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 Post subject: Cable between Flight stick and antenna
PostPosted: Sun Mar 05, 2017 3:18 pm 
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biekerc - FlightAware user avatar

Joined: Sat Jul 16, 2016 2:17 am
Posts: 39
I compared two antenna, a spider and the FA antenna + plus filter a while ago, both being located in the attic.

The one thing I did not change during this time was the connection between antenna and usb stick, the spider was always connected via a 3m RG316 pigtail cable, the FA antenna directly to the Pro stick/filter.

At the time it seemed the spider performed comparable or even somewhat better, e.g. higher mes/s count. Now I use the pigtail with a Pro Stick plus and the FA antenna, and now this setup seems to perform better than the Pro stick did with the external filter and FA antenna, especially the message/s count seems higher.

In short, I assumed a direct connection is better, but could this type of pigtail actually help to pick up signals?


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 Post subject: Re: Cable between Flight stick and antenna
PostPosted: Sun Mar 05, 2017 8:04 pm 
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k6rtm - FlightAware user avatar

Joined: Tue Nov 18, 2014 10:18 pm
Posts: 408
Location: Silicon Valley
biekerc wrote:
I compared two antenna, a spider and the FA antenna + plus filter a while ago, both being located in the attic.

The one thing I did not change during this time was the connection between antenna and usb stick, the spider was always connected via a 3m RG316 pigtail cable, the FA antenna directly to the Pro stick/filter.

At the time it seemed the spider performed comparable or even somewhat better, e.g. higher mes/s count. Now I use the pigtail with a Pro Stick plus and the FA antenna, and now this setup seems to perform better than the Pro stick did with the external filter and FA antenna, especially the message/s count seems higher.

In short, I assumed a direct connection is better, but could this type of pigtail actually help to pick up signals?

Ah, or the pigtail gets the antenna away from sources of noise that cause you problems, such as the usb stick, Pi, power supplies, and other such stuff. 3m of 316 isn't going to introduce a whole lot of loss.

The other variable is antenna elevation -- a few feet increase in elevation can let your antenna "see" a lot more, so examine that possibility as well.

bob k6rtm


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 Post subject: Re: Cable between Flight stick and antenna
PostPosted: Mon Mar 06, 2017 7:04 pm 
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zeek70706 - FlightAware user avatar

Joined: Wed Apr 23, 2008 6:00 am
Posts: 65
Location: Baton Rouge KBTR
I keep trying to mount my RPi and Prostick directly to my FA antenna on my tower and every time I get 1/2 of the messages even after adjusting the gain.

My current and best setup so far is RPi>Prostick>pigtail>40ft RG6>F-N adapter>FA 50" antenna 35ft AGL.

I have tried:
RPi>3m USB cable>Prostick>SMA-N adapter>FA 50" antenna 35ft AGL
RPi>Prostick>SMA-N adapter>FA 50" antenna 35ft AGL
RPi>Prostick>FA Filter>SMA-N adapter>FA 50" antenna 35ft AGL

In all cases RPi is using WiFi and the antenna is on a 30ft tower on a 5ft wooden stick.
During all trials I ran an extension cord up the tower to power the RPi near the top.

I have ordered a different SMA-N adapter to try. (I hope this is the issue)
I have added an all metal RTL-SDR case/heatsink to the Prostick.


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 Post subject: Re: Cable between Flight stick and antenna
PostPosted: Mon Mar 06, 2017 8:37 pm 
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k6rtm - FlightAware user avatar

Joined: Tue Nov 18, 2014 10:18 pm
Posts: 408
Location: Silicon Valley
zeek70706 wrote:
I keep trying to mount my RPi and Prostick directly to my FA antenna on my tower and every time I get 1/2 of the messages even after adjusting the gain.

Ya know what would be interesting, do some wideband scans with something like rtl-power to see what kind of signal environment you're in. You might (probably) have some high power sources nearby, cell towers, digital TV, business band stuff, that is overloading the front end of the Prostick.

The prostick front end has a (wideband) LNA, then the normal SDR. The Prostick Plus adds a very narrow ADS-B filter between the LNA and the normal SDR.

Because of the wideband design of the SDR, strong out of band (non ADS-B) signals can turn everything into garbage.

I know in my environment, I get better results with the FLightAware filter between the antenna and my Prostick Plus SDR because of local transmitters, which include businesses, FM, and cell towers.

If you find culprits on a few select frequencies, you can look at what kind of filter to use to knock them out. I'd probably order one of the FlightAware filters ($20 from Amazon if you're in the U.S.)

