Today's Message Index:
----------------------
1. 05:12 AM - Re: ELT Antenna (msmeredith)
2. 05:32 AM - Re: ELT Antenna (msmeredith)
3. 07:09 AM - Re: Re: ELT Antenna (The Kuffels)
4. 10:18 AM - Re: ELT Antenna (msmeredith)
5. 10:51 AM - Re: ELT Antenna (msmeredith)
6. 12:46 PM - Re: Change to Shottky? (Robert L. Nuckolls, III)
7. 01:30 PM - Re: Change to Shottky? (Roger Evenson)
8. 02:53 PM - Re: ELT Antenna (Robert L. Nuckolls, III)
9. 05:32 PM - Re: Re: ELT Antenna (The Kuffels)
10. 06:46 PM - Re: Re: ELT Antenna (Stuart Hutchison)
11. 07:17 PM - Re: Re: ELT Antenna (Kelly McMullen)
12. 07:47 PM - Re: Re: ELT Antenna (Tim Andres)
13. 07:55 PM - Re: Re: ELT Antenna (Kelly McMullen)
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The longer answer involves not only the shielding effect caused by the
aluminum but also the feed mismatch, both of which will reduce signal
output. But the application is so direct there is no doubt you could be
heard by a satellite. If you wish to be sure, build a mock up with foil
over cardboard and scrap tubing. See how it works with and without the
foil. Don't forget the rules about when and how to test ELTs.
Tom Kuffel[/quote]
Tom,
Good idea. What do I need to measure the output with this mockup?
--------
Mark Meredith
Super Chipmunk N7DW
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=416930#416930
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stuart(at)stuarthutchison wrote:
> I'll be making an
> angled mount with fibreglass fairing like a COM antenna for the underside of
> my Rocket, since I also have a manual 406 GPS PLB.
> Kind regards, Stu
>
> F1 Rocket VH-FLY http://www.mykitlog.com/RockFLY
> www.teamrocketaircraft.com
> --
Stu,
I've thought about the "impact" of a rollover which is why I added the rollbar.
But think I'll stick with an assumption the airplane is still airborne or upright
in big pieces if the ELT is ever activated!
I have a very small cockpit and don't plan to carry a PLB. There are very few
places to put even a portable GPS for trips, so I went with the installed ELT
(best I can tell, aircraft has never had one since it was built in 1951). Kannad
has an internal antenna also so works without the whip in a handheld mode,
though I'd need a screwdriver and a good hand to access it...
--------
Mark Meredith
Super Chipmunk N7DW
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=416931#416931
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Mark,
<< works with and without the foil. .... Good idea. What do I need
to measure the output with this mockup? >>
The ELT still transmits on 121.5 so any aircraft band hand held will do
the job. Most hand helds have a signal strength indicator but a better
way (although tedious) is to see how far away (over flat ground) you can
hear it without the foil/cardboard. Then try it with the shield. No
guarantee it will be just as good at 406MHz but the odds are likely.
Or contact a local amateur radio club (find at arrl.org). Many ham UHF
hand helds can receive 406MHz. You will easily find a ham who would
enjoy helping with your experiment.
<< But think I'll stick with an assumption the airplane is still
airborne or upright in big pieces if the ELT is ever activated! >>
My experience suggests this is not a valid assumption. When this is
true, the people are ambulatory, can remove the ELT from its mount,
attach the portable antenna, or just talk on the aircraft radio. But in
most crashes I have seen, if the occupants are badly injured (and so
really need an ELT) then most external antennas are no longer working.
Carrying a PRB in your pocket might be a good Plan B.
If you do run the test, let us know the results.
Tom Kuffel
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[quote="kuffel(at)cyberport.net"]Mark,
The ELT still transmits on 121.5 so any aircraft band hand held will do the job.
Most hand helds have a signal strength indicator but a better way (although
tedious) is to see how far away (over flat ground) you can hear it without
the foil/cardboard. Then try it with the shield. No guarantee it will be
just as good at 406MHz but the odds are likely.
Or contact a local amateur radio club (find at arrl.org). Many ham UHF hand
helds can receive 406MHz. You will easily find a ham who would enjoy helping
with your experiment.
