AirNav Systems Forum

AirNav RadarBox and RadarBox24.com => AirNav RadarBox and RadarBox24.com Discussion => Topic started by: mdobuk21 on November 11, 2008, 10:10:31 PM

Title: antenna placing
Post by: mdobuk21 on November 11, 2008, 10:10:31 PM
hi, at present my antenna is outside on my bedroom window cill and i recieve around 500 flights in mylog a day (liv in leeds 7mile from LBA), do you think i may get a bigger reception if my antenna was in the loft? sometimes i have no flights at all in myflights coloumn?!

cheers
Mark
Title: Re: antenna placing
Post by: Blackthorn on November 11, 2008, 10:23:31 PM
Hi Mark

I have my antenna in the loft and track up to 120 flights via my radarbox at a time, I get excellent coverage from the South Coast to the Scottish Borders. I did have an external antenna but the results were not much better (Maybe cable loss etc) so I took it down.

The draw back for me is the supplied antenna only has 3 metres of cable where as my previous SBS had 5 which enabled me to get to the apex of the loft.

Kevin
Title: Re: antenna placing
Post by: CoastGuardJon on November 11, 2008, 10:28:43 PM
Hi Mark, the higher and clearer in the air you can get your antenna, the better will be your range and reception.   1090 MHz is line of sight (although certain weather and atmospheric conditions can give some freaky reception of all radio frequencies).    A masthead amp or pre-amp just inside the loft where cable is routed in will also help.    A pre-amp needs to be as close to the antenna itself as possible, so it can amplify the desired RF signal rather than background "noise".   Some have a pre-amp at the rear of the Box, but (IMO) I don't see how this is really going to help anything, as the insertion of the pre-amp causes some loss of desired signal and is just boosting the whole signal unless there are some very efficient and clever filters built in.    Hope this helps and doesn't just confuse!
Title: Re: antenna placing
Post by: mdobuk21 on November 11, 2008, 10:29:37 PM
cheers kevin! my polar diagram shows coverage to newcastle to the north and around walasey to the west, just wanted to know if i could get a bit better coverage to the south!!
Title: Re: antenna placing
Post by: CoastGuardJon on November 11, 2008, 10:31:36 PM
Hi Mark, what have you got in the way of obstructions to the south - if it's trees you'll probably notice a difference as the leaves fall.
Title: Re: antenna placing
Post by: mdobuk21 on November 11, 2008, 10:31:47 PM
cheers coastguardjon, not confusing at all! think im being greedy, just want a bit more coverage!
Title: Re: antenna placing
Post by: mdobuk21 on November 11, 2008, 10:32:44 PM
yeah its trees and houses thats why i thought if i put the antenna in the loft it may help?!
Title: Re: antenna placing
Post by: Tailwinds on November 11, 2008, 10:46:24 PM
Can you only put the antenna in the loft if it is near a loft window or skylight? I was thinking about putting mine in the loft but I thought signals would be blocked by the roof tiles. I too have my antenna on the upstairs bedroom window sill with fairly good results for Heathrow which is my nearest.
Title: Re: antenna placing
Post by: Blackthorn on November 11, 2008, 10:47:52 PM
The roof tiles do not obstruct my reception only the house next door :-(

Try it, you may be surprised.
Title: Re: antenna placing
Post by: mdobuk21 on November 11, 2008, 11:01:50 PM
just put my antenna in the loft ,see what results i get through the night!

mark
Title: Re: antenna placing
Post by: Blackthorn on November 12, 2008, 01:31:03 PM
Mark

Try and place it as high as possible in the loft.

Kevin
Title: Re: antenna placing
Post by: Blackthorn on November 12, 2008, 01:36:28 PM
Whilst on the subject of antennas I notice that some members have both SBS and Airnav systems, has anyone tried the SBS mobile whip on the Airnav and if so what were the results?

I would like to get the mobile whip a bit higher in the loft but the Radarbox antenna is only 3 metres but you can get the SBS one with 5 metres.

Kevin
Title: Re: antenna placing
Post by: viking9 on November 12, 2008, 04:50:44 PM
Whilst on the subject of antennas I notice that some members have both SBS and Airnav systems, has anyone tried the SBS mobile whip on the Airnav and if so what were the results?

I would like to get the mobile whip a bit higher in the loft but the Radarbox antenna is only 3 metres but you can get the SBS one with 5 metres.

Kevin

Kevin,

Why not get somebody like Moonraker to make up a patch lead with a male SMA connector on one end and a female SMA on the other.

Incidentally, I just bought a Moonraker Radar 100 vertical antenna and although it's just in a temporary position about 8 feet off the ground it is giving a much improved coverage.

BTW, I just got some nice pics of the NASA WB57 at Mildenhall this afternoon. I rushed over there having seen it on the climbout on the RB.

Regards,

Tom
Title: Re: antenna placing
Post by: RodBearden on November 12, 2008, 05:14:24 PM
Tom - do you want to put a WB57 pic in the Intersting Aircraft thread?

Rod
Title: Re: antenna placing
Post by: viking9 on November 12, 2008, 06:15:54 PM
Rod,

Yes - I didn't know there was an interesting aircraft thread. Where is it?

Tom
Title: Re: antenna placing
Post by: Blackthorn on November 12, 2008, 06:34:08 PM
Hi Tom

Well some people have all the luck, clear skies and a WB57 on the same day!!!

I am not sure about using a patch lead because of introducing loss in to the cable. Back in the days of my SBS I paid to have the Kinetic antenna installed on the roof and that resulted in little improvement over my loft setup so I am relectant to throw too much money in to antennas.

