Today's Message Index:
----------------------
1. 05:36 AM - Can radials of home made ground plane be tapered? (rparigoris)
2. 08:57 AM - Re: Can radials of home made ground plane be tapered? (prestonkavanagh)
3. 10:18 AM - Re: Can radials of home made ground plane be tapered? (rparigoris)
4. 12:06 PM - Re: Can radials of home made ground plane be tapered? (Robert L. Nuckolls, III)
5. 01:45 PM - Re: Can radials of home made ground plane be tapered? (rparigoris)
6. 02:59 PM - Re: Re: How do you figure C-Rating of a battery? (Charlie England)
7. 04:50 PM - Re: Can radials of home made ground plane be tapered? (user9253)
8. 04:53 PM - Re: Re: Can radials of home made ground plane be tapered? (Robert L. Nuckolls, III)
9. 05:20 PM - Re: antenna analyzer? Antennas (Finn Lassen)
10. 05:52 PM - Re: antenna analyzer? Antennas (Charlie England)
11. 06:26 PM - Re: antenna analyzer? Antennas (Robert L. Nuckolls, III)
12. 07:46 PM - Re: evolution of lithium technologies (Charlie England)
13. 08:53 PM - Re: evolution of lithium technologies (Robert L. Nuckolls, III)
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| Subject: | Can radials of home made ground plane be tapered? |
Hi Group I have a home made ground plane made out of aluminium for a Garmin GA-35
GPS / WAAS antenna. It has 8 radials 1" wide and ~7.75" long. I'm using the
ground plane to support the antenna. It will be living under the ceiling of the
baggage bay in a Europa. After cutting out the ground plane I find that it's
plenty strong enough to support the antenna. Is it OK to taper the radials from
1" at the root to 1/2" at the tip? I could shave off some weight from the
existing 8oz. Ron P.
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http://forums.matronics.com/viewtopic.php?p=498564#498564
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| Subject: | Re: Can radials of home made ground plane be tapered? |
Others will respond on the radio theory aspect. I'll say that 8 oz is a heck of
a lot of weight, and you can do better. I believe the Europa has most of the
fiberglass work done at the factory, but I'm guessing you have some supplies
around. Slice off a thin piece of foam, shape it to fit, inset a washer with
ID equal to the antenna mount OD, one layer of BID on each side and you have
something stiff, strong and light. Top it with super thin copper sheet (below
is the one I like), and get a 2 oz mount and ground plane ready to attach to
the airplane.
Or find a friend among the composite builders! Let me know if you are close to
Tampa - I can help. PK
https://www.amazon.com/Conductive-Adhesive-Shielding-Electrical-Grounding/dp/B07R8BS843/ref=sr_1_7?dchild=1&keywords=copper+sheet+foil&qid=1601221863&sr=8-7
--------
PBK3
PA-12, BD-4, RV6a, gliders
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http://forums.matronics.com/viewtopic.php?p=498565#498565
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| Subject: | Re: Can radials of home made ground plane be tapered? |
Hi PK I already had all of my antennas installed and the FAA now requires an ADS-B
Out which I need to accommodate. For my situation the most logical position
for my Garmin GA-35 antenna is below the ceiling above the baggage area. The
ceiling slopes and is in a constant changing 3D equation where to lay up something
or attempt to make a metal shelf would be a chore and not look very nice.
My 8 radial .063" ground plane is not just a ground plane but the support for
the antenna. It needs to support ~12 lbs. The antenna with screws is over 8oz.
My Spider / Ninja Shuriken doesn't look too bad, it's honest. I mocked up
a shelf and it looks mucked up. I was thinking about doing exactly as you suggest,
thin glass, some thin foam and some thin glass and cover with copper foil
that I have. The antenna needs to be close to level to the longitudinal axis
which will put the front radial about 2" below the ceiling. Thx. for your offer,
I'm in NY. Aeroplanes are compromises and I'm happy with Spider / Ninja Shuriken.
