Today's Message Index:
----------------------
1. 06:15 AM - Re: Avionics-List: Garmin SL-30 poor VOR reception (D L Josephson)
2. 08:30 AM - Re: Re: SL-30 Poor VOR reception (Robert L. Nuckolls, III)
3. 09:16 AM - Speaking of coax (Robert L. Nuckolls, III)
4. 01:13 PM - OT: power supply noise (rayj)
5. 02:13 PM - Single ground vs. distributed ground (donjohnston)
6. 04:38 PM - Re: Single ground vs. distributed ground (Tim Andres)
7. 05:05 PM - Re: Single ground vs. distributed ground (donjohnston)
8. 07:13 PM - Re: OT: power supply noise (Charlie England)
9. 08:57 PM - Re: OT: power supply noise (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Avionics-List: Garmin SL-30 poor VOR reception |
This question is being discussed both here and on the avionics list.
Commercial RG-58A, mil spec RG-58 (MIL-DTL-17 M17/28-RG058) such as
Belden 9203, RG-142 and RG400/LMR400 are all rated between 3.3 and 4.9
dB per 100 ft at 100 MHz -- around 1 dB for a practical airplane
installation. Belden 9203 RG58 is among the lowest loss and is mil QPL
qualified. Cable loss is not really a factor in a VOR/LOC/GS
installation; well made RG58 cable is fine. Cheap RG-58 "type" cable of
unknown impedance and bend resistance, who knows.
Original RG-58 (solid center conductor, solid PE dielectric) was just
fine for decades with receivers far worse than the Garmin. In my
experience, connectors are the problem nine times out of ten. Commercial
grade crimp connectors from a manufacturer that also supplies military
grade connectors (Amp, Amphenol, Kings) crimped with the
manufacturer-specified or mil-spec tool checked for the correct crimp
dimensions by someone experienced with this process is the key. Original
military soldered connectors are also OK but only if the installer is
experienced enough to get the dimensions right without melting the
dielectric.
Quick test, after you've confirmed that the cable has continuity end to
end and isn't shorted: grab the cable in one hand and the body of the
connector or the crimp sleeve in the other. Using moderate force, can
you rotate the connector body with respect to the cable? If so, cut it
off and try again, it is not terminated correctly. This isn't the cause
of all problems but is usually diagnostic of whether it was crimped
right in the first place.
The tests Bob suggested are good. A nav receiver will work well -- not
optimally for IFR but well enough -- on a comm antenna.
Message 2
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| Subject: | Re: SL-30 Poor VOR reception |
At 04:47 PM 4/25/2014, you wrote:
>
>I agree with connector issues. I do NOT agree with cable issues.
>Ever since the VOR came on the scene, RG-58 has proved more than
>adequate on factory built spam cans. Most have runs of over 20 ft
>from panel to top of tail. Often with one or more connectors in the
>line. I had such on a Cessna that would easily receive 100nm on H
>class VOR at 10,000 ft. I could connect handheld to splitter for
>same antenna and it also would receive same 100+ nm range. RG 142
>and 400 are better, but not 6 times better, which is the price
>difference. I doubt they are even 50% better.
Agreed. The strength of vor transmitters and the
fundamentally line-of-sight operation makes
signal loss in coax a non-issue. The greatest
gain for a modern coax is in quality of insulation.
Legacy RG-58 is pvc and polyethylene while
the modern plastics are tefzel and more robust
cousins.
RG-400 and siblings are preferred for new
construction but I wouldn't replace RG-58
already in place.
Bob . . .
Message 3
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| Subject: | Speaking of coax |
While we're on the subject, know that there's a new
line of coax cables being offered as lower loss and
better shielded than the legacy RG products of PVC/PE . . .
They are part of the LMR series products like this
http://tinyurl.com/l2xbbqr
The value of the part numbers is the outside
diameter in thousandths. Hence, LMR195 is the
same physical size as RG58 and RG400.
The insulation is not high temperature rated,
it's more on the order of that stated for RG58
so soldering connectors to this stuff takes some
practice.
However, for all crimped joints, there's little
difference between the LMR and any other style.
The LMR195 has a solid center conductor which
harkens back to the days when solid center
conductor RG58 can short to the shield if
installed with a sharp bend radius and then
subjected to many years of temperature cycling.
This is a low-risk failure . . . I've only heard
of it one time and that was while I was still
at Cessna the first time.
The center conductor insulation is foamed
which produces a lower loss than legacy RG-58.
The shield is a combination of braid over
foil which offers near perfect shielding.
. . . and the price is right.
Bob . . .
