Today's Message Index:
----------------------
1. 08:07 AM - Re: Off topic electric drag racer (Noel Loveys)
2. 08:16 AM - Re: tool multitasking (Noel Loveys)
3. 08:17 AM - Re: Comm Antenna & SWR Reading -- Too High? (Noel Loveys)
4. 08:42 AM - Re: Off topic electric drag racer (Noel Loveys)
5. 08:52 AM - Re: Comm Antenna & SWR Reading -- Too High? (Ron Quillin)
6. 09:30 AM - Re: tool multitasking (jonlaury)
7. 10:38 AM - Re: "Emacs!" in Response: Was Comm Antenna & SWR Reading (Bob Falstad)
8. 10:56 AM - Re: tool multitasking (Jeff Page)
9. 11:09 AM - Re: Comm Antenna & SWR Reading (paul wilson)
10. 12:50 PM - Comm Antenna & SWR Reading: Additional Info (Bob Falstad)
11. 12:56 PM - cable ties (Janet Amtmann)
12. 01:15 PM - Re: Re: "Emacs!" in Response: Was Comm Antenna & SWR Reading (Robert L. Nuckolls, III)
13. 01:15 PM - Re: Comm Antenna & SWR Reading: Additional Info (Dj Merrill)
14. 01:50 PM - RG-400 Strechable? ()
15. 03:22 PM - Re: Off topic electric drag racer (William Slaughter)
16. 06:03 PM - Re: Comm Antenna & SWR Reading: Additional Info (Robert L. Nuckolls, III)
17. 06:03 PM - Re: RG-400 Strechable? (Robert L. Nuckolls, III)
18. 07:19 PM - Re: Off topic electric drag racer (user9253)
19. 07:39 PM - transponder groundplane (Mike Welch)
20. 07:39 PM - Flush Cutting Cable Ties (Dennis Johnson)
21. 07:41 PM - Off topic -- Slowing an electric motor (Dan O'Brien)
22. 09:19 PM - Re: transponder groundplane (Robert L. Nuckolls, III)
Message 1
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Subject: | Off topic electric drag racer |
Too bad about the LORAN... It has a few advantages over GPS. It's cheaper
and it's on the ground where it is somewhat more protected from things man
made and otherwise hurtling through space. I remember once when a C-band
satellite was knocked into by a meteor. For a period of time there was a
loss of signal. It could have been much worse as all geostationary
satellites are in a over the equator. I hope we never get in the situation
where we could benefit by those now lost advantages.
Noel
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: January 23, 2011 10:09 PM
Subject: RE: AeroElectric-List: Off topic electric drag racer
<nuckolls.bob@aeroelectric.com>
>
>Bob, I'm a bit surprised you didn't mention the serious work
>thousands of amateur radio buffs did on digital controls let alone
>digital emissions. I still remember sending full colour photographs
>around the world through a 1 khz bandwidth.
Yeah, there was a lot of packet work begin done in the late '80s
and slow-scan tv predates that by 10 years or more. There
are no doubt thousands of examples of 'leading edge' process
and technology that laid the groundwork for the future
of today's product. But we were talking about systems
and components that provide low risk, useful services in
the airplane.
Development costs need to be amortized over great
numbers for them to become insignificant. Little
airplanes don't represent much of a market! Our
demonstrated reservoir of successful recipes
have come from the volume consumer markets.
The SVLA battery has been around commercially
since 1970 but it wasn't until 1990 that they got a real
toe holed in OBAM aviation . . . and only then after
the un-interruptible power supply market bloomed.
When LORAN was still king and a panel mounted GPS was
prohibitively expensive, I bought a perfectly serviceable
GPS for airplanes from a Boat US catalog for $200.
I didn't mean to 'slight' any of the guys who
did it first. But doing if first doesn't immediately
and directly translate into useful, cost-effective
product.
Bob . . .
Message 2
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Subject: | tool multitasking |
Use the same cuts. But most of the other guys I know are using regular
sidecuts and they are not too careful about trimming/sanding the ends of the
tie wraps.
Noel
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: January 23, 2011 10:15 PM
Subject: RE: AeroElectric-List: tool multitasking
. . . we cut totally flush with a special pair of diagonal cutters easily
available on the market. No sliced hands so far.