If I taper the radials I think I can down to 6oz. The ground plane needs
to stay below the base of the antenna which if mounting the antenna inside
out of the slip stream negates ability to put on ceiling. If I mounted it on top
in the slip stream then I could put copper foil inside but I would need to
lift the rear of the antenna and build sort of a submarine bias cut conning tower.
Ron P.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=498566#498566
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| Subject: | Re: Can radials of home made ground plane be tapered? |
At 07:34 AM 9/27/2020, you wrote:
>
>Hi Group I have a home made ground plane made out of aluminium for a
>Garmin GA-35 GPS / WAAS antenna. It has 8 radials 1" wide and ~7.75"
>long. I'm using the ground plane to support the antenna. It will be
>living under the ceiling of the baggage bay in a Europa. After
>cutting out the ground plane I find that it's plenty strong enough
>to support the antenna. Is it OK to taper the radials from 1" at the
>root to 1/2" at the tip? I could shave off some weight from the
>existing 8oz. Ron P.
Where did you find recommendations/requirements for
a 'ground plane' on this antenna. I've looked at
some garmin docs and only find references to
antenna/coax grounding to skin . . . no requirements
for any 'tuned' or 'resonant' ground plane in
a plastic airplane.
Bob . . .
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| Subject: | Re: Can radials of home made ground plane be tapered? |
Hi Bob
See page 2-5 of GA-35 antenna installation manual: https://static.garmin.com/pumac/190-00848-00_f.pdf
See page 6-8 of GDL-82 installation manual: https://static.garmin.com/pumac/190-01810-00_06.pdf
Ron P.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=498569#498569
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| Subject: | Re: How do you figure C-Rating of a battery? |
On Mon, Sep 14, 2020 at 1:09 PM rparigoris <rparigor@hotmail.com> wrote:
> rparigor@hotmail.com>
>
> Hi Bob Thank you for your review. I will post schematic when it's
> completed. A few points: I'm not too worried about LiFe batteries getting
> thermal runaway, but I am about LiPo batteries getting to a thermal
> runaway. You posted a link to: https://tinyurl.com/y4oulfy9 As far as
> LiFe batteries go, I think mfg has done a reasonable amount of homework but
> fact is there is potential for problems that Lead Acid does not have and
> they can still fail opened. Good enough for me to use. I'm not worried
> about soldered and crimped connection to aluminium wires, but the terminal
> connections can get a high resistance. Keeping connections clean and tight
> mitigate majority of problems, but not all. As far as keeping NiMh pack
> charged, using one of my AstroFlight delta peak chargers (110D or 112D),
> once or twice a year will give them a C/10 for ~ 15 hours to balance, then
> delta peak charge the rest of the times. Unless battery is very flat,
> peaking at 1C takes less time than a pre-flight. 1x!
> a year will capacity test down to 1V per cell and fuel pump equivalent
> load. BTW have you ever used an AstroFlight Whatt Meter (Whatt is correctly
> spelled)? Pretty slick meter that shows volts, amps and watt hours. Pricey
> though, here's an alternative that works pretty good:
> https://hobbyking.com/en_us/turnigy-180a-watt-meter-and-power-analyzer.html?queryID=7b349d17e0c87dff11877b2ea51342de&objectID=42854&indexName=hbk_live_magento_en_us_products
> Ron P
Ron,
I may have stumbled upon your solution. I know you don't want LiPo in the
cockpit (I can understand that). But if you're comfortable with LiFe for
your main battery....
This:
https://www.harborfreight.com/lithium-ion-jump-starter-and-power-pack-62749.html?_br_psugg_q=jump+starter
At 1st glance, I was sure that it was LiPo. There's nothing in the HF ad
that tells us anything different. But I just saw a video that shows it's
actually a LiFePO4 battery.
https://www.youtube.com/watch?v=EbIQhskJho0&t=636s
The video shows both the label on the back of the case and the label on the
battery module itself, inside the case. Now, I'm not defending the
'installation technique' he used, but the video does show what you'd be
buying. You can see the case at around 3:30 in the video.
