Today's Message Index:
----------------------
1. 02:52 AM - Re: Battery Contactors (Noel Karppinen)
2. 02:54 AM - Re: Battery Contactors (Noel Karppinen)
3. 05:35 AM - Re: SD-8 Alternator OFF Annunciator? (Robert L. Nuckolls, III)
4. 05:38 AM - Re: Switched hot bus (Robert L. Nuckolls, III)
5. 07:05 AM - Amp 59250 t-head tool (Robert L. Nuckolls, III)
6. 07:28 AM - Re: Amp 59250 t-head tool (BobsV35B@aol.com)
7. 08:24 AM - Alternator whine in audio (wgill10@comcast.net)
8. 08:40 AM - Firewall Placement Of Electrical Components (DaveG601XL)
9. 08:43 AM - Re: Alternator whine in audio (Hinde, Frank George (Corvallis))
10. 09:52 AM - Re: Alternator whine in audio (Ron Quillin)
11. 10:42 AM - Re: Alternator whine in audio (wgill10@comcast.net)
12. 11:54 AM - RV-List: good warning labe (Charles Brame)
13. 12:11 PM - swapping two radios using 3P/DT switch? (Lincoln Keill)
14. 12:48 PM - Re: swapping two radios using 3P/DT switch? (Rob Turk)
15. 12:48 PM - Re: swapping two radios using 3P/DT switch? (Robert Borger)
16. 01:41 PM - Re: swapping two radios using 3P/DT switch? (jetboy)
17. 02:26 PM - Re: Audio isolation amp questions (nauga@brick.net)
18. 03:34 PM - Re: swapping two radios using 3P/DT switch? (JOHN TIPTON)
Message 1
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Subject: | Re: Battery Contactors |
Hi Peter
The resistance of mine is 16 Ohms when cold, so it is right in the ball
park.
Noel
----- Original Message -----
Noel
Check the resistance on the coil. A continuous duty contactor will show
a resistance of 10 to 18 ohms. An intermittant one will show 3 to 5 ohms
Peter
Message 2
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Subject: | Re: Battery Contactors |
Thanks for that comprehensive reply, Bob. Now I am completely convinced
that there is nothing to worry about.
Noel
----- Original Message -----
>"Richard T. Schaefer"
><<mailto:schaefer@rts-services.com>schaefer@rts-services.com> wrote:
> >It's normal for them to be a little too warm to touch. The
current is
> about right. Look at this at a 10W heater. It will get warm!
>
Dead on target Richard. In times past that this
conversation was conducted, I went to the bench
and held one of our stock battery contactors
in an energized condition until its temperature
stabilized. See:
http://www.aeroelectric.com/Pictures/Contactors/Battery_Contactor_Temp
s_1.jpg
The effects of temperature rise were obvious
too in terms of the current draw for the
contactor. Room temperature current draw
was on the order of 0.8 amps. But after
two hours of operation . . .
http://www.aeroelectric.com/Pictures/Contactors/Battery_Contactor_Temp
s_2.jpg
. . . current draw is down to about
0.56 amps. This phenomenon is a function
of the positive temperature coefficient of
copper wire used to wind the coil. As the
device warms up, it's resistance goes up
and the current goes down.
In terms of a gross test of a contactor's
intermittent or continuous duty status, if
it's still functioning after 5 minutes of
continuous operation then it MUST be a
continuous duty device. The intermittent
duty devices tailored for starter motor
control would have spit out all their smoke
after 5 minutes!
It's not often that we are physically able
to "feel" a piece of operating equipment and
find that it's too hot to touch but it can
raise concerns when the device is not
OBVIOUSLY designed to run hot . . . like
engines and exhaust stacks.
The contactors that dissipate about 10
watts don't heat up real fast . . . but in
still air they'll get pretty toasty.
Bob . . .
