Today's Message Index:
----------------------
1. 05:47 AM - Alternator and Battery ON & OFF (Owen Baker)
2. 07:23 AM - Re: Alternator and Battery ON & OFF (Robert L. Nuckolls, III)
3. 08:11 AM - Re: Alternator and Battery ON & OFF (user9253)
4. 08:46 AM - Re: Transmitting with no antenna? (Robert L. Nuckolls, III)
5. 10:57 AM - Re: Z13 fusible link, circuit breaker, same circuit? (user9253)
6. 02:01 PM - Re: Re: Alternator and Battery ON & OFF (Justin Jones)
7. 04:44 PM - Re: Transmitting with no antenna? (donjohnston)
8. 05:28 PM - Re: Re: Transmitting with no antenna? (Eric Page)
Message 1
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| Subject: | Alternator and Battery ON & OFF |
7/22/2014
Hello Joe (Unknown) and Bob Nuckolls, The B&C wiring diagram accessed by
the link given below by Joe has this warning:
=9CImportant =93 Battery contactor and alternator should
come on and off together.=9D
Can someone please explain to me why that is important? What bad things
will happen if they don=99t come on and off together?
Thank you,
OC
'O C' Baker says "The best investment you can make is the effort to
gather and understand information."
PS: My procedure: On start up, Turn the alternator ON after engine is
running. On shut down, Turn the alternator OFF while engine is still
running to get a flashing low voltage light to confirm that my low
voltage warning system is working. I have entirely separate Battery
(battery contactor) and Alternator switches.
===========
Time: 07:41:41 AM PST US
Subject: AeroElectric-List: Re: Are 'serial' contactors really needed?
From: "user9253" <fransew@gmail.com>
> it says to hook the ovm to regulator in & to the master switch
No it doesn't.
B&C schematic link: http://www.bandc.biz/pdfs/OVM_wiringdiagram.pdf
The B&C schematic shows the black wire of the O.V. module connected to
ground.
They just happened to use the same ground that the master switch is
connected
to. You can connect the black wire to any convenient ground.
I think that B&C drew the schematic that way for two reasons: 1. It is
easy to
draw. 2. It is easy to wire directly at the master switch because both
ground
and the alternator field circuit are available there (if your master
switch is
wired like B&C's switch is wired).
As for the colored wire (orange?) of the O.V., B&C shows it connected to
the alternator-field
half of the master switch. Electrically speaking, this is the
same as connecting to the voltage regulator input. In either case,
power is coming
from the 5 amp breaker.
Now if you want to connect the O.V. module directly to the 5 amp
breaker, I see
no reason why that will not work. I hope others will correct me if
wrong. Just
make sure that it is connected to the down stream side and not the
always
hot side of the breaker.
In summary, connect the O.V. black wire to ground. And connect the
other wire
to some point between the 5 amp breaker and the input to the voltage
regulator.
Joe
Message 2
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| Subject: | Re: Alternator and Battery ON & OFF |
At 07:45 AM 7/22/2014, you wrote:
7/22/2014
Hello Joe (Unknown) and Bob Nuckolls, The B&C
wiring diagram accessed by the link given below by Joe has this warning:
"Important Battery contactor and alternator
should ccome on and off together."
Can someone please explain to me why that is
important? What bad things will happen if they don't come on and off together?
Hmmmm . . . hadn't noticed that. It's a not-so-accurate
acknowledgement of the history of alternators in airplanes.
When our vehicles with big fans and wings carried
generators, there were two relatively independent
sources of power. A battery and a generator. Generators
were by nature self-exciting (after the field was
'flashed') and output from the machine was relatively
smooth. Ship's electro-whizzies would run well on
battery, generator or both.
When we pressed the Ford alternators into service
on airplanes in the 60's, two noteworthy differences
in the alternator's characteristics took center
stage. Alternators were reluctant to self-excite;
you couldn't simply turn a spinning alternator ON
and expect it to come on line. Further, voltage
regulation dynamics for alternators was a fledgling
technology . . . having a battery on line aided
in the task stabilizing bus voltage and the battery
prevented the alternator from suffering a stalling
event should it be hit with a large inrush like
klieg-lights on the wings or an electro-hydraulic
landing gear system.
It was clear that the legacy separation of BATTERY
and GENERATOR switches was fraught with some risk
for confusing pilots familiar with how the electrical
system worked in the older airplanes. What's an
itty-bitty airplane factory to do?
The airplanes at Cessna were already being fitted
with the stylish rocker switches from Carling. The
pilots, engineers and switch-guys put their heads
together and the split-rocker DC MASTER switch
was birthed. Mechanical linkage between the rockers
allowed you to operate battery-only but that the
alternator could not be on without having the battery
on also.
