Today's Message Index:
----------------------
1. 07:44 AM - Re: Re: Odyssey Battery (Rob Logan)
2. 08:12 AM - Re: GPS wiring? (Lockamy, Jack L)
3. 09:02 AM - Re: Aircraft Theft Protection (Robert L. Nuckolls, III)
4. 09:20 AM - Re: GPS wiring? (rd2@evenlink.com)
5. 10:16 AM - Re: Re: Odyssey Battery (Terry Watson)
6. 10:33 AM - Re: Dynon Efis (Steve Sampson)
7. 10:49 AM - Re: Re: 1/4 wave groundplane? (Malcolm Thomson)
8. 11:34 AM - Re: Re: Odyssey Battery (Rob Logan)
9. 11:53 AM - Re: Re: 1/4 wave groundplane? (Rob Logan)
10. 12:01 PM - Re: Re: 1/4 wave groundplane? (Steve Sampson)
11. 12:07 PM - Re: Re: 1/4 wave groundplane? (Robert L. Nuckolls, III)
12. 02:52 PM - Re: Re: 1/4 wave groundplane? (Malcolm Thomson)
13. 02:52 PM - Switching GPS Data Signals ()
14. 06:22 PM - Re: Effects of feedline length on Standing Wave Ratio (Robert L. Nuckolls, III)
15. 06:25 PM - Re: Re: 1/4 wave groundplane? (Robert L. Nuckolls, III)
16. 06:30 PM - Re: Switching GPS Data Signals (Robert L. Nuckolls, III)
17. 06:54 PM - Re: Switching GPS Data Signals (rv-9a-online)
18. 07:04 PM - Bent whip "radiators" question (Turbo Tom)
19. 07:30 PM - Re: Switching GPS Data Signals (Brian Kraut)
20. 08:29 PM - Re: Switching GPS Data Signals (rv-9a-online)
21. 09:46 PM - Re: Z13a Pre-flight alt test procedure? (Mike Holland)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Odyssey Battery |
--> AeroElectric-List message posted by: "Rob Logan" <rob@logan.com>
> There is nothing "wrong" with the Odyssey battery . . .
> the notion that BATTERY MAINTENANCE should include either ...
> replacement of the battery IN SPITE of the fact that it still cranks
Odyssey PC680 battery is listed as
> 30% state of charge still provides sufficient starting amps
> 50% state of charge after 2 years if stored at room temperature
> eight year design life or
> 400 [cycles] when fully discharged or
> 500 [cycles] when discharged to 80%
so at 150 cycles a year, that replace every third annual. but
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=4519882933
claims its 7.27'' x 3.11'' x 6.67'' in
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=4520579883
claims its 7.0" in length, 3.0" wide, and 6 9/16" tall.
not sure what http://www.bandc.biz/BC116-1.pdf is but its
claims 7.1" 6.6" 3.0"
did the first guy just get his size wrong or am I missing something
or how big is the non MJ PC680?
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
--> AeroElectric-List message posted by: "Lockamy, Jack L" <jack.lockamy@navy.mil>
Mickey,
Go to www.ebay.com. Do a search for Garmin 010-10082-00. This should get you a large list of available cables at much better prices than you will get from buying direct from Garmin. I think I paid $10 for the cable I'm using on my Garmin 196 connected to a TRIO Avionics Autopilot.
Jack Lockamy
Camarillo, CA
-7A FWF (almost done...)
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Aircraft Theft Protection |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 01:40 AM 1/20/2005 -0500, you wrote:
>--> AeroElectric-List message posted by: Dww0708@aol.com
>
>During" oneday on the flight line "an old man started his 182 with one of
>those chain gangs on the prop, snapped three of the four engine mounts
>before
>he realized what he had done. I mean you could see the cross grain of the
>castings where they exceeded their yield strength, probably makes you go
>sentimental. That BE 1900 looks like it is covered in Gill Liner
>internally. Did
>yall do that cargo mod. I did a few cargo mods on some DO228 s. Love
>hearing stuff from the Big Shops. David
At least he didn't get off the ground before he became aware
of a critical check-list item. Wonder if he looked into his
fuel tanks too . . .
Don't know anything about this particular airplane. It was
sitting inside the avionics hangar at RAS Wichita two weeks
ago during the ice storm and was outside on the ramp Monday
when I took the picture.
Bob . . .