Message 3
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Subject: | Re: SD-8 Alternator OFF Annunciator? |
At 07:50 AM 10/2/2007 -0700, you wrote:
>
>"With Z-13, you leave the SD-8 off until needed when
>it is determined that the main alternator is off line
>(lv light on). You drop to e-bus loads, open battery
>contactor, turn SD-8 on and continue to airport of
>intended destination. If the SD-8 is not overloaded,
>the lv warning light will go back out."
>
>With regards to the SD-8 and the lv light, Z-13 has a single lv light on
>the diagram. The descripton for the PV/OV crows foot kit available from B
>and C states that "The PM/OV was designed to give over voltage protection
>to the permanet magnet alternator. The yellow light will annunciate if the
>alternator switch is left off, or the crowbar over voltage protection has
>been tripped. "
>
>So, will the single lv light depicted on Z-13 light if either the main alt
>or the SD-8 are off line?
>
>If the SD-8 has its own unique lv light as described on the B and C site,
>does it light if the aux alt selection switch is OFF? Or, does it only
>light if the aux alt selector switch is ON AND the SD-8 is off line? If
>the first case is true, during normal operation, the aux lv light will
>alway remain lit which would not be an ideal situation.
I don't think I've ever suggested the ALL OFF
warning light for the SD-8 as used in Z-13/8. The warning
light is useful when the SD-8 is a sole-source of engine
driven power in simple systems where there is no
real LV monitoring and warning system.
I've written many times in the past that the most
important electrical "instrument" in the electrical
system is the calibrated LOW VOLTS warning light
set to illuminate when the bus is below 13.0 volts.
Figure Z-13/8 suggests the AEC9005-101 LV Warning
module (or equivalent) and does not show the SD-8
ALT OFF light which is included in the B&C SD-8
installation kit. This indicator is not useful
in the Z-13/8 architecture.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 4
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Subject: | Re: Switched hot bus |
At 03:36 PM 10/3/2007 +0000, you wrote:
>All
>
>
>I am currently working on my wiring diagram for my FADEC equipped
>plane. I will be using a slightly modified version of the Z-14
>diagram. I found a fellow builder with the same setup as me and got a
>hold of his wiring diagram. Attached is a snippet of that diagram. My
>question pertains to the guarded switch for FADEC bus #1 (there is a
>similar setup for FADEC bus #2). The diagram is showing 4 AWG wire
>between the battery and guarded switch. Shouldn t there be a relay or
>something here?
>
>
>Thanks,
>
>
>Jason
>
>
>image001.png
I would rather see the FADEC equipment drive from
the Main Battery Bus with switching for each feeder
supplied downstream of the fuses as appropriate.
Without having detailed data on the functionality
of your FADEC system and its failure modes, it's
not possible to offer a well considered recommendation.
If your system demands an architecture like you've
illustrated, then the switch should be a relay (solid
state perhaps?) right at the battery. The 4AWG wire
cited can probably be MUCH smaller.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 5
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Subject: | Amp 59250 t-head tool |
See item 150197086208 on ebay
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 6
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Subject: | Re: Amp 59250 t-head tool |
Good Morning 'Lectric Bob,
You mentioned once that you had sent your T head crimper in for a rebuild.
Do you know if such a service is still available?
If so, where and how much ? <G>
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Air Park LL22
Downers Grove, IL 60516
630 985-8503
In a message dated 12/20/2007 9:08:28 A.M. Central Standard Time,
nuckolls.bob@cox.net writes:
See item 150197086208 on ebay
Bob . . .
**************************************See AOL's top rated recipes
(http://food.aol.com/top-rated-recipes?NCID=aoltop00030000000004)
Message 7
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Subject: | Alternator whine in audio |
Hello All,
I have a PlanePower alternator and have noticed a whine noise in the David Clark
headset audio. It is really noisy if the headset volume is high; however, if
I turn the headset volume down low and turn the comm radio volume up to compensate,
the whine is barely detectable. Can anyone explain this and/or provide
possible solutions? I called PlanePower to inquire about filter and they informed
me that their product has internal noise filtering and that I must have an
audio ground problem. When the alternator is switched off-line, the audio is
crystal clear. If there was an audio grounding issue I would expect to hear ignition
noise too, but thats not the case. Can additional filtering be installed
external to the alternator? Suggestions please.
