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Author Topic: Antenna Query From New Radarbox User  (Read 23899 times)

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covernotes

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Antenna Query From New Radarbox User
« on: January 25, 2010, 01:09:43 PM »
Hi All,
I have had my AirNav Radarbox for less than two weeks.
I am situated in Melbourne Australia.
The supplied antenna has been comfortably been receiving aircraft in a radius of up to 40 nm
Today I made and installed the 1090 Mhz ADS-B Vertical Antenna (10/08/2006).
I have been very disappointed with the results.
It has only increased my catchment by approx 25% to a radius of 50nm extending to 70nm due south over Port Phillip Bay.
I have attached pictures of its construction. Any clues where I have gone wrong or how I can improve its range.
http://img200.imageshack.us/img200/3553/aerial007.jpg
http://img59.imageshack.us/img59/5025/aerial008.jpg
http://img686.imageshack.us/img686/4458/aerial010.jpg
http://img402.imageshack.us/img402/7271/aerial019.jpg
Many thanks......
Covernotes (Melbourne)

Allocator

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Re: Antenna Query From New Radarbox User
« Reply #1 on: January 25, 2010, 01:47:16 PM »
Hi Covernotes,

When you used your standard antenna, did you have it on the roof as well?  Losses in the antenna cable at 1090MHz can be significant, so if you are running a long cable, you could easily be reducing the advantage of having the antenna up high.

The standard RB antenna is actually very good.  I see aircraft out to 150 miles with the standard antenna in the window ledge of a third floor building.  I'm surprised that you were only getting 40 miles before.

Jeremy

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Re: Antenna Query From New Radarbox User
« Reply #2 on: January 25, 2010, 03:07:25 PM »
Test for a short across the coax plug into the RB to make sure the coax and fly lead is OK. It should be open. Connection into RB ok?
J.
G4DOQ
QRZ.com

orkney

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Re: Antenna Query From New Radarbox User
« Reply #3 on: January 25, 2010, 05:01:08 PM »
Hi,

Dont know if you should maybe get your box checked. When we started out we used the standard antenna on our ground floor windowsill and got around 200 nm, sometimes more.  This was obviously in the direction the window was pointing but the other side of the house was 50nm or more.

Claire

Allocator

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Re: Antenna Query From New Radarbox User
« Reply #4 on: January 25, 2010, 05:09:57 PM »
Hi,

Dont know if you should maybe get your box checked. When we started out we used the standard antenna on our ground floor windowsill and got around 200 nm, sometimes more.  This was obviously in the direction the window was pointing but the other side of the house was 50nm or more.

Claire

Depends where/how he installed his original antenna.  If it was inside or on the end of a long cable, he would have been lucky to get much more than 40 miles!

Of course it does depend just what traffic is around too!

GreekSpy2001

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Re: Antenna Query From New Radarbox User
« Reply #5 on: January 25, 2010, 05:27:40 PM »
Interested in testing my setup as I only get approx 100 miles in range.  Thru necessity I am some distance from my aerial by have used a very low loss coax cable.

Now this is academic for my as I'm only interested in what I can see from my vantage point and 100m around does give me ample warning. But would like to know if the are simple tests I can perform to see it  my setup is losing signal.

Thanks

Graham
PS complete novice to this side of things so explainations may have to be fairly basic ;-)

Allocator

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Re: Antenna Query From New Radarbox User
« Reply #6 on: January 25, 2010, 05:31:41 PM »
Graham,

Very easy - install RB on a laptop and take it out in the open along with your RB and the standard antenna.

I was somewhat distressed to see that I could get better range with the standard RB antenna on the roof of the car out in the open away from buildings - than I can from my external antenna mounted 30 feet higher than the roof of the car.  This can only be due to cable losses I guess.

GreekSpy2001

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Re: Antenna Query From New Radarbox User
« Reply #7 on: January 25, 2010, 06:00:07 PM »
mmm.  I'll try but lots of houses around so unless I can get on the roof not sure I can get a good enough replica of the potential field of view.  Still when the weather warms up maybe I'll try from the car roof ;-)

Terry

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Re: Antenna Query From New Radarbox User
« Reply #8 on: January 25, 2010, 09:07:58 PM »
Hi Covernotes,
                     I notice you used a PL259 fitting on your antenna,personally i would have used an "N" type as PL269s are not very efficient at high frequencies.Also i noted the 2 loops at the bottom of the antenna and into your house,by using just 1-4" bend at the gable end you will be able to reduce your co-axial length by about a metre,Also try not loop the co-axial on itself as this too may have an adverse effect.

