Attic mounting vs. roof mounting

Jim Wyman

Jim Wyman

New Member
Hello All,
I am new here so forgive me if I miss something or appear "noobish".....

I an using Radarbox with a DIY collinear Coax (8-element, 1/4 whip on top) antenna in my attic, mounted right at the roof peak. My roof is ~ 25-30 ft in height and is made of wood and shingle (non- metallic). I am using a diplexer to split out the 980 and above signals along with an antenna broadband pre-amp. I am feeding this down to my study room where the Radarbox and PC are located.

I am rarely getting out beyond 80 miles consistently, with an occasionally target 115 miles to my southwest.

I live within the Washington DC metro area so traffic is never an issue.

My question is, how much of an improvement will I see by mounting my antenna on the roof vs. having it within the attic? I don't want to waste all the time and expense putting a mount up and running cables when there is a possibility that I may not see any better range/signal improvement.

Thanks!

Jim
 
Jim Wyman said:
Hello All,
I am new here so forgive me if I miss something or appear "noobish".....

I an using Radarbox with a DIY collinear Coax (8-element, 1/4 whip on top) antenna in my attic, mounted right at the roof peak. My roof is ~ 25-30 ft in height and is made of wood and shingle (non- metallic). I am using a diplexer to split out the 980 and above signals along with an antenna broadband pre-amp. I am feeding this down to my study room where the Radarbox and PC are located.

I am rarely getting out beyond 80 miles consistently, with an occasionally target 115 miles to my southwest.

I live within the Washington DC metro area so traffic is never an issue.

My question is, how much of an improvement will I see by mounting my antenna on the roof vs. having it within the attic? I don't want to waste all the time and expense putting a mount up and running cables when there is a possibility that I may not see any better range/signal improvement.

Thanks!

Jim
Click to expand...


Hi there Jim,
Nice to meet you.
Washington DC, what great location for ADSB monitoring !
I would say that your DIY/Homebrew Coax Colinear (coco) would be at fault there, not so much the location of it on your monitoring site although high up and in the clear is best.
Fact is Jim, Im afraid all the guides and videos out there on "how to make a coco" dont really reflect the degree of difficulty.
The coco is a bit of a tricky one to get right for your first DIY antenna.
A self confession here Jim, I have made 2 for adsb..very carefully, both are garbage !
There are so many variables in coax itself, critical lengths and possibility of getting it all together but unkowingly have a couple of shorted elements to rain on your party. I suspect you may be suffering the effects from one of the above.
I would without a doubt encourage you to make a spider antenna, there are many variations based on the same theme of a 1/4 wave element (68mm) made out of wire, and four 68mm matching wire legs known as a ground plane.
These are very easy to make, very cheaply, and perform very well.
Little can go wrong in making one of these, just make sure your measuring is good..Like the old saying..measure twice-cut once.
There are other similar easy to make antennas similar to the spider (cantenna and plantenna) based on known theory, they work superbly too.
All these designs will work well indoors and out.

You could look at the following post/guide below to get you started posted kindly by "The Professor of the Antenna" member ab cd.


http://forum.planefinder.net/threads/three-easy-antennas-for-beginners.248/

When you have made one, or need some help making one join us to compare notes here

http://forum.planefinder.net/threads/ads-b-diy-antenna.23/page-130#post-3796

Sorry I did not reply to your post earlier, but there is much activity on the above thread and I tend to get a bit "lost" in it sometimes.

Regards,
Mike (England,UK)
 
Mike,
thanks for the tip. I guess I will go make spider and see if that improves things...

Regards,

JIm
 
Holy crap on a spider cracker! Just build a 1/2 wave spider and have it out my first floor window.... I am seeing stuff close to 60 miles with no height and no preamp/splitter in tow! Can't wait to get this thing up higher!
 
Nice result Jim.
You will now have to bend legs,fine trim/cut etc for best performance.
Perhaps even add more legs.
We are always tweaking !
The spider is a favorite antenna of choice for many adsb listening stations.
Member xforce30164 is an expert at making spiders, his handy work is of a very high standard indeed.
Glad it went well and you are getting better performance now.
 
UPDATE:

Placed the Spider in the attic with no amp no band pass, used very short antenna-> receiver run - horrible results.....

Put CoCo back in place and results like before - 120 miles at best in one direction - mostly 80 nm range.....

Conclusion: Spider did great on first floor with no amplification - got out to 60 miles. Did horrible in attic with 2 places at 10 nm....

I suspect the attic setup is really causing a great amount of signal loss...

Next step (big Step) - Roof time!
 
I suspect like most say.. 1090 MHZ is strictly line of sight.. Even with trees, you can get some blockage.... I suspect that the wood rafters/beams along with the 1/2 inch plywood with shingles on top is reducing the gain somewhat....
 
Jim Wyman said:
I suspect like most say.. 1090 MHZ is strictly line of sight.. Even with trees, you can get some blockage.... I suspect that the wood rafters/beams along with the 1/2 inch plywood with shingles on top is reducing the gain somewhat....
Click to expand...

sort of....this freq needs line-of-sight in true words....no blockage..
 
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