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 Post subject: Collinear Antenna
PostPosted: Thu May 11, 2017 3:26 am 
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Liam89 - FlightAware user avatar

Joined: Thu Feb 16, 2017 5:37 am
Posts: 1
Hi all, Just a quick question,
I have a Diamond X-300 2/70 antenna on the side of the house for my amateur radio, and I want to install an ads-b 1090mhz collinear next to it about 1-2 foot apart for the piaware tracking, due to restrictions then this is the only place I can get it,
Would transmitting at 50w through my X-300 damage or interfere with the ads-b collinear with it being close
by ?,
At the moment my adsb collinear is stuck inside in the window,
I want to get it outside and high up next to my amateur radio antenna is the only plausible option,
Just don't want to go ahead and do it then to transmit on my amateur radio and blow out the antenna and the Pi,
Any help would be great,
Been stuck for weeks without an answer
Thank you


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 Post subject: Re: Collinear Antenna
PostPosted: Thu May 11, 2017 6:06 am 
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FlightAware Staff
obj - FlightAware user avatar

Joined: Tue Sep 30, 2014 7:14 pm
Posts: 3676
Interfere, definitely.
Damage, possibly - I don't know offhand what the maximums on the dongle frontend are, but they are set up for receiving 200W transmitters at 300km, 50W at 1ft is probably pushing it!

edit: specs I found say +10dBm (= 10mW) maximum input power (that is at the tuner, so after antenna / feedline / etc losses). You will need to find something like 45dB of losses..

Can you mount the ads-b antenna above/below the other antenna where it's mostly out of the radiation pattern perhaps?


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 Post subject: Re: Collinear Antenna
PostPosted: Thu May 11, 2017 11:40 am 
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FlightAware Staff
david.baker - FlightAware user avatar

Joined: Thu Jan 23, 2014 12:34 pm
Posts: 164
The FA band pass filter can filter out about 30dB of power but it isn't rated for 50W continuous power dissipation.
I am assuming that you aren't transmitting all the time so this might work fine for you.
Otherwise you might have to use a higher power high pass filter and then the FA band pass filter.

Here are the specs on the FA bandpass filter.

Frequency Range 5 ~ 2000 MHz
Pass Band Frequency Range 980 ~ 1150
Pass Band Insertion Loss < 2.5 (1.5 Typ.)
Pass Band Return Loss > 13.0 (16 Typ.)
Stop Band Rejection 5 to 884 MHz > 30.0 (35 Typ.)
1270 to 2000 MHz > 30.0 (35 Typ.)

I have also run a couple Watts of power through the front end of the prostick and I didn't see any permanent damaged. It of course can't see anything with so much power going through the front end but works fine after the signal was removed.

We have a few airport locations running for almost 2 years and haven't seen any problems. The super Jumbo jets output 500W on ADSB and they are a few thousand feet away from the antenna. Most planes are in the 200-300W range but they can go down to 5W and up to 500W.


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 Post subject: Re: Collinear Antenna
PostPosted: Thu May 11, 2017 3:36 pm 
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FlightAware Member
Skibox - FlightAware user avatar

Joined: Tue Nov 17, 2015 12:33 pm
Posts: 84
If you have to install them like that I would opt for a cavity filter. Luckily, all your transmission is out-of-band compared to the 1090 MHz receiver. A good cavity will provide 80-90 dB rejection or more to your VHF/UHF frequencies

But, both antennas will be notably compromised by having another antenna in their respective near-field. But, sometimes there is no other option.


david.baker wrote:
The FA band pass filter can filter out about 30dB of power but it isn't rated for 50W continuous power dissipation.


It's not even remotely possible to couple the entire output power from one omni antenna into another. You would only get 50 W into the filter if you actually connected the 2 coaxial cables without any antennas...

/M


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 Post subject: Re: Collinear Antenna
PostPosted: Thu May 11, 2017 8:07 pm 
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k6rtm - FlightAware user avatar

Joined: Tue Nov 18, 2014 10:18 pm
Posts: 426
Location: Silicon Valley
For one of my ADS-B trackers, I use a discone on the roof -- it's wideband, 54 - 1200 MHz roughly.

It's fed by 9913 and has a Comet CF-413B duplexer on it in my office/ham shack.
http://www.universal-radio.com/catalog/hamantm/2758.html

The low-pass side of the CF-413B is 1 - 460 MHz more or less. That side goes to my Icom 2m/440 radio, occasionally switched to my HF-6m radio.

The high pass side is 840 - 1300 MHz, and goes to the ADS-B system through a FlightAware bandpass filter.

I ran a lot of tests, and didn't see any dips in ADS-B performance while transmitting on either 2m or 440, at full power (around 40W). Haven't done any high power transmitting through the discone on HF-6.

The Comet docs show attenuation probably exceeding 60dB below 50 MHz, and 50dB or better in the 2m and 440 ham bands. Follow that up with the FlightAware filter and you should be good at the 50 watt level on 2 and 440.

I also use high quality cables in the shack -- no cheepie 8x or RG-58, and have good RF grounds.

Very satisfied with performance of the CF-413B for combined ADS-B and VHF/UHF work. You could try using it as a high pass filter, properly terminating the low-pass port, and running the high-pass port through the FLightAware filter to your ADSB system.

best 73-

Bob K6RTM


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 Post subject: Re: Collinear Antenna
PostPosted: Fri May 12, 2017 4:45 pm 
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KK4PP - FlightAware user avatar

Joined: Tue Feb 28, 2017 3:54 pm
Posts: 21
I have a 440 MHz D-Star repeater antenna 50' away transmitting 5w into a Comet GP-6 at the same elevation as my ADS-B antenna. When the repeater keys up, the planes disappeared. So it will definitely interfere. Damage--who knows. My solution was to install the $20 FA inline filter even though the blue FA Pro Stick Plus has a filter built in. I installed the filter and it fixed my issue. You are at 50w and much closer proximity so I would expect to have some issues.

I also have a 1w 440 MHz antenna 1' from my ADS-B antenna and have no issues with it.

You probably need to figure out how to get the ADS-B antenna either a few feet above or below the Diamond. Then you should be fine...


73,

Jason
KK4PP


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