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02-20-2012, 04:58 PM
Mike | Transponder
Where do you all have your transponder antenna located on/in your plane?
Traveling from NY to Fl and back I noticed that ATC was receiving intermittent signals from my transponder. This is due to the location of the antenna in the starboard nose of the plane. I noticed with a scope and a small length of wire..... as I walked around the plane the strongest signal was from the 12 o clock to the 4 o'clock position, basically out the copilots side. It seems that the NLG and the radio stack stops the signal from getting out the pilots side of the plane.
There are several problems associated with the placement of the antenna.
Antenna Position (mounting) - Since we have a composite plane we need to choose an antenna that doesn't need a ground plane. The problem with this style of antenna is that the distance of the transmitted signal is generally less than that of an antenna with a ground plane. If we choose an antenna that needs a ground plane, one will need to add a thin plate of metal or foil tape to the back of the antenna. (ground plane would be the metal airframe in most cases)
Line loss (coax) - Line loss is a big problem. The further away from the transponder with the antenna the less power will be supplied to the antenna. RG400 max run is 6'1.3" while ECS 310801 is 30'.
I am in the process of relocating a new antenna in the rear of the plane.
Well that's the short story.....any more out there?
Mike
02-20-2012, 06:36 PM
Fred Lohr
interesting. jack ardoyno and I had a lot of complaints from ATC on lack of transponder signal on the way down to florida last fall. my problem turned out to be, in part, one or two inches of water in the rt nose gear compartment that houses the ground plate (under battery) and antenna. once the water was drained at our halfway stop, and the antenna was no longer under water, it worked a lot better. the only other time this happened was when a bag of lead shot i had in front for ballast broke on a water takeoff, and all the bb's ran down around the antennae. It must be hard to transmit thru lead, cause the transponder kept overheating and quitting, which also happened with the water.
so the next best place might be project down thru the the floor next to the right sided support beam. The grounding plate, (aluminum disk ) could sit on top of the floor with the approx three inch antenna projecting downward. Under the foward part of passenger seat, closer to the midline would be nice so the cable is short and out of the way. Is there enough depth there? plate could be raised up a bit so tip of antennae does not project thru hull but is just at the inside surface of hull. what do you think.
What do you think
02-20-2012, 10:25 PM
Russ Kotlarek | Antenna Placement
Please note the Transponder is one radio that supplies an enormous amount of power >200W on a frequency of 1090 Mhz. I addition it is a transmitter that continually is transmitting. The radiation from this transmitter specifically is rather unhealthy to have too close to crew or passengers.
An artificial ground plane as Mike suggested is a great way to boost its effectiveness. Indeed the longer the cable the greater the cable loss even more so depending on the type of cable used. The newer style aviation grade low loss cable does pretty well but keeping it to the minimal length and connectors is something to strive for. But keeping it away from you is even a better thing to strive for.
Comms only produce < 25 Watts and at a frequency about 10 times lower and rarely used in flight so sitting near that one is not nearly as bad.
Interesting enough the best location for the Lake amphib is on the bottom of the hull behind the step. Yep a hole in the bottom. I do not have mine there for obvious reasons but I guess it works. Anything that shorts out the antenna like water or lead shot obviously will hamper the output but could easily drive the final output circuit of the Transponder into failure so the environment is also important.
I do not have the answer but in making this decision these points might be important. How about a normal 4" or so Transponder antenna mounted on a light weight aluminum plate or foil inside the wing for a good ground plane bonded to bottom of the top skin inside?
Russ
02-20-2012, 10:58 PM
keithw | Transponder antena
My transponder antena is directly below the pilots seat. It has a metal disc typ ground plane attached and works very well. At the time of installation I was told that all radiation would be down and away from pilot and others. I have had very good trans/rec. performance. Keith N80CC P S No bb s or water prob I just drilled a small hole in the floor below the pilots seat (approx center) and then had antena pushed thru with the ground plane flush mtd on the floor. Carpet is installed around cable mounting end.
03-02-2014, 09:49 PM
Rusty | Xpndr antenna
Quote:
Originally Posted by keithw View Post
My transponder antena is directly below the pilots seat. It has a metal disc typ ground plane attached and works very well. At the time of installation I was told that all radiation would be down and away from pilot and others. I have had very good trans/rec. performance. Keith N80CC P S No bb s or water prob I just drilled a small hole in the floor below the pilots seat (approx center) and then had antena pushed thru with the ground plane flush mtd on the floor. Carpet is installed around cable mounting end.
Did you buy that antenna, or make it yourself? I just received my complete avionics package from GRT and find nothing that looks like a transponder antenna. Back in the dark ages when I started this project, Dean Rickerson advised a copper ground plane in the top of the vertical tail to which I expected to attach one rod down for transponder, one rod up for GPS. Other comments here say keep the coax from xpndr to antenna short. Using a Trig remote xpndr, I could mount it back there, but your idea sounds better. Any concerns about that high frequency high energy source running continuously under the family jewels?
03-06-2014, 04:51 PM
Mike
At our age.... Hell no.