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
--> AeroElectric-List message posted by: rd2@evenlink.com
I got one for 196 from ebay last year, cheap.
Sometime thereafter 1/2 of the 4-hole connector broke off (apparently
couldn't take the PA winter), so I had to get one from Garmin (the
connector seems made from better material). Now it's holding up (cable is
always connected in the airplane, GPS unit is taken out
disconnected/connected almost every day).
Maybe just my experience...
Rumen
do not archive
_____________________Original message __________________________
(received from Lockamy, Jack L; Date: 08:10 AM 1/20/2005
-0800)
--> AeroElectric-List message posted by: "Lockamy, Jack L"
<jack.lockamy@navy.mil>
Mickey,
Go to www.ebay.com. Do a search for Garmin 010-10082-00. This should get
you a large list of available cables at much better prices than you will
get from buying direct from Garmin. I think I paid $10 for the cable I'm
using on my Garmin 196 connected to a TRIO Avionics Autopilot.
Jack Lockamy
Camarillo, CA
-7A FWF (almost done...)
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Odyssey Battery |
--> AeroElectric-List message posted by: "Terry Watson" <terry@tcwatson.com>
Rob,
Here's a page that has a PDF reference for the specs on Odyssey batteries:
http://www.batterymart.com/c-odyssey.html
Terry
did the first guy just get his size wrong or am I missing something
or how big is the non MJ PC680?
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
--> AeroElectric-List message posted by: "Steve Sampson" <steve@lbho.freeserve.co.uk>
Kevin - thanks for that. I was testing the ASI the other day in the hanger
by pressurising the pitot line and was amazed to see the Dynon compass swing
quite aggressively. I guess it percieved it as an acceleration as the
pressure came on and the software moved the compass to counteract the non
existant acceleration error. (It was facing about 240)I think that clears
that up. This is a D10 with a remote compass and the software that was
current last year at S&F. I dont have the version number to hand.
Steve.
RV9a 9036
G-IINI
PS Have you tested your entire pitot system with the Dynon Pitot/AoA head
on. I dont see how to do it because Dynon have a built in leak. Its very
small but they have confirmed it is meant to be there.
>
I'd like to confirm one thing - did you have the Dynon EFIS connected
to the pitot and static systems? The reason I ask is that I
understand that they use the airspeed input to partially correct for
acceleration errors. The unit might behave strangely if it saw
accelerations but no airspeed.
Thanks for the Dynon report.
--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Message 7
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: 1/4 wave groundplane? |
--> AeroElectric-List message posted by: "Malcolm Thomson" <mdthomson@attglobal.net>
Bob, I have been given some conflicting information regarding "ground
planes" and this post leaves me still more confused about this business
of ground planes.
I have an airplane which is nearly all carbon. Unlike fiberglass, I am
told that all antenna's must be on the outside of the carbon structure
just like you would place them on an metal airplane. The basis for this
is that "carbon acts like metal and does not let the radio frequencies
through". With this said, one might assume then that the carbon will
also act as a ground plane but I am also told that it does not.
So, do I need to add a ground plane? If so, what would be the approach?
Should I install some thin aluminum inside the aircraft, mount the
antenna's on the outside, their bolts passing through the carbon and
aluminum thereby making the electrical connection to the ground plane?
What is the smallest ground plane you'd recommended for a COM antenna
and does the antenna have to be mounted in the middle of it?
Thanks
Malcolm.
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Robert L. Nuckolls, III
Subject: AeroElectric-List: Re: 1/4 wave groundplane?
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
--> <b.nuckolls@cox.net>
At 06:35 PM 1/19/2005 +0000, you wrote:
>--> AeroElectric-List message posted by: "Steve Sampson"
><steve@lbho.freeserve.co.uk>
>
>Oops! That was meant to go to aeroelectric
>
> > -----Original Message-----
> > From: Steve Sampson [mailto:Steve@lbho.freeserve.co.uk]
> > Sent: 19 January 2005 18:09
> > To: RV Squadron (E-mail)
> > Subject: [rvsqn] 1/4 wave groundplane
> >
> > Bob - I would welcome your comments.
> >
> > In the bumph the PFA (roughly the British EAA) gives out there is
> > some stuff about aerials. It includes......
