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Antenna for backup G5?

claycookiemonster

claycookiemonster

Well Known Member
My setup has a Garmin GNC355 and a Dynon Skyview HDX system. both systems have their own GPS receiver. I also have a Garmin G5 as a backup.
The G5 has a coax input for its own GPS receiver, but also according to Garmin, has its own internal GPS antenna. I assume it is also receiving GPS data from the GNC355.
What's the over/under on giving the G5 its own antenna? Added weight. Added cost. Is there added redundancy or accuracy? Since it's only a matter of adding an antenna now, I'm inclined to do it.
Thoughts?
 
IMHO the value depends on what your use of the G5 is for...primary navigation or dissimilar backup. My G5 is just backup to the IFD and AFS EFIS, both of which have their own GPS's and antennae. The G5 has a different power source plus its own backup battery. The G5 is serial-wired to the IFD and displays track. Those two navigators plus the iPad, iPhone, and Apple Watch more than cover my navigation redundancy needs.
 
Our flying club has a Piper Dakota with a pair of G5's. Out on the ramp the G5's bezel-mounted internal antenna picks up a half dozen or more satellites. I would guess that under a glass canopy the G5 would perform even better. You could always test it and decide, the signal status screen is a menu selection.
 
Halleffect said:
Our flying club has a Piper Dakota with a pair of G5's. Out on the ramp the G5's bezel-mounted internal antenna picks up a half dozen or more satellites. I would guess that under a glass canopy the G5 would perform even better. You could always test it and decide, the signal status screen is a menu selection.
Click to expand...
FYI, the G5 when installed as an ADI per STC requires a GPS source, either an approved navigator or an external GPS antenna.
 
This from Garmin as originally posted on Pilots of America forum. I found it a concise and useful summary:


The G5 primary mode attitude solution uses GPS aiding to correct for attitude sensor drift. The G5 has a strong preference for using GPS aiding for the primary mode of operation to be immune from an iced/blocked pitot/static affecting the attitude solution. Some say they can detect a blocked pitot/static affecting the attitude solution, but in reality, this is very difficult, if not impossible, to detect.

In the degraded mode failure scenario, GPS is lost (reliably recognized failure) and aiding is done with air data. DO-334 degraded mode required accuracy is attained using only air data drift correction. When we fly the 2+ hours of degraded mode flight tests, we disable the internal G5 GPS receiver, and shut down any external MapMX data being provided by GTX/GNS/GTN. The DO-334 maneuvers are designed to challenge an ADAHRS while it is using an alternate means of aiding (in this case air data).

The G5 does support operation without either air data or GPS data, but we don't spec performance below the dual failure of GPS (primary aiding) and air data (secondary aiding).

Increased availability of primary mode GPS aiding is one of the reasons we built a high performance WAAS GPS into the G5. The most failure resistant installation uses an external antenna for the internal GPS receiver connected to the G5 (which of course is also backed up by the 4 hr backup battery) AND has the RS-232 input wired to receive GPS data from a GNS/GTN.

The G5 will first prefer using the internal GPS, next the externally supplied GPS data from the GNS/GTN, then finally the air data. It is important to recognize that aiding of any kind is only needed occasionally to correct sensor drift.

The GNS/GTN supplied data isn't really required, but some customers prefer this over another GPS antenna and don't mind losing the independence of the WAAS GPS receiver built-into the G5.

As stated above, flight into an area with no GPS service is readily detected by the G5 and air data aiding is used.

We have many thousands of G5 units in the field, and it is very rare for an installation to be completed per the installation manual where the G5 ends up not having a solid source of GPS data. To the best of my knowledge, this was never present in this aircraft until the installation deficiency was addressed.

One additional relevant piece of information. The STC installation manual does not support using a non-WAAS GNS 4XX/5XX as a source of GPS data for the G5. A non-WAAS GNS 4XX/5XX interface uses the Aviation format instead of the MapMX format, and doesn't contain the information needed for the G5 to use it for GPS aiding of the attitude sensors. In an installation with a non-WAAS navigator, the G5 internal GPS receiver must always be used.

