Today's Message Index:
----------------------
1. 06:53 AM - Aero-Electric Chat Room (John Wayne)
2. 07:31 AM - AEC9011 and other worries . . . (Robert L. Nuckolls, III)
3. 07:44 AM - BATTERY MASTER SWITCH (Fergus Kyle)
4. 08:09 AM - Re: Aero-Electric Chat Room (Robert L. Nuckolls, III)
5. 08:33 AM - Re: Intermittent vs. Continuous Duty Contactors (was batteries)... (John McMahon)
6. 09:32 AM - Optimal bus voltage set point . . . (Robert L. Nuckolls, III)
7. 09:35 AM - Re: Intermittent vs. Continuous Duty Contactors (was batteries)... (Robert L. Nuckolls, III)
8. 01:37 PM - Strobe whoop whoop wine (Ken)
9. 02:21 PM - Re: ...T-shirts.. (Gilles Thesee)
10. 06:11 PM - Antenna for second com radio ()
11. 06:14 PM - Powering a Camcorder to Record Flight Tests (r falstad)
12. 06:44 PM - Re: Powering a Camcorder to Record Flight Tests (Carl Morgan)
13. 07:11 PM - Re: Powering a Camcorder to Record Flight Tests (Eric M. Jones)
14. 07:13 PM - Re: Powering a Camcorder to Record Flight Tests (Ernest Christley)
15. 07:32 PM - Re: Powering a Camcorder to Record Flight Tests (Bob McCallum)
16. 07:50 PM - Re: Powering a Camcorder to Record Flight Tests (Ron Quillin)
17. 09:10 PM - Re: Powering a Camcorder to Record Flight Tests (S. Ramirez)
18. 10:00 PM - Re: Homemade Aviation Headset (Carl Peters)
19. 10:05 PM - Re: Homemade Aviation Headset (Bill Maxwell)
Message 1
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| Subject: | Aero-Electric Chat Room |
I have recently found the AeroElectric-List Digest Archive.
Unfortunately, it appears to have become a chat room instead of a
constructive exchange of useful information.
I would hope that it