It should easily serve the dual requirements of running the fuel pump
alone, or supplying an emergency jump start if you're off-airport
somewhere. I'd find $85 hard to argue with....
Charlie
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| Subject: | Re: Can radials of home made ground plane be tapered? |
Maybe you should call Garmin to find out if a ground plane is really necessary.
Other GPS antenna installations do not call for a ground plane.
Garmin G3X Support
g3xpert at garmin dot com
eight six six -854-8433 - 7 to 7 Central Time M to F
--------
Joe Gores
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http://forums.matronics.com/viewtopic.php?p=498571#498571
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| Subject: | Re: Can radials of home made ground plane be |
tapered?
At 03:41 PM 9/27/2020, you wrote:
>
>Hi Bob
>
>See page 2-5 of GA-35 antenna installation manual:
>https://static.garmin.com/pumac/190-00848-00_f.pdf See page 6-8 of
>GDL-82 installation manual: https://static.garmin.com/pumac/190-01810-00_06.pdf
>
>Ron P.
Okay, my copy is rev B and doesn't speak to adding
a ground plane.
I'm a bit mystified by this requirement. The gps/waas
antennas are active devices meaning that the rf samples
from the 'ether' are non-resonant 'probes'
that cannot deliver useful energy into a 50-ohm coax
without electronic (active) augmentation . . .
nor do they have the same capture area of a tuned
and/or multi-element antenna. Ground planes cannot
participate in the delivery of energy to the active
antenna's feedline . . . only in shaping radiation
(reception) patterns.
We've got all manner of gps devices from wrist
watches and little drones to telephones and
cameras. All must depend on active antennas,
in horribly challenging environs . . . no
room for a really efficient antenna.
Now we have a gps system on the backbone of
an airplane, completely free of terrestrial
noise and shadowing with an uncluttered view
of the sky . . . yet the installation instructions
speak of 'optimizing' performance with the
addition of a ground plane under an active
antenna? Hmmm . . .
What's missing from these documents is any
calibration on bang-for-the-buck. I.e. just
how much do I gain with this optimization?
There's a whole bunch of hocky-puck, gps
antennas flying with no ground plane. It
would be interesting to install both
configurations on an airplane with an A-B
switch . . . to observe just how much
optimization is secured with addition
of the ground plane.
I'd be surprised if the optimization offers
more than a little wiggle in the already
more-than-adequate signal strength displays.
Thanks for the update on the manual . . .
Bob . . .
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| Subject: | Re: antenna analyzer? Antennas |
Finally got around to playing with nanoVNA and DDRR antenna.
I don't see that it can be used for a Comm antenna (118-136MHz). Too
narrow bandwidth. Tried different things like changing gap, tap point,
height and length. Formulas seem to be off. Found needed smaller circle
(circumference). Also tap location closer to 0.5" that the 2.5 to 2.8"
calculated points. I used a relatively thin wire as opposed to the
recommended 1/4" to 1/2" tubing, hoping it would broaden the bandwidth
(according to this remark:"The larger D is the higher efficiency is").
Bob tried to answer that for me but I'm still not sure if "efficiency"
is related to bandwidth ("Q"). Perhaps I misunderstood that and should
try 1/4" tubing?
With a whip antenna, the bigger the diameter, the broader the bandwidth.
However, for an ELT antenna it will be perfect under engine cowling or
on turtle deck. Saw SWR below 1:1.10 while fiddling with it. Some have
installed their ELT antenna in their RV-4 under the canopy between pilot
and passenger. Obviously without measuring SWR. A hand (much less a head
or the rollover structure) severely affect SWR. Of course ground plane
is very much in question in that location.
I also tried a 3/32" brass tube originating at very rear of canopy
(ground contact to turtle deck) extending forward and up along the
canopy. Very odd frequency response and very SWR sensitive to a hand
near the tip.