I suspect the "special" cutters are commonly referred to
as jewelers flush cutters. The come in a variety of
qualities and prices. The ones I've been using around
here for awhile are.
http://tinyurl.com/4nptpy5
These are not yer granpa's fence wire tool. Apply
these judiciously.
Bob . . .
Message 3
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Subject: | Comm Antenna & SWR Reading -- Too High? |
Bob what did you use to measure the forward and reverse power? A bird or
just a regular SWR meter?
Noel
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Dj
Merrill
Sent: January 23, 2011 11:51 PM
Subject: Re: AeroElectric-List: Comm Antenna & SWR Reading -- Too High?
On 1/23/2011 2:27 PM, Bob Falstad wrote:
>
> Test 1: 122.9 MHz (the CTAF at my base): Forward Power: 0.8;
Reverse Power: 0.43; VSWR 6.5
> Test 2: 125.0 MHz Forward
Power: 0.8; Reverse Power: 0.4; VSWR 5.8
> Test 3: 130.0 MHz Forward
Power: 0.8; Reverse Power: 0.4; VSWR 5.8
Hi Bob,
In my opinion, anything greater than 2:1 would be unacceptable for
use in my ham station or my airplane. The very high SWR you have
indicates a significant loss of signal. At an SWR of 6.5 to 1, you are
losing over 50% of your radio signal (ie, less than half of your signal
is being transmitted out the antenna, and the rest is being reflected
back into your radio).
Google SWR for a ton of info on the topic, with a good reference at
http://en.wikipedia.org/wiki/Standing_wave_ratio (Scroll down to the
Practical Applications section)
and an online calculator showing percent of loss at:
http://www.csgnetwork.com/vswrlosscalc.html
6.5:1 indicates you may be losing 53% of your signal. 2:1 is only
11%. The better (lower) the SWR, the better the performance, and IMHO
if I were going IMC with it, I'd want the best performance I could get.
Will it work at 6.5:1? Yes, it will. Is it "the best we know how
to do"? In my opinion, no. I'd ask your Ham buddy to look it over to
see if anything can be done to help.
Some things I can think of to try:
- With the Glastar's metal cage and landing legs, if the antenna is
installed close enough to either that might have an effect on SWR. Even
the rudder and elevator cables running down the center of the baggage
area could possibly have an effect. Does the SWR change of your move
the rudder or the control stick for the elevator? You might try taking
the antenna out of the plane, installing it on a ground plane on your
work bench and test it there to see if you can duplicate the results.
- The Glastar has a fairly thick fiberglass shell. When you
installed the antenna, did you carve out the fiberglass so that the
antenna is touching the ground plane, or did you install it such that
there is a gap between the antenna and ground plane (ie, the thickness
of the fiberglass)? This could have a significant difference in SWR if
the antenna is supposed to be mounted directly to the ground plane with
no gap, as in the case of a metal plane.
- Is there an adjustment on the antenna itself?
- Double check that all of your coax lines are good, and there are
no stray pieces of the shield material that might be shorting out to the
center conductor.
Good luck! Please report back and let us know what you find if you
decide to look into it further.
-Dj
--
Dj Merrill - N1JOV
Glastar Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/
Please use Netiquette Guidelines http://tools.ietf.org/html/rfc1855
Kindly TRIM your email replies and post AFTER the relevant text
Message 4
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Subject: | Off topic electric drag racer |
Reminds me of the story about the money NASA spent to build a ball point pen
for space... The Russians used a pencil. Now what was not said. The
pencil leaves dust floating around every time it is used The point can break
off and jam equipment and on at least one occasion the pen was disassembled
and used to actually save a mission. On the surface it looked foolish but
in the long run it was money well spent.
Noel
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert
Mitchell
Sent: January 24, 2011 12:34 AM
Subject: Re: AeroElectric-List: Off topic electric drag racer
<rmitch1@hughes.net>
And, don't forget all the free hand me down benefits we get from NASA thru
taxpayer dollars.