> >
> > "Even some professional radio installers seem to think that if the
> > braid of the feeder coax is firmly connected to the metal fuselageat
> > the base of the aerial, then it will do the job. Wrong! At any given
> > frequency the length of the driven element ...is calculated to be
> > resonant as a 1/4 wavelength................................But the
> > 'counterpoise' or other half must also be of similar dimensions so
> > as to present the trans/rec witha 1/2 wavelength total. The entire
> > fuselage however presents no such thing and completely unbalances
> > the system................causing a variety of problems, not least
> > interference and much degraded performance........ At the base of
> > the aerial the braid should also be connected to a tuned groundplane
> > either in the form of a down going insulated wire or number of wires
> > measuring 5% less in length than the driven
> > element..........................It doe not matter that the airframe
> > is also connected at its centre..................the oscilating
> > pulses in the aerial will choose the resonant path both
> > ways........................................."
> >
> > What is your reaction to this? I have never seen this reccomendation
> > before. He seems to be trying to turn a 1/4 wave into a dipole with
> > half the aerial inside and half outside. Surely this would cause
> > energy to bounce around inside a metal aircraft?
The writer is not "wrong" but he's making a mountain out of
a molehill. An airplane is not a perfect world for antennas.
Further, his concerns for "degraded performance" generally don't
surface as significant realities.
VHF Comm antennas have been installed on aircraft for over 60
years. Installations range from nearly ideal (antenna sits on
large area of metal "radiating" several wavelengths in all
directions. 747s and their like make really good airborne
antenna farms. As the airplane gets smaller, the real estate
for ground plane goes down. As the airplane becomes fabric
over tube, opportunities for using existing features on
the airplane as a ground plane or "counterpoise" degrades
further and ultimately becomes non-existent on the glass-n-
plastic machines.
Yes, if you went to the antenna range and quantified
performance of the various compromise antennas that have
flown on ultra-lights through 747s, one could cheer
the data plots on the 747 installation and cry in lots
of beer over the results of tests for the ultra-light.
Let us consider the most compromised antenna of all - the
"rubber duckie" common to bizillions of hand held radios
ranging from CB frequencies (27 Mhz) to near microwave
(wi-fi products at 5 Ghz). NONE of these products are
favored with anything like the ideal antenna when it comes
to ground planes. Your hand-held vhf comm transceiver
not only has a foreshortened antenna (it should be 23.6
inches long), it has only your very small body capacity
to couple thorough to approach anything like a useful
ground plane.
Bottom line for USEFULNESS of ANY antenna installation
is whether or not it serves the intended purpose while
avoiding interference with other systems (some folks
can use the outside-antenna comm transceiver with no
problems while hand-held comm with rubber-duck in cockpit
drives some panel mounted stuff zonkers). I've often
remarked here on the list about the disparity of comments
on Bob Archer's wing tip comm antennas (VERY compromised).
One user says, "piece of crap" while another says, "greatest
thing since sliced bread". Turns out that one guy never
needs to talk to stations more than 10 miles away and the
other guy was gunching about not hitting an RCO 40 miles
away while he was flying 2000 feet above the terrain.
We KNOW that a hand-held performs MUCH better plumbed
into the ship's external antenna (no matter how compromised)
than it does using just a rubber-duck from the cockpit.
However, I'm not going to pitch the rubber-ducks on my
hand-helds in favor of an "ideal" antenna with an
optimal ground plane. This umbrella sized device would
be difficult to open and use in the cockpit.
All this stuff applies only to resonant, un-amplified
antennas that drive low impedance feedlines (50 ohm coax).
There's a whole other world of antennas like amplified
GPS antennas, loran antennas, ADF antennas, AM antenna
on your car, etc. which are e-field receptors and have
their own special worlds that do not (indeed some cannot)
depend on any kind of resonant counterpoise or ground plane.
The writer was perfectly founded in the physics of
the ideal antenna structure but appears unaware of
the practical realities of antenna compromise that
have performed to the degree EXPECTED and ACCEPTED
on airplanes of all sizes for for decades. He may be
familiar with the efforts that antenna designers expend
to get the most from a broadcast or ground based
communications antenna where the GOAL is ANTENNA
performance. Our goal is to optimize FLIGHT SYSTEM
performance wherein most situations will tolerate
"degraded" antenna performance. Please feel free to
forward this note to the original author and invite
him to join us here on the List.
Bob . . .