>
My experience suggests this is not a valid assumption. When this is true, the
people are ambulatory, can remove the ELT from its mount, attach the portable
antenna, or just talk on the aircraft radio. But in most crashes I have seen,
if the occupants are badly injured (and so really need an ELT) then most
external antennas are no longer working. Carrying a PRB in your pocket might
be a good Plan B.
If you do run the test, let us know the results.
Tom Kuffel
> [b]
Tom,
Thanks. I'll run the test and let you know. I have some extra .025 alum so will
use that for the mockup.
--------
Mark Meredith
Super Chipmunk N7DW
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=416949#416949
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kuffel(at)cyberport.net wrote:
> Mark,
>
>
>
> The ELT still transmits on 121.5 so any aircraft band hand held will do the
job. Most hand helds have a signal strength indicator but a better way (although
tedious) is to see how far away (over flat ground) you can hear it without
the foil/cardboard. Then try it with the shield. No guarantee it will be
just as good at 406MHz but the odds are likely.
>
> Or contact a local amateur radio club (find at arrl.org). Many ham UHF hand
helds can receive 406MHz. You will easily find a ham who would enjoy helping
with your experiment.
>
> >
>
> My experience suggests this is not a valid assumption. When this is true,
the people are ambulatory, can remove the ELT from its mount, attach the portable
antenna, or just talk on the aircraft radio. But in most crashes I have
seen, if the occupants are badly injured (and so really need an ELT) then most
external antennas are no longer working. Carrying a PRB in your pocket might
be a good Plan B.
>
> If you do run the test, let us know the results.
>
> Tom Kuffel
Tom and other listers,
Second thoughts. My bent comm and blade transponder antennas are under the belly
amidships behind the wing, close to the ELT transmitter's position above them.
If I mount the ELT whip antenna underneath also, can I bend the steel rod
beyond the black base so it's shaped similar to my comm antenna? Would I need
a large bend radius to prevent it from breaking, and would this affect the transmit
functionality? I could move it forward a foot or so (just aft the flaps)
to separate it from the comm antennas. I just need to be careful not to
tune my radio to 121.5 when testing the ELT.
Of course that round antenna base will be a big source of drag, but mounting it
underneath would solve the rollover and aesthetic issues. Though now the assumption
is the landing gear stay with the airplane!
--------
Mark Meredith
Super Chipmunk N7DW
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=416954#416954
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Subject: | Re: Change to Shottky? |
At 01:20 PM 1/14/2014, you wrote:
At Bob's suggestion, I've been looking at double anode - single
cathode arrangements in a TO-247 case, wired so that current goes
through both diodes. My average amperage will be 6-7 amps (12 to 14
total) and I can find packages that will have voltage drops of 0.3
volts or less. The tradeoff is higher leakage, but I don't see how a
few tens of mA will cause problems. With only 4 watts or so, Bob
suggested using the aluminum already behind the panel. Even if you
don't have enough sheet aluminum, there are light-weight heat sinks
for the TO-247 package that only cost a couple of bucks and weigh an
ounce or so. The TO-247 does have to be solder connected and mounted
with an electrically resistive pad, which adds little to cost or weight.
You're not going to find Schottky devices with rated
for such low voltage drops at their rated current.
To push the drop down, you use oversized to grossly
oversized diodes lightly loaded and yes, your
drop will go down a tad.
The advantage of Schottky diodes is that they have less voltage drop
than silicon diodes. Silicon is approx 0.7 volts and Schottky about
0.5 volts. The advantage being that Schottkys dissipate a little less energy.
Using your numbers for typical load:
Existing diode:
P = IE
6 * .7 = 4.2W
Schottky diode:
6 * .5 = 3.0W
I agree w/ your conclusion, probably not worth changing anything for
a delta of 1.2W.'
Agreed . . . The only time the diode is 'wasting'
energy is when the alternator is running and if you're
running a 40A+ alternator, the energy 'savings'
is trivial.
I wired Z11 with the earlier recommended endurance bus diode w/15
watt heatsink. My loads are 11.5 amps intermittent maximum, 6.1a.
typical, and if alternator quits, I could shut things off to get to
about 3.3 amps for comfortable endurance use. I see 13.1-13.3 volts
on this bus during flight. I have had no issues in 350 hours.
That heatsink is WAaayyyy bigger than you need for this
application.