Happy holidays,
Bill Gill
RV-7 Lee's Summit, MO
<html><body>
<DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY:
Arial">Hello All,<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office"
/><o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY:
Arial"><o:p> </o:p></SPAN></FONT><FONT face=Arial size=2><SPAN style="FONT-SIZE:
10pt; FONT-FAMILY: Arial">I have a PlanePower alternator and have
noticed a whine noise in the David Clark headset audio. It is really noisy
if the headset volume is high; however, if I turn the headset volume down low
and turn the comm radio volume up to compensate, the whine is barely detectable.
Can anyone explain this and/or provide possible solutions? I called PlanePower
to inquire about filter and they informed me that their product has internal
noise filtering and that I must have an audio ground problem. When the alternator
is switched off-line, the audio is crystal clear. If there was an audio
grounding issue I would expect to hear ignition noise too, but thats not the
case. Can additional filtering be installed external to the alternator? Suggestions
please.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY:
Arial"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY:
Arial">Happy holidays,</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY:
Arial">Bill Gill</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY:
Arial">RV-7 Lee's Summit, MO</SPAN></FONT></P></DIV>
<pre><b><font size=2 color="#000000" face="courier new,courier">
</b></font></pre></body></html>
Message 8
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Subject: | Firewall Placement Of Electrical Components |
I am building a Zenith 601 and using a variation of the Z16 drawing. I am currently
working on placing my regulator, S704-1 OV relay and capacitor. The B&C
instructions are pretty clear that this stuff should be mounted on the cockpit
side of the firewall and away from engine heat. In this configuration, the
Z16 would have me running a 12GA from the capacitor, through the firewall, and
out to the up-leg screw on the starter relay. I would also have a 12GA going
from the down-leg screw of the battery relay, through the firewall, and to the
main distribution bus. My question is two-fold:
1. Is it critical that these electrical parts be on the backside of the firewall.
I have seen photos of this stuff on the engine side on other airplanes.
2. If I follow B&C's recommendation on placement, can I run the alternator lead
from the capacitor straight to the main distribution bus? This would only require
one 12GA wire firewall penetration from the bus to the battery relay.
Thanks,
--------
David Gallagher
601 XL, tail and wings completed,
fueslage almost done. Working engine and electrical systems.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=153287#153287
Message 9
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Subject: | Alternator whine in audio |
Have you got a good connection between the alternator case and the engine b
lock?....I had kinds of noise issues before i realised that painting the al
ternator bracket is a very bad idea and is provides a hi resistance path...
Ooops.
My plane power alt has been trouble free...no noise.
Frank
RV 7a IO360
________________________________
From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectr
ic-list-server@matronics.com] On Behalf Of wgill10@comcast.net
Sent: Thursday, December 20, 2007 8:21 AM
Subject: AeroElectric-List: Alternator whine in audio
Hello All,
I have a PlanePower alternator and have noticed a whine noise in the David
Clark headset audio. It is really noisy if the headset volume is high; how
ever, if I turn the headset volume down low and turn the comm radio volume
up to compensate, the whine is barely detectable. Can anyone explain this a
nd/or provide possible solutions? I called PlanePower to inquire about filt
er and they informed me that their product has internal noise filtering and
that I must have an audio ground problem. When the alternator is switched
off-line, the audio is crystal clear. If there was an audio grounding issue
I would expect to hear ignition noise too, but that's not the case. Can ad
ditional filtering be installed external to the alternator? Suggestions ple
ase.