Message 8
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Odyssey Battery |
--> AeroElectric-List message posted by: "Rob Logan" <rob@logan.com>
> http://www.batterymart.com/c-odyssey.html
this lists the PC680 as
Length 7 in. Width 3 1/16 in. Height 6 5/8 in.
but has a link to
http://www.batterymart.com/pdf_files/odyssey_guide.pdf
that lists the PC680 as 7.27" 3.11" 6.67"
so I'm still confused.... how big is a PC680? will
it fit in a box I made for a B&C 16Ah battery?
Rob
Message 9
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: 1/4 wave groundplane? |
--> AeroElectric-List message posted by: "Rob Logan" <rob@logan.com>
> What is the smallest ground plane you'd recommended for a COM antenna
> and does the antenna have to be mounted in the middle of it?
mounted my antennas to the outside carbon, but attached 4
copper radials (striped house wire) to the nut plates... the
length of the ground planes isn't nearly as critical as
the vertical. what matters is the SWR, or reflected energy
back into the radio, this can be adjusted by coax feed
length if you can't cut your floxed in radials like me.
http://mars.comportco.com/~w5alt/antennas/notes/ant-notes.php?pg=22
> The writer is not "wrong" but he's making a mountain out of
> a molehill. An airplane is not a perfect world for antennas.
4 radials of "close" size are easy to glass in (3 would work, but
more than 4 is overkill) and fine tune SWR with feed length.. no
math required... one would notice loss of impedance fuel level
converters for 30secs long before the tower asks you to "say again"
-Rob
Message 10
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: 1/4 wave groundplane? |
--> AeroElectric-List message posted by: "Steve Sampson" <steve@lbho.freeserve.co.uk>
Bob - thanks for that. As I thought, theoretically correct but not
pragmatic. The story of so much in UK engineering in the last 60 years.
Steve.
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of Robert
L. Nuckolls, III
Subject: AeroElectric-List: Re: 1/4 wave groundplane?
--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Message 11
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: 1/4 wave groundplane? |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 11:48 AM 1/20/2005 -0700, you wrote:
>--> AeroElectric-List message posted by: "Malcolm Thomson"
><mdthomson@attglobal.net>
>
>Bob, I have been given some conflicting information regarding "ground
>planes" and this post leaves me still more confused about this business
>of ground planes.
>
>I have an airplane which is nearly all carbon. Unlike fiberglass, I am
>told that all antenna's must be on the outside of the carbon structure
>just like you would place them on an metal airplane. The basis for this
>is that "carbon acts like metal and does not let the radio frequencies
>through".
Correct . . .
> With this said, one might assume then that the carbon will
>also act as a ground plane but I am also told that it does not.
. . . sorta correct. We tried using carbon fiber as ground
plane on several projects and abandoned the idea. It's EASY
to add a good ground plane in most cases . . . so why not?
>So, do I need to add a ground plane? If so, what would be the approach?
>Should I install some thin aluminum inside the aircraft, mount the
>antenna's on the outside, their bolts passing through the carbon and
>aluminum thereby making the electrical connection to the ground plane?
>What is the smallest ground plane you'd recommended for a COM antenna
>and does the antenna have to be mounted in the middle of it?
The ground plane is easiest to fabricate and install if you
cut strips of aluminum or copper foil about 1" wide and 22 inches
long. RADIATE minimum of 4, maximum of 8 radials from base of antenna
on inside of fuselage. Run along contours. If you have to "hop"
over structure or stiffeners, don't change length of material, just
run it, secure it with adhesive and let it be.
The radials should connect to a common plate under the footprint
of the antenna. If you make the plate out of brass and the radials
out of brass shim stock, all can be neatly soldered together
at the center. On a graphite airplane, a solid
pieced of brass shim stock conformed to the inside contours
for as far as practical in each direction with a max desired
dimension of 22" from base of antenna would be an attractive
compromise too.
Other antennas are built the same way . . . transponder antennas
can use a full circular disk of brass or aluminum, 5.2" in diameter.
See chapter on antennas in the 'Connection.
Now, if for some reason you can only get three or two radials
installed, the thing will probably do just fine anyhow. Antennas
on airplanes can be VERY poor compared to the best-we-know-how-to-
do and still function adequately.
Bob . . .
Message 12
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: 1/4 wave groundplane? |
--> AeroElectric-List message posted by: "Malcolm Thomson" <mdthomson@attglobal.net>
Bob, how significant is the use of brass vs. aluminum?
Thanks.
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Robert L. Nuckolls, III
Subject: RE: AeroElectric-List: Re: 1/4 wave groundplane?