At this point I'm looking at designing a streamline base for my 3/32"
brass tubing in Solidworks and 3D printing it, mounting the antenna
traditionally just behind the aft canopy skirt. Perhaps squeezing the
tubing into a somewhat streamline and/or stepping down to 1/8" after the
first 12" piece.
Finn
On 7/15/2020 11:47 PM, Robert L. Nuckolls, III wrote:
> At 04:36 PM 7/15/2020, you wrote:
>
>> I ordered this https://www.ebay.com/itm/283898850600
>> <https://www.ebay.com/itm/283898850600> ten days ago. Will probably
>> be several weeks before I get it.
>>
>> You can get them a lot cheaper, but I wanted one that'll also be
>> useful checking transponder (and ADS-B) cable and antenna. (1GHz)
>>
>> Still haven't given up on the idea of putting VHF comm antenna under
>> the RV-4 canopy. Other than vertical polarization, ground plane will
>> probably be the biggest issue (and impedance matching if I can't get
>> the ground plane right). Got three 12" 5/32"OD brass tubes from
>> Hobby Lobby. Should give a reasonably wide bandwidth.
>>
>> Finn
>
> Check out this article from a 1971 issue of QST Magazine
>
> http://www.aeroelectric.com/articles/Antennas/DDRR_Antenna.PDF
> <http://www.aeroelectric.com/articles/Antennas/DDRR_Antenna.PDF>
>
> A 2 meter (146 Mhz) version of this antenna
> is 6" in diameter and sets about 1" off the
> ground plane. An aviation version would be
> about 7" in diameter.
>
> It's bandwidth is probably pretty narrow . . .
> you'd have to build one and sweep it to
> see if it's usable. Would this fit on
> the deck just behind the rear seat?
>
> I've got one of those analyzers but haven't
> had time to make it sing, dance and do dishes.
> I've been using the VNA Tiny which is a good
> bit more expensive. It seems to work well.
> Let us know how that 'baby' VNA works for you!
>
>
> Bob . . .
>
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| Subject: | Re: antenna analyzer? Antennas |
I can't imagine a smaller dia wire spreading the freq peak, but then
I've never seen that style antenna, either. :-) Maybe 'efficiency' in
this context means usability across more of the frequency spectrum
(lower Q). Certainly seems worth trying with 3/8 or 1/2 tubing, or 1/2"
copper tape wrapped around something. Don't know if you care, but most
ELTs require using their dedicated antenna to be 'legal', somewhat
analogous to the silliness in FAA rules for GPS for IFR operations. I
don't worry about the FAA that much, but if you insure the plane, it
could give the ins co an out after an accident.
I assume you're using an old style 121Mhz ELT, right? The new dual freq
models seem to require highly specialized antennas.
RE: brass for antenna. If you're talking about outside the canopy, you
might want to re-think it. My 1st RV4 had the stainless wire whip ELT
antenna mounted there, until it didn't. It broke off at the stress riser
where it entered the long composite mounting cone. Behind the canopy is
a really 'dirty', turbulent area. Maybe you could silver-solder a length
of stainless tubing? Or 1/2" copper tape wrapped on a 'glass arrow
shaft. I bet it'll still need some kind of support a few inches above
the skin.
Have fun...
Charlie
On 9/27/2020 7:17 PM, Finn Lassen wrote:
>
> Finally got around to playing with nanoVNA and DDRR antenna.
>
> I don't see that it can be used for a Comm antenna (118-136MHz). Too
> narrow bandwidth. Tried different things like changing gap, tap point,
> height and length. Formulas seem to be off. Found needed smaller
> circle (circumference). Also tap location closer to 0.5" that the 2.5
> to 2.8" calculated points. I used a relatively thin wire as opposed to
> the recommended 1/4" to 1/2" tubing, hoping it would broaden the
> bandwidth (according to this remark:"The larger D is the higher
> efficiency is"). Bob tried to answer that for me but I'm still not
> sure if "efficiency" is related to bandwidth ("Q"). Perhaps I
> misunderstood that and should try 1/4" tubing?
>
>
> With a whip antenna, the bigger the diameter, the broader the bandwidth.
