Today's Message Index:
----------------------
1. 12:00 AM - Re: Re: Z-12 Twist? (Valin & Allyson Thorn)
2. 06:25 AM - is a balun necessary (Mike Welch)
3. 07:03 AM - Re: is a balun necessary (Bill Boyd)
4. 07:17 AM - Re: is a balun necessary (Robert L. Nuckolls, III)
5. 08:03 AM - Re: is a balun necessary (Mike Welch)
6. 08:49 AM - Re: is a balun necessary (John Cox)
7. 08:52 AM - Bussmann fuse blocks (Jef Vervoort)
8. 10:31 AM - Re: Bussmann fuse blocks (James Kilford)
9. 11:28 AM - Re: Bussmann fuse blocks (Peter Pengilly)
Message 1
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Hi Longg,
Yes, our Legacy's weight and c.g. location are one of my focus areas of
concern. Houston is just too hot and humid to not have an A/C in an
airplane like the Legacy with a bubble canopy. I figure half our flights
will be local, low altitude with no relief from the temps with altitude. To
make up for the 40 lb A/C unit behind the seats, I've saved 17 lbs with an
MT propeller vs. the Hartzell. Of course, that weight behind the seats
hurts the aft c.g. tendency of the basic design. So the batteries (30 lbs)
are going on the firewall. Also, we plan on a G900X integrated avionics
system which is going to hurt weight but help move the c.g. forward. Also,
the A/C unit is easily removable for winter months or when the payload
capability is needed.
On the electrical configuration, I subscribe to the design goal that the
failure of an alternator in flight should not prevent comfortably continuing
on to your destination - at least VFR. I do have a Dynon PFD planned as a
backup. With the SD-20, though, I can cover the G900X system with Wx Link
and Traffic Awareness systems off.
Valin
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
longg@pjm.com
Sent: Tuesday, April 13, 2010 11:19 AM
Subject: RE: AeroElectric-List: Re: Z-12 Twist?
Wow,
The Legacy is already CG sensitive with the big motor, then you install
the air-conditioning stuff which moves the CG aft and you've stopped the
big guys from sweating so they're no longer losing weight which makes
the plane more sensitive to gross weight when you fill up the 32.5 gal
fuel tanks. Now, you either need more power or you need to buy a 40 amp
alternator to save 4 pounds so you can carry a change of clothes for the
weekend. To save more weight I'd install the SD-8 and when #1 goes
south, shut down the air-conditioning, turn out all the lights and run
home on a 1 amp Dynon. When the 100 amp job goes you'll be sweating
bullets anyway so the air-conditioning will simply become camping gear
at that point.
That said, I really do enjoy the Legacy.
Message 2
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Subject: | is a balun necessary |
Guys=2C
I'm building a 1/4 wave com antenna and have most of it completed=2C exce
pt for adding a balun.
Can someone answer this question for me=3B do I need a balun=2C or more p
recisely=2C what is it about an antenna that tells you you should install o
ne?
If I need one=2C the time to add it is now!! Easy now=2C not so easy lat
er!
My antenna has (4) 1/2" wide copper foil strips=2C soldered to form an "X
" (plus enough copper strips soldered to form a 2" x 2" sq. plate). Mounte
d in the center of the X is a 1/8" steel mast (welding rod). The coax shie
ld solders directly to the groundplane=2C and the coax's center conductor i
s fastened under a little screw that secures the mast.
Upon initial construction=2C the lengths of all the components are extra
long. The copper radials are 24" at the moment. The mast will start off a
t 23". Does an anyone have an opinion as to the lengths I should trim thes
e parts down to?
I DO have an SWR meter that I will be using to check for standing waves.
One more quick question regarding the antenna's components lengths. Wher
e is it that the length supposedly begins? If you have a 2" x 2" square co
pper plate=2C and each of the 4 copper tape radials are soldered to the pla
te=2C where is the radials length considered to begin? Is it from the very
center of the 2" x 2" plate=2C or is it from the point where the tape leav
es the edge of the plate...and actually begins being just copper foil arm?