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
--> <b.nuckolls@cox.net>
At 11:48 AM 1/20/2005 -0700, you wrote:
>--> AeroElectric-List message posted by: "Malcolm Thomson"
><mdthomson@attglobal.net>
>
>Bob, I have been given some conflicting information regarding "ground
>planes" and this post leaves me still more confused about this business
>of ground planes.
>
>I have an airplane which is nearly all carbon. Unlike fiberglass, I am
>told that all antenna's must be on the outside of the carbon structure
>just like you would place them on an metal airplane. The basis for
>this is that "carbon acts like metal and does not let the radio
>frequencies through".
Correct . . .
> With this said, one might assume then that the carbon will also act
>as a ground plane but I am also told that it does not.
. . . sorta correct. We tried using carbon fiber as ground
plane on several projects and abandoned the idea. It's EASY
to add a good ground plane in most cases . . . so why not?
>So, do I need to add a ground plane? If so, what would be the approach?
>Should I install some thin aluminum inside the aircraft, mount the
>antenna's on the outside, their bolts passing through the carbon and
>aluminum thereby making the electrical connection to the ground plane?
>What is the smallest ground plane you'd recommended for a COM antenna
>and does the antenna have to be mounted in the middle of it?
The ground plane is easiest to fabricate and install if you
cut strips of aluminum or copper foil about 1" wide and 22 inches
long. RADIATE minimum of 4, maximum of 8 radials from base of antenna
on inside of fuselage. Run along contours. If you have to "hop"
over structure or stiffeners, don't change length of material, just
run it, secure it with adhesive and let it be.
The radials should connect to a common plate under the footprint
of the antenna. If you make the plate out of brass and the radials
out of brass shim stock, all can be neatly soldered together
at the center. On a graphite airplane, a solid
pieced of brass shim stock conformed to the inside contours
for as far as practical in each direction with a max desired
dimension of 22" from base of antenna would be an attractive
compromise too.
Other antennas are built the same way . . . transponder antennas
can use a full circular disk of brass or aluminum, 5.2" in diameter.
See chapter on antennas in the 'Connection.
Now, if for some reason you can only get three or two radials
installed, the thing will probably do just fine anyhow. Antennas
on airplanes can be VERY poor compared to the best-we-know-how-to-
do and still function adequately.
Bob . . .
Message 13
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Switching GPS Data Signals |
--> AeroElectric-List message posted by: <tgrazian@bellsouth.net>
I am currently wiring the panel for my Zodiac 601XL. I am installing a Trio EZ
Pilot II autopilot, which accepts NMEA 0183 signals for tracking. I also have
on order a Blue Mountain EFIS Lite Gen 3, which has a built in GPS. I would
like to be able to use my Garmin 295 and the EFIS Lite to supply the GPS data.
Does anyone have any comments on the advisability of using a "2-8" type DPDT switch
to change the GPS data in/out from the above two sources? I have no idea
if putting the signals through a switch would result in unacceptable signal loss.
Tony Graziano
Zodiac 601XL; N493TG
Message 14
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Effects of feedline length on Standing Wave Ratio |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
> > What is the smallest ground plane you'd recommended for a COM antenna
> > and does the antenna have to be mounted in the middle of it?
>
>mounted my antennas to the outside carbon, but attached 4
>copper radials (striped house wire) to the nut plates... the
>length of the ground planes isn't nearly as critical as
>the vertical. what matters is the SWR, or reflected energy
>back into the radio, this can be adjusted by coax feed
>length if you can't cut your floxed in radials like me.
>http://mars.comportco.com/~w5alt/antennas/notes/ant-notes.php?pg=22
>
> > The writer is not "wrong" but he's making a mountain out of
> > a molehill. An airplane is not a perfect world for antennas.
>4 radials of "close" size are easy to glass in (3 would work, but
>more than 4 is overkill) and fine tune SWR with feed length.. no
>math required... one would notice loss of impedance fuel level
>converters for 30secs long before the tower asks you to "say again"
Antenna feedline has no effect on SWR. When SWR is very
poor, the transmitter may be HAPPIER attempting to transfer
energy to the antenna/feedline system but SWR is SWR is SWR.