Since completing my RV in 2010, I have been absent from the
aeroelectric list. I have noticed that the Shottky diode is now recommended.
It's an OPTION . . . one of several.
Did a search to attempt to 'catch up' with the discussion and have
tentatively concluded that this change would be purely optional, and
not 'highly recommended' for some electrical reason.
EXACTLY. I would not recommend anyone swap out
an existing rectifier installation. The Schotty devices
are attractive for new construction. My product uses
the airframe for heat management . . . a bit more compact
than the rectifier . . .
There are VERY few incarnations of the e-bus that
demands a finned heat-sink for the rectifier. Either
the silicon junction rectifier -OR- the Schottky
device should exist quite happily simply sinked
to the airplane.
Products like this
http://tinyurl.com/mfp9k7a
probably make sense in a composite airplane but I
suspect that few installations in metal airplanes
need the extra heat-sink.
I'm on a weight reduction kick, so my only objective to change to the
Shottky would only be to eliminate the 1/2 lb. of the heat-sink.
1/2 pound? Which heat-sink are you using?
Bob, et al: I'm looking for some assurance. Have I missed something
pertinent to this decision or am I on track?
Is this a metal airplane? Have you looked at simply
bolting the diode to local sheet metal?
Bob . . .
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Subject: | Re: Change to Shottky? |
Bob: To answer your questions, this is an RV7, all metal airplane. The heat sink
I used was the 15 watt one, the larger of the two offered at B&C. It weighs
7 oz.
I will remove it and install directly to the aluminum subpanel.
Would you change your recommendation if you knew I was in Arizona, occasionally
flying in 100+ temperatures?
Thanks. Roger
----- Original Message -----
From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
Sent: Wednesday, January 15, 2014 1:43:39 PM
Subject: Re: AeroElectric-List: Change to Shottky?
At 01:20 PM 1/14/2014, you wrote:
At Bob's suggestion, I've been looking at double anode - single
cathode arrangements in a TO-247 case, wired so that current goes
through both diodes. My average amperage will be 6-7 amps (12 to 14
total) and I can find packages that will have voltage drops of 0.3
volts or less. The tradeoff is higher leakage, but I don't see how a
few tens of mA will cause problems. With only 4 watts or so, Bob
suggested using the aluminum already behind the panel. Even if you
don't have enough sheet aluminum, there are light-weight heat sinks
for the TO-247 package that only cost a couple of bucks and weigh an
ounce or so. The TO-247 does have to be solder connected and mounted
with an electrically resistive pad, which adds little to cost or weight.
You're not going to find Schottky devices with rated
for such low voltage drops at their rated current.
To push the drop down, you use oversized to grossly
oversized diodes lightly loaded and yes, your
drop will go down a tad.
The advantage of Schottky diodes is that they have less voltage drop
than silicon diodes. Silicon is approx 0.7 volts and Schottky about
0.5 volts. The advantage being that Schottkys dissipate a little less energy.
Using your numbers for typical load:
Existing diode:
P = IE
6 * .7 = 4.2W
Schottky diode:
6 * .5 = 3.0W
I agree w/ your conclusion, probably not worth changing anything for
a delta of 1.2W.'
Agreed . . . The only time the diode is 'wasting'
energy is when the alternator is running and if you're
running a 40A+ alternator, the energy 'savings'
is trivial.
I wired Z11 with the earlier recommended endurance bus diode w/15
watt heatsink. My loads are 11.5 amps intermittent maximum, 6.1a.
typical, and if alternator quits, I could shut things off to get to
about 3.3 amps for comfortable endurance use. I see 13.1-13.3 volts
on this bus during flight. I have had no issues in 350 hours.
That heatsink is WAaayyyy bigger than you need for this
application.
Since completing my RV in 2010, I have been absent from the
aeroelectric list. I have noticed that the Shottky diode is now recommended.
It's an OPTION . . . one of several.
Did a search to attempt to 'catch up' with the discussion and have
tentatively concluded that this change would be purely optional, and
not 'highly recommended' for some electrical reason.
EXACTLY. I would not recommend anyone swap out
an existing rectifier installation. The Schotty devices
are attractive for new construction. My product uses
the airframe for heat management . . . a bit more compact
than the rectifier . . .
