Today's Message Index:
----------------------
1. 08:16 AM - USB "tester" (rayj)
2. 09:17 AM - Re: Panel mounted USB power ports for Apple devices? (Dj Merrill)
3. 12:24 PM - Half wave copper foil dipole transponder antenna (rnbraud)
4. 01:46 PM - Re: Half wave copper foil dipole transponder antenna (Kent or Jackie Ashton)
5. 01:57 PM - Re: Half wave copper foil dipole transponder antenna (rnbraud)
6. 02:41 PM - Re: Re: Half wave copper foil dipole transponder antenna (Kent or Jackie Ashton)
7. 06:27 PM - Re: Half wave copper foil dipole transponder antenna (Robert L. Nuckolls, III)
Message 1
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I don't know anything about this item:
http://www.mpja.com/08-05-14.asp?r=376592&s=4
It looks like it might be useful for those installing usb power outlets.
My experience with this supplier has been positive.
FWIW
--
Raymond Julian
Kettle River, MN
The things we admire in men, kindness and generosity, openness, honesty,
understanding and feeling are the concomitants of failure in our system.
And those traits we detest, sharpness, greed, acquisitiveness, meanness,
egotism and self-interest are the traits of success. And while men
admire the quality of the first they love the produce of the second.
-John Steinbeck, novelist, Nobel laureate (1902-1968)
Message 2
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Subject: | Re: Panel mounted USB power ports for Apple devices? |
On 8/4/2014 11:49 AM, Dj Merrill wrote:
> I ended up hacking the end of the iPad's USB cable to add the
> resistors (actually I added a micro-sized potentiometer adjusted to
> the proper resistance), which is now dedicated to the airplane, and it
> charges the ipad just fine.
>
> Not difficult, but not as "clean" an installation as I had originally
> envisioned.
I had an inquiry about how I did this and thought I would share with the
group.
The micro-sized potentiometer I grabbed from my junk bin and don't
remember the exact value, probably 100 ohms or 1K. It isn't critical.
Here is the guide I used:
http://www.instructables.com/id/THE-Simplest-iPod-iPad-iPhone-charger-circuit/?ALLSTEPS
You'll want to read through it for the general idea. I used the "trim
pot" method shown in step 4.
If you are using the power supply that Bob sent out
(http://tinyurl.com/m8kfz6h), all you need is the the trim pot, and none
of the other parts mentioned in the article.
All you are doing is connecting the middle connection on the trim pot to
pins 2 and 3 of the USB cable, and the other two pins on the trim pot go
to pin 1 and pin 4 respectively. Then adjust the trim pot until you get
a value of 2 volts between the center pin on the trim pot and pin 4 on
the USB (which is GND).
The right half of this diagram sums it up nicely:
http://cdn.instructables.com/FOD/L2X9/HJKBMVWW/FODL2X9HJKBMVWW.LARGE.jpg
I added this to the USB cable itself rather than the power supply
because the power supply and plugs are all molded plastic and there
wasn't an easy way to get inside without making a mess. The USB cable
simply had a plastic cover that slid back along the cable and was much
easier to work with. When I was finished adjusting the trim pot I put
some heat shrink over the entire assembly (USB cable, connector,
potentiometer and all) so it is sealed up and won't be accidentally turned.
This is similar to the micro-potentiometer that I used:
http://www.ebay.com/itm/Horizontal-PCB-Mount-Micro-Potentiometer-Japan-VTG-271-280-Archer-Radio-Shack-/191238164441
-Dj
--
Dj Merrill - N1JOV - VP EAA Chapter 87
Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/
Glastar Flyer N866RH - http://deej.net/glastar/
Message 3
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Subject: | Half wave copper foil dipole transponder antenna |
I hope this isn't a duplicate, but I was unable to find sufficient info on this
topic in the archives.
I have successfully built and tested several copper foil/tape comm antennas for
my Cozy MkIV and would like to build a transponder antenna the same way.
Will the following work for a Mode S transponder:
1. Vertically oriented 1/2 wave dipole.
2. 1/2" copper tape with ferrites
3. Each leg 6.25" long
Thanks.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=428048#428048
Message 4
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Subject: | Re: Half wave copper foil dipole transponder antenna |
See. http://www.cozybuilders.org/ref_info/RST_82704.pdf
The transponder is a little different than the other antennae. The reference discusses
it. Keep the coax run short and put it on the bottom of the airplane.
Mine is under removable front seats. You can make the antenna from an AN bolt
but they are very cheap on ebay.
-kent
> On Aug 5, 2014, at 3:23 PM, "rnbraud" <rnbraud@yahoo.com> wrote:
>
>
> I hope this isn't a duplicate, but I was unable to find sufficient info on this
topic in the archives.
>
> I have successfully built and tested several copper foil/tape comm antennas for
my Cozy MkIV and would like to build a transponder antenna the same way.
>
> Will the following work for a Mode S transponder:
>
> 1. Vertically oriented 1/2 wave dipole.
> 2. 1/2" copper tape with ferrites
> 3. Each leg 6.25" long
>
> Thanks.
