Attic vs. roof.....

jwyman · April 05, 2015, 04:32:23 PM

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

Runway 31 · April 05, 2015, 05:07:11 PM

I have my DPD antenna in the attic and can get over traffic over 100 miles out and my attic is only about 12ft in height in a timber and tile roof. Maybe a better antenna could be the answer rather than the expense of moving it out side.

I have thought about moving it outside but am wary of weather problems and anyway the network gives me the coverage further out and even in the blackspots within my coverage area..

Alan

CYYZGUY · April 05, 2015, 06:01:39 PM

Hello sir, I have my antenna mounted to a 15 foot mast at the side of my house, total height is around 40 Feet total. I am getting a very good range of around 200 Nm in all directions,

Attached is a photo of my setup, since that picture was taken, I have raised it about another 6 feet. I am also using a DPD antenna and I consider it to be one of the best. You can never beat having an antenna outside.

Also attached is a picture of my polar diagram.

DSC_0879 by CYYZGUY, on Flickr

CYYZGUY POLAR by CYYZGUY, on Flickr

Runway 31 · April 05, 2015, 06:51:20 PM

Got to agree outside is always best but other things need to be considered as well such as antenna, cable and length of run

Alan

CYYZGUY · April 05, 2015, 06:59:44 PM

Good point, here in North America, if you are serious, use LMR400 low loss coax. I think in europe they call it westflex???

Before I moved in to the house, I was living in an apartment and had my antenna on the roof, I had a run of 80 feet or so of LMR400, with quality connectors and proper Weatherproofing! I cannot stress enough how waterproofing your connections are important. First seal them with electrical tape, then put on a few coats of liquid electrical tape, Coax-Seal or something similar to prevent any moisture from getting in!

jwyman · April 05, 2015, 07:06:10 PM

Thanks to all for your response.... What kind of messages/sec rate are you getting? Mine seem to go to 60 to 160 , bouncing back and fourth...Rarely consistent.....

CYYZGUY · April 05, 2015, 07:21:53 PM

This varies depending on the amount of traffic in your area. Right now I am see around 400 to 900

Jason

jwyman · April 05, 2015, 07:38:33 PM

Holy crap! there must be something terribly wrong... I know that an external, high antenna likes yours will achieve higher numbers but I can't believe I am this low....

Kenny · April 06, 2015, 06:26:05 AM

Hi,

Got mine on top of 2nd floor roof 11m hight with 10D-FB cable route back to RB on 2nd floor, no preamp. Got around 160-200 nm on most direction. 200-300 messages/sec and about 1900 flights per day.

The location is Bangkok, Thailand.

Kenny

Runway 31 · April 06, 2015, 07:02:00 AM

Your messages per second will be determined by the traffic you are picking up jwyman. How many aircraft do you have in myflights

Alan

jwyman · April 06, 2015, 12:25:41 PM

I will check when I get home...

bratters · April 06, 2015, 06:13:07 PM

Jim - remember that you do not need to see your box! Simply site the box as near to your external antenna as possible, maybe in the top of the loft. As there is NO signal loss with USB cable, use the shortest possible run of coax from antenna into loft then run extended USB cabling down through the house to connect with your PC.

I've got various electrical/water pipes dropping through from my loft so an extra bit of cable was child's play.

jwyman · April 06, 2015, 08:18:24 PM

Here is what is going on now....

jwyman · April 06, 2015, 08:33:20 PM

Here's another shot with the polar diagram on - ~ 14 aircraft with 95-230 msgs/sec.. Fluxuating wildly...

Runway 31 · April 07, 2015, 08:59:30 AM

Fluctuations are nothing to be worried about. I have 21 aircraft and it is going between 88-237 and is to be expected. I don't really see any problems with your diagrams.

You are seeing better to the west but there can be a number of reasons for that, usually obstructions whether it is other buildings, trees, hills etc. Putting it higher may get get over the obstructions and allow you to plot further away, remember it work by line of sight so if there is something between you and the aircraft it will be blind to it. The same will be true of outside versus inside as obstructions in your attic such as storage items will cause blind spots even your timber roof trusses can cause this.

Alan