Today's Message Index:
----------------------
1. 09:53 AM - Re: antenna analyzer? (N804RV)
2. 01:56 PM - ground planes - new source for copper foil and questions (prestonkavanagh)
3. 02:38 PM - Re: ground planes - new source for copper foil and questions (Robert L. Nuckolls, III)
4. 02:39 PM - Re: Re: antenna analyzer? (Robert L. Nuckolls, III)
5. 05:57 PM - Re: IS a COM ANTENNA GROUND PLANE NECESSARY (user9253)
6. 10:21 PM - Re: Re: IS a COM ANTENNA GROUND PLANE NECESSARY (James Kale)
Message 1
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| Subject: | Re: antenna analyzer? |
merlewagner2 wrote:
> For anyone interested in the VNA-
>
> First educate yourself on what to purchase. There are too many clones out there
and you must be very careful in what you purchase. I have 3 different units
which effectively do the same thing but the user interface is different in each.
>
> Go to the VNA user group at https://groups.io/g/nanovna-users and start researching
the info. The WIKI has a TON of information....
Outstanding! There really is "A TON of info" in the VNA user group.
I was looking at these a couple of months ago. But, was a little leary of them.
I've been using the MFJ-259. It does the basic job.
But, now after reading this thread, I bought the Seesii NanoVNA off Amazon for
$68. Can't wait to start using it!
--------
Ken W.
Sonerai IIL Bought and Flying
RV-8 Fuselage in work
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=497351#497351
Message 2
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| Subject: | ground planes - new source for copper foil and questions |
I have been working on a transponder antenna for a fiberglass airplane (Cozy IV).
I tried thin copper sheet, then copper flashing. I hated the weight of the
first one I built (and the Frankenstein look of the riveted, soldered seam),
the second one was better and on the 3rd try I got a keeper. The reason is a
new super thin copper foil. $14 bought 10 sheets, enough to make multiple transponder
antennae. See
https://www.amazon.com/gp/product/B07R8BS843/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
The foil comes with a conductive adhesive backing, so I don't have to rivet and
solder. The following were consistent measurements:
- internal resistance, multi-meter: 0.4 ohm
- resistance across face of sheet: 0.4 ohm
- resistance from face of sheet and across adhesive: 0.5 ohm
A package with 10 sheets weighs 201 grams, for weight per sheet of 20 grams (less
than an ounce). The sheet size is 300 mm x 200 mm (11.81" x 1.87").
Are there optimal / resonant shapes and sizes for the ground plane? The bible
calls for a circle with 5.5" diameter (p. 13-2). I can fit an 11" circle under
the co-pilot seat of the Cozy. Stick with 5.5"?. And I believe I need a second,
mirror image install for the ADSB. Is that right?
Thanks for the help. PK
--------
PBK3
PA-12, BD-4, RV6a, gliders
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=497352#497352
Attachments:
http://forums.matronics.com//files/copper_foil_283.jpg
Message 3
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| Subject: | Re: ground planes - new source for copper foil and |
questions
>The foil comes with a conductive adhesive backing, so I don't have
>to rivet and solder. The following were consistent measurements:
>- internal resistance, multi-meter: 0.4 ohm
>- resistance across face of sheet: 0.4 ohm
>- resistance from face of sheet and across adhesive: 0.5 ohm
>
>A package with 10 sheets weighs 201 grams, for weight per sheet of
>20 grams (less than an ounce). The sheet size is 300 mm x 200 mm
>(11.81" x 1.87").
>
>Are there optimal / resonant shapes and sizes for the ground
>plane? The bible calls for a circle with 5.5" diameter (p.
>13-2). I can fit an 11" circle under the co-pilot seat of the
>Cozy. Stick with 5.5"?. And I believe I need a second, mirror
>image install for the ADSB. Is that right?
Yes . . . there are 'tuned' ground planes 1/4
wave radius around the base of the antenna.
That's were the 5.5" figure comes from . . .
it's 1/2 the height of the XPNDR antenna.
Be cautious of thin copper foils. Copper,
like aluminum, is a non-ferrous material with
a service life under bending vibrations
and other external forces. Stay with 5.5"
o.d. and consider something more robust like
0.040 aluminum disk.
Had a builder fabricate a comm dipole
on the inside surface of a fiberglas
tail many years back. Used copper foil
bonded to inside of structural shell.
A few years of stress cycles due to
temperature coefficient of expansion
of two materials developed cracks in
the elements.
The solid aluminum disk can simply lay on
the inside of the skin like a big
washer . . . works good, lasts a long time.
Bob . . .
Message 4
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| Subject: | Re: antenna analyzer? |
>attaching photo of my NAV/ILS antenna. Used RG174 to feed.
>
>Merle
>
>--------
>KC1DNJ
>General Radiotelephone
>Commercial SEL
>A&P
>Building scale P51, rebuilding Tailwind W10
>
>Read this topic online here:
>
>Attachments:
>
>http://forums.matronics.com//files/nav_ils_632.jpg
>
I note that the UHF elements (glide slope)
appear much shorter than the expected 33%
or so of a VOR/LOC antenna. Do you think
proximity to structure de-tuned your antenna
downward in frequency?
As a practical matter, a barefooted VOR/LOC
antenna works fine on GS too. They are harmonically
related and LOC/GS signals off the approach
end of the runway are HUGE . . . but it
would be interesting to see the VNA sweeps
of the as-installed antenna. Thanks for
sharing the picture!
Bob . . .
Message 5
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| Subject: | Re: IS a COM ANTENNA GROUND PLANE NECESSARY |
I took my SWR meter to the airport today and checked my friend's com antenna.
The SWR was 3.8
Now he knows that his antenna installation will not work very well.
He is considering mounting a new antenna on top of the fuselage.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=497356#497356
Message 6
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| Subject: | Re: IS a COM ANTENNA GROUND PLANE NECESSARY |
At 3.8 SWR the transmitter is in danger of over heating to the point of meltdown!!!!!
Sent from my iPhone
> On Jul 17, 2020, at 8:12 PM, user9253 <fransew@gmail.com> wrote:
>
>
> I took my SWR meter to the airport today and checked my friend's com antenna.
The SWR was 3.8
> Now he knows that his antenna installation will not work very well.
> He is considering mounting a new antenna on top of the fuselage.
>
> --------
> Joe Gores
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=497356#497356
>
>
>
>
>
>
>
>
>
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