Happy holidays,
Bill Gill
RV-7 Lee's Summit, MO
Message 10
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Subject: | Re: Alternator whine in audio |
At 08:20 12/20/2007, you wrote:
> I have a PlanePower alternator and have noticed a whine noise in
> the David Clark headset audio. It is really noisy if the headset
> volume is high; however, if I turn the headset volume down low and
> turn the comm radio volume up to compensate, the whine is barely
> detectable. Can anyone explain this and/or provide possible solutions?
Is this something new, and if so, what has changed?
Only your headset, or also pax headsets?
You don't mention what you have for an audio/intercom system....
A question.
Is each and every headset audio and microphone jack ground bushing
insulated from and do not rely on an airframe connection for the
'return' to the source equipment? That is, are there dedicated
ground returns for the microphone and headset from each and every
jack returning to the audio source, be it radio, audio panel or intercom?
Your audio source to the headset will amplify whatever signal it sees
between its' input and input common, generally audio lo, chassis or
some other airframe referenced ground connection. Likewise, what
ever is connected to its' output will hear whatever voltage is seen
between the hot or high connection and lo, return, chassis or
whatever you wish to call it. Should some unwanted voltage also get
stuck in there, it too will be heard. As you turn up the comm audio
and the offending noise is not increased, it would be safe to assume
the offending signal is after the volume control you are
adjusting. In a similar manner, you adjust headset volume and the
noise changes; the source is before the control.
Your headphones may well just be hearing some voltage drop caused by
airframe currents between the jack where you connect them and the
piece of gear at the other end of the wire to the jack.
>I called PlanePower to inquire about filter and they informed me
>that their product has internal noise filtering and that I must have
>an audio ground problem. When the alternator is switched off-line,
>the audio is crystal clear.
So the offending source would seem to be the alternator; it's off, no
noise. But how is the alternator noise getting into the
headset? Even a good alternator is going to make some noise when
under load. It's our duty to minimize how that noise can make it into
unwanted places.
>If there was an audio grounding issue I would expect to hear
>ignition noise too, but that's not the case.
Generally ignition noise is radiated noise, not noise in the form of
airframe current, so you could easily have (or not) ignition noise
(generally) totally unrelated to stray currents causing unwanted
voltage drops in audio circuits.
>Can additional filtering be installed external to the alternator?
>Suggestions please.
Generally, additional filtering can be added and may help. But is
that just a band aid covering up some other undiscovered issue that,
if corrected, would yield an even better solution...
Ron Q.
Message 11
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Subject: | Re: Alternator whine in audio |
Thanks Ron.
This is a new RV-7 aircraft and installation...been there since day one on both
audio jacks . I have a Garmin 347 audio panel with an SL-40 comm...both prewired
by Stark's. I do have the insulating washers on the jacks with a dedicated
ground (unshielded) wired to a central ground. I also have a KX 155 navcomm w/glideslope
-- the noise is there with either comm.
Bill
-------------- Original message --------------
From: Ron Quillin <rjquillin@gmail.com>
At 08:20 12/20/2007, you wrote:
I have a PlanePower alternator and have noticed a whine noise in the David Clark
headset audio. It is really noisy if the headset volume is high; however, if
I turn the headset volume down low and turn the comm radio volume up to compensate,
the whine is barely detectable. Can anyone explain this and/or provide
possible solutions?
Is this something new, and if so, what has changed?
Only your headset, or also pax headsets?
You don't mention what you have for an audio/intercom system....
A question.
Is each and every headset audio and microphone jack ground bushing insulated from
and do not rely on an airframe connection for the 'return' to the source equipment?
That is, are there dedicated ground returns for the microphone and headset
from each and every jack returning to the audio source, be it radio, audio
panel or intercom?
Your audio source to the headset will amplify whatever signal it sees between its'
input and input common, generally audio lo, chassis or some other airframe
referenced ground connection. Likewise, what ever is connected to its' output
will hear whatever voltage is seen between the hot or high connection and lo,
return, chassis or whatever you wish to call it. Should some unwanted voltage
also get stuck in there, it too will be heard. As you turn up the comm audio
and the offending noise is not increased, it would be safe to assume the offending
signal is after the volume control you are adjusting. In a similar manner,
you adjust headset volume and the noise changes; the source is before the
control.
