

Nice and simple Sinus. Dangle it from a window and no-one would know.

Haha! Yeh deffo more stealth than a conventional dipole! I did take it outdoors for a quick test, The results were not great?

I suspect i didnt have it high enough above ground (1 Metre ish) and needs a bit more tweaking?

I have not thrown in the towel just yet! I am determined to get it working!

PS I used a 'Portable Rig' to do the test! One which you may recognise!

Portable Rig.png

Haha yessss. With the antenna that's a great autonomous rig setup.

I got out a mile with mine from about 30' up with my diy roll up slim jim. It was uni directional as a huge building blocked the other direction but still pretty impressive. The sd card player kept stopping last time I used it but overall I was pretty impressed and sound quality was good too. Good to see you're getting to play with yours.