The PRIMARY effect on SWR is overall length of the radiating
element . . . i.e. the antenna itself. SECONDARY effects
that stack on top of each other is the sum of the reactances
of what purports to be a 'ground plane' combined with any
attempts with lumped constant inductors and capacitors to
optimize the 1/4-wave antenna feed-point impedance to 50 ohms.
It naturally falls close to 35 ohms.
It's always a good thing to do an SWR plot of a multi-frequency
antenna (COMM runs 118-135 MHz) and see if the SWR is MINIMUM
near the center of the range of interest (126.5) and that it doesn't
get outrageously high at the ends. SWR of 3:1 is generally quite
acceptable. It may be that minimum occurs somewhere OTHER than
right in the middle but as long as it's less than 3:1 over
the range, the antenna is at least a reasonable LOAD for
energies put out by the transmitter. This says NOTHING
about the antenna's efficiency as a radiator (and conversely
a receptor) of radio frequency energies. One WISHES that
the whole 50 ohms impedance of a 1:1 antenna also represents
its RADIATION resistance as well. Never quite so. Very sad
antennas can have RADIATION resistances in the 1-10 ohm range
while the rest is resistive losses. A 50 ohm resistor has
an impedance of 50 ohms but a radiation resistor in the
milliohms range. This is why they make good "DUMMY LOADS".
See: http://www.aeroelectric.com/Pictures/DummyLoad.jpg
. . . this is a VERY poor antenna but the transmitter
doesn't know it. SWR is 1:1 but it radiates little or
nothing.
Be very suspicious of any instructions suggesting that
you "adjust the length of the feedline for improved
matching or reduction of SWR". This is a big red flag
that says something is seriously wrong with the
design of the antenna and/or feedline system.
Bob . . .
Message 15
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: 1/4 wave groundplane? |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 03:51 PM 1/20/2005 -0700, you wrote:
>--> AeroElectric-List message posted by: "Malcolm Thomson"
><mdthomson@attglobal.net>
>
>Bob, how significant is the use of brass vs. aluminum?
Brass and copper can be soldered to . . . VERY long lived
joints. Aluminum is an acceptable performer but must be
"fastened" with high pressure methods to achieve and maintain
gas-tight joints over the lifetime of the airplane. If
you must use aluminum, I'd rivet the radials on. When a
rivet swells in the properly sized hole . . . it's about
as gas tight as you can get . . . but my personal preference
is for copper or brass. I just LUV soldering things together.
Bob . . .
Message 16
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Switching GPS Data Signals |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 04:50 PM 1/20/2005 -0600, you wrote:
>--> AeroElectric-List message posted by: <tgrazian@bellsouth.net>
>
>I am currently wiring the panel for my Zodiac 601XL. I am installing a
>Trio EZ Pilot II autopilot, which accepts NMEA 0183 signals for
>tracking. I also have on order a Blue Mountain EFIS Lite Gen 3, which has
>a built in GPS. I would like to be able to use my Garmin 295 and the EFIS
>Lite to supply the GPS data.
>
>Does anyone have any comments on the advisability of using a "2-8" type
>DPDT switch to change the GPS data in/out from the above two sources? I
>have no idea if putting the signals through a switch would result in
>unacceptable signal loss.
Digital signals are essentially "lossless" . . . and dependent
on how much LOAD the receiving device places on the transmitting
device. My designs are always robust with respect to the transmitter.
My gizmos can "talk" to dozens of devices interested in serial data
with no degradation. When you have multiple transmitters or sources,
then some kind of either-or switching arrangement is in order.
Given that most GPS data is one-way (meaning that it's
simply spewed out with no regard for how the receiving equipment
is accepting it) a simple single pole, two position switch (1-3) should
suffice to select between the two sources. All the grounds can
run together and the switch used to select which source signal line
drives the receivers.
Bob . . .
Message 17
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Switching GPS Data Signals |
--> AeroElectric-List message posted by: rv-9a-online <rv-9a-online@telus.net>
One issue with the Garmin 295 is (I believe) that it's serial output
does not put out true-RS-232C signal levels, but rather TTL level
signals. Normally, this should not be a problem, but it may may make
the GPS serial data signals more susceptible to interference. Level
converters are available to fix this, send me an email off-line if you
are interested and I'll send you a link.
Vern Little, RV-9A
tgrazian@bellsouth.net wrote:
>--> AeroElectric-List message posted by: <tgrazian@bellsouth.net>
>
>I am currently wiring the panel for my Zodiac 601XL. I am installing a Trio EZ
Pilot II autopilot, which accepts NMEA 0183 signals for tracking. I also have
on order a Blue Mountain EFIS Lite Gen 3, which has a built in GPS. I would
like to be able to use my Garmin 295 and the EFIS Lite to supply the GPS data.
