VHF/GPS combo antennas?

[Alex G.]

I just did the math and with all my planned avionics upgrades, I will end up with 4 GPS WAAS antennas on top of my TB20, along with 2 other VHF antennas and an ELT one.

I am starting to worry this will change the aerodynamics and possible reduce the speed by a few more knots…

I saw there are some combo VHF/GPS antennas out there (e. g. COMANT CI 2580-200) that will help mitigate this issue, by reducing the total number of installed antennas.

Do you have any experience with these? Will the quality of the VHF or GPS signal degrade compared to a standard, single purpose, let’s say Garmin GA35 antenna? And more important, will the $800 difference in price make any sense over the presumed loss of speed?

 

[Ryan Klems]

Wow, what are you planning that requires 4 WAAS antennas? There are some specialized GPS splitters on the market (not cheap, but could possibly be worth it if you really need direct signal to this many devices). I have no experience with the combo antennas, but I have seen people talk about them on some other forums and folks seem to be satisfied with them, but they are quite pricey.

 

[Alex G.]

I need 2 for the Avidyne GPS receivers, 1 for the Garmin G5 AI and 1 for the Lynx NGT-9000 transponder.

 

[Ryan Klems]

Why not just 2 for the Avidyne GPS receivers and provide GPS source from the 2 receivers over RS232 to the G5 and transponder and keep it to 2 antennas?

 

[EdFred]

Lynx needs its own antenna.

 

[Alex G.]

The NGT-9000 transponder needs its own roof mounted WAAS antenna. Theoretically I could feed the G5 via RS232 from one of the Avidynes, but they usually don't speak the same NMEA language and it would be a single point of failure I would like to avoid...

 

[Ryan Klems]

Lynx needs its own antenna.

I hadn't realized that was required, good to know!

 

[weirdjim]

There are some specialized GPS splitters on the market (not cheap, but could possibly be worth it if you really need direct signal to this many devices).

What if I told you that I could make a GPS splitter, sell it for $50 and still make a decent profit at it?

Jim

 

[Ryan Klems]

What if I told you that I could make a GPS splitter, sell it for $50 and still make a decent profit at it?

Jim

Wouldn’t surprise me in the least, I was just going by what I’ve seen as commercially available.

 

[Martin Pauly]

What's happening to signal strength when you split a GPS signal, and is it a practical concern in real life?
I considered a splitter when I installed my Lynx ADS-B transponder a couple of years ago, but the avionics shop suggested to have separate antennas instead for better GPS availability.

 

[Ryan Klems]

What's happening to signal strength when you split a GPS signal, and is it a practical concern in real life?
I considered a splitter when I installed my Lynx ADS-B transponder a couple of years ago, but the avionics shop suggested to have separate antennas instead for better GPS availability.

A passive splitter, you would lose strength of course, this one: https://www.edmo.com/products/anten...ntenna-splitter-with-tnc-connector.-ldcbs1x2t appears to have about 4dB loss (and being logarithmic this is a bit more than half) ... what that means to your GPS receiver, I can't really say, but would definitely have impact I'd think.

Same manufacturer has some that are amplified such as:
https://www.edmo.com/products/test-...tenna-splitter-with-tnc-connector.-aldcbs1x2t

Certainly this also adds a failure point, but if it was 2 antennas vs 4, you have some redundancy still and don't have as many holes and warts. I have no experience with these splitters, so I couldn't even begin to know how well they work in practice, I just have seen people on various forums talk about using them to reduce antenna count.

 

[weirdjim]

[QUOTE="Ryan Klems, post: 2688076, member: 33623" ... what that means to your GPS receiver, I can't really say,

. I have no experience with these splitters, so I couldn't even begin to know how well they work in practice,.[/QUOTE]

Then why in the hell do you come on here with zero experience making observations that have no basis in reality? There is enough WAG in these groups without adding more.

Jim