RG400 Bundled

[ethand]

Is it safe to bundle multiple RG400 antenna runs in the corrugated tube wire conduit or do I need to separate them?

Thanks
E

 

[Jesse]

It depends mainly what signals they are carrying. Generally the Transponder wire should be separate from others. Receive-only wires have less interference than transmitting ones.

 

[ethand]

Thanks Jesse. These would be Com antenna (x2) and GPS antenna (X2) and depending on room the VOR/Glideslope

E

 

[Jesse]

There are other people that can answer better than I can, but I have regularly had COM coax mixed with NAV coax for short to medium runs with no problems. I always keep the transponder coax separate and short. If you use RG-400 it should be ok, but try not to keep them too tight for too long.

 

[GeraldC]

I'm a newbie to aviation, but I've spent lots of time in my day job chasing down interference between different RF signals, and I personally would avoid bundling the com transmit antenna with the gps receive antenna if at all possible. By bundling those, you would be bundling a cable with a HUGE transmit signal right next to an important antenna that's trying to receive a TINY signal.

It will probably work if the shielding is good and harmonics are low, but if it doesn't, it will most likely only be a problem when you transmit on certain frequencies whose harmonics land near the gps signal. Given that you won't know the problem exists until you try to use those frequencies, I'd personally try to put some distance between the two antennas.

 

[Mich48041]

Bob Nuckolls is an electrical engineer who wrote the book by which many homebuilt aircraft have been wired. Read what he has to say about running coax together.
http://www.matronics.com/searching/getmsg_script.cgi?INDEX=43279707?KEYS=if_they%27re_both_modern_coax_(rg400_or_rg142)_you_can?LISTNAME=AeroElectric?HITNUMBER=1?SERIAL=0955406797?SHOWBUTTONS=YES

 

[BobTurner]

but....

Bob Nuckolls is an electrical engineer who wrote the book by which many homebuilt aircraft have been wired. Read what he has to say about running coax together.
http://www.matronics.com/searching/getmsg_script.cgi?INDEX=43279707?KEYS=if_they%27re_both_modern_coax_(rg400_or_rg142)_you_can?LISTNAME=AeroElectric?HITNUMBER=1?SERIAL=0955406797?SHOWBUTTONS=YES

Note this answer is ten years old, and specifically referred to a vfr gps. Who cared if you lost signal lock for 30 seconds? But if you're in IMC 30 seconds can be an eternity.
If you can avoid running gps cables next to transmitter cables (com, transponder) then do so. If you cannot avoid it, be sure to test the gps for interference from the transmittr prior to actual IMC.

 

[RV7A Flyer]

I'm a newbie to aviation, but I've spent lots of time in my day job chasing down interference between different RF signals, and I personally would avoid bundling the com transmit antenna with the gps receive antenna if at all possible. By bundling those, you would be bundling a cable with a HUGE transmit signal right next to an important antenna that's trying to receive a TINY signal.

It will probably work if the shielding is good and harmonics are low, but if it doesn't, it will most likely only be a problem when you transmit on certain frequencies whose harmonics land near the gps signal. Given that you won't know the problem exists until you try to use those frequencies, I'd personally try to put some distance between the two antennas.

FYI, my 430W install manual lists the following frequencies to be checked for interference with GPS:

121.150 MHz ? 131.225 MHz
? 121.175 MHz ? 131.250 MHz
? 121.200 MHz ? 131.275 MHz
? 121.225 MHz ? 131.300 MHz
? 121.250 MHz ? 131.325 MHz
? 131.200 MHz ? 131.350 MHz

and for 8.33 kHz spacing, add

121.185 MHz ? 130.285 MHz
? 121.190 MHz ? 131.290 MHz

IIRC, these are near the odd harmonics of GPS L1 frequency.