Routing Coax For Sv83 and Transponder.

[sunfish]

I have two SV83 radios and am about to buy a Skyview Transponder. I have already mounted the antennas and run RG400 coax to behind the instrument panel which is about the only location for them that makes sense.

My concern is that for about three feet the coaxs need to run as a bundle before they go their separate ways - its just the way the Zenith Ch750 is built - there are only so many paths forward.

I know the Dynon installation manual says "avoid" doing this but is it going to ruin the installation and degrade transponder and/or radio performance? Changing things now is going to be difficult as i purposely separated fuel, strobes, audio and coax already.

 

[jakej]

IMO the RG400 is so good with its own shielding that you do not need to do any special separate routing,I actually sometimes bundle it with other wires, other than #10 awg or heavier, without any issues in many different types of airframes.
In the old days when RG58 was the standard coax then you really had to avoid routing it with other power wires. Anyone using RG58 now is asking for trouble especially considering modern avionics & other digital systems are much more sensitive to RF & EMI generally, that is one of the reasons RG58 is not approved in new certified aircraft anymore.

 

[mrdaud]

I agree with Jake. All my Dynon black boxes are behind my panel and are fed by bundled wires. I used RG142a for most of my antenna requirements, but found the "a" format is very difficult to prep for connectors because it does not have a solid insulation core. RG400 is the way to go. I mounted my ADS-B in antenna in my wingtip so went with a very high gain wire, as my wire run was about 22 feet. Everything has been working fine, except for dealing with the current ADS-B problem. Just to note, the Dynon install manual indicates RG58 is still acceptable, but as Jake recommends, use the RG400.

 

[Raymo]

I'll echo what Jake and N214ST said except that RG142 is solid core (not familiar with the 'a' format), which I find easier to terminate when using TNC connectors. RG400 will work but you have to be very careful when installing the pin. It is a very tight fit and some strands may need careful trimming if they don't go in.

The down-side to 142 is more limited bending radius compared to 400.

From ACS.

RG142
Double shielded solid conductor, MIL-C-17 spec.
Approved for certified aircraft.
PN 11-00043

 

[mrdaud]

Ray, the RG142a has a wrapped teflon core (like teflon tape), so it is really difficult to cut clean, and you have a greater chance of nicking the core wire. I had to buy a $100 coax trimmer to make it work so I didn't have to make every cut by hand. It supposedly has better transmission characteristics than standard RG142 or RG400. The RG142a actually has a bend radius better than the RG400, probably due to the soft core insulation, but it is just too hard to work with regarding connector installation. I originally purchased it from Perihelion Design some years ago, but I just go with the RG400 these days.