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Mauledriver(at)nc.rr.com
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 Posted: Wed Aug 29, 2012 11:53 am Post subject: ELT Antenna |
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Given all the carbuncles and antenna I have hanging off my '10,
especially after adding the NavWorx ADSb box, I regretted not having
installed my ELT antenna in the tail. Then I had an experience that not
only removed the regret but in fact added another antenna to the
slipstream. I'll share the experience FWIW....
My panel includes a G430w and an SL30. Based on previous experience, I
knew my primary comm radio would be the SL30. The comm on the G430w
would only be used occassionally for stuff like pre-startup clearances
and as a backup for the primary.
So for antennas I decided to connect the SL30 to a belly mounted bent
whip and the G430 comm to a Bob Archer wingtip antenna. The units
share a Bob Archer wingtip nav antenna. The G430's GPS antenna is
mounted on top free and clear. A few other GPS and Wx antenna are
mounted underneath the windshield.
This all worked perfectly. I was convinced that the Bob Archer Comm
would not perform optimally and that was true. It did not have the Tx
or Rx range of the SL30 and it's belly whip but it performed well in
it's intended role. I knew that normal operations would be GPS-centric
so I was comfortable with possibly suboptimal performance from the
navs. In fact, the setup appears to work quite well particularly in
approach operations where I can find no deficiencies.
At about 150 hours, I decided to take our longest trip to date from NC
to AZ. It all went well until our arrival at KSDL when we flew under a
line of storms and probably took an electrical hit of some sort. We
lost more than 50% of our SL30's function (limited range, intermittent
RX and lot's of static). I switched to the G430 for the rest of the
arrival (it was just good enough).
At least we made our destination but it was not lost on me that the
failure occurred at maximum distance from home.
I'm thinking at this point that while the G430/Bob Archer works, it is
not the radio I can rely on for the return legs because of it's somewhat
limited range. In other words, my backup turns out not to be a real
backup. It was good enough to get into KSDL but not for the distances
involved or for the IFR operations required to get home.
With some help from a local RV10 builder, I was able to get behind the
panel and swap antenna so that my belly mount was connected to the
G430. That was not as simple as it sounds. It required ferrying the
airplane across town and a 1.5 days of our trip to arrange. Moreover,
isolating the fault (SL30 or PM9000EX or ?) was complicated by a second
fault that occurred during the antenna swap, but that's another story.
The bottom line was that I had installed and invested in dual comms
where I considered 1 little more than a backup. But when I needed a
backup, it effectively was not there for me. And it ended up costing
more time and money than it should have.
This experience changed my perspective a bit:
I put a 2nd belly whip in for my comm2 because it has to perform as well
as my comm1 when needed.
I'm glad I did a TSO compliant ELT antenna installation and didn't opt
for a more streamlined installation (though I'm not convinced that the
tail fairing installation is any more or less likely to perform as
needed, if needed). In any case, I'll probably haul that draggy whip
for thousands of miles and never use it once, but... you know.
I'm happy with my Bob Archer nav antenna because I know it will do what
I need it to do.
I'm glad I did a optimal GPS antenna install for the G430 rather than
trying to elegantly hide it. I depend on it for 99.999% of my navigation.
Anyway, thanks for letting me share.
Bill "sitting underneath a Bob Archer comm antenna hung on my wall" Watson
| Quote: |
I am looking at installing my ACK E-04 antenna under the tail
intersection fiberglass fairing. I've read through a good discussion
on the AeroElectric list and feel the trade-off of horizontal
polarization, vs protection from impact and eliminating the drag is
worth it. I know that Mooney got approval for similar antenna instal
for a 406 antenna in fiberglass ventral fin.
My question is if anyone has done this and gotten any grief from their
DAR. My only concern is to fully meet the TSO on the ELT you are
supposed to comply with the install instructions, that call for
vertical mounting withing 30 degrees.
Kelly
40866
forever finishing
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nukeflyboy
Joined: 05 Jan 2008
Posts: 162
Location: Granbury, TX
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| Posted: Wed Aug 29, 2012 9:37 pm Post subject: Re: ELT Antenna |
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My 406 manual said it needed a 24 in radius ground plane, if I remember correctly. As Tim said it should be located where it will remain intact and connected antenna to box. There are not a lot of options if you take the ground plane requirement seriously. My ELT is behind the baggage bulkhead and the antenna just behind it on the top of the tailbone. It sticks out, which I don't like, but at least it should work per the specs if ever needed.
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_________________
Dave Moore
RV-6 built and sold
RV-10 built and flying |
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Kelly McMullen
Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ
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| Posted: Thu Aug 30, 2012 7:13 am Post subject: ELT Antenna |
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Just checked my ELT E-04 manual. What it really says is "IF the
antenna is being mounted on a NON-CONDUCTIVE portion of the airframe,
a SUPPLEMENTARY ground plane must be installed. The supplemental
ground plane must have a minimum diamenter of 24", however 48" will
provide maximum power at 121.5 MHz and is recommended.
I don't know of anywhere you could get a 48" radius on an RV-10 except
in the middle of a wing, but is a spurious discussion unless you mount
the antenna on the fiberglass canopy without grounding to the metal
airframe.
On Wed, Aug 29, 2012 at 10:37 PM, nukeflyboy <flymoore(at)charter.net> wrote:
| Quote: |
My 406 manual said it needed a 24 in radius ground plane, if I remember correctly. As Tim said it should be located where it will remain intact and connected antenna to box. There are not a lot of options if you take the ground plane requirement seriously. My ELT is behind the baggage bulkhead and the antenna just behind it on the top of the tailbone. It sticks out, which I don't like, but at least it should work per the specs if ever needed.
--------
Dave Moore
RV-6 flying
RV-10 QB - flying
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=382125#382125
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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor
KCHD |
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rv10flyer
Joined: 25 Aug 2009
Posts: 364
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| Posted: Thu Aug 30, 2012 6:45 pm Post subject: Re: ELT Antenna |
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Mine is on the right side of the rear seat cross brace. Out of the way. Did not need any more aft cg with pc680 aux bat already back there. Left slack in coax on each end. If we lose our coax connection, I would bet it won't matter then. The backup ant is strapped to the elt if someone miraculously survives.
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Wayne G. |
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Kelly McMullen
Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ
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| Posted: Thu Aug 30, 2012 6:55 pm Post subject: ELT Antenna |
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Your antenna or the ELT is located on the cross brace? I think the
antenna there is a fine location, as long as it doesn't offend your
SO/FO/CFO's sensibilities for interior "appearance". I may very well
use that exact spot if DAR doesn't like horizontal under the tail
fairing.
On Thu, Aug 30, 2012 at 7:45 PM, rv10flyer <wayne.gillispie(at)gmail.com> wrote:
| Quote: |
Mine is on the right side of the rear seat cross brace. Out of the way. Did not need any more aft cg with pc680 aux bat already back there. Left slack in coax on each end. If we lose our coax connection, I would bet it won't matter then. The backup ant is strapped to the elt if someone miraculously survives.
--------
Wayne Gillispie, A&P 05/93 PP 10/08
40983SB 12/1/2009-12/1/2011
N715WD 382nd Flying. TT= 74
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=382170#382170
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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor
KCHD |
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