A small beam ?...

[Oatmeal]

Like to know, how far above a tin roof would a beam need to be ?....

My Imax 2k, its 9ft above the tin roof and the swr is a 1.1 or less around the band, so if I can get a small beam this height above the roof, the swr should be good as well, shouldnt it ?...

 

[Beetle]

9 feet is ~1/4WL on 11 meters (which may or may not make a difference...).

Put it up and see. Might work; might not.

 

[Oatmeal]

10-4, well thats just it, I wouldnt be able to get any height, Im still looking at trying to put a beam in here...Id rather have that than a GP......

Have those stinking power lines out back, and that sux...

Ive been checking things out and if I put a beam out back, the reflector wouldnt be but 3ft away from the power lines when it was turned into the west....

So a beam would need to be somewhere else here at the shack, dont matter where it went, dont think Id get but 21-27ft at the max on height...man this sux...

The last 3 ele beam I had up, I had a 3" piece of pipe in the grd 3ft and put rebar around the pipe, and filled the hole with cement and made sure it didnt go anywhere, and I put seems like 12ft of 2" pipe inside the 3" pipe....and went to a 1.25" pipe and it was 21ft long inside the 2" and dropped 3ft inside it and drilled 2 holes in them and bolted them together....and had the beam on this, and turned it with a pipe wrench....talked good there for years..
If I can put a beam up here Id do the same thing with it, but not as high...

 

[W5LZ]

Hate to say it, but sometimes you just don't have the space for putting up some types of antennas. Being only 3 feet or so from a power line is NOT a good idea (and I figure you know that). Getting it up only a few feet above the roof isn't the 'best' thing either, but if that's all you can do, then that's all that you can do. I would think it would still 'out-do' an omnidirectional antenna but no idea by how much. We all have limitations of some sort. You work 'around' them as much as you can and then 'deal' with the results.
Good luck.
- 'Doc

 

[TonyV225]

I was going to say get a Gizmotchy 3 element but...... The horizontal elements becuse their angled would be close to the roof so it may or maynot affect it. You may have to go with a typical Yago or staright horizontal beam because of the 9 feet up limitation.



I think anything thats vertical will be a problem because the lower element length being so close to the roof but you may not have an issue at all. Ive seen and done some crazy things myself that shouldnt have worked but they indeed did.

 

[gator-4200]

I have a 3 element yagi and it is only 8-9 feet above metal roof, SWR is good. I made contact withe the states from Honduras on a little 5w radio with it several times.
My understanding of antenna theory is that it will increase the take off angle of the beam being so close to a "perfect ground" so while not ideal for a beam still functional obviously.


Sent from my homebrew wooden jungle box using morse code.

 

[Beetle]

As far as "SWR" being good, don't forget that a dummy load's SWR is very close to perfect. Doesn't mean you're going to radiate much.

 

[gator-4200]

Yeah so make sure you use an antenna and not a dummy load when transmitting.


Sent from my homebrew wooden jungle box using morse code.

 

[Yankee]

What shape is the tin roof? Are you just going up beside it, or in the middle?

 

[gator-4200]

Mine is a gable and I'm attached to a concrete pillar. Awwe heck ill post a pic.

Granted this is not the best setup, this does work.


Sent from my homebrew wooden jungle box using morse code.

 

[Oatmeal]

Gator-4200, nice pic, Id say it talks really well there...

The beam would be up against the side of the trailer on the mast pipe...
The beam would be a Maco 3 ele, well thats what Id like to have up here..

But if I can, Ive found a hotspot out toward the driveway end, and if the beam was in the center it would indeed be at the center of the peaked roof, and then Id be about 16-17ft away from the lines out back...I dont own the last, Id have to get premission to do this...but if I did this, still would go but maybe 21ft off the top of the ground...Id set it up to put some of a mast pipe in the grd and turn it with a pipe wrench...

Yea, theres not much room here at the shack for anything, this is why for years my antenna was on the mountain....

 

[hotrod]

if room i a problem then id suggest considering a smaller beam
1/gizmotchy makes a small 2 element beam. 5or 6 foot boom.
2/sirio makes a dipole .could mount that up on the flat and im sure
that will kick some butt in dx land. the boom i think is only around
2-3 feet long
now of course these wont be quite as good as the 3 ele. but if space is limited
and near power lines i think if it were me id consider these two

 

[Oatmeal]

10-4, thanks Ill look at the 2 ele Gizmotchy beam..

 

[northern35s]

How are your home construction skills? a Moxon rectangle is quite easy to build, excellent F/B ratio, similar forward gain to a conventional 2 element beam, 50 ohm feedpoint impedence, and a much reduced turning circle, think win win

Moxon Antenna Project

 

[Mr Clean]

Mine is a gable and I'm attached to a concrete pillar. Awwe heck ill post a pic.
View attachment 9943
Granted this is not the best setup, this does work.


Sent from my homebrew wooden jungle box using morse code.

Looks like a very nice place. Are you out by yourself.