Message 4
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| Subject: | OT: power supply noise |
Greetings,
I'm considering putting an unregulated power supply (transformers,
diodes, and a condenser) in an old computer box along with the
electronics to run several stepper motors for a CNC system.
I'm wondering if noise radiated from the power supply will cause
problems for the stepper motor drivers.
Thanks for any brilliant insight or wild ass guesses about this
situation.:>)
do not archive
--
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 5
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| Subject: | Single ground vs. distributed ground |
I'm in the process of wiring the panel and avionics on my Velocity (composite,
canard).
I have built an Avionics Shelf which runs the width of the cabin just behind the
panel. The shelf is made out of a pair of 1" aluminum angle stock and a sheet
of aluminum on top.
On the right side of the shelf I have mounted a ground block that connects to the
battery via 2AWG welding cable.
As I am connecting wires, the number of wires that are attaching to the ground
block keeps increasing. [Embarassed]
I can think of a couple of solutions:
1) crimp multiple wires to a single terminal. With the 22AWG wires, I could get
up to four wires in a single (red) terminal .
2) Make another ground block and mount it to the left side on the avionics shelf.
This would have the added benefit of eliminating ground wires from the bundle
crossing over to the right side ground block.
I'm leaning towards #2, but I'm wondering what the opinions are on these solutions
or if there's one I haven't thought of.
Thanks in advance.
Don
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=422415#422415
Message 6
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| Subject: | Re: Single ground vs. distributed ground |
Buy an avionics ground bus from Bob K. Sweet and simple single point ground system
for the avionics.
Just wondering....why 2awg wire to the avionics? Seems rather large.
Tim
> On Apr 26, 2014, at 2:12 PM, "donjohnston" <don@velocity-xl.com> wrote:
>
>
> I'm in the process of wiring the panel and avionics on my Velocity (composite,
canard).
>
> I have built an Avionics Shelf which runs the width of the cabin just behind
the panel. The shelf is made out of a pair of 1" aluminum angle stock and a sheet
of aluminum on top.
>
> On the right side of the shelf I have mounted a ground block that connects to
the battery via 2AWG welding cable.
>
> As I am connecting wires, the number of wires that are attaching to the ground
block keeps increasing. [Embarassed]
>
> I can think of a couple of solutions:
>
> 1) crimp multiple wires to a single terminal. With the 22AWG wires, I could get
up to four wires in a single (red) terminal .
>
> 2) Make another ground block and mount it to the left side on the avionics shelf.
This would have the added benefit of eliminating ground wires from the bundle
crossing over to the right side ground block.
>
> I'm leaning towards #2, but I'm wondering what the opinions are on these solutions
or if there's one I haven't thought of.
>
> Thanks in advance.
> Don
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=422415#422415
>
>
>
>
>
>
>
>
>
>
Message 7
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| Subject: | Re: Single ground vs. distributed ground |
tim2542(at)sbcglobal.net wrote:
> Buy an avionics ground bus from Bob K.
Well that would result in scrapping and undoing what I've already done.
> Just wondering....why 2awg wire to the avionics? Seems rather large.
Couple of reason: 1) I have more than just the avionics being grounded at that
block (trim motor, AP servo, cooling fan, etc.). 2) I had the wire and the room.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=422418#422418
Message 8
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| Subject: | Re: OT: power supply noise |
On 4/26/2014 3:10 PM, rayj wrote:
>
> Greetings,
>
> I'm considering putting an unregulated power supply (transformers,
> diodes, and a condenser) in an old computer box along with the
> electronics to run several stepper motors for a CNC system.
>
> I'm wondering if noise radiated from the power supply will cause
> problems for the stepper motor drivers.
>
> Thanks for any brilliant insight or wild ass guesses about this
> situation.:>)
>
> do not archive
>
If you're talking about a regular 60 hz line transformer, with properly
sized capacitors after the diodes to filter out the 60 hz AC sine-wave
ripple voltage, you should be fine.
Message 9
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| Subject: | Re: OT: power supply noise |
At 03:10 PM 4/26/2014, you wrote:
>
>Greetings,
>
>I'm considering putting an unregulated power supply (transformers,
>diodes, and a condenser) in an old computer box along with the
>electronics to run several stepper motors for a CNC system.
>
>I'm wondering if noise radiated from the power supply will cause
>problems for the stepper motor drivers.
Probably not. Do you have these parts already in hand?
Regulated, clean power supplies up to 350W are pretty
cheap on eBay. I seldom build a supply any more, the labor
alone is more than the cost of an off-the-shelf, plug-n-play
device.
Bob . . .
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