What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

WAAS ANTENNA SPLITTER

T

txcarguy

I'm New Here
I have a GNS430 non WAAS and will be installing a Garmin G5 that requires a WAAS ant. and a ADS-B that requires a WAAS ant. Is there a splitter that is made that will work for this if I change out my GNS430's antenna and use a WAAS antenna so I don't have all these antennas sticking out?
 
Short answer is no. Any splitting reduces the signal, and it's already tiny. Also, some boxes/antennas have a preamp in the antenna, so you have D.C. power running up the coax. Best not to mix.
 
You cannot share an antenna, but the G430 can output a position source to both other items via RS232. Also, the G5 has a built-in antenna that is usually adequate.
 
BobTurner said:
Short answer is no. Any splitting reduces the signal, and it's already tiny. Also, some boxes/antennas have a preamp in the antenna, so you have D.C. power running up the coax. Best not to mix.
Click to expand...

EXACTLY! Besides, do you really want to risk damaging your $$$ G430 unit? :(
 
BobTurner said:
Short answer is no. Any splitting reduces the signal, and it's already tiny. Also, some boxes/antennas have a preamp in the antenna, so you have D.C. power running up the coax. Best not to mix.
Click to expand...

Especially if you are using the navigator for IFR. Even though we're E-AB, for IFR I'd recommend following the Garmin installation instructions regarding anything dealing with antennas to the letter. YMMV....
 
Not only is it possible, it is trivially simple. Especially so if you have an "active" gps antenna, one that has 25-30 dB of gain to overcome the loss of the coax going from the antenna to the GPS.

What is another 3 dB (a perfect power split) with a simple Wilkinson coupler?

Watch this thread. I'm working on one right now. So far the least expensive splitter I've found is north of $200. If I can't do it for less than $73 I won't bother taking your time.

Of course, as with all RST Engineering stuff it will be a kit that you have to assemble yourself, but it will probably be half a dozen solder joints at the max.

Jim
 
jweir43 said:
What is another 3 dB (a perfect power split) with a simple Wilkinson coupler?
Click to expand...
Because 3db is a 50% reduction in power. Not trivial when the total available power at earth level is around 100 attowats.

That many GPS receivers will work at even much lower levels is a given, but I am not risking my life flying actual IMC with a GPS receiving 50% of what it should be getting. I justify spending that extra $$$ the same way I justify spending $$$ on insurance. Rather have it and not need it, than need it and not have it. YMMV

:cool:
 
Last edited:
jweir43 said:
Not only is it possible, it is trivially simple. Especially so if you have an "active" gps antenna, one that has 25-30 dB of gain to overcome the loss of the coax going from the antenna to the GPS.

What is another 3 dB (a perfect power split) with a simple Wilkinson coupler?

Watch this thread. I'm working on one right now. So far the least expensive splitter I've found is north of $200. If I can't do it for less than $73 I won't bother taking your time.

Of course, as with all RST Engineering stuff it will be a kit that you have to assemble yourself, but it will probably be half a dozen solder joints at the max.

Jim
Click to expand...


Jim has been my hero since I could read Kitplanes! I swear the all of the electrons in the known universe are just sitting around waiting for him to tell them which way to go!

I STILL have articles I tore out of magazines as I was building over the years. :)

Vic
 
Jesse said:
You cannot share an antenna, but the G430 can output a position source to both other items via RS232. Also, the G5 has a built-in antenna that is usually adequate.
Click to expand...

Since he said the 430 is non-WAAS, I think it cannot serve as an adsb position source.
I?m going to reverse myself. Since the 430 installation instructions call for a certain minimum and maximum cable loss, I think a splitter is okay as long as you stay within the specs, AND make sure the dc power gets to the antenna okay and does not cause problems with other receivers.
 
BobTurner said:
Since he said the 430 is non-WAAS, I think it cannot serve as an adsb position source.
I’m going to reverse myself. Since the 430 installation instructions call for a certain minimum and maximum cable loss, I think a splitter is okay as long as you stay within the specs, AND make sure the dc power gets to the antenna okay and does not cause problems with other receivers.
Click to expand...

My 430W manual calls for a cable loss of 1.5 to 6.5 dB. With the manual stating that 1.5 dB loss is 6.5 ft of RG-400 with a connector on each end (0.2 dB each) - a few calculations, no long cable runs and not too many connections should let a 3 dB splitter in the system as you say. :)
 
az_gila said:
My 430W manual calls for a cable loss of 1.5 to 6.5 dB. With the manual stating that 1.5 dB loss is 6.5 ft of RG-400 with a connector on each end (0.2 dB each) - a few calculations, no long cable runs and not too many connections should let a 3 dB splitter in the system as you say. :)
Click to expand...
Agree 100%. Stay within a max of 6.5db total loss to the 430 and whatever max loss is acceptable for the other unit.

:cool:
 
Splitting one antenna into two receivers is pretty standard and easy; I do this all the time at work.