There are VERY few incarnations of the e-bus that
demands a finned heat-sink for the rectifier. Either
the silicon junction rectifier -OR- the Schottky
device should exist quite happily simply sinked
to the airplane.
Products like this
http://tinyurl.com/mfp9k7a
probably make sense in a composite airplane but I
suspect that few installations in metal airplanes
need the extra heat-sink.
I'm on a weight reduction kick, so my only objective to change to the
Shottky would only be to eliminate the 1/2 lb. of the heat-sink.
1/2 pound? Which heat-sink are you using?
Bob, et al: I'm looking for some assurance. Have I missed something
pertinent to this decision or am I on track?
Is this a metal airplane? Have you looked at simply
bolting the diode to local sheet metal?
Bob . . .
Message 8
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At 09:04 PM 1/14/2014, you wrote:
Hi - I'm installing a Kannad Integra 406AF ELT with built in
GPS. The cheapest antenna for this ELT is the whip, which is what I
bought with it. The blade/vane for this unit are hundreds/thousands
more expensive. But now I'm trying to figure out where to put the
whip! It's a monstrosity.
I presume you're talking about the AV-200 described in
Kannad's manual . . . .
http://tinyurl.com/olaccxt
This is an unusual Chippy - it's single seat open cockpit, and I
installed an 8 foot long turtleback/headrest to conceal a rollover
bar behind the rear seat. It's .025 alum, about a foot high/wide at
the cockpit then tapering to about 4 inches at the fin. I'd like to
mount the antenna 2 feet back on the top of the main fuselage
structure, so the rubber part is inside the turtleback, then poke the
steel whip out the top through a small hole/grommet. That approach
would be unobtrusive, avoid an ugly 2 foot tall antenna with fat
black base, and avoid beefing up the turtleback top to support
it. My question: would the ELT still be heard with the bottom 8
inches or so of base hidden under .025 alum?
Probably not. That "bottom 8" is probably the 406 mHz
part of the antenna. Further, given that this product
doesn't have a separate GPS antenna, I'm assuming that
the single antenna assembly serves the GPS receiver
as well.
I think you should take pains to install per the
manufacturer's recommendations.
Bob . . .
Message 9
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Mark,
<< If I mount the ELT whip antenna underneath also >>
This is probably the worst location for an ELT antenna. Any kind of brush
at an off-airport landing will wipe it off the fuselage.
<< can I bend the steel rod beyond the black base so it's shaped similar to
my comm antenna? >>
Don't know why not.
<< Would I need a large bend radius to prevent it from breaking, >>
No idea. If the antenna there is just a steel rod as you say, then bending
it around a 1" pipe or so should work. But once again, this is a very bad
location.
<< would this affect the transmit functionality? I could move it forward a
foot or so (just aft the flaps) to separate it from the comm antennas. >>
The nearness of other VHF antennas will affect performance more than a bend.
The above fuselage location has two ground planes of isolation from your Com
antenna.
Is it time yet to consider making the cover out of fiberglass instead of
aluminum?
Tom Kuffel
Message 10
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The ELT antenna is almost never radiating and when it is activated, COM
radio performance is unlikely to be relevant. Bob may be able to confirm,
but I believe the ELT antenna proximity to VHF COM antennas can be
problematic because radio transmissions have been known to activate the ELT.
I acknowledge Mark's comment about the possibility of an underbelly antenna
being wiped off, which is why the base of mine will be firmly mounted
(midships) angled aft at about 45 deg (rather than bend the whip element)
and the fat part faired with fibreglass to minimise/absorb antenna impact
damage and or carve a path through the brush/grass. Perhaps different with
a tricycle undercarriage, but I can expect the taildragger to be upside down
if I land in scrub (with the main wheels so far forward and a heavy engine),
so my priority is to have the antenna less shielded by the aircraft when
inverted. If it were mounted on top, then it may also wiped off as the
aircraft comes to rest inverted or be pinned flat against the ally skin.
Preserving the coax link between the transmitter and antenna is a known
problem in major crashes, so keep the coax run short, protected and flexible
too if possible.