Let me also state that we are always looking for ways to improve our products, and we won't hesitate to implement improvements where needed.

This is only a high level description of a very complicated system with lots of safeguards, so please don't try to pick apart the design based on an internet posting.

Hope this answers your questions.
 
On a standalone operation I experienced twice attitude loss and the G5 going into align mode, whilst flying in moderate turbulence.
Normal GPS acquisition is thru my GNX375 and it's WAAS antenna, but this was switched off for operational reasons, luckily in VFR 🙂
 
Depends on your plane and wiring. I put it center panel in an RV-9 slider (center steel brace) and the internal antenna couldn't pick up enough satellites. Rather than the $200 Garmin add on antenna, I found one online for less than $30 (not an option for an STC installation) that had a BNC connector and it worked great with just the puck on the glare screen.

Interestingly, I moved the G5 to the left side of the panel during a rework and the internal antenna was sufficient.

In order for the G5 to receive GPS data from the GNC355, it needs a GAD29 converter or an RS-232 direct connection.
 
AF_Alan said:
Depends on your plane and wiring. I put it center panel in an RV-9 slider (center steel brace) and the internal antenna couldn't pick up enough satellites. Rather than the $200 Garmin add on antenna, I found one online for less than $30 (not an option for an STC installation) that had a BNC connector and it worked great with just the puck on the glare screen.

Interestingly, I moved the G5 to the left side of the panel during a rework and the internal antenna was sufficient.

In order for the G5 to receive GPS data from the GNC355, it needs a GAD29 converter or an RS-232 direct connection.
Click to expand...
The GA26X is $115 at ACS.
 
Do it!
Listen to Walt on antenna p/n.
Worse case scenario... It's in the panel in case of total electrical failure (ie, electrical fire). In this scenario it's working all alone. It needs it's own solid GPS signal.
 
Yes, listen to Walt ;) - I have had personal experience losing attitude information on the G5 (standalone) that did not have an external antenna. After adding the antenna, the problem was resolved.
 
I bought this antenna and connector from Mouser Electronics, 960-AA105301111 and 523-31-315-RFX, for $17 plus s&h for use with my G5.
My G5 sits in the upper left corner of my panel and may be shadowed by the glareshield. I have a 9A slider.
 
With almost 1.5K invested in a G5, I personally would be reluctant to roll my own antenna, GPS WAAS antennas are active and source power from the unit and must be well matched gain wise, is it really worth saving 50 bucks and take that risk?
 
Here I am with two G5s for the past 6-years and 300 flight hours without a GPS antenna(e). The only time I have lost GPS signal with the built in antenna is when doing ACM. (Air Combat Maneuvering / aerobatic with abrupt attitude changes). GPS comes back in a few seconds of level flight.
 
RV6_flyer said:
two G5s for the past 6-years and 300 flight hours without a GPS antenna(e)
Click to expand...
and here we are with the same kind of configs, but different experiences... and experience, >1.5Khrs in 5 years.

My actual set-up started 5 years ago when I installed a single G5 as a primary AI in my then VFR ship, no external antenna. Having the G5 loosing attitude and going into ALIGN whilst flying in moderate turb one day, and recovering more than 10 minutes later, luckily in VMC, was food for thought.
Since I wanted an IMC capable configuration, the next upgrade to a dual G5s (used as primary flight displays) and a GNX375, saw the addition of an AV20S as an eventual life saver. In normal ops the G5s get their GPS thru the GNX's 375 WAAS antenna, and I never had a problem. Until that day last year, when flying thru the Alps again in moderate turb with the GNX375 offline, and guess what... the G5 went into ALIGN. Garmin had a look at the data and confirmed that the G5 had lost GPS signal from its internal antenna.