Bob Mitchell
Sent from my iPad
On Jan 23, 2011, at 6:39 PM, "Robert L. Nuckolls, III"
<nuckolls.bob@aeroelectric.com> wrote:
<nuckolls.bob@aeroelectric.com>
>
>
>>
>> Bob, I'm a bit surprised you didn't mention the serious work thousands of
amateur radio buffs did on digital controls let alone digital emissions. I
still remember sending full colour photographs around the world through a 1
khz bandwidth.
>
> Yeah, there was a lot of packet work begin done in the late '80s
> and slow-scan tv predates that by 10 years or more. There
> are no doubt thousands of examples of 'leading edge' process
> and technology that laid the groundwork for the future
> of today's product. But we were talking about systems
> and components that provide low risk, useful services in
> the airplane.
>
> Development costs need to be amortized over great
> numbers for them to become insignificant. Little
> airplanes don't represent much of a market! Our
> demonstrated reservoir of successful recipes
> have come from the volume consumer markets.
>
> The SVLA battery has been around commercially
> since 1970 but it wasn't until 1990 that they got a real
> toe holed in OBAM aviation . . . and only then after
> the un-interruptible power supply market bloomed.
>
> When LORAN was still king and a panel mounted GPS was
> prohibitively expensive, I bought a perfectly serviceable
> GPS for airplanes from a Boat US catalog for $200.
>
> I didn't mean to 'slight' any of the guys who
> did it first. But doing if first doesn't immediately
> and directly translate into useful, cost-effective
> product.
>
>
> Bob . . .
>
>
>
>
Message 5
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Subject: | Re: Comm Antenna & SWR Reading -- Too High? |
Has there been any consideration given to ground proximity to the antenna?
Some years ago I too measured VSWR on a belly mounted bent whip of a
Bellanca Viking while on the ground and got rather disappointing
results, however the same test repeated with the aircraft airborne
yielded startlingly different, and acceptable, readings.
At 19:20 1/23/2011, you wrote:
>
>On 1/23/2011 2:27 PM, Bob Falstad wrote:
>>Test 1: 122.9 MHz (the CTAF at my base): Forward
>>Power: 0.8; Reverse Power: 0.43; VSWR 6.5
>>Test 2: 125.0
>>MHz Forward
>>Power: 0.8; Reverse Power: 0.4; VSWR 5.8
>>Test 3: 130.0
>>MHz Forward
>>Power: 0.8; Reverse Power: 0.4; VSWR 5.8
>
>Hi Bob,
> In my opinion, anything greater than 2:1 would be unacceptable
> for use in my ham station or my airplane. The very high SWR you
> have indicates a significant loss of signal. At an SWR of 6.5 to
> 1, you are losing over 50% of your radio signal (ie, less than half
> of your signal is being transmitted out the antenna, and the rest
> is being reflected back into your radio).
Message 6
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Subject: | Re: tool multitasking |
For wire marking, I tried a Brother lableler, but the tape is expensive and it
wastes a lot and it's a bit large. Then I tried printing 8 pt labels on paper
and cutting them out as I needed and slipped under clear heatshrink. But I always
ended up needing a label at the hangar that I hadn't thought of at home.
I ended up hand-printing the lablel that I wanted on 1/8" masking tape (auto body
shop supply) that just goes around awg 20 and slipping under heat shrink. That
ended up being the cheapest, quickest, neatest and most effective. Solid color
heat shrink for coding. Labels on both ends indicate origination, device
served, leg, wire size.
My Franklin engine logs came from Poland, hand printed in a beautiful style, the
machined parts of the engine had a similar hand-etched style. It reminded me
that these engines were actually built by a person. I like that same look on
my wiring and ditto for the poly-tape tied wire run bundles FWF.
John
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=328223#328223
Message 7
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Subject: | Re: "Emacs!" in Response: Was Comm Antenna & SWR Reading |
Bob,
Many thanks for your quick and detailed response. However, your response had three
"Emacs!" in it that appear to refer to graphics that I can't view. I searched
the AeroElectric lists archives and the most detailed message re "Emacs!"
was yours dated July 31, 2009. I couldn't find any other relevant messages
on how to view your graphics/photos.
I'm using a Macbook with OS 10.4.6 (Snow Leopard) that also has a full install
of Windows XP in it. I opened your reply in three different browsers -- Safari,
Firefox and Internet Explorer 8 but no joy.