Same for the mast. If I take a 1/8th" solid steel rod=2C and form a loop
on one end (to be able to mount it to a small plexiglass block)=2C where i
s the zero point on the rod? Is it the point where the coax fastens to the
mounting bolt=2C the end of the coax where it parts from the sheilding=2C
etc?
I know for a com radio we're shooting for 22"-23" roughly=2C for the ante
nna's lengths. I'm just a little lost on where those lengths actually begi
n. Plus=2C what if the radials are a little extra long? Does that hurt re
ception?
Thanks for your help=2C
Mike Welch
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Message 3
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Subject: | Re: is a balun necessary |
I'll take a stab at it. Conventional wisdom is to make the radials 3-5%
longer than the radiating element (mast). For optimum impedance matching of
antenna to coax, the angle between the mast and radials should be about 120
degrees. A 90 degree angle is going to produce a lower impedance, closer to
36 ohms, and a resulting higher VSWR at resonance. In other words, no
matter how precisely you trim everything, hunting for lowest SWR, it won't
reach 1:1 unless the antenna impedance at resonance is 52 ohms, just like
the coax. I don't know the exact math on this, but I'll eyeball a guess
that 1.3:1 - 1.5:1 is the best you'll see with radials at right angles to
the mast. NOT likely to matter in practice, except that the air band spans
a wide % frequency range, and an antenna broadband enough to cover 118-136
MHz needs to have as low as possible a resonant (center-frequency) SWR in
order not to have a high SWR at the band edges. You want less than 2:5:1 at
the limits to keep the transmitter happy and prevent power output fold-back
from the radio's protective circuits. On receive, you'll never hear the
difference.
A balun will make no practical difference in the operation of a quarter-wave
vertical whip antenna such as you are building. I twill add weight, cost,
complexity and exact a small" efficiency surcharge." I'd strongly recommend
leaving it out.
Make your measurements from the point where the conductors leave the coax
shield. The radius of the copper plate counts as part of the radial length.
Any center conductor beyond the coax braid counts as part of the mast
length. In practice, the dimensions matter little except as a starting
point for trimming with the SWR meter.
Enjoy the exercise.
Bill Boyd
On Fri, Apr 16, 2010 at 9:16 AM, Mike Welch <mdnanwelch7@hotmail.com> wrote:
> Guys,
>
> I'm building a 1/4 wave com antenna and have most of it completed, except
> for adding a balun.
> Can someone answer this question for me; do I need a balun, or more
> precisely, what is it about an antenna that tells you you should install
> one?
> If I need one, the time to add it is now!! Easy now, not so easy later!
>
>
> My antenna has (4) 1/2" wide copper foil strips, soldered to form an "X"
> (plus enough copper strips soldered to form a 2" x 2" sq. plate). Mounted
> in the center of the X is a 1/8" steel mast (welding rod). The coax shield
> solders directly to the groundplane, and the coax's center conductor is
> fastened under a little screw that secures the mast.
>
> Upon initial construction, the lengths of all the components are extra
> long. The copper radials are 24" at the moment. The mast will start off at
> 23". Does an anyone have an opinion as to the lengths I should trim these
> parts down to?
> I DO have an SWR meter that I will be using to check for standing waves.
>
> One more quick question regarding the antenna's components lengths.
> Where is it that the length supposedly begins? If you have a 2" x 2" square
> copper plate, and each of the 4 copper tape radials are soldered to the
> plate, where is the radials length considered to begin? Is it from the very
> center of the 2" x 2" plate, or is it from the point where the tape leaves
> the edge of the plate...and actually begins being just copper foil arm?
>
> Same for the mast. If I take a 1/8th" solid steel rod, and form a loop
> on one end (to be able to mount it to a small plexiglass block), where is
> the zero point on the rod? Is it the point where the coax fastens to the
> mounting bolt, the end of the coax where it parts from the sheilding, etc?
