ADSB receiver in the tail?

..now in a separate topic for all of us who needs to make a decision which ADS-B System to get. I will be moving ADS-B topics into this section. If I missed some please send me a link via email to the ADS-B topic to ‚CK at forums url‘
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norcal64d
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ADSB receiver in the tail?

Post by norcal64d »

I have a Stratux ADSB receiver that sits on my dash and I would like to clean things up on in the cockpit a bit. I am thinking of running a usb cord under the floor back to the tail boom area behind the baggage compartment and mounting the receiver back there. I am thinking it would get good reception there since it would primarily be surrounded by fabric but I thought I was see if anyone else tried this? Any other options for a out of sight ADSB receiver?
Tim
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Re: ADSB receiver in the tail?

Post by HeavyLoad »

I use the dynon adsb receiver. And have a few adel clamps that attach to the cross bar at the top near the wing root. So it gets it out of the way for the most part. Then hide the charging cable under the panel covers. Works good. And mostly clean install.

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https://www.dynonavionics.com/drx-portable-adsb.php
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Re: ADSB receiver in the tail?

Post by norcal64d »

That's a neat little unit for sure. I have my 406 PLB mounted in that exact spot actually. I did some reading on various forums and it sounds like other aircraft have good luck mounting ADSB receivers back behind panels and such so I am going to give the tail boom area a try.
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Re: ADSB receiver in the tail?

Post by andy »

I have a Stratus 2 portable unit that I used to use when the aircraft that I was flying didn't have an ADS-B In receiver. I used a suction cup mount on the right rear window. It needs to be aligned with the longitudinal axis of the aircraft for the AHRS to work properly. It also needs to be within reach of the pilot in case you forget to turn it on before getting into the pilot seat. I put it on the right side so that I could see the lights by turning my head. It needs to be behind the wing so that the sky isn't blocked by the metal wing. Otherwise, the internal GPS might have problems. Most instrument panels have a metal shroud which doesn't completely block the signals from the ADS-B ground stations but can create a "shadow" area of reduced sensitivity if it's between the Stratus and the ground stations.

I debated clamping the Stratus cradle mount to one of the V-tubes above the glare shield but my Rosen sun visors would get in the way and the metal glare shield shroud might reduce the sensitivity.
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Re: ADSB receiver in the tail?

Post by Mog »

I use a sentry on the back window. Long USB cord going to it and it suctions to the window. It’s out of the way for the most part and is within reach of the pilot. It has been flawless to date. I did have some issues with the Carbon Monoxide detector going off but that seemed to be related to being mounted in the lower corner of my windscreen. Guess there was no airflow there and it didn’t like it.

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Re: ADSB receiver in the tail?

Post by andy »

I have an Appareo ESG/Stratus 2i ADS-B In/Out transponder system. The Stratus 2i receiver is mounted behind the right copilot kick panel. The 2i uses the ADS-B and GPS antennas in the ESG, which are mounted on the bottom of the cowling and top of the wing. Works great and I've never had any problems getting good signals. If you put a portable ADS-B receiver in that area, you would probably want to use an external GPS antenna mounted in the tail cone. The airplane fabric won't block the GPS signal as long it's not coated with anything metallic. The internal ADS-B In antenna of a portable receiver should work fine as long as the floorboards aren't replaced with something metallic. I don't think a metal belly pan is far enough aft to block the signal. You could always use an external ADS-B antenna as well. I thought of fabricating a bracket that would attach to the tubing in the tail cone with Adel clamps with the external GPS antenna pointing up and the external ADS-B antenna pointing down. Everything would be out of the way and out of sight then. The only downside would be that the Stratus would not be very portable.
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Re: ADSB receiver in the tail?

Post by Andy Young »

I have a Stratus portable for ADS-B in. It sits on top of my glare shield, right in the middle. Most of the top of my glare shield is aluminum. I also have a full aluminum belly, all the way from the firewall to the tailwheel. I have not had any reception issues with this set-up.

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Re: ADSB receiver in the tail?

Post by andy »

1090 MHz and 978 MHz radio signals bounce around metal objects easily since so many things are within multiples of their wavelengths but every time a bounce occurs there is some signal loss and out of phase reflections can cancel one another out at the receive antenna. In strong signal areas you would never know this. In a weak signal area the ADS-B status indicator in something like ForeFlight/iPad might indicate "No Towers" or "Marginal" instead of "Good". It's hard to notice when you're busy flying. In ForeFlight you can also click the gear icon, select your receiver and select Ownship to see the status of your ADS-B receiver. If it's green, the received signal is good. One way to check the sensitivity of your ADS-B receiver is to fly into an area where the ADS-B status is "Marginal" and move the receiver around the airplane to see if it changes to "Good". If it does, then something is blocking or canceling your signal.
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Re: ADSB receiver in the tail?