Any thoughts on how I can retrieve/view your "Emacs!" graphical inserts?
Best regards,
Bob Falstad
Message 8
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Subject: | Re: tool multitasking |
The printer seems reasonable at $75.
However, 5 feet of heatshrink for $28 is quite expensive !
Has anyone found a more competitive source ?
I assume you cannot load standard heatshrink in the unit ?
Thanks,
Jeff Page
Dream Aircraft Tundra #10
> On our Sportsman 2+2 we have been using a Dymo Rhino 3000 printer
> and use the Rhino printable heat shrink and labels. It does a
> smashing job of allowing us to put any text label on our wires which
> we do on each end. The printer prints on the flat heatshrink
> available in colors, so we can color code white wire and label in
> plain English or any sort of code we want. Not cheap but very
> professional. We use some basic wire colors too to generally
> delineate power/ground/signal wires.
> Dee Whittington
Message 9
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Subject: | Comm Antenna & SWR Reading |
I am not Bob , but I use a forward/reflected SWR meter. Its a low
cost unit that did not have serious badmouthing from the Ham guys.
MFJ-862 SWR/Wattmeter. It has a 30 and 300w max range setting
PaulW
========
At 08:14 AM 1/24/2011, Noel Loveys wrote:
>
>Bob what did you use to measure the forward and reverse power? A bird or
>just a regular SWR meter?
>
>Noel
Message 10
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Subject: | Comm Antenna & SWR Reading: Additional Info |
Bob, et al,
Here is some additional information:
To Bob's inquiry "It would be interesting to do an ohmmeter test from center pin
on the antenna's connector and ground. If is shows a 'short', I suspect that
some sort of matching system is installed.", my ohmmeter showed a complete open
between the center pin and the shell of the BNC connector on the antenna base.
To Dj Merrill's questions:
1. The antenna base is about 16" aft of the aft portion of the GlaStar's metal
cage steel tubing and about 54" aft of the main gear legs (my 'Star is a taildragger).
The bent whip portion of the antenna trails aft, obviously, from the
base. We didn't check the SWR while moving the empennage control cables --
they run about 3" - 4" above the antenna base. (But I just installed in the tail
cone about 18" above the control cables a magnetometer for a Dynon EFIS and
the indicated heading didn't change when I moved the elevator controls if that
info is relevant to this discussion.)
2. The antenna base is installed on the exterior surface of the composite fuselage
and the ground plane is on the inside surface. They are about 7/16" of an
inch apart and, as I mentioned before, electrically bonded by the four stainless
machine screws that mount the antenna to the airplane. I haven't researched
whether the antenna must be mounted directly on the ground plane -- if so,
that will be an issue since some composite surgery will be required that I'd
really rather avoid.
3. I didn't see any adjustment on the antenna itself.
Based on the responses, it looks like I've got some more tweaking/testing to do.
Specifically:
Re-test the antennas (including the cat's whisker) and their feed lines separately,
and then together after I've got the feed lines cut to final length and with
their final BNC connectors in place. The RG-400 feed line from the Comm 1
antenna to the Garmin 430W will be about 10' long. I can vary (i.e., lengthen)
that length if it will help performance. Is there a rule of thumb in how long
to make antenna feed lines for optimum performance?
When re-running the tests, would it make any difference to use a more powerful
transmitter than my little hand-held? Or should I stick with what I used originally
to eliminate one more variable that might affect the follow-on data?
Thanks for the helpful advice.
Best regards,
Bob
Message 11
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|
To those of you having trouble with cable tie injuries, try a relatively
inexpensive ($31) tensioning tool from Waytek. It has a cutter that cuts s
o
close to the tie head that you can't feel the edges. Try tool #412, and us
e
Thomas & Betts "Ty-Rap" brand ties. Never had a problem with injuries with
this combination. The jewelers' diags that Bob mentioned work also on a
lower budget.