>
> I know for a com radio we're shooting for 22"-23" roughly, for the
> antenna's lengths. I'm just a little lost on where those lengths actually
> begin. Plus, what if the radials are a little extra long? Does that hurt
> reception?
>
> Thanks for your help,
>
> Mike Welch
>
> ------------------------------
> The New Busy is not the too busy. Combine all your e-mail accounts with
> Hotmail. Get busy.<http://www.windowslive.com/campaign/thenewbusy?tile=multiaccount&ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_4>
>
> *
>
> *
>
>
Message 4
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Subject: | Re: is a balun necessary |
At 08:16 AM 4/16/2010, you wrote:
Guys,
I'm building a 1/4 wave com antenna and have most of it completed,
except for adding a balun.
Can someone answer this question for me; do I need a balun, or more
precisely, what is it about an antenna that tells you you should install one?
The chapter on antennas and feedlines in the 'Connection
explains this. A 1/4-wave, bottom feed whip antenna
is an UNbalanced antenna and does not need a balun
to accept connection to a coaxial feed line.
My antenna has (4) 1/2" wide copper foil strips, soldered to form an
"X" (plus enough copper strips soldered to form a 2" x 2" sq.
plate). Mounted in the center of the X is a 1/8" steel mast (welding
rod). The coax shield solders directly to the groundplane, and the
coax's center conductor is fastened under a little screw that secures the mast.
How did you insulate the mast from the ground plate?
How is the mast attached to the rest of the assembly?
Upon initial construction, the lengths of all the components are
extra long. The copper radials are 24" at the moment. The mast will
start off at 23". Does an anyone have an opinion as to the lengths I
should trim these parts down to?
I DO have an SWR meter that I will be using to check for standing waves.
Suggest you cut the radials and antenna to 22". Use
the SWR meter at the transceiver to assure that SWR
is 3:1 or less over 118 to 135 mHz.
One more quick question regarding the antenna's components
lengths. Where is it that the length supposedly begins? If you have
a 2" x 2" square copper plate, and each of the 4 copper tape radials
are soldered to the plate, where is the radials length considered to
begin? Is it from the very center of the 2" x 2" plate, or is it
from the point where the tape leaves the edge of the plate...and
actually begins being just copper foil arm?
At the center.
Same for the mast. If I take a 1/8th" solid steel rod, and form a
loop on one end (to be able to mount it to a small plexiglass block),
Hmmmm . . . What kind of airplane are we talking about here?
Plexiglas is not particularly "structural" and a single
fastener through a loop on the end of the antenna
rod is not terribly resistant to rotation and loosening.
Antennas tend to be ignored until AFTER the radio quits
working. The design you describe is not particularly robust.
Have you considered using a CB antenna adapter like I linked in a
posting earlier this week?
http://tinyurl.com/y3a4lpf
You can drill a hole in a 3/8-24 bolt to accept your antenna rod
and silver-solder the rod to the bolt. The "booger" the treads of
the bolt and lube it with grease before you screw it into
the top fitting of the adapter. This makes a nice, gas-tight
electrical and robust mechanical fit between the adapter and
the antenna rod.
The other end is fitted with a common coax connector which
is easy to adapt to your feedline.
. . . where is the zero point on the rod? Is it the point where the
coax fastens to the mounting bolt,
Yes.
or the end of the coax where it parts from the sheilding, etc?
Exposed center conductor ADDS to overall length
and should be minimized. But this is pretty easy
to keep at or below 1" and is not significant in
terms of antenna performance.
I know for a com radio we're shooting for 22"-23" roughly, for the
antenna's lengths. I'm just a little lost on where those lengths
actually begin. Plus, what if the radials are a little extra
long? Does that hurt reception?
No, the radials are not critical. If you were cutting
your copper foil strips from a large sheet, I would have
made them wider for robustness . . . 1-2" would have
been nice. But if you're working with 1/2" wide tape,
then what you have is what you have and will work fine.