Post by Andy Young »

andy wrote:
Mon Mar 29, 2021 2:04 pm
1090 MHz and 978 MHz radio signals bounce around metal objects easily since so many things are within multiples of their wavelengths but every time a bounce occurs there is some signal loss and out of phase reflections can cancel one another out at the receive antenna. In strong signal areas you would never know this. In a weak signal area the ADS-B status indicator in something like ForeFlight/iPad might indicate "No Towers" or "Marginal" instead of "Good". It's hard to notice when you're busy flying. In ForeFlight you can also click the gear icon, select your receiver and select Ownship to see the status of your ADS-B receiver. If it's green, the received signal is good. One way to check the sensitivity of your ADS-B receiver is to fly into an area where the ADS-B status is "Marginal" and move the receiver around the airplane to see if it changes to "Good". If it does, then something is blocking or canceling your signal.
That makes sense. I’m headed back to Alaska soon, where the signal is almost always marginal (unless it’s not available at all). This will be a good test: To see if I still have signal where I used to, or now have no signal where it used to be marginal. If so, I’ll have to figure out another place to put the Stratus.

All that said, isn’t the Stratus intended to used on top of the glareshield on light aircraft, most of which are Cessnas, which are all aluminum?

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Re: ADSB receiver in the tail?

Post by Kirk »

The Stratus manual doesn’t necessarily recommend glare shield installation. It gives examples of side window etc installations. It does have a lot of precautions about heat buildup for the glareshield.

Like others, I have had very good results with the rear window starboard side. Like Andy said, it’s easy to see and reach. I found the power cord long enough to reach from the 12 volt receptacle on the panel.

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Re: ADSB receiver in the tail?

Post by Andy Young »

And yet it comes with a slide-resistant rubber mounting tray that could only be intended to sit on a flat surface. What surface could that be, other than the glareshield?

I’ve never had a problem with mine overheating, although I am in Alaska from April to October. I suspect if a I was hotter place, my results with this might be different.

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Re: ADSB receiver in the tail?

Post by andy »

Stratus glare shield mounts are mostly intended for a clear view of the sky for the GPS satellites. I guess they figure that you are likely to be within 2 miles of the ground but 12,550 miles from the satellites. Of course there are lots of other variables such as the power output, antenna orientation and gain of the ADS-B ground stations vs. the satellites. I think they are just trying to offer a convenient option for pilots who want to mount the Stratus quickly and easily. ForeFlight support has some tips to improve reception at: https://support.foreflight.com/hc/en-us ... g-options-
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Re: ADSB receiver in the tail?

Post by Andy Young »

I had a long think on this while I was flying today (six hour cross-country, so plenty of time to ponder...). Given that I’m usually flying between 500’ and 2000’ AGL, my Stratus would always be picking up signals from the side, not from below (unless I’m VERY, VERY close to a tower). So maybe that’s why it has always seemed to work fine on the glareshield; the glareshield and the metal belly are not in the way of the signals from the towers, as those signals are coming in from the side.

Out here in the mountain west, towers are few and far between, especially away from major cities, like Denver. There is rarely more than one within range. I can see where they all are on my moving map. I often have to zoom way, way out just to find the nearest one. Today, somewhere in northern Wyoming or Southern Montana, I was picking up one that was 35 miles away, while I was at 800’ AGL, and there was a higher ridge between us!

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Re: ADSB receiver in the tail?

Post by Andy Young »

According to this map, Wyoming has only nine towers, and is roughly 95,000 square miles!


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Re: ADSB receiver in the tail?

Post by andy »

The glare shield and belly metal would only affect ADS-B ground stations if they were below you. I think the GPS and ADS-B antennas in the Stratus 3 are on either side of the main circuit board, although I couldn't find anything on the Internet to confirm this. When it's sitting flat on the glare shield, the ADS-B antenna would pick up signals from the side if the station wasn't directly below you. In that regard you are actually better off at lower altitudes. As you increase altitude the metal glare shield and belly pan shadow a larger area although terrain doesn't block signals as much. Also, ADS-B ground stations are not all the same. There are high, medium and low towers to improve coverage. Here's a good article that describes it: https://ipadpilotnews.com/2012/05/flyin ... rspective/

Did you fly past Devil's Tower? I flew by it on the way back from McCall ID in 2016 and took some photos as the ceiling kept getting lower. The comment on sectional charts about national security still puzzles me. Someone in the charting office had a sense of humor.
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