>
> However, for an ELT antenna it will be perfect under engine cowling or
> on turtle deck. Saw SWR below 1:1.10 while fiddling with it. Some have
> installed their ELT antenna in their RV-4 under the canopy between
> pilot and passenger. Obviously without measuring SWR. A hand (much
> less a head or the rollover structure) severely affect SWR. Of course
> ground plane is very much in question in that location.
>
> I also tried a 3/32" brass tube originating at very rear of canopy
> (ground contact to turtle deck) extending forward and up along the
> canopy. Very odd frequency response and very SWR sensitive to a hand
> near the tip.
>
> At this point I'm looking at designing a streamline base for my 3/32"
> brass tubing in Solidworks and 3D printing it, mounting the antenna
> traditionally just behind the aft canopy skirt. Perhaps squeezing the
> tubing into a somewhat streamline and/or stepping down to 1/8" after
> the first 12" piece.
>
> Finn
>
>
> On 7/15/2020 11:47 PM, Robert L. Nuckolls, III wrote:
>> At 04:36 PM 7/15/2020, you wrote:
>>
>>> I ordered this https://www.ebay.com/itm/283898850600
>>> <https://www.ebay.com/itm/283898850600> ten days ago. Will
>>> probably be several weeks before I get it.
>>>
>>> You can get them a lot cheaper, but I wanted one that'll also be
>>> useful checking transponder (and ADS-B) cable and antenna. (1GHz)
>>>
>>> Still haven't given up on the idea of putting VHF comm antenna under
>>> the RV-4 canopy. Other than vertical polarization, ground plane will
>>> probably be the biggest issue (and impedance matching if I can't get
>>> the ground plane right). Got three 12" 5/32"OD brass tubes from
>>> Hobby Lobby. Should give a reasonably wide bandwidth.
>>>
>>> Finn
>>
>> Check out this article from a 1971 issue of QST Magazine
>>
>> http://www.aeroelectric.com/articles/Antennas/DDRR_Antenna.PDF
>> <http://www.aeroelectric.com/articles/Antennas/DDRR_Antenna.PDF>
>>
>> A 2 meter (146 Mhz) version of this antenna
>> is 6" in diameter and sets about 1" off the
>> ground plane. An aviation version would be
>> about 7" in diameter.
>>
>> It's bandwidth is probably pretty narrow . . .
>> you'd have to build one and sweep it to
>> see if it's usable. Would this fit on
>> the deck just behind the rear seat?
>>
>> I've got one of those analyzers but haven't
>> had time to make it sing, dance and do dishes.
>> I've been using the VNA Tiny which is a good
>> bit more expensive. It seems to work well.
>> Let us know how that 'baby' VNA works for you!
>>
>>
>> Bob . . .
>>
>
>
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| Subject: | Re: antenna analyzer? Antennas |
>I used a relatively thin wire as opposed to the recommended 1/4"
>to 1/2" tubing, hoping it would broaden the bandwidth (according to
>this remark:"The larger D is the higher efficiency is").
>Bob tried to answer that for me but I'm still not sure if
>"efficiency" is related to bandwidth ("Q").
>Perhaps I misunderstood that and should try 1/4" tubing?
Or even a radiator fabricated from flat sheet?
The larger the diameter, the greater the bandwidth.
Efficiency has to do with ohmic losses (how much
energy goes off in heat) and again, a larger surface
area of the radiator has lower resistance. Recall that
currents at these frequencies flow on the skin
of the conductor. At DC, there is a substantial
difference between say a 1" diameter rod and a 1"
thin wall tube. At 100 MHz there is virtually
no difference 'cause all the 'happening' is at
the surface.
>With a whip antenna, the bigger the diameter, the broader the bandwidth.
Exactly . . .
>I also tried a 3/32" brass tube originating at very rear of canopy
>(ground contact to turtle deck) extending forward and up along the
>canopy. Very odd frequency response and very SWR sensitive to a hand
>near the tip.
Interesting observation . . .