Kevin
Title: Re: antenna placing
Post by: tarbat on November 12, 2008, 07:02:37 PM
Worth considering a pre-amp if your antenna is in the loft.  Mine's been running in the loft for a few weeks now with a pre-amp, and I've now seen 100% improvement in coverage over the standard antenna without a pre-amp.

See previous thread - http://www.airnavsystems.com/forum/index.php?topic=1302.msg10765#msg10765
Title: Re: antenna placing
Post by: RodBearden on November 12, 2008, 07:23:32 PM
Tom - it's here: http://www.airnavsystems.com/forum/index.php?topic=543.0 (http://www.airnavsystems.com/forum/index.php?topic=543.0)

Rod
Title: Re: antenna placing
Post by: mdobuk21 on November 12, 2008, 08:20:30 PM
hi antenna reception was shocking in the loft wih only 34 flights in mylog! from 12am to 7:45am!

Mark
Title: Re: antenna placing
Post by: Blackthorn on November 12, 2008, 09:55:10 PM
Thats a shame Mark but it was worth trying, I am currently tracking 72 in myflights.
Title: Re: antenna placing
Post by: viking9 on November 12, 2008, 10:55:20 PM
Hi Tom

Well some people have all the luck, clear skies and a WB57 on the same day!!!

I am not sure about using a patch lead because of introducing loss in to the cable. Back in the days of my SBS I paid to have the Kinetic antenna installed on the roof and that resulted in little improvement over my loft setup so I am relectant to throw too much money in to antennas.

Kevin

Luck! Luck didn't come into it Kevin. I've spent at least ten days in total waiting at the Hall for that aircraft to show up. I was lucky with the weather though. I've posted a couple of the pics in the 'Interesting Aircraft' thread.

Regarding the patch cable, I was only suggesting a short length, perhaps a couple of metres, to allow you to get  a bit more height. As a former radio ham I know all about losses in cables. I've found that to have any improvement from the Radar 100 vertical which has a 6 dB gain at 1090 MHz, over the supplied whip, I have to keep the cable length down to 3 metres. Testing it yesterday I was getting between 190 and 205 messages/second as opposed to 75/120 with the whip.

Tom
Title: Re: antenna placing
Post by: Blackthorn on November 13, 2008, 06:58:28 PM
Tom, when you get sunshine and a rare aircraft at the same time thats luck in the UK ;-)

Kevin
Title: Re: antenna placing
Post by: CoastGuardJon on November 13, 2008, 08:25:46 PM
As a former radio ham I know all about losses in cables. I've found that to have any improvement from the Radar 100 vertical which has a 6 dB gain at 1090 MHz, over the supplied whip, I have to keep the cable length down to 3 metres.

Hi Tom, I have to ask, what cable are you referring to, to get such losses, could there be a poor connection somewhere?
Title: Re: antenna placing
Post by: viking9 on November 14, 2008, 05:41:10 PM
The cable is RG58/5mm.  The loss per 10M @ 100MHZ is around 1.5 dBd. I've no idea what it is at 1090 MHz.

Tom
Title: Re: antenna placing
Post by: CoastGuardJon on November 14, 2008, 07:37:41 PM
Hi Tom, I've had a dig around, this is the spec. for Maplin's RG58

A screened RF cable having a stranded core 17/0·19mm tinned copper conductor with a solid polyethylene insulator and a braided copper screen.Sheathed overall in black PVC.

Back to Top
Technical Specification

   
Specifications: 
Overall diameter: 5mm 
Centre conductor: 17/019mm 
Nominal impedance: 50? 
Attenuation per 10m: 2dB at 100MHz 
 76dB at 1000MHz 

I must admit I'm astonished that the losses are that high, from what I remember 3db loss = 50% reduction of signal?
Title: Re: antenna placing
Post by: CAM on November 14, 2008, 09:10:29 PM
I have recently moved my aerial and box into the loft, using a USB extender. My flights have increased from an average of 30 to aroud 70.

I have only really moved the antena about another 6 foot up but the increase is amazing.(Plus there is another 4 foot to go, after some DIY)

I can now receive flight at high altitude over north London & south Wales.

Not bad for only £20.00, well worth a try.

Cam
Title: Re: antenna placing
Post by: Tailwinds on November 27, 2008, 08:46:19 PM

The roof tiles do not obstruct my reception only the house next door

Try it, you may be surprised.

Well I did. Crikey! I'm amazed. I'm using the supplied ANRB antenna and I placed it in the loft almost to the apex. I drilled a little hole in the bedroom ceiling for the antenna cable to go through and my Radar box is right up near the ceiling on a little shelf. My reception has improved a great deal. I now pick up a regular 80/100 in "My Flights" whereas before, when it was on the upstairs bedroom window cill, I was only getting approx 30/45 in "My Flights".
I thought that the roof tiles would block out the signals but surprisingly they haven't.
Title: Re: antenna placing
Post by: Blackthorn on November 27, 2008, 10:34:23 PM
Hi Tailwinds

I am glad someone else has the same success as me using just the whip antenna in the loft.

Kevin
Title: Re: antenna placing
Post by: nbquidditch on November 28, 2008, 09:05:58 AM
I'm glad I live on a narrowboat! The boat is steel hull so I simply mount the antenna directly onto the roof. I can see as far East as the Wash and right down to the South Coast and North as far as Blackpool form my position on the canal. I'm almost smack in the centre of England & right on the flight path's for Coventry, Birmingham & East Midlands! I'm getting over 1000 flights a day:)


NBQuidditch