>
>Does anyone have any comments on the advisability of using a "2-8" type DPDT switch
to change the GPS data in/out from the above two sources? I have no idea
if putting the signals through a switch would result in unacceptable signal
loss.
>
>Tony Graziano
>Zodiac 601XL; N493TG
>
>
>
>
Message 18
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Bent whip "radiators" question |
--> AeroElectric-List message posted by: "Turbo Tom" <turbotom@mindspring.com>
>
> See: http://www.aeroelectric.com/Pictures/DummyLoad.jpg
>
> . . . this is a VERY poor antenna but the transmitter
> doesn't know it. SWR is 1:1 but it radiates little or
> nothing.
>
That was very well-explaned, Bob! The super-low SWR but non-radiator
illustration was outstanding.
I for one, would like to know just what effects the bending of the typical
1/4-wave whip 'aft' would have on radiation [transmission and reception].
How do those composite streamlined "Commant" [sp] stack up against a
straight or bent wire on the bottom of the fuselage of the typical RV?
They all seem to work "OK", but do you have an opinion on which is best, or
worse. I've seen quite a few bent wires lately that were swept completely
aft, and not all that far from the belly. Are there practical differences?
One last related question; if the antenna is mounted between the gearlegs,
[mine are aluminum] does that have a real-world effect?
TT
RV-8 ATL GA
Message 19
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Switching GPS Data Signals |
--> AeroElectric-List message posted by: "Brian Kraut" <brian.kraut@engalt.com>
NMEA standard is RS-422, not 232, although it is quite common for devices to
put out TTL levels which works fine. RS-422 is much more imune to noise
than 232.
RS-422 is a differential signal that goes to +5V on a logic 1 and -5V on a
logic 0. TTL goes to +5V on a logic 1 and 0V on a logic 0. Since in their
infinite wisdom the originators of NMEA decided to use a RS-422 transmitter
as standard and an optocoupler as an input in this weird mismatched
arrangement the -5V gets clipped to 0V by the optocoupler in the receiver
end so it is essentially TTL anyway.
Because some transmitters, including the devices I manufacture, use a real
RS-422 driver where the A and B signal lines are isolated from ground and
some use TTL with a ground reference I recommend using a double pole, double
throw toggle switch to switch both sides of the signal simultaneously. The
shields can all be tied together. While a single pole switch works almost
all of the time, a double pole switch works every time.
Some manufacturers also have a shield connection at the receive side of the
signal, but it is normally common practice, in marine electronics anyway,
to connect the shield only on the transmit side to prevent ground loops.
Brian Kraut
Engineering Alternatives, Inc.
www.engalt.com
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of
rv-9a-online
Subject: Re: AeroElectric-List: Switching GPS Data Signals
--> AeroElectric-List message posted by: rv-9a-online
<rv-9a-online@telus.net>
One issue with the Garmin 295 is (I believe) that it's serial output
does not put out true-RS-232C signal levels, but rather TTL level
signals. Normally, this should not be a problem, but it may may make
the GPS serial data signals more susceptible to interference. Level
converters are available to fix this, send me an email off-line if you
are interested and I'll send you a link.
Vern Little, RV-9A
tgrazian@bellsouth.net wrote:
>--> AeroElectric-List message posted by: <tgrazian@bellsouth.net>
>
>I am currently wiring the panel for my Zodiac 601XL. I am installing a
Trio EZ Pilot II autopilot, which accepts NMEA 0183 signals for tracking. I
also have on order a Blue Mountain EFIS Lite Gen 3, which has a built in
GPS. I would like to be able to use my Garmin 295 and the EFIS Lite to
supply the GPS data.
>
>Does anyone have any comments on the advisability of using a "2-8" type
DPDT switch to change the GPS data in/out from the above two sources? I
have no idea if putting the signals through a switch would result in
unacceptable signal loss.
>
>Tony Graziano
>Zodiac 601XL; N493TG
>
>
Message 20
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Switching GPS Data Signals |
--> AeroElectric-List message posted by: rv-9a-online <rv-9a-online@telus.net>
The Trio datasheet appears to allow either RS-422 single ended, RS-422
differential, RS-232, or perhaps even TTL inputs.