Do not archive
J=FCrgen Amtmann
Message 12
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Subject: | Re: "Emacs!" in Response: Was Comm Antenna & |
SWR Reading
At 01:30 PM 1/24/2011, you wrote:
>
>Bob,
>
>Many thanks for your quick and detailed response. However, your
>response had three "Emacs!" in it that appear to refer to graphics
>that I can't view. I searched the AeroElectric lists archives and
>the most detailed message re "Emacs!" was yours dated July 31,
>2009. I couldn't find any other relevant messages on how to view
>your graphics/photos.
>
>I'm using a Macbook with OS 10.4.6 (Snow Leopard) that also has a
>full install of Windows XP in it. I opened your reply in three
>different browsers -- Safari, Firefox and Internet Explorer 8 but no joy.
>
>Any thoughts on how I can retrieve/view your "Emacs!" graphical inserts?
scroll down in the archival postings to see
if the images are down there.
I've revisited some references and filtered my
test values through the credibility filter.
The jury is still out. I'd forgotten that
the raw quarter-wave over a good ground plane
should have a resistive component on the order
of 37 ohms at resonance, not 12 ohms. I need
to resolve the discrepancy.
I think I mentioned in another post that the
CI-122 antenna is called out as anything from
1.5:1 (best match?) to 3:1 (not to exceed)
and some numbers in between depending on who's
advertisements you're reading.
I'm not finished unpacking my electro-whizzies
and don't know where my Model 43 meter is. I
seem to recall having a high sensitivity slug
for it that I could drive with a 100 mW unit
oscillator. It will be a couple of weeks
but I'm going to revisit the experiment. I'll
also conduct a calibration procedure on the
MFJ-259 to make sure it hasn't wandered off
into the weeds.
Another Lister cited a marked difference
bewteen on the ground and airborne SWR
readings on a belly mounted antenna. What
would be really cool is to see what your
antenna shows mounted to the center of a
sheet of aluminum on saw horses.
Bob . . .
Bob . . .
Message 13
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Subject: | Re: Comm Antenna & SWR Reading: Additional Info |
On 01/24/2011 03:24 PM, Bob Falstad wrote:
> Is there a rule of thumb in how long to make antenna feed lines for optimum performance?
Typically the longer the cable run, the higher the loss induced by the
cable, so I strive to make the cable runs as short as practical while
still leaving adequate length for maintenance, moving things, etc. An
extra foot or two won't make much difference, but I wouldn't leave an
extra ten feet, for example.
>
> When re-running the tests, would it make any difference to use a more powerful
transmitter than my little hand-held? Or should I stick with what I used originally
to eliminate one more variable that might affect the follow-on data?
I typically test with a 5 watt handheld. I can see no reason to throw
more power at it. However, it might be worth trying the test with a
different handheld to remove the radio itself as a potential source of
the problem.
-Dj
--
Dj Merrill - N1JOV
Glastar Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/
Please use Netiquette Guidelines http://tools.ietf.org/html/rfc1855
Kindly TRIM your email replies and post AFTER the relevant text
Message 14
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Subject: | RG-400 Strechable? |
Some time ago while taking the wing off my airplane the RG-400 cable to
the NAV antenna cable took a pretty good pull when the weight of the
wing hung on it.
Question:
While no damage was visible, is it possible to damage the core even
though there was no damage to the external jacket?
Thanks,
Glenn
Message 15
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Subject: | Off topic electric drag racer |
Both US and Russia started out with pencils, and the hazards mentioned are
true. However, Fisher pen developed it on their own nickel, and it ended up
being used by both sides. Search "nasa space pen" at Snopes.com for the
detailed story.
William
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Noel
Loveys
Sent: Monday, January 24, 2011 10:20 AM
Subject: RE: AeroElectric-List: Off topic electric drag racer
Reminds me of the story about the money NASA spent to build a ball point pen
for space... The Russians used a pencil. Now what was not said. The
pencil leaves dust floating around every time it is used The point can break
off and jam equipment and on at least one occasion the pen was disassembled
and used to actually save a mission. On the surface it looked foolish but
in the long run it was money well spent.
Noel
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert
Mitchell
Sent: January 24, 2011 12:34 AM
Subject: Re: AeroElectric-List: Off topic electric drag racer
<rmitch1@hughes.net>
And, don't forget all the free hand me down benefits we get from NASA thru
taxpayer dollars.