In short my guess is that, depending on installation, a standalone G5 is susceptible to loose GPS acquisition one day. Not a problem in VMC, but serious IMC flying would require an external GPS antenna.
 
Steve said:
I bought this antenna and connector from Mouser Electronics, 960-AA105301111 and 523-31-315-RFX, for $17 plus s&h for use with my G5.
My G5 sits in the upper left corner of my panel and may be shadowed by the glareshield. I have a 9A slider.
Click to expand...
Bought same and had signal strength issues.
 
I spent months tracking various GSU25 AHRS issues and looked at this extensively. It turned out to be vibration related for me, but as part of my experimenting it was very clear that the G5 had far more and stronger satellite reception with the GA26 than without.
Whether this would manifest in better AHRS performance in the G5 or not I can’t answer - but the difference was stark.
This was an RV10 so I can’t speak to the impact of the composite cabin top.
 
Am I the only person that has had no to minimal issue with the built in GPS antenna? (only issue with abrupt attitude changes over six years of use)

It is common sense that an external antenna will provide a stronger signal. Not sure where one can see the GPS signal strength on a G5 screen. Only know when there is LOSS of signal lock.

I do not believe that I am the only one operating satisfactory without the external antenna. Yes I believe that some require the external antenna.

I was an early adopter so my two G5 are older units. I am not aware if Garmin changed any components internally that would make the GPS antenna now not work as well as my older units.
 
RV6_flyer said:
not aware if Garmin changed any components internally
Click to expand...
Neither am I. What I'm aware of is that there were several G5s loosing attitude, and Garmin reacted with a hardware revision that supposedly cured the problem.

Logically the placement of any said G5 will influence how good its GPS reception's gonna be, so one airplane will be different from another. As an example mine sports a slider with the aluminum glareshield with some non-reflective matt, and this stuff, as well as other antennas in the vicinity, will affect reception.

Now when one is thrusting his life to electronic indicators to differentiate between the blue from the brown portions of the sky, I'll use the recommended install procedure and associated antenna. Of course, that might be only me ;)
 
Dan 57 said:
Logically the placement of any said G5 will influence how good its GPS reception's gonna be, so one airplane will be different from another. As an example mine sports a slider with the aluminum glareshield with some non-reflective matt, and this stuff, as well as other antennas in the vicinity, will affect reception.

I'll use the recommended install procedure and associated antenna. Of course, that might be only me ;)
Click to expand...

Both of my G5s work great in with same slider and glareshield and no antenna(e).

Six years ago, the antenna was OPTIONAL and NOT required. Garmin did say that some installations MAY need the OPTIONAL GPS antenna.
 
RV6_flyer said:
Am I the only person that has had no to minimal issue with the built in GPS antenna? (only issue with abrupt attitude changes over six years of use)
Click to expand...

Mine's always been fine with the internal antenna.

RV-6 tip-up with the G5 mounted in the far left of the panel. Good strong signal bars on all GPS channels.

I do kinda wonder how many GPS antennas I'm supposed to have. There's a GA26 on the glareshield for the G3X Touch PFD, another antenna outside for the 430W, and the internal one on the G5. I guess I could put another GA26 on the GDL51R and another one on the G5 and another one on the MFD. Maybe mount a few on the belly so I don't lose GPS when I'm upside down, another one on each wingtip so there's a clear view of the sky when I'm knife-edge.

I'm sure I could maximize GPS reliability here somehow, but I'd need to reweigh the aircraft after I was done.

- mark
 
2 Walt questions.

I have an 2 GA56. Would it be a good choice and while asking, would it also be a good choice for the GDU460?

I used them for testing when building the panel and they seem to work well.
 
Last edited:
Webb said:
2 Walt questions.

I have an 2 GA56. Would it be a good choice and while asking, would it also be a good choice for the GDU460?

I used them for testing when building the panel and they seem to work well.
Click to expand...
GA56 is listed as supported antenna in the 460's install manual.
 
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