EARLY in the history of AeroElectric Connection
architectures, the split-rocker was replaced with
a two-pole, ON-OFF switch to operated battery and
alternator together. The crowbar OVM called for
use of a field supply breaker . . . which could
be pulled for battery-only operations either
airborne or ground test.
Later, I discovered the Carling catalog and sources
for the three position 2-10 switch that would emulate
the split-rocker functionality . . .
http://tinyurl.com/q9pbjks
Over the years, the simple DPDT+breaker configuration
was replaced with the DP3T, ON-ON-ON (2-10) switch.
Now that you have the history, I can explain that
the admonition on the B&C drawing is an artifact
of the "days before 2-10 switches" and was further
mis-interpreted as an imperative . . . don't recall
now who wrote those words but they are in error.
Now that you have the "Rest of the Story" you are
free to select from the whole array of available
switches including (1) simple, DPDT+breaker (2) DP3T
ON-ON-ON, or (3) a living artifact of the early days
of alternators in light aircraft, the split rocker switch.
Bob . . .
Message 3
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| Subject: | Re: Alternator and Battery ON & OFF |
> Important Battery contactor and alternator should come on and off together.
> Can someone please explain to me why that is important? What bad things will
happen if they dont come on and off together?
I think that it is good operating practice to turn the master contactor and alternator
on and off simultaneously. But I do not think that bad things will
happen if not operated that way. TC aircraft have a split master switch and the
Z figures have a progressive transfer master switch that allows the alternator
to be shut off.
Most pilots expect the the master switch will shut off every single electrical
circuit on the airplane. If the master contactor and alternator are controlled
by separate switches and if only the contactor is shut off, then it is possible
(or even likely, depending on the alternator) for the alternator to keep supplying
power to the aircraft. This is not necessarily a bad thing, but could
be if the pilot does not understand how the aircraft is wired.
Another consideration is flying with the master contactor on and the alternator
off. The battery will not be recharged. If the alternator is then turned
on, could there be a voltage surge? I do not know. Maybe Bob N will answer that.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=427139#427139
Message 4
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| Subject: | Re: Transmitting with no antenna? |
At 08:43 PM 7/21/20, you wrote:
><nuckolls.bob@aeroelectric.com>
>
> At 03:27 PM 7/21/2014, you wrote:
>
>I'm working on an audio panel/radio problem and I was told that
>pressing the PTT (transmitting) without an antenna will fry the
>radio. [Embarassed]
>
>Is this correct or is it an OWT?
After crafting my reply last night I was curious as to
modern approaches to crafting SWR ruggedness into a
VHF transmitter.
The last time I dug through the innards of a solid state
vhf transmitter, the output stage was crafted from NPN
silicon junction transistors . . . about 4 of them in
push-pull for 100W of output at 145MHz. The antenna
matching network was fitted with a directional coupler
(SWR meter) that sampled reverse-voltage as a product of
high SWR . . . that voltage was used to reduce drive
to the output stage for the purpose of protecting the
transistors should the transmitter be presented with
a high swr. Works good, lasts a long time.
Just for grins, I got a copy of the KX165 transceiver
service manual to bone up on contemporary design
philosophies. Got an interesting surprise.
Here is an excerpt from the transmitter schematic . . .
Yup . . . there it is . . . the expected directional
coupler. But when I read the accompanying text, I was
informed that the directional coupler output was
used to sample FORWARD power for the purpose of leveling
the transmitter's output power. No mention was made
for 'high SWR protection' . . .
In fact, a search of the entire service manual
for "standing" or "SWR" produced no hits. Say
what????
Emacs!
Here are some excerpts from the manufacturer's data sheets
on the KX165 powuer output transistor.
Emacs!
This is a MOSFET rated at 80W of output in VHF operation.
Further we read the following . . .
Emacs!
Down in the tabulation of characteristics we also
find . . .
Emacs!
I was pleased to find that my original assertion was
correct but for the wrong reasons. It seems the MOSFET is
immune to damage from the stresses that would have
shot its ancestors out of the saddle. Hence no wrap-around
protection was needed. The directional coupler was still
there but pressed into service other than output
stage protection.
Another interesting feature from the schematic excerpt:
Notice the "stub" depiction on the antenna output line.
A search of the manual doesn't speak to its existence
or purpose. Given that this is a deign from the hallowed
halls of the Nav/Comm gods, I suspect that 'stub' is an
shunt filter element tuned to reject transmitter harmonics
that fall on or close to GPS frequencies. Garmin used to
offer a 330-00067-00 Notch Filter intended to be 'scabbed
on' to the nav/comm antenna connector.
Emacs!
Bob . . .
Message 5
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| Subject: | Re: Z13 fusible link, circuit breaker, same circuit? |
> What is the function of the 22AWG fusible link in this circuit?