Bob Mitchell
Sent from my iPad
On Jan 23, 2011, at 6:39 PM, "Robert L. Nuckolls, III"
<nuckolls.bob@aeroelectric.com> wrote:
<nuckolls.bob@aeroelectric.com>
>
>
>>
>> Bob, I'm a bit surprised you didn't mention the serious work thousands of
amateur radio buffs did on digital controls let alone digital emissions. I
still remember sending full colour photographs around the world through a 1
khz bandwidth.
>
> Yeah, there was a lot of packet work begin done in the late '80s
> and slow-scan tv predates that by 10 years or more. There
> are no doubt thousands of examples of 'leading edge' process
> and technology that laid the groundwork for the future
> of today's product. But we were talking about systems
> and components that provide low risk, useful services in
> the airplane.
>
> Development costs need to be amortized over great
> numbers for them to become insignificant. Little
> airplanes don't represent much of a market! Our
> demonstrated reservoir of successful recipes
> have come from the volume consumer markets.
>
> The SVLA battery has been around commercially
> since 1970 but it wasn't until 1990 that they got a real
> toe holed in OBAM aviation . . . and only then after
> the un-interruptible power supply market bloomed.
>
> When LORAN was still king and a panel mounted GPS was
> prohibitively expensive, I bought a perfectly serviceable
> GPS for airplanes from a Boat US catalog for $200.
>
> I didn't mean to 'slight' any of the guys who
> did it first. But doing if first doesn't immediately
> and directly translate into useful, cost-effective
> product.
>
>
> Bob . . .
>
>
>
>
Message 16
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Subject: | Re: Comm Antenna & SWR Reading: Additional Info |
At 03:24 PM 1/24/2011, you wrote:
Bob, et al,
Here is some additional information:
To Bob's inquiry "It would be interesting to do an ohmmeter test from
center pin on the antenna's connector and ground. If is shows a
'short', I suspect that some sort of matching system is installed.",
my ohmmeter showed a complete open between the center pin and the
shell of the BNC connector on the antenna base.
Okay, that's not a guarantee that there's
no networking components in the base, the
matching system could be capacitively
coupled . . . but interesting info.
2. The antenna base is installed on the exterior surface of the
composite fuselage and the ground plane is on the inside
surface. They are about 7/16" of an inch apart and, as I mentioned
before, electrically bonded by the four stainless machine screws that
mount the antenna to the airplane. I haven't researched whether the
antenna must be mounted directly on the ground plane -- if so, that
will be an issue since some composite surgery will be required that
I'd really rather avoid.
Not necessarily right ON the ground plane but
if your antenna mounting screws put a "crush"
on anything other than metal, their long
term integrity as electrical conductors is
suspect. I think you mentioned 10-32 attach
hardware. I'd fabricate some spacers with 10-32
clearance holes and just shy of structure thickness
for length. The goal is to have the spacers mate
up with the base of the antenna and the lower
surface of the ground plane. The majority of attach
bolt tension goes to maintaining crush on
the spacer. Your looking for PRESSURE on the
ends of the spacers, they don't need to be
real big in diameter, say 3/8"?
Of course the ends of the spacers and the
surfaces they contact should be bright at
bolt-up time. Use washer's under the nuts on
top of the ground plane to get a flattening
of the ground plane to the top of the
spacer. Torque the hardware to 80% of
limits.
3. I didn't see any adjustment on the antenna itself.
And typically, no TSO/DO qualified antenna would
have any adjustments . . .
Based on the responses, it looks like I've got some more
tweaking/testing to do. Specifically:
Re-test the antennas (including the cat's whisker) and their feed
lines separately, and then together after I've got the feed lines cut
to final length and with their final BNC connectors in place.
I have never seen an antenna "go bad" . . . they're just
too simple and quite robust. If they're not obviously
broken, the probability is that it's okay.
Coax feed lines with properly installed connectors are
high probability performers too. Given what we know
of your installation right now, ground plane bonding
offers the most exciting hypothesis for the measurements
you observed.
The RG-400 feed line from the Comm 1 antenna to the Garmin 430W will
be about 10' long. I can vary (i.e., lengthen) that length if it
will help performance. Is there a rule of thumb in how long to make
antenna feed lines for optimum performance?