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=428048#428048
>
>
>
>
>
>
>
>
>
>
Message 5
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Subject: | Re: Half wave copper foil dipole transponder antenna |
Hello Kent,
I am trying to avoid the antenna sticking out of the airplane. I see where Advanced
Aircraft Electronics makes an "L2" transponder antenna which looks a lot
like my other foil tape antennas.
I was hoping maybe I could make my own "L2" type of antenna with my leftover RST
antenna kit.
Just want to confirm if it is feasible and if the leg lengths and vertical orientation
is correct.
If this does not work, I will make my transponder antenna as you mentioned and
place it either out at the end of the strake or right under the pilot seat protruding
out of the fuselage.
Thanks.
kjashton(at)vnet.net wrote:
> See. http://www.cozybuilders.org/ref_info/RST_82704.pdf
>
> The transponder is a little different than the other antennae. The reference
discusses it. Keep the coax run short and put it on the bottom of the airplane.
Mine is under removable front seats. You can make the antenna from an AN
bolt but they are very cheap on ebay.
> -kent
>
>
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=428053#428053
Message 6
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Subject: | Re: Half wave copper foil dipole transponder antenna |
As I understand it, a ground plane made of copper foils will work as well as the
solid ground plane. And vertical orientation sounds right. As for where to
put it, just consider that folks who try to put them in the nose of a canard
airplane or up front on the airplane often run into problems climbing out away
from the radar station because the bodies of the crew (bags of salt-water) and
the engine blank off line-of sight with the radar.
Quick: When you are 30 miles from a station at 5000', the angle to the station
from the horizon is ___. :-)
ANS: 1.57 degrees. I doesn't take much nose up deck angle to hide the antenna.
Ask me how I know.
-Kent
On Aug 5, 2014, at 4:56 PM, rnbraud wrote:
>
> Hello Kent,
>
> I am trying to avoid the antenna sticking out of the airplane. I see where Advanced
Aircraft Electronics makes an "L2" transponder antenna which looks a lot
like my other foil tape antennas.
>
> I was hoping maybe I could make my own "L2" type of antenna with my leftover
RST antenna kit.
>
> Just want to confirm if it is feasible and if the leg lengths and vertical orientation
is correct.
>
> If this does not work, I will make my transponder antenna as you mentioned and
place it either out at the end of the strake or right under the pilot seat protruding
out of the fuselage.
>
> Thanks.
>
>
>
> kjashton(at)vnet.net wrote:
>> See. http://www.cozybuilders.org/ref_info/RST_82704.pdf
>>
>> The transponder is a little different than the other antennae. The reference
discusses it. Keep the coax run short and put it on the bottom of the airplane.
Mine is under removable front seats. You can make the antenna from an AN
bolt but they are very cheap on ebay.
>> -kent
>>
>>
>
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=428053#428053
>
>
>
>
>
>
>
>
>
>
Message 7
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Subject: | Re: Half wave copper foil dipole transponder antenna |
At 02:23 PM 8/5/2014, you wrote:
>
>I hope this isn't a duplicate, but I was unable to find sufficient
>info on this topic in the archives.
>
>I have successfully built and tested several copper foil/tape comm
>antennas for my Cozy MkIV and would like to build a transponder
>antenna the same way.
>
>Will the following work for a Mode S transponder:
>
>1. Vertically oriented 1/2 wave dipole.
yes . . .
>2. 1/2" copper tape with ferrites
not particularly useful at VHF, useless
at uhf
>3. Each leg 6.25" long
Yeah . . . about that. Suggest you look over the
Bob Archer SA-005 descriptions and pictures
on the 'net.
http://tinyurl.com/mdho4z8
Bob uses double sided ECB material to craft an
antenna and matching section all in one piece.
As you can see . . . his 'dipole' is rather
wide . . . which yields a low SWR over a rather
wide frequency range . . . not that you NEED
the bandwidth . . . but the wider elements makes
their length less critical.
Here's Bob's narratives on transponder
antennas.
http://tinyurl.com/lwgonmx
Suggest you consider a dipole of at last 1/2"
wide material . . . 1" wouldn't hurt. Assembled
onto a sheet of plexiglas and attached to the
feedline with a Pawsey stub balun.
http://tinyurl.com/lnjhmem
http://tinyurl.com/lxzlpky
The 'thing' about ferrite beads strung onto the
feedline has been popularly circulated through
many venues but there are caveats . . .
First, the torroid material must be a pretty
good performer at the frquency of interest . . .
NO torroid materials I'm aware of are suited
for service at 1000mHz.
Second, the inductance presented by a coil of
wire on a core varies as the SQUARE of the
turns on the core. Effective use of torroid
cores as de-coupling baluns calls for MULTIPLE
turns on one core. This picture shows 7 passes
of wire through the core for an effective
inductance 47x that of a single pass.
[]
Hence, one would need to string 47 single
cores onto the coax as a string of beads to
equal the effectiveness of one core wound with
seven turns . . . but generally useful only
at 200mHz and below.
There used to be a commercial vhf comm antenna
offered that used the multi-turn torroid de-coupling
philosophy. I think it was called the "airwhip" . . .
don't find anything about the company now . . .
it's been a few years.
Now that I have ready access to an EMC lab,
any antenna you'd like to fabricate as
a shippable assembly could be mailed to me
for a quick look-see in the lab.
Bob . . .
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