GTX-335 antenna install

Working through the GTX-335 install, just about finished. With the RV-4 I can’t install the GPS antenna just behind the panel because the avionics cover is sheet metal and would block the signal. Don’t want to put a white antenna on the black paint job on top. Thinking about the engine side of the firewall underneath the fiberglass top engine cowl. Anyone done this? Considerations?

- Any problems with heat or vibration from the engine compartment damaging the antenna?
- The manual says I need 9” spacing from any other antenna. I have a small antenna already in the engine bay for the G5 (which works fine), is this really going to affect the 335 antenna?

olyolson said:

Working through the GTX-335 install, just about finished. With the RV-4 I can’t install the GPS antenna just behind the panel because the avionics cover is sheet metal and would block the signal. Don’t want to put a white antenna on the black paint job on top. Thinking about the engine side of the firewall underneath the fiberglass top engine cowl. Anyone done this? Considerations?

- Any problems with heat or vibration from the engine compartment damaging the antenna?
- The manual says I need 9” spacing from any other antenna. I have a small antenna already in the engine bay for the G5 (which works fine), is this really going to affect the 335 antenna?

Click to expand...

Got any RS232 hooked to the G5? You should be able to get GPS to the G5 from the 335 via RS232. (When the GTX335 has an internal GPS reveicer)

Interesting ides. I am working on my GTX 345 install. I had resigned to the fact that I would have to put it behind my canopy (dark grey paint). This might be worth a try. I can always move it if there are issues. The only problem is it is tight up there under the cowling.
I have my music radio antenna under my cowl and find I do get rather poor reception...

GTX-335 antenna

How about this?

I ran an RS 232 (out) line for data (and a signal ground) from the G5 (out) to the 335 (RS232 in) to eliminate the need for an altitude encoder as suggested by the G3 experts.

How about if I connect the 335 antenna into the G5- would the RS 232 line then provide both altitude and gps position source to the 335?

I could then eliminate the existing gps antenna that is hooked to the G5 and use the 335 antenna in it’s place instead.

Would this work?

olyolson said:

How about this?

I ran an RS 232 (out) line for data (and a signal ground) from the G5 (out) to the 335 (RS232 in) to eliminate the need for an altitude encoder as suggested by the G3 experts.

How about if I connect the 335 antenna into the G5- would the RS 232 line then provide both altitude and gps position source to the 335?

I could then eliminate the existing gps antenna that is hooked to the G5 and use the 335 antenna in it?s place instead.

Would this work?

Click to expand...

Don't think so.

olyolson said:

Working through the GTX-335 install, just about finished. With the RV-4 I can?t install the GPS antenna just behind the panel because the avionics cover is sheet metal and would block the signal. Don?t want to put a white antenna on the black paint job on top. Thinking about the engine side of the firewall underneath the fiberglass top engine cowl. Anyone done this? Considerations?

- Any problems with heat or vibration from the engine compartment damaging the antenna?
- The manual says I need 9? spacing from any other antenna. I have a small antenna already in the engine bay for the G5 (which works fine), is this really going to affect the 335 antenna?

Click to expand...

Remember this particular antenna is a part of a required (and certified) system for ADSB-out.

The STC instruction should really be followed for this antenna installation.

I installed my under the fiberglass cowl

olyolson said:

Working through the GTX-335 install, just about finished. ......Thinking about the engine side of the firewall underneath the fiberglass top engine cowl. Anyone done this? Considerations?

- Any problems with heat or vibration from the engine compartment damaging the antenna?
- The manual says I need 9? spacing from any other antenna. I have a small antenna already in the engine bay for the G5 (which works fine), is this really going to affect the 335 antenna?

Click to expand...

Last summer I installed a GTX335 and put the WAAS antenna under my engine cowl near the back firewall on a shelf I made for its mounting. Make sure it?s mounted clear of the metal rim the cowl hooks to.

Yea, it does get warm (Oklahoma summers can be real hot) but it fits between two other Garmin gps antennas (dual GNS430s non-WAAS) that have been there since the RV7A was built (2008). I?ve had absolutely no problems with my other gps antennas. Depending on who you talk to the 9 inch antenna separation is or is not that critical. However what is very critical is having at least 8 feet of cable between the antenna and the unit. I was told by SteinAir to just loop the cable under my panel. They also made me a conversion cable to facilitate the GTX330 to GTX335 swap out.

One consideration you need to think about is placement. Make sure your placement doesn?t interfere with either battery or oil filter replacement. Don?t ask me why I say this!

Good luck! I love my GTX335 and together with my FlightBox gps ?in? (hard wired to my GRT Horizon WS EFIS) enjoy traffic and weather to both my iPad and EFIS.

My RV-8 came with a little black felt beanie cap to cover the white antenna.

GTX-335 Antenna

The only place available was in the engine compartment. I decided to go ahead and make another gps bracket and separate it from the existing gps antenna I use for the G5. I had to mount it on the back of the sheet metal holding the baffling at the back of the cylinders. Maybe not the optinum location but should have a clear view of the satellites. We?ll see how heat and vibration affect everything.

Thanks for all the inputs everyone.

I am hard-pressed to think of a worse location (heat, vibration).

GTX-335 GPS antenna

Good point Bob but I was trying to save myself some work by not running the antenna all the way back to mount it on top of the fuselage behind the back seat. The other option I had was to mount it on top of the avionics cover in my RV-4 which would put the white antenna directly in front of me in the wind stream on a black avionics cover panel.

If it doesn't work out I may have to run it all the way back. Ed mentioned a black felt beanie cap that fits over the white antenna, I didn't get one of those in the box. I could run the coax rearward and mount the antenna on top but inside the canopy and cover it with the beanie cap I suppose. Anyone know a source for those?