Your headphones may well just be hearing some voltage drop caused by airframe currents
between the jack where you connect them and the piece of gear at the other
end of the wire to the jack.
I called PlanePower to inquire about filter and they informed me that their product
has internal noise filtering and that I must have an audio ground problem.
When the alternator is switched off-line, the audio is crystal clear.
So the offending source would seem to be the alternator; it's off, no noise. But
how is the alternator noise getting into the headset? Even a good alternator
is going to make some noise when under load. It's our duty to minimize how that
noise can make it into unwanted places.
If there was an audio grounding issue I would expect to hear ignition noise too,
but thats not the case.
Generally ignition noise is radiated noise, not noise in the form of airframe current,
so you could easily have (or not) ignition noise (generally) totally unrelated
to stray currents causing unwanted voltage drops in audio circuits.
Can additional filtering be installed external to the alternator? Suggestions please.
Generally, additional filtering can be added and may help. But is that just a band
aid covering up some other undiscovered issue that, if corrected, would yield
an even better solution...
Ron Q.
<html><body>
<DIV>Thanks Ron.</DIV>
<DIV> </DIV>
<DIV>This is a new RV-7 aircraft and installation...been there since day one on
both audio jacks . I have a Garmin 347 audio panel with an SL-40 comm...both
prewired by Stark's. I do have the insulating washers on the jacks with a
dedicated ground (unshielded) wired to a central ground. I also have a KX 155
navcomm w/glideslope -- the noise is there with either comm.</DIV>
<DIV> </DIV>
<DIV>Bill</DIV>
<DIV> </DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px
solid">-------------- Original message -------------- <BR>From: Ron Quillin
<rjquillin@gmail.com> <BR>At 08:20 12/20/2007, you wrote:<BR>
<BLOCKQUOTE class=cite cite="" type="cite"><FONT size=2> I have a PlanePower
alternator and have noticed a whine noise in the David Clark headset audio.
It is really noisy if the headset volume is high; however, if I turn the headset
volume down low and turn the comm radio volume up to compensate, the whine
is barely detectable. Can anyone explain this and/or provide possible solutions?
</FONT></BLOCKQUOTE><BR>Is this something new, and if so, what has changed?<BR>Only
your headset, or also pax headsets?<BR>You don't mention what you have
for an audio/intercom system....<BR><BR>A question.<BR>Is each and every headset
audio and microphone jack ground bushing insulated from and do not rely
on an airframe connection for the 'return' to the source equipment? That
is, are there dedicated ground returns for the microphone and headset from each
and every jack returning to the audio source, be it radio, audio panel or intercom?<BR><BR>Your
audio source to the headset will
ampli
fy whatever signal it sees between its' input and input common, generally audio
lo, chassis or some other airframe referenced ground connection. Likewise,
what ever is connected to its' output will hear whatever voltage is seen between
the hot or high connection and lo, return, chassis or whatever you wish
to call it. Should some unwanted voltage also get stuck in there, it too
will be heard. As you turn up the comm audio and the offending noise is
not increased, it would be safe to assume the offending signal is after the
volume control you are adjusting. In a similar manner, you adjust headset
volume and the noise changes; the source is before the control. <BR><BR>Your
headphones may well just be hearing some voltage drop caused by airframe
currents between the jack where you connect them and the piece of gear at the
other end of the wire to the jack.<BR><BR>
<BLOCKQUOTE class=cite cite="" type="cite"><FONT size=2>I called PlanePower to
inquire about filter and they informed me that their product has internal noise
filtering and that I must have an audio ground problem. When the alternator
is switched off-line, the audio is crystal clear. </FONT></BLOCKQUOTE><BR>So the
offending source would seem to be the alternator; it's off, no noise. But how
is the alternator noise getting into the headset? Even a good alternator
is going to make some noise when under load. It's our duty to minimize how
that noise can make it into unwanted places.<BR><BR>
<BLOCKQUOTE class=cite cite="" type="cite"><FONT size=2>If there was an audio grounding
issue I would expect to hear ignition noise too, but thats not the case.