You'll need a splitter/combiner that will pass both the GPS signal (1575 MHz) and DC power to the antenna (the receiver sends a DC voltage up the center conductor to power the amp in the antenna) Both the G5 and 430 provide DC power to the antenna, and you will need to "block" one of the power sources, so the two don't fight one another ... Use a DC block for that.

I didn't see anything in the documentation for either unit that indicates that they check for "antenna faults" ... if the antenna is not drawing the expected current (over some wide range) the unit will sound an alarm. A DC block will cause such a fault if such a test is used; no DC power will be sourced to the antenna through the DC block. Any experts out there who know whether these units actively detect an antenna fault?

I'd hook it up like this:

430 <--------------------> Splitter Port 1 | |Common port <--> Antenna
G5 <---> DC block <---> Splitter Port 2 | |

A good quality splitter is about $60; the DC block about $25.

MiniCircuits has good quality components ... I'd use these for this application:

https://www.minicircuits.com/pdfs/ZAPD-2+.pdf
https://www.minicircuits.com/pdfs/BLK-222+.pdf

And for the folks who have concerns about GPS signal strength ... for aviation applications, there is PLENTY. Good quality active antennas, horizon to horizon views of the sky. It doesn't get any better than this. (the opposite: cell phones. Compromised antennas, low power electronics, lots of nearby jammers - WiFi, bluetooth, Cell, LTE, etc)
 
Last edited:
txcarguy said:
I have a GNS430 non WAAS and will be installing a Garmin G5 that requires a WAAS ant. and a ADS-B that requires a WAAS ant. Is there a splitter that is made that will work for this if I change out my GNS430's antenna and use a WAAS antenna so I don't have all these antennas sticking out?
Click to expand...

This thread is fascinating in the way it brings out all these experts. Impressive! And, the pointers to specific products. Who knew?

One question though, your original post indicates you want to drive THREE boxes from the one antenna, correct? I suppose that?s feasable, if the splitter box was to contain an amp to boost the signal. I wonder if anyone makes that kind of device.

Sorry for the semi-intelligent questions. I guess its the old ham radio (K2GOC) op in me! 😏
 
BobTurner said:
Since he said the 430 is non-WAAS, I think it cannot serve as an adsb position source.
I?m going to reverse myself. Since the 430 installation instructions call for a certain minimum and maximum cable loss, I think a splitter is okay as long as you stay within the specs, AND make sure the dc power gets to the antenna okay and does not cause problems with other receivers.
Click to expand...

Precisely, Bob. If you have an antenna with a 25-30dB gain over a non-amplified antenna and you have a receiver that will overload if you don't use some loss between the antenna and the receiver, then 3 dB is a nickel to a rich man if you have to coil up extra cable to make the minimum loss.

As to the dc power, you identify one output port as dc coupled, the other one as ac coupled, and the problem is solved. One nickel capacitor in the ac coupled line and you are home free. Quarter wave sections on the split channels on fiberglass pc board, one nickel resistor make up the whole thing. The TNC connectors are actually the most expensive thing in the whole process.

Jim
 
vic syracuse said:
Jim has been my hero since I could read Kitplanes! I swear the all of the electrons in the known universe are just sitting around waiting for him to tell them which way to go!

I STILL have articles I tore out of magazines as I was building over the years. :)

Vic
Click to expand...

Blush

Thanks, Vic. Y'know it's kind of funny looking back over a 60 year career in electronics, mostly in RF and microwave. I graduated as a semiconductor physicist, moved over to engineer, did it for my first 20 years, then started RST Engineering, which is only teaching my friends how to build electronic stuff for themselves. Then started writing for Kitplanes, which is teaching my friends how to build electronic stuff for themselves. Then started teaching in the Community college.

I guess teaching is what I was meant to do, but it required that first 20 years of doing hard design and learning what the #e!! this stuff was all about. Glad I was able to help.

JIm
 
Last edited:
wjb said:
I didn't see anything in the documentation for either unit that indicates that they check for "antenna faults" ... if the antenna is not drawing the expected current (over some wide range) the unit will sound an alarm.
Click to expand...

Most of them don't Bill, but a simple 200 ohm load resistor from the dc isolated port to ground will take care of that for those that do. Another nickel in the parts count.

Jim
 
jweir43 said:
Blush

Thanks, Vic. Y'know it's kind of funny looking back over a 60 year career in electronics, mostly in RF and microwave. I graduated as a semiconductor physicist, moved over to engineer, did it for my first 20 years, then started RST Engineering, which is only teaching my friends how to build electronic stuff for themselves. Then started writing for Kitplanes, which is teaching my friends how to build electronic stuff for themselves. Then started teaching in the Community college.

I guess teaching is what I was meant to do, but it required that first 20 years of doing hard design and learning what the #e!! this stuff was all about. Glad I was able to help.

JIm
Click to expand...

Great stuff, too, Jim, from RST. Especially for those of us who grew up on Heathkits. I built the RST audio panel and radio for my RV-4. :)
 
I want to add a thumbs up for Jim as well. I learned to fly in 1978 and built a 4 place intercom from his kit and it worked!! His easy to build kits have put many smiles on the faces of us amateurs.
 
You must log in or register to reply here.
Back
Top