Kind regards, Stu
F1 Rocket VH-FLY http://www.mykitlog.com/RockFLY
www.teamrocketaircraft.com
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of The
Kuffels
Sent: Thursday, January 16, 2014 12:32 PM
Subject: Re: AeroElectric-List: Re: ELT Antenna
--> <kuffel@cyberport.net>
Mark,
<< If I mount the ELT whip antenna underneath also >>
This is probably the worst location for an ELT antenna. Any kind of brush
at an off-airport landing will wipe it off the fuselage.
<< can I bend the steel rod beyond the black base so it's shaped similar to
my comm antenna? >>
Don't know why not.
<< Would I need a large bend radius to prevent it from breaking, >>
No idea. If the antenna there is just a steel rod as you say, then bending
it around a 1" pipe or so should work. But once again, this is a very bad
location.
<< would this affect the transmit functionality? I could move it forward a
foot or so (just aft the flaps) to separate it from the comm antennas. >>
The nearness of other VHF antennas will affect performance more than a bend.
The above fuselage location has two ground planes of isolation from your Com
antenna.
Is it time yet to consider making the cover out of fiberglass instead of
aluminum?
Tom Kuffel
Message 11
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Almost all ELTs, especially the older ones do in fact radiate anytime
they are near high powered VHF transmitters in the FM, TV, etc bands.
That radiation will in fact severely affect Com radio reception.
The antenna for ELT is integral to its TSO so no home brew antennas
fullfill the TSO. While I think most DAR's are somewhat tolerant as to
antenna placement, most install instructions do call for installation on
top of the fuselage, and the install instructions are also part of the
TSO approval.
So while you may have valid points about final resting of a crash being
upside down, during the touchdown, prior to rollout odds are very high
that any belly antenna will be wiped off the airframe. IMHO, with about
equal experience between tail wheel(mostly off pavement in Alaska) and
nose dragging aircraft, in off field landing situations of soft surface,
nose wheel is far more likely to cause flipping than tail wheel.
Non-compliance with TSO is between you and your DAR, but most discussed
here will be at least technical non-compliance.
Kelly
On 1/15/2014 7:47 PM, Stuart Hutchison wrote:
>
> The ELT antenna is almost never radiating and when it is activated, COM
> radio performance is unlikely to be relevant. Bob may be able to confirm,
> but I believe the ELT antenna proximity to VHF COM antennas can be
> problematic because radio transmissions have been known to activate the ELT.
>
> I acknowledge Mark's comment about the possibility of an underbelly antenna
> being wiped off, which is why the base of mine will be firmly mounted
> (midships) angled aft at about 45 deg (rather than bend the whip element)
> and the fat part faired with fibreglass to minimise/absorb antenna impact
> damage and or carve a path through the brush/grass. Perhaps different with
> a tricycle undercarriage, but I can expect the taildragger to be upside down
> if I land in scrub (with the main wheels so far forward and a heavy engine),
> so my priority is to have the antenna less shielded by the aircraft when
> inverted. If it were mounted on top, then it may also wiped off as the
> aircraft comes to rest inverted or be pinned flat against the ally skin.
> Preserving the coax link between the transmitter and antenna is a known
> problem in major crashes, so keep the coax run short, protected and flexible
> too if possible.
>
> Kind regards, Stu
>
> F1 Rocket VH-FLY http://www.mykitlog.com/RockFLY
> www.teamrocketaircraft.com
>
>
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of The
> Kuffels
> Sent: Thursday, January 16, 2014 12:32 PM
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Re: ELT Antenna
>
> --> <kuffel@cyberport.net>
>
> Mark,
>
> << If I mount the ELT whip antenna underneath also >>
>
> This is probably the worst location for an ELT antenna. Any kind of brush
> at an off-airport landing will wipe it off the fuselage.
>
> << can I bend the steel rod beyond the black base so it's shaped similar to
> my comm antenna? >>
>
> Don't know why not.
>
> << Would I need a large bend radius to prevent it from breaking, >>
>
> No idea. If the antenna there is just a steel rod as you say, then bending
> it around a 1" pipe or so should work. But once again, this is a very bad
> location.
>
> << would this affect the transmit functionality? I could move it forward a
>
> foot or so (just aft the flaps) to separate it from the comm antennas. >>
>
> The nearness of other VHF antennas will affect performance more than a bend.
>
> The above fuselage location has two ground planes of isolation from your Com
> antenna.