Short as practical but allow some service loops if it's
necessary to dismount a black box and withdraw it some
distance before you can access connectors. This goes for
other harnesses as well. Don't agonize over an 'extra' foot
or two of coax at either end.
When re-running the tests, would it make any difference to use a more
powerful transmitter than my little hand-held? Or should I stick
with what I used originally to eliminate one more variable that might
affect the follow-on data?
The Bird 43 is the gold-standard for test equipment
we unwashed can afford. Although with a 5w slug,
you ARE way down on the best linearity curve for
the detector diode. More power MIGHT be helpful.
And yes, measure the SWR at the end of the coax
that attaches to your transceiver.
Bob . . .
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Subject: | Re: RG-400 Strechable? |
At 04:47 PM 1/24/2011, you wrote:
>Some time ago while taking the wing off my airplane the RG-400 cable
>to the NAV antenna cable took a pretty good pull when the weight of
>the wing hung on it.
>
>Question:
>
>While no damage was visible, is it possible to damage the core even
>though there was no damage to the external jacket?
I don't think so. That whole build up has a pretty
good tensile strength. Probably in the hundreds of
pounds.
Bob . . .
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Subject: | Re: Off topic electric drag racer |
> The cart had a couple of truck batteries in it. I think I remember it had a chain
drive from the motor to a differential with the drive wheels in the back,
with a single wheel in the front steered by a vertical tiller with a handle at
the top that fit between my legs when I got tall enough. You stood on a platform
at the back that was the forward-reverse and speed control. Lean forward
for forward; back to stop or reverse. Leaning to the side turned the front wheel.
We typically hauled maybe 200 pounds of mink feed on it. It was a very useful
little vehicle around the ranch, but it didnt do well on rough ground.
It sounds like a Segway doesn't it? LOL
Joe
Do not archive
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=328347#328347
Message 19
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Subject: | transponder groundplane |
Group=2C
I went ahead and bought one of those TED 2.6" steel rod antennas
for my transponder.
I intended to installed it on the underside of my fuselage (steel frame
with Poly Fiber covering). I do have a piece of 21" X 23" of .050 AL
under the left seat=2C snuggley laying on the fabric=2C and riveted on some
edges.
Would this be a good transponder groundplane? I could very easily
cut a 1/2" circle in the fabric=2C and mount the TED antenna directly
against the aluminum sheet.
Or=2C I could make a copper "X" groundplane=2C from some 1/2" wide
copper tape I have=2C and secure this one to the fabric=2C leaving a clean
1/2" hole in the fabric for the direct mounting of the antenna against
the copper.
If I make the copper X=2C how long should the legs be? 3" long enough?
Thanks=2C
Mike welch
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Subject: | Flush Cutting Cable Ties |
For cutting nylon cable ties, I've had good luck with these cheap flush
cutters from Harbor Freight:
http://www.harborfreight.com/micro-flush-cutter-90708.html
They cut the loose end of a plastic cable tie flush and don't leave a
sharp edge. Buy a few because they are cheap and don't last forever.
But if you don't try to cut anything other than plastic cable ties or
copper wire, they'll last for most of an airplane project.
Dennis
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Subject: | Off topic -- Slowing an electric motor |
Just following up on my question last week about slowing a permanent split
capacitor motor for a wind tunnel I built for my son's science project. A
poster indicated that one can slow such motors with a dimmer switch, which
is what I did. Worked great. We were able to measure the drag
coefficients of golf balls with different dimple patterns at different
Reynolds numbers. Cool project. I've attached a compressed picture of the
wind tunnel as one poster requested.
Thanks for the help guys!
Dan O'Brien
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Subject: | Re: transponder groundplane |
At 10:20 PM 1/24/2011, you wrote:
>Group,
>
> I went ahead and bought one of those TED 2.6" steel rod antennas
>for my transponder.
>
> I intended to installed it on the underside of my fuselage (steel frame
>with Poly Fiber covering). I do have a piece of 21" X 23" of .050 AL
>under the left seat, snuggley laying on the fabric, and riveted on some
>edges.
> Would this be a good transponder groundplane?
Yes.
Bob . . .
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