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gengrumpy(at)aol.com
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 Posted: Thu Jul 09, 2009 12:27 pm Post subject: Nav antenna location |
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My experience is the same as Tim, with mine mounted bottom underneath
the tail section and facing backwards (or...V pointed forward!)
grumpy
N184JM
On Jul 9, 2009, at 3:17 PM, Tim Olson wrote:
[quote]
Aren't they way way more expensive? I remember flying along just over
100nm away from a station in front of me, receiving it with my
backwards mounted (V facing forward) NAV antenna, mounted under
the tail. Now, it may be more sensitive mounted facing forward,
and it may work better mounted on the top of the VS, but I
was pretty happy with it, considering it's generally used as
backup navigation for me. My Archer nav doesn't perform nearly
as well and not nearly as well from any direction. Blade
antennas might work great, but last I saw they were very
expensive, too. I guess everyone has their tradeoff as to
what they are both wanting and willing to accept. I can only
speak for what I installed, and note that it's working plenty
well for me. The V's might be more sensitive in the forward
direction, but really, VOR's should be well received in all
directions or they aren't as useful as they should be.
Tim Olson - RV-10 N104CD
do not archive
Kelly McMullen wrote:
> If that were much of an issue, why not go with the more sensitive
> and balanced blade antennas? Most new production aircraft use them.
> IIRC they were designed to optimize VOR/DME RNAV performance.
> On Thu, Jul 9, 2009 at 12:32 PM, David McNeill <dlm46007(at)cox.net <mailto:dlm46007(at)cox.net
> >> wrote:
>
> <mailto:dlm46007(at)cox.net>>
> Marketing I assume. Swept back is cool. A lot of serious IFR
> aircraft have
> them swept forward to more accurately know where one is going
> rather
> than
> where one has been. IFR magazine had an article of an aircraft in
> IMC that
> hit a mountain while traveling between Port Angeles and Seattle
> along an
> airway. The cause was determined to be a bent VOR signal and the
> sensitivity
> of the antennas. I don't recall the particulars but do know that
> the
> sensitivity is in the direction of the elements of the V.
> --
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pitts_pilot(at)bellsouth.
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| Posted: Thu Jul 09, 2009 1:18 pm Post subject: Nav antenna location |
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Bear with me David ..... it's been a long time since I did antennas.
AFAIK, the direction the VOR antenna points (V forward or backward) has
nothing to do with sensitivity. The VOR antenna is a relatively
standard center fed dipole. The BALUN matches the balanced antenna with
the unbalanced coax (BAL UN). With most center fed dipoles, the 'arms'
are in line like a rod. Think of that FM antenna made from twin-lead. I
think the 'bent' dipole is an attempt at reducing the drag associated
with that straight antenna. The max sensitivity of a straight dipole
would be perpendicular to the 'straight' antenna. But, since the VOR
station may be anywhere within the 360 degree circle around the
aircraft, and will, at some time end up off the 'point' of the antenna
..... the reception would be poor at that point. By bending the
antenna we also get better 360 degree reception since more of the
antenna is broadside to the incoming signal as we fly around in a circle
(Vs. off the point at 90/270 to the signal).
If I'm wrong .... like I said ... been a long time .... please point me
to some 'educational material'.
Linn
David McNeill wrote:
| Quote: |
Marketing I assume. Swept back is cool. A lot of serious IFR aircraft have
them swept forward to more accurately know where one is going rather than
where one has been. IFR magazine had an article of an aircraft in IMC that
hit a mountain while traveling between Port Angeles and Seattle along an
airway. The cause was determined to be a bent VOR signal and the sensitivity
of the antennas. I don't recall the particulars but do know that the
sensitivity is in the direction of the elements of the V.
|
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rebrunk42(at)gmail.com
Guest
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| Posted: Thu Jul 09, 2009 1:27 pm Post subject: Nav antenna location |
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i have two blades. i love them. robert
On Jul 9, 2009, at 3:20 PM, John Cox wrote:
[quote]
Looks (aesthetics) often override antennae ground plane theory. No
one
should casually dismiss correct orientation solely on appearance.
Builders should consider manufacturer avionics and their best antennae
selection choice long before the aircraft is entering finish. But
alas,
all too often the thought doesn't enter early enough into radiation
patterns, placement, interference, ground plane (signal propagation),
coaxial run lengths or aesthetics until much too late to be as
effective.
"That is the case." Now....tradeoffs, that is more to the reality
of
choice during the long build process.
You can always look to the over 214 flying RV-10s and follow the
leaders.
John Cox
W7COX
#40600
--
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dlm46007(at)cox.net
Guest
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| Posted: Thu Jul 09, 2009 3:19 pm Post subject: Nav antenna location |
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I did not do antennas but somewhere in my distant past I remember pictures
of propagation/reception patterns. IIRC the propagation patterns were pear
shapes about the elements of the V where the large end of the pear coincided
with the tip of the element.
--
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Kelly McMullen
Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ
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| Posted: Thu Jul 09, 2009 4:12 pm Post subject: Nav antenna location |
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You are correct....about 4 times more expensive.,,,,,,wow!
On Thu, Jul 9, 2009 at 1:17 PM, Tim Olson <Tim(at)myrv10.com (Tim(at)myrv10.com)> wrote:
[quote]--> RV10-List message posted by: Tim Olson <Tim(at)myrv10.com (Tim(at)myrv10.com)>
Aren't they way way more expensive? I remember flying along just over
100nm away from a station in front of me, receiving it with my
backwards mounted (V facing forward) NAV antenna, mounted under
the tail. Now, it may be more sensitive mounted facing forward,
and it may work better mounted on the top of the VS, but I
was pretty happy with it, considering it's generally used as
backup navigation for me. My Archer nav doesn't perform nearly
as well and not nearly as well from any direction. Blade
antennas might work great, but last I saw they were very
expensive, too. I guess everyone has their tradeoff as to
what they are both wanting and willing to accept. I can only
speak for what I installed, and note that it's working plenty
well for me. The V's might be more sensitive in the forward
direction, but really, VOR's should be well received in all
directions or they aren't as useful as they should be.
Tim Olson - RV-10 N104CD
do not archive
Kelly McMullen wrote:
[quote] If that were much of an issue, why not go with the more sensitive and balanced blade antennas? Most new production aircraft use them. IIRC they were designed to optimize VOR/DME RNAV performance.
On Thu, Jul 9, 2009 at 12:32 PM, David McNeill <dlm46007(at)cox.net (dlm46007(at)cox.net) <mailto:dlm46007(at)cox.net (dlm46007(at)cox.net)>> wrote:
--> RV10-List message posted by: "David McNeill" <dlm46007(at)cox.net (dlm46007(at)cox.net)
<mailto:dlm46007(at)cox.net (dlm46007(at)cox.net)>>
Marketing I assume. Swept back is cool. A lot of serious IFR
aircraft have
them swept forward to more accurately know where one is going rather
than
where one has been. IFR magazine had an article of an aircraft in
IMC that
hit a mountain while traveling between Port Angeles and Seattle along an
airway. The cause was determined to be a bent VOR signal and the
sensitivity
of the antennas. I don't recall the particulars but do know that the
sensitivity is in the direction of the elements of the V.
--
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV10-List |
|
_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor
KCHD |
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