The wire (if very long) between the main power bus and the circuit breaker needs
to be protected against short circuits. A fusible link provides this protection.
The circuit breaker does not offer protection because short circuit current
in this wire will not pass through the circuit breaker. A fuse can not
be used because, in case of over voltage, a fuse will blow before the circuit
breaker trips.
> Shouldn't the wire from the 5A circuit breaker to the Bat/Alt DC Power switch
and the wire from the Bat/Alt DC Power switch terminal 4 to the voltage regulator
terminal A also be 18AWG?
No, heavier wire is not needed because O.V. module current does not flow through
the 20 AWG wire.
> shouldn't all wires in this circuit be 20AWG and the fusible link be 16 AWG,
i.e. 4 sizes smaller?
If the fusible link is made from smaller wire, then it might burn open before the
5 amp breaker trips. So leave it at 22 AWG. The wire attached to the fusible
link must be 4 sizes bigger, thus 18 AWG. 20 AWG is adequate downstream from
the circuit breaker because it is protected by the circuit breaker.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=427156#427156
Message 6
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| Subject: | Re: Alternator and Battery ON & OFF |
Most of the split alt/bat switches that I have experience with allow the battery
to be on without the alternator but not the alternator on without the battery.
The function is an internal mechanical function in the switch itself. I like
to call it army proof.
On Jul 22, 2014, at 7:09, "user9253" <fransew@gmail.com> wrote:
>
>
>> Important Battery contactor and alternator should come on and off together.
>> Can someone please explain to me why that is important? What bad things will
happen if they dont come on and off together?
>
> I think that it is good operating practice to turn the master contactor and
alternator on and off simultaneously. But I do not think that bad things will
happen if not operated that way. TC aircraft have a split master switch and
the Z figures have a progressive transfer master switch that allows the alternator
to be shut off.
> Most pilots expect the the master switch will shut off every single electrical
circuit on the airplane. If the master contactor and alternator are controlled
by separate switches and if only the contactor is shut off, then it is possible
(or even likely, depending on the alternator) for the alternator to keep
supplying power to the aircraft. This is not necessarily a bad thing, but could
be if the pilot does not understand how the aircraft is wired.
> Another consideration is flying with the master contactor on and the alternator
off. The battery will not be recharged. If the alternator is then turned
on, could there be a voltage surge? I do not know. Maybe Bob N will answer
that.
>
> --------
> Joe Gores
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=427139#427139
>
>
>
>
>
>
>
>
>
>
Message 7
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| Subject: | Re: Transmitting with no antenna? |
nuckolls.bob(at)aeroelect wrote:
> At 03:27 PM 7/21/2014, you wrote:
>
>
> I'm working on an audio panel/radio problem and I was told that
> pressing the PTT (transmitting) without an antenna will fry the
> radio. [Embarassed]
>
> Is this correct or is it an OWT?
>
>
> I wouldn't make a habit of it . . . there's no
> good reason to do it. If you need to listen to
> your transmitted signal without radiating it more
> than a few dozen yards, build yourself a dummy
> load to put on the transmitter's coax connector.
>
> http://tinyurl.com/cchp3pf
>
> This load is good for 2W continuous and will handle
> 10W transmitters for the few seconds necessary to make
> a vocal test transmission to deduce audio quality.
> If you need a bigger load, it too can be fabricated
> from R-S parts.
>
> But the caveat about keying a transmitter into
> an open antenna jack is a carry-over from the state
> of solid state radios of the 60-70's. It didn't
> take the industry long to figure out ways to build
> protections into their products . . . so keying
> an unloaded transmitter no longer represents
> a serious hazard.
>
>
> Bob . . .
Using the logic of "if some is good, more must be better", I picked up some 10w,
100ohm resistors. :)
Checked with the manufacture (Val) and they said that I'm probably okay:
> In regards to circuit protection, the COM 2KR doesn't have any active protection
against keying the unit without a proper load attached. As such, you run
a small risk of damaging your radios keying them up without an antenna. However,
the radios are resistant to damage from being keyed without an antenna and
should be fine.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=427184#427184
Message 8
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| Subject: | Re: Transmitting with no antenna? |
Don,
Just be sure the resistors you sourced are not wire-wound types. At a 10W rating,
most are. These are inductive and will make a very poor dummy load.
Examples to avoid: http://bit.ly/1A3zd7U -or- http://bit.ly/1rImumj
Bob's 2W-10W dummy load appears to be built with Metal Film or Metal Oxide resistors.
Eric
> On Jul 22, 2014, at 7:42 PM, "donjohnston" <don@velocity-xl.com> wrote:
>
> Using the logic of "if some is good, more must be better", I picked up some 10w,
100ohm resistors. :)
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