They are starting to make remote ponders and comms...best way to go
Mike | Transponder
Where do you all have your transponder antenna located on/in your plane?
Traveling from NY to Fl and back I noticed that ATC was receiving intermittent signals from my transponder. This is due to the location of the antenna in the starboard nose of the plane. I noticed with a scope and a small length of wire..... as I walked around the plane the strongest signal was from the 12 o clock to the 4 o'clock position, basically out the copilots side. It seems that the NLG and the radio stack stops the signal from getting out the pilots side of the plane.
There are several problems associated with the placement of the antenna.
Antenna Position (mounting) - Since we have a composite plane we need to choose an antenna that doesn't need a ground plane. The problem with this style of antenna is that the distance of the transmitted signal is generally less than that of an antenna with a ground plane. If we choose an antenna that needs a ground plane, one will need to add a thin plate of metal or foil tape to the back of the antenna. (ground plane would be the metal airframe in most cases)
Line loss (coax) - Line loss is a big problem. The further away from the transponder with the antenna the less power will be supplied to the antenna. RG400 max run is 6'1.3" while ECS 310801 is 30'.
I am in the process of relocating a new antenna in the rear of the plane.
Well that's the short story.....any more out there?
Mike
02-20-2012, 06:36 PM
Fred Lohr
interesting. jack ardoyno and I had a lot of complaints from ATC on lack of transponder signal on the way down to florida last fall. my problem turned out to be, in part, one or two inches of water in the rt nose gear compartment that houses the ground plate (under battery) and antenna. once the water was drained at our halfway stop, and the antenna was no longer under water, it worked a lot better. the only other time this happened was when a bag of lead shot i had in front for ballast broke on a water takeoff, and all the bb's ran down around the antennae. It must be hard to transmit thru lead, cause the transponder kept overheating and quitting, which also happened with the water.
so the next best place might be project down thru the the floor next to the right sided support beam. The grounding plate, (aluminum disk ) could sit on top of the floor with the approx three inch antenna projecting downward. Under the foward part of passenger seat, closer to the midline would be nice so the cable is short and out of the way. Is there enough depth there? plate could be raised up a bit so tip of antennae does not project thru hull but is just at the inside surface of hull. what do you think.
What do you think
02-20-2012, 10:25 PM
Russ Kotlarek | Antenna Placement
Please note the Transponder is one radio that supplies an enormous amount of power >200W on a frequency of 1090 Mhz. I addition it is a transmitter that continually is transmitting. The radiation from this transmitter specifically is rather unhealthy to have too close to crew or passengers.
An artificial ground plane as Mike suggested is a great way to boost its effectiveness. Indeed the longer the cable the greater the cable loss even more so depending on the type of cable used. The newer style aviation grade low loss cable does pretty well but keeping it to the minimal length and connectors is something to strive for. But keeping it away from you is even a better thing to strive for.
Comms only produce < 25 Watts and at a frequency about 10 times lower and rarely used in flight so sitting near that one is not nearly as bad.
Interesting enough the best location for the Lake amphib is on the bottom of the hull behind the step. Yep a hole in the bottom. I do not have mine there for obvious reasons but I guess it works. Anything that shorts out the antenna like water or lead shot obviously will hamper the output but could easily drive the final output circuit of the Transponder into failure so the environment is also important.
I do not have the answer but in making this decision these points might be important. How about a normal 4" or so Transponder antenna mounted on a light weight aluminum plate or foil inside the wing for a good ground plane bonded to bottom of the top skin inside?
Russ
02-20-2012, 10:58 PM
keithw | Transponder antena
My transponder antena is directly below the pilots seat. It has a metal disc typ ground plane attached and works very well. At the time of installation I was told that all radiation would be down and away from pilot and others. I have had very good trans/rec. performance. Keith N80CC P S No bb s or water prob I just drilled a small hole in the floor below the pilots seat (approx center) and then had antena pushed thru with the ground plane flush mtd on the floor. Carpet is installed around cable mounting end.
03-02-2014, 09:49 PM
Rusty | Xpndr antenna
Quote:
Originally Posted by keithw View Post
My transponder antena is directly below the pilots seat. It has a metal disc typ ground plane attached and works very well. At the time of installation I was told that all radiation would be down and away from pilot and others. I have had very good trans/rec. performance. Keith N80CC P S No bb s or water prob I just drilled a small hole in the floor below the pilots seat (approx center) and then had antena pushed thru with the ground plane flush mtd on the floor. Carpet is installed around cable mounting end.
Did you buy that antenna, or make it yourself? I just received my complete avionics package from GRT and find nothing that looks like a transponder antenna. Back in the dark ages when I started this project, Dean Rickerson advised a copper ground plane in the top of the vertical tail to which I expected to attach one rod down for transponder, one rod up for GPS. Other comments here say keep the coax from xpndr to antenna short. Using a Trig remote xpndr, I could mount it back there, but your idea sounds better. Any concerns about that high frequency high energy source running continuously under the family jewels?
03-06-2014, 04:51 PM
Mike
At our age.... Hell no.
They are starting to make remote ponders and comms...best way to go
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