</FONT></BLOCKQUOTE><BR>Generally ignition noise is radiated noise, not noise
in the form of airframe current, so you could easily have (or not) ignition
noise (generally) totally unrelated to stray currents causing unwanted voltage
drops in audio circuits.<BR><BR>
<BLOCKQUOTE class=cite cite="" type="cite"><FONT size=2>Can additional filtering
be installed external to the alternator? Suggestions please.</FONT></BLOCKQUOTE><BR>Generally,
additional filtering can be added and may help. But is that
just a band aid covering up some other undiscovered issue that, if corrected,
would yield an even better solution...<BR><BR>Ron Q.<BR><BR><PRE><B><FONT face="courier
new,courier" color=#000000 size=2>
</B></FONT></PRE></BLOCKQUOTE>
<pre><b><font size=2 color="#000000" face="courier new,courier">
</b></font></pre></body></html>
Message 12
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Subject: | RV-List: good warning labe |
I got some beautiful braided steel lines from Earl's Indy. Purchased
via the telephone. Great service. However, I failed to specify 37=B0
fittings. Auto use 45=B0 fittings. I had to reorder which was an
expensive lesson. Earl's Indy did stock the 37=B0 fittings and didn't
blanch when I said it was for an experimental airplane.
Earl's Indy =BB 1-800-331-INDY
Earl's Indy, Your one stop for Earl's Performance Parts.
www.earlsindy.com/ - 5k - Cached - Similar pages
Charlie Brame
RV-6A N11CB
San Antonio
-------------------------------------------
Time: 03:10:44 PM PST US
From: "Don Hall" <dhall@donka.net>
Subject: RV-List: good warning label.
Your ironic humor for today:
I'm adding the matco parking brake and needed to order some shorter
brake
lines. Found some 20" steel braided straight an4 lines from an online
auto/performance website.
They came with the label: "Warning: Competition/Off Road Use Only. Not
approved for highway use."
Hmmm. Well. I do hope to go "off road", so I'm thinking I should be
good.
******************************************
Don Hall
N517DG (registered)
rv7 finishing
******************************************
Message 13
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Subject: | swapping two radios using 3P/DT switch? |
Bob and/or other electronics gurus--
I'm using revision 11 and looking at chapter 11 (switches) and also the FAQ's...I
have attached an excerpt from the FAQ's that I think applies to my question
as well...it's a gentleman inquiring about using either a "3PDT" switch (I
think numerically this is a "3-3 switch"?) to change between two comm radios.
If I have a panel mount comm radio (with it's own antenna) and a portable comm
radio (an SP-200 with it's own antenna) and a simple two-place intercom system
(i.e. PM 3000), I believe I need the above referenced three-pole double-throw
(3-3) switch to swap between the two radios: a pole for the wire going to
the headset earphones, a pole for the wire coming from the headset microphone,
and a pole to swap the PTT line. By doing this, I can swap radios without having
to go through the intercom system which is in-line with your philosophy (which
I agree with) of minimizing knob-twisting distractions. I don't see any
examples of triple pole switches in the book and I can't find any in the Spruce
catalog, but if I'm thinking correctly, do you have a suggested resource for
obtaining one? Otherwise is there another switching logic I should consider?
Once again, everyone please feel free to shoot holes in my ideas. Thanks.