Of these, the most robust would be RS-422 differential, but not many GPS
devices provide it. Many devices (Garmin panel units for example)
provide RS-232 levels (+/- 10 volts approx), and some (portable GPS)
provide TTL levels. Of the last two, the RS-232 level is more noise
immune (the marking level of -10V has about 11 volts of noise immunity,
the spacing level of +10 volts around 8 volts of noise immunity).
TTL levels, or single-ended RS-422 provide about 1 to 2 volts of noise
immunity. These are estimates from memory, but you can see that single
ended 5 Volt signals are not as robust as RS-232 levels. Differential
RS-422 run as a twisted pair with a shield is the best.... but not common.
What does this mean to Tony who's head is probably spinning right now?
Not too much. Unless you are in a high electrical noise environment you
can probably safely ignore the subtleties and just run your wires
through the switches. If you have autopilot problems later, this would
be one area to investigate, however.
Vern Little
Brian Kraut wrote:
>--> AeroElectric-List message posted by: "Brian Kraut" <brian.kraut@engalt.com>
>
>NMEA standard is RS-422, not 232, although it is quite common for devices to
>put out TTL levels which works fine. RS-422 is much more imune to noise
>than 232.
>
>RS-422 is a differential signal that goes to +5V on a logic 1 and -5V on a
>logic 0. TTL goes to +5V on a logic 1 and 0V on a logic 0. Since in their
>infinite wisdom the originators of NMEA decided to use a RS-422 transmitter
>as standard and an optocoupler as an input in this weird mismatched
>arrangement the -5V gets clipped to 0V by the optocoupler in the receiver
>end so it is essentially TTL anyway.
>
>Because some transmitters, including the devices I manufacture, use a real
>RS-422 driver where the A and B signal lines are isolated from ground and
>some use TTL with a ground reference I recommend using a double pole, double
>throw toggle switch to switch both sides of the signal simultaneously. The
>shields can all be tied together. While a single pole switch works almost
>all of the time, a double pole switch works every time.
>
>Some manufacturers also have a shield connection at the receive side of the
>signal, but it is normally common practice, in marine electronics anyway,
>to connect the shield only on the transmit side to prevent ground loops.
>
>Brian Kraut
>Engineering Alternatives, Inc.
>www.engalt.com
>
>-----Original Message-----
>From: owner-aeroelectric-list-server@matronics.com
>[mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of
>rv-9a-online
>To: aeroelectric-list@matronics.com
>Subject: Re: AeroElectric-List: Switching GPS Data Signals
>
>
>--> AeroElectric-List message posted by: rv-9a-online
><rv-9a-online@telus.net>
>
>One issue with the Garmin 295 is (I believe) that it's serial output
>does not put out true-RS-232C signal levels, but rather TTL level
>signals. Normally, this should not be a problem, but it may may make
>the GPS serial data signals more susceptible to interference. Level
>converters are available to fix this, send me an email off-line if you
>are interested and I'll send you a link.
>
>Vern Little, RV-9A
>
>tgrazian@bellsouth.net wrote:
>
>
>
>>--> AeroElectric-List message posted by: <tgrazian@bellsouth.net>
>>
>>I am currently wiring the panel for my Zodiac 601XL. I am installing a
>>
>>
>Trio EZ Pilot II autopilot, which accepts NMEA 0183 signals for tracking. I
>also have on order a Blue Mountain EFIS Lite Gen 3, which has a built in
>GPS. I would like to be able to use my Garmin 295 and the EFIS Lite to
>supply the GPS data.
>
>
>>Does anyone have any comments on the advisability of using a "2-8" type
>>
>>
>DPDT switch to change the GPS data in/out from the above two sources? I
>have no idea if putting the signals through a switch would result in
>unacceptable signal loss.
>
>
>>Tony Graziano
>>Zodiac 601XL; N493TG
>>
>>
>>
>>
>
>
>
>
Message 21
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Z13a Pre-flight alt test procedure? |
--> AeroElectric-List message posted by: "Mike Holland" <hollandm@pacbell.net>
Bob, I have the SD8, with indicator light and wired per Z13. What problem is there
with having both alternators active? If the SD8 will come on-line at idle
speed the indicator light would go out and that would indicate it was active
without having to shut down the main alternator.
If it matters I have Hall effect sensors on both B leads.
Thanks
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|