Make periodic inspections of the joints where the
tape comes onto the grounding plate.
Bob . . .
Message 5
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Subject: | is a balun necessary |
Bill & Bob=2C
Thanks for your help. I think I have information at the point to complet
e the antenna and generate some results. I'll plot the SWR graph=2C and ge
t back to you.
Re: the plexiglass. No=2C Bob=2C none of the airplane uses it for=2C fra
nkly=2C anything!! Without you seeing what I'm doing=2C I know it's hard t
o understand what I'm actually building.
The plexiglass I referred to in only a 2" x 2"=2C 3/8" thick block=2C tha
t the antenna is built from. It allows for securing the copper tapes on th
e bottom=2C and a way to bolt the steel mast through it.
I'm sending a photo of essentially what it looks like. I know this photo
is of a halfwave dipole. My plexiglass block is serving a similar functio
n.....just a way to make everything secure. See photo #10 for my similar m
ounting method.
http://forums.matronics.com//files/antenna_design_118.pdf
Mike Welch
_________________________________________________________________
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Message 6
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Subject: | is a balun necessary |
Mike, can you expound on the process to plot the SWR graph on your
project? Dean Scott's pdf referenced the EZNEC 4.0 plot which was
fascinating.
John Cox
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Mike
Welch
Sent: Friday, April 16, 2010 7:51 AM
Subject: RE: AeroElectric-List: is a balun necessary
Bill & Bob,
Thanks for your help. I think I have information at the point to
complete the antenna and generate some results. I'll plot the SWR
graph, and get back to you.
Re: the plexiglass. No, Bob, none of the airplane uses it for,
frankly, anything!! Without you seeing what I'm doing, I know it's hard
to understand what I'm actually building.
The plexiglass I referred to in only a 2" x 2", 3/8" thick block, that
the antenna is built from. It allows for securing the copper tapes on
the bottom, and a way to bolt the steel mast through it.
I'm sending a photo of essentially what it looks like. I know this
photo is of a halfwave dipole. My plexiglass block is serving a similar
function.....just a way to make everything secure. See photo #10 for my
similar mounting method.
http://forums.matronics.com//files/antenna_design_118.pdf
<http://forums.matronics.com/files/antenna_design_118.pdf>
Mike Welch
________________________________
The New Busy is not the too busy. Combine all your e-mail accounts with
Hotmail. Get busy.
<http://www.windowslive.com/campaign/thenewbusy?tile=multiaccount&ocid=
P
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Message 7
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Subject: | Bussmann fuse blocks |
Bob and all,
I'm interested in using the Bussman fuse block, as suggested in Appendix Z
Note 19.
Where could I find these?
Jef in Belgium, 91031.
Message 8
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Subject: | Re: Bussmann fuse blocks |
Jef,
I ordered mine from B&C Specialty. Got here in no time (to the UK).
http://www.bandc.biz/circuit-protective-devices.aspx
James
On Fri, Apr 16, 2010 at 4:26 PM, Jef Vervoort <jef.vervoortw@telenet.be> wrote:
> Bob and all,
>
>
> Im interested in using the Bussman fuse block, as suggested in Appendix Z
> Note 19.
>
>
> Where could I find these?
>
>
> Jef in Belgium, 91031.
>
>
Message 9
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Subject: | Re: Bussmann fuse blocks |
Jef,
You could try Vehicle Wiring Products
<http://www.vehicle-wiring-products.eu/VWP-onlinestore/home/homepage.php> in
the UK - should be cheaper than importing from the US.
Peter
On 16/04/2010 16:26, Jef Vervoort wrote:
>
> Bob and all,
>
> I'm interested in using the Bussman fuse block, as suggested in
> Appendix Z Note 19.
>
> Where could I find these?
>
> Jef in Belgium, 91031.
>
> *
>
>
> *
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