Lincoln Keill
Sacramento, CA
My plane is equipped with an old King KX170B, Microair 720, with a Sigtronics
SPA 400
intercom. I have interconnected them with a simple switching arrangement that
allows selecting
comm1 (King), comm 2, (MicroAir), both (audio only), nav (audio for ident). My
problem is, I've
describe my circuitry to a good A&P, and I think I've improperly wired the switches
for comm
selection. I've used a DPDT miniature toggle to switch the Mic audio and Headset
audio to
either comm1, or comm 2, with a SPST miniature toggle to either connect or remain
open
across the headset audio switch lugs of the DPDT switch. The configuration works,
and
communications are clear, according to all reports I've received during the last
year. My A&P
tells me that I should have also included the transmitter key line in the switch,
using a 3PDT
switch, so as to key up the proper transmitter. My gut tells me he's right, but
now I'm curious to
know why the simpler circuit I've used hasn't caused problems during the last
year. Many times
I've had both radios tuned to the same frequency, and keying the mike has never
created the
squeal normally associated with two transmitters using the same frequency at
the same time. In
fact, the radio not selected will receive the information transmitted by the
other. I've used a
hand-held radio to double check, and can not detect any keying of the transmitter
section of the
non-selected radio when the PTT switch is keyed, and I know that the transmit
key line is
connected to both radios directly. What am I missing?
A If you have confirmed that the non-selected transmitter is indeed passive then
you're
probably okay. I'm at a loss to explain why you are not having problems . . .
the standard
practice since day one has been to switch both mic-audio and PTT lines for the
selected
transmitter. The only thing I can think of is that some modern transmitters I've
seen don't need
the PTT line to make the transfer from receive to transmit. Microphones should
break both the
PTT and Mic-Audio lines when the PTT button is relaxed. This allows different
microphones to
share the same input to the transmitter without interfering with each other.
Many modern amateur transmitters sense the microphone power current draw when
a
microphone is connected to the audio circuit via the PTT switch and use this
to deduce the need
to transfer from receive to transmit.
Message 14
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Subject: | Re: swapping two radios using 3P/DT switch? |
3PDT and 4PDT switches are easy to get at online electronics stores like
Digikey.
----- Original Message -----
From: Lincoln Keill
To: aeroelectric-list@matronics.com
Sent: Thursday, December 20, 2007 9:09 PM
Subject: AeroElectric-List: swapping two radios using 3P/DT switch?
Bob and/or other electronics gurus--
I'm using revision 11 and looking at chapter 11 (switches) and also
the FAQ's...I have attached an excerpt from the FAQ's that I think
applies to my question as well...it's a gentleman inquiring about using
either a "3PDT" switch (I think numerically this is a "3-3 switch"?) to
change between two comm radios.
If I have a panel mount comm radio (with it's own antenna) and a
portable comm radio (an SP-200 with it's own antenna) and a simple
two-place intercom system (i.e. PM 3000), I believe I need the above
referenced three-pole double-throw (3-3) switch to swap between the two
radios: a pole for the wire going to the headset earphones, a pole for
the wire coming from the headset microphone, and a pole to swap the PTT
line. By doing this, I can swap radios without having to go through the
intercom system which is in-line with your philosophy (which I agree
with) of minimizing knob-twisting distractions. I don't see any
examples of triple pole switches in the book and I can't find any in the
Spruce catalog, but if I'm thinking correctly, do you have a suggested
resource for obtaining one? Otherwise is there another switching logic
I should consider? Once again, everyone please feel free to shoot holes
in my ideas. Thanks.
Lincoln Keill
Sacramento, CA
Message 15
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Subject: | Re: swapping two radios using 3P/DT switch? |
Lincoln,
Check ebay Item number: 180195626322
They seem to be primarily used in audio (musical instruments, guitar parts) circuits.
It's a push-button (foot operated) switch but might could be adapted to
your use.
I just found a 3PDT toggle switch available from MPJA (Marlin P. Jones & Associates)
online
http://www.MPJA.com/ ( http://www.mpja.com/prodinfo.asp?number=16075+SW )
Try to search 3PDT switch in Google for more options.