                            Best Regards Terry.

covernotes

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Re: Antenna Query From New Radarbox User
« Reply #9 on: January 26, 2010, 02:18:46 AM »
Thank you all for your advice.
I will take it all onboard.
The supplied RB antenna was ever only used inside on a window sill.
The only antenna that has been on the roof is the new home brew.
I was unable to source 3.0mm copper wire in Australia.
I used 2.5mm copper wire that is used in car starter motors.
Is this measurement critical.
Things to do - Shorten the co-ax run-in by 20%.
Get on the roof top with a laptop and test the home brew on a short lead-in.
Also test the RB supplied antenna on the roof.
Try out a commercial ground plane collinear antenna. (N Socket) (for comparison)
Can anyone help me with a schematic of a simple pre-amplifer for 1090 mhz.
Any advice where one could be purchased cheaply.
I am open to any other advice that anyone wishes to give.
Thank you all again...
Covernotes (Melbourne)

ww7y

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Re: Antenna Query From New Radarbox User
« Reply #10 on: January 26, 2010, 04:49:20 AM »
I built a homebrew 9dB gain collinear antenna similiar to the commercial DPD.  It consists of 10 1/2wave sections of coax.  It is discussed here:

http://www.airnavsystems.com/forum/index.php?topic=3995.0

It works very well and I get aircraft out to about 220 nm.  I have it on a tower at 30 ft and fed it with very low loss LMR coax.


bratters

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Re: Antenna Query From New Radarbox User
« Reply #11 on: January 26, 2010, 10:29:13 AM »

The standard RB antenna is actually very good.  I see aircraft out to 150 miles with the standard antenna in the window ledge of a third floor building.  I'm surprised that you were only getting 40 miles before.


I couldn't agree more with you Allocator. Also your point about sticking it on a car roof serves to emphasise the "eccentricity" of aerial reception.

Like most I have experimented with different aerials, different cables and different positions and after a year's effort would offer the following advice:

Signal loss from aerial cable is considerable but there is no loss from USB cables. Replacing 12 metres of antenna cable with a 12 metre USB and moving my box away from the PC but close to the aerial totally transformed my expectations. Do you need to get at the box? If not, then bung it up near the aerial and cut out as much antenna cable as possible.

For indoor & loft use I have found that the supplied antenna is as good as, in fact better than, any of three "specialist" (expensive) antennas I have tried.

Position is clearly everything but it's seems to me to be a black art. For reasons I cannot explain, distances as little as a foot (or less!) seem to make vast - and I mean vast - differences. My supplied aerial is now perched on top of large round metal biscuit tin as high as possible in the loft. One would have thought dead centre would be best? Forget it. It is not placed centrally lengthways, but 3/4 of the length and is also a touch off-centre widthways.

It took a couple of weeks of trial and error to get it exactly right and as a result MyFlights have risen to 90/120  - an astounding figure considering that my virtually sea-level site is amid other houses and all previous efforts suggested 50/60 would be absolute maximum.

My Loft is now locked shut!

Good luck covernotes- it's worth persevering.


juangelb

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Re: Antenna Query From New Radarbox User
« Reply #12 on: January 26, 2010, 11:06:46 AM »
Hi Covernotes

I build two of this antennas and both works fine. (better than Wimo)
Receiving 240 NM from clear line of sight areas.
The first thing i noticed from your pictures is that You used a VHF coax connector... The right thing would be to use a UHF connector Type N.

Tell me please what coax cable did you used and how long running  it is.
It needs to be a low loss  cable suitable for UHF frequencies, and preferrable not exeding 10 meters...
Also the antenna needs to have a clear line og sight to horizon in all diections (very seldom possible)

Cheers


Mike_Tassy

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Re: Antenna Query From New Radarbox User
« Reply #13 on: January 26, 2010, 11:26:16 AM »
Hi covernotes, I have that same antenna as you and I can receive almost to the NSW / VIC border  - I live in Burnie,Tas  ......beyond 250nm

http://www.users.on.net/~silver.eagle/ADS-B.html

I have 10 mtrs of heliax attached  -  I used a  "N" type connector
Dimensions need to be exact to the 1mm , so you might need to try trimming / extending the top section 1 mm at a time, then  try it for a day or so.
Unfortunately building antennas blindly at these freqs without test gear is purely hit and miss  (in my experience)  .  Also try to use a single length of coax - no adaptors or joiners as these introduce huge losses
Keep at it
Mike

covernotes

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Re: Antenna Query From New Radarbox User
« Reply #14 on: January 31, 2010, 07:51:22 AM »
Thank you one and all.
Clambered up on the roof with a laptop only to find that the pin in the SMA connector had disappeared.
That was before I attached it to the RB.
It does not appear to be in the RB as the RB antenna still attaches smoothly.
I have done all the wrong things.
20 metres of cheap co-ax cable, lots of adapters and I did not use an N connector in the construction of the antenna.
I plan to rebuild the antenna using an N connector (no adapters)
Also will use 15 metres of LMR 400 low loss cable.
The question I ask is will the the loss from this run of cable still be too much.
Mike from Burnie is an inspiration.
I will listen to any further advice that may be offered.
Covernotes.