Experiment and let us know what you learn.

bob k6rtm


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 Post subject: Re: Cable between Flight stick and antenna
PostPosted: Mon Mar 06, 2017 9:01 pm 
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chrisjohnston50 - FlightAware user avatar

Joined: Fri Apr 01, 2016 3:29 am
Posts: 148
Location: Fort Lauderdale
I agree with Bob.

Try something like this:

Image


Image


Image


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 Post subject: Re: Cable between Flight stick and antenna
PostPosted: Mon Mar 06, 2017 9:43 pm 
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zeek70706 - FlightAware user avatar

Joined: Wed Apr 23, 2008 6:00 am
Posts: 65
Location: Baton Rouge KBTR
Actually what I am going for is exactly what Chris has.

I have a FA filter and tried it in some of my tests.
RPi>Prostick>FA Filter>SMA-N adapter>FA 50" antenna 35ft AGL

My current setup works better without the filter. But I have tried it several times on the test setups with no effect.

On a side note, my antenna is mounted to the tower with wood. Is it important for it to be mounted with metal for grounding? It has always worked well on the stick but i have never tried metal.


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 Post subject: Re: Cable between Flight stick and antenna
PostPosted: Tue Mar 07, 2017 2:29 am 
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chrisjohnston50 - FlightAware user avatar

Joined: Fri Apr 01, 2016 3:29 am
Posts: 148
Location: Fort Lauderdale
zeek70706 wrote:
Actually what I am going for is exactly what Chris has.

I have a FA filter and tried it in some of my tests.
RPi>Prostick>FA Filter>SMA-N adapter>FA 50" antenna 35ft AGL

My current setup works better without the filter. But I have tried it several times on the test setups with no effect.

On a side note, my antenna is mounted to the tower with wood. Is it important for it to be mounted with metal for grounding? It has always worked well on the stick but i have never tried metal.


Zeek,

I've never tried it without grounding, so I can't say it works better one way or another. Sorry.

The setup with the funnel is no longer active. I was using it for experimental purposes and never used it without the FA filter because I needed the extra length to make it work with the funnel.

Currently, I'm running my Pi in my living room, connected to the network via ethernet and running a 3' pigtail through the wall to LMR400 and up about 24' AGL to a 26" FA antenna which, at my location, ends up being about 33' MSL. That's the LMR400 you see running up the main mast in the lower photo.

Here is my source for the pigtail: https://www.amazon.com/gp/product/B00VP ... UTF8&psc=1


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 Post subject: Re: Cable between Flight stick and antenna
PostPosted: Tue Mar 07, 2017 12:33 pm 
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zeek70706 - FlightAware user avatar

Joined: Wed Apr 23, 2008 6:00 am
Posts: 65
Location: Baton Rouge KBTR
Here is my original plan until I discovered reception issues.
PVC pipe containing RPi and powersupply.
Image

Then a USB extension to the Prostick and adapter on the antenna inside of the conduit.
Image

After this all of my tests have been without the pvc and conduit. I just hang the Prostick and RPi directly from the antenna and put it up for a while.

My reception has been the same every time. The only part I can't change is the SMA-N adapter so I'm hoping the new adapter I have on order will do the trick.


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 Post subject: Re: Cable between Flight stick and antenna
PostPosted: Sun Mar 12, 2017 3:20 pm 
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zeek70706 - FlightAware user avatar

Joined: Wed Apr 23, 2008 6:00 am
Posts: 65
Location: Baton Rouge KBTR
Prostick(orange) connected directly to the 49" antenna will not work. I cant make it work. If I connect 6 feet of RG6, my msg rate goes from 30 to 80 per sec. at ground level. The FA filter does not help. No gain settings help any significant amount. I even have the metal case on it from RTL-SDR.


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 Post subject: Re: Cable between Flight stick and antenna
PostPosted: Sun Mar 12, 2017 9:54 pm 
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zeek70706 - FlightAware user avatar

Joined: Wed Apr 23, 2008 6:00 am
Posts: 65
Location: Baton Rouge KBTR
Here are data charts during my tests with the new SMA-N adapter. Same results as before.
Notice the noise goes up without the cable and reception goes way down. 1500-1600 is with 6ft of RG6 and the tower up. Beginning and end are the normal setup with 40ft of RG6. I tried with and without the FA filter and with and without a 9.5 ft USB cable between the Pi and the Prostick. Do the charts shed light on the issue?


Image


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