Good building and great flying,
Bob Borger
On Thursday, December 20, 2007, at 02:26PM, "Lincoln Keill" <airlincoln@sbcglobal.net>
wrote:
>Bob and/or other electronics gurus--
>
> I'm using revision 11 and looking at chapter 11 (switches) and also the FAQ's...I
have attached an excerpt from the FAQ's that I think applies to my question
as well...it's a gentleman inquiring about using either a "3PDT" switch (I
think numerically this is a "3-3 switch"?) to change between two comm radios.
>
> If I have a panel mount comm radio (with it's own antenna) and a portable comm
radio (an SP-200 with it's own antenna) and a simple two-place intercom system
(i.e. PM 3000), I believe I need the above referenced three-pole double-throw
(3-3) switch to swap between the two radios: a pole for the wire going to
the headset earphones, a pole for the wire coming from the headset microphone,
and a pole to swap the PTT line. By doing this, I can swap radios without having
to go through the intercom system which is in-line with your philosophy
(which I agree with) of minimizing knob-twisting distractions. I don't see any
examples of triple pole switches in the book and I can't find any in the Spruce
catalog, but if I'm thinking correctly, do you have a suggested resource for
obtaining one? Otherwise is there another switching logic I should consider?
Once again, everyone please feel free to shoot holes in my ideas. Thanks.
>
> Lincoln Keill
> Sacramento, CA
Message 16
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Subject: | Re: swapping two radios using 3P/DT switch? |
wouldnt you want to leave both audios available? This can be done by joining the
audio lines or through series resistors of around 100 ohms if you dont use an
audio panel. Just turn the volume down on the radio not being used.
Most GA aircraft use a DPDT toggle switch (C150) or DP rotary switch (C152/C172-182)
to select the transmitter for the mic / PTT.
Ralph
--------
Ralph - CH701 / 2200a
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=153361#153361
Message 17
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Subject: | Re: Audio isolation amp questions |
Thanks for the response, Bob. I did a little more thorough search of the archives
and found answers to everything in there (don't know why I couldn't find them
for the past few days), but thanks for taking the time anyway.
Dave Hyde
Message 18
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Subject: | Re: swapping two radios using 3P/DT switch? |
Steinair have a selection, which they say are used for audio switching
etc
----- Original Message -----
From: Rob Turk
To: aeroelectric-list@matronics.com
Sent: Thursday, December 20, 2007 8:46 PM
Subject: Re: AeroElectric-List: swapping two radios using 3P/DT
switch?
3PDT and 4PDT switches are easy to get at online electronics stores
like Digikey.
----- Original Message -----
From: Lincoln Keill
To: aeroelectric-list@matronics.com
Sent: Thursday, December 20, 2007 9:09 PM
Subject: AeroElectric-List: swapping two radios using 3P/DT switch?
Bob and/or other electronics gurus--
I'm using revision 11 and looking at chapter 11 (switches) and also
the FAQ's...I have attached an excerpt from the FAQ's that I think
applies to my question as well...it's a gentleman inquiring about using
either a "3PDT" switch (I think numerically this is a "3-3 switch"?) to
change between two comm radios.
If I have a panel mount comm radio (with it's own antenna) and a
portable comm radio (an SP-200 with it's own antenna) and a simple
two-place intercom system (i.e. PM 3000), I believe I need the above
referenced three-pole double-throw (3-3) switch to swap between the two
radios: a pole for the wire going to the headset earphones, a pole for
the wire coming from the headset microphone, and a pole to swap the PTT
line. By doing this, I can swap radios without having to go through the
intercom system which is in-line with your philosophy (which I agree
with) of minimizing knob-twisting distractions. I don't see any
examples of triple pole switches in the book and I can't find any in the
Spruce catalog, but if I'm thinking correctly, do you have a suggested
resource for obtaining one? Otherwise is there another switching logic
I should consider? Once again, everyone please feel free to shoot holes
in my ideas. Thanks.
Lincoln Keill
Sacramento, CA
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