>
> Is it time yet to consider making the cover out of fiberglass instead of
> aluminum?
>
> Tom Kuffel
>
>
Message 12
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DAR approval not needed as the ELT is not even required unless there are 2 or more
seats, or for phase 1 testing. Not saying its wise or will work, but it will
not be required to be present for airworthiness.
Tim
> On Jan 15, 2014, at 7:16 PM, Kelly McMullen <kellym@aviating.com> wrote:
>
>
> Almost all ELTs, especially the older ones do in fact radiate anytime they are
near high powered VHF transmitters in the FM, TV, etc bands.
> That radiation will in fact severely affect Com radio reception.
> The antenna for ELT is integral to its TSO so no home brew antennas fullfill
the TSO. While I think most DAR's are somewhat tolerant as to antenna placement,
most install instructions do call for installation on top of the fuselage,
and the install instructions are also part of the TSO approval.
> So while you may have valid points about final resting of a crash being upside
down, during the touchdown, prior to rollout odds are very high that any belly
antenna will be wiped off the airframe. IMHO, with about equal experience between
tail wheel(mostly off pavement in Alaska) and nose dragging aircraft, in
off field landing situations of soft surface, nose wheel is far more likely
to cause flipping than tail wheel.
> Non-compliance with TSO is between you and your DAR, but most discussed here
will be at least technical non-compliance.
> Kelly
>> On 1/15/2014 7:47 PM, Stuart Hutchison wrote:
>>
>> The ELT antenna is almost never radiating and when it is activated, COM
>> radio performance is unlikely to be relevant. Bob may be able to confirm,
>> but I believe the ELT antenna proximity to VHF COM antennas can be
>> problematic because radio transmissions have been known to activate the ELT.
>>
>> I acknowledge Mark's comment about the possibility of an underbelly antenna
>> being wiped off, which is why the base of mine will be firmly mounted
>> (midships) angled aft at about 45 deg (rather than bend the whip element)
>> and the fat part faired with fibreglass to minimise/absorb antenna impact
>> damage and or carve a path through the brush/grass. Perhaps different with
>> a tricycle undercarriage, but I can expect the taildragger to be upside down
>> if I land in scrub (with the main wheels so far forward and a heavy engine),
>> so my priority is to have the antenna less shielded by the aircraft when
>> inverted. If it were mounted on top, then it may also wiped off as the
>> aircraft comes to rest inverted or be pinned flat against the ally skin.
>> Preserving the coax link between the transmitter and antenna is a known
>> problem in major crashes, so keep the coax run short, protected and flexible
>> too if possible.
>>
>> Kind regards, Stu
>>
>> F1 Rocket VH-FLY http://www.mykitlog.com/RockFLY
>> www.teamrocketaircraft.com
>>
>>
>>
>> -----Original Message-----
>> From: owner-aeroelectric-list-server@matronics.com
>> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of The
>> Kuffels
>> Sent: Thursday, January 16, 2014 12:32 PM
>> To: aeroelectric-list@matronics.com
>> Subject: Re: AeroElectric-List: Re: ELT Antenna
>>
>> --> <kuffel@cyberport.net>
>>
>> Mark,
>>
>> << If I mount the ELT whip antenna underneath also >>
>>
>> This is probably the worst location for an ELT antenna. Any kind of brush
>> at an off-airport landing will wipe it off the fuselage.
>>
>> << can I bend the steel rod beyond the black base so it's shaped similar to
>> my comm antenna? >>
>>
>> Don't know why not.
>>
>> << Would I need a large bend radius to prevent it from breaking, >>
>>
>> No idea. If the antenna there is just a steel rod as you say, then bending
>> it around a 1" pipe or so should work. But once again, this is a very bad
>> location.
>>
>> << would this affect the transmit functionality? I could move it forward a
>>
>> foot or so (just aft the flaps) to separate it from the comm antennas. >>
>>
>> The nearness of other VHF antennas will affect performance more than a bend.
>>
>> The above fuselage location has two ground planes of isolation from your Com
>> antenna.
>>
>> Is it time yet to consider making the cover out of fiberglass instead of
>> aluminum?
>>
>> Tom Kuffel
>
>
>
>
>
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Agreed if a single seater is all that is involved.