>At this point I'm looking at designing a streamline base for my
>3/32" brass tubing in Solidworks and 3D printing it, mounting the
>antenna traditionally just behind the aft canopy skirt. Perhaps
>squeezing the tubing into a somewhat streamline and/or stepping down
>to 1/8" after the first 12" piece.
Also interesting . . . let us know
what you discover.
I am pleased that you've availed yourself
of this unusual piece of test equipment. You're
gaining knowledge and experience in a manner
that you will not forget . . . and will become
valuable information source for those who
follow.
Bob . . .
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| Subject: | Re: evolution of lithium technologies |
On 9/21/2020 11:03 AM, Charlie England wrote:
>
>
> On Sun, Sep 20, 2020 at 11:56 AM Robert L. Nuckolls, III
> <nuckolls.bob@aeroelectric.com <mailto:nuckolls.bob@aeroelectric.com>>
> wrote:
>
>
> I've been studying current options for lithium
> cells on the market. Discovered some interesting
> things. For example . . . this excerpt from the
> engineering data sheet on an 18650 cell cited
> as suitable for battery powered tools:
>
> [snippped]
> What insults might these cells endure if
> incorporated into a flight system? Any worse
> than those cited above? Just thinking . . .
>
>
> Bob . . .
>
> That got me thinking (and searching).
> A wade into the shallow end of the data pool yields only damp feet
> when it comes to actual *power* capacity. The highest 'continuous
> current' rating I could find on 18650 cells is around 30A. That would
> imply, at 1st glance, at least 10 parallel cells per link in the
> serial chain. Many were limited to around 2A continuous. I couldn't
> find any specs on peak current, either on the bigger vendor sites, or
> on actual mfgr data sheet pdfs. Descriptions of, and differences
> among, the various chemistries and naming conventions, are all over
> the map, depending on which interweb 'authority' you choose to accept.
> Obviously more going on than I can see in the normal data sheets,
> since there are dozens of functional examples of starting batteries on
> the market.
>
> I'd certainly be game for rolling my own battery, but picking the
> right cell seems a task not suited to mere mortals.
>
> Charlie
As a followup,
Do LiFePO4 batteries used for starting have altered chemistry or cell
size, as compared to the 'deep cycle' versions? What about charging
profiles? If not,
https://www.amazon.com/LiFePO4-Battery-Miady-Rechargeable-Maintenance-Free/dp/B07X7MD2JK/ref=sr_1_3?dchild=1&keywords=12V+LiFePO4&qid=1601260110&sr=8-3
Looks interesting as the starting point for the DIY battery idea Bob
mentioned earlier. The terminals are obviously inadequate as made, but
it would be interesting to see what it looks like inside. If larger
terminals could be installed...
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| Subject: | Re: evolution of lithium technologies |
>As a followup,
>Do LiFePO4 batteries used for starting have altered chemistry or
>cell size, as compared to the 'deep cycle' versions? What about
>charging profiles?
Probably. The no-iron lithium products
demonstrate performance all over the map.
I suspect there are similar variations on the
LiFe theme
> If not,
><https://www.amazon.com/LiFePO4-Battery-Miady-Rechargeable-Maintenance-Free/dp/B07X7MD2JK/ref=sr_1_3?dchild=1&keywords=12V+LiFePO4&qid=1601260110&sr=8-3>https://www.amazon.com/LiFePO4-Battery-Miady-Rechargeable-Maintenance-Free/dp/B07X7MD2JK/ref=sr_1_3?dchild=1&keywords=12V+LiFePO4&qid=1601260110&sr=8-3
>Looks interesting as the starting point for the DIY battery idea Bob
>mentioned earlier. The terminals are obviously inadequate as made,
>but it would be interesting to see what it looks like inside. If
>larger terminals could be installed...
Interesting product. Q&A's seem forthright.
He says it's got a BMS that current limits
so upsizing terminals is not likely to let
it crank engines.
It sold with free returns . . . i've ordered one
to shake out.
Bob . . .
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