On 1/15/2014 8:47 PM, Tim Andres wrote:
>
> DAR approval not needed as the ELT is not even required unless there are 2 or
more seats, or for phase 1 testing. Not saying its wise or will work, but it
will not be required to be present for airworthiness.
>
> Tim
>
>> On Jan 15, 2014, at 7:16 PM, Kelly McMullen <kellym@aviating.com> wrote:
>>
>>
>> Almost all ELTs, especially the older ones do in fact radiate anytime they are
near high powered VHF transmitters in the FM, TV, etc bands.
>> That radiation will in fact severely affect Com radio reception.
>> The antenna for ELT is integral to its TSO so no home brew antennas fullfill
the TSO. While I think most DAR's are somewhat tolerant as to antenna placement,
most install instructions do call for installation on top of the fuselage,
and the install instructions are also part of the TSO approval.
>> So while you may have valid points about final resting of a crash being upside
down, during the touchdown, prior to rollout odds are very high that any belly
antenna will be wiped off the airframe. IMHO, with about equal experience
between tail wheel(mostly off pavement in Alaska) and nose dragging aircraft,
in off field landing situations of soft surface, nose wheel is far more likely
to cause flipping than tail wheel.
>> Non-compliance with TSO is between you and your DAR, but most discussed here
will be at least technical non-compliance.
>> Kelly
>>> On 1/15/2014 7:47 PM, Stuart Hutchison wrote:
>>>
>>> The ELT antenna is almost never radiating and when it is activated, COM
>>> radio performance is unlikely to be relevant. Bob may be able to confirm,
>>> but I believe the ELT antenna proximity to VHF COM antennas can be
>>> problematic because radio transmissions have been known to activate the ELT.
>>>
>>> I acknowledge Mark's comment about the possibility of an underbelly antenna
>>> being wiped off, which is why the base of mine will be firmly mounted
>>> (midships) angled aft at about 45 deg (rather than bend the whip element)
>>> and the fat part faired with fibreglass to minimise/absorb antenna impact
>>> damage and or carve a path through the brush/grass. Perhaps different with
>>> a tricycle undercarriage, but I can expect the taildragger to be upside down
>>> if I land in scrub (with the main wheels so far forward and a heavy engine),
>>> so my priority is to have the antenna less shielded by the aircraft when
>>> inverted. If it were mounted on top, then it may also wiped off as the
>>> aircraft comes to rest inverted or be pinned flat against the ally skin.
>>> Preserving the coax link between the transmitter and antenna is a known
>>> problem in major crashes, so keep the coax run short, protected and flexible
>>> too if possible.
>>>
>>> Kind regards, Stu
>>>
>>> F1 Rocket VH-FLY http://www.mykitlog.com/RockFLY
>>> www.teamrocketaircraft.com
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: owner-aeroelectric-list-server@matronics.com
>>> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of The
>>> Kuffels
>>> Sent: Thursday, January 16, 2014 12:32 PM
>>> To: aeroelectric-list@matronics.com
>>> Subject: Re: AeroElectric-List: Re: ELT Antenna
>>>
>>> --> <kuffel@cyberport.net>
>>>
>>> Mark,
>>>
>>> << If I mount the ELT whip antenna underneath also >>
>>>
>>> This is probably the worst location for an ELT antenna. Any kind of brush
>>> at an off-airport landing will wipe it off the fuselage.
>>>
>>> << can I bend the steel rod beyond the black base so it's shaped similar to
>>> my comm antenna? >>
>>>
>>> Don't know why not.
>>>
>>> << Would I need a large bend radius to prevent it from breaking, >>
>>>
>>> No idea. If the antenna there is just a steel rod as you say, then bending
>>> it around a 1" pipe or so should work. But once again, this is a very bad
>>> location.
>>>
>>> << would this affect the transmit functionality? I could move it forward
a
>>>
>>> foot or so (just aft the flaps) to separate it from the comm antennas. >>
>>>
>>> The nearness of other VHF antennas will affect performance more than a bend.
>>>
>>> The above fuselage location has two ground planes of isolation from your Com
>>> antenna.
>>>
>>> Is it time yet to consider making the cover out of fiberglass instead of
>>> aluminum?
>>>
>>> Tom Kuffel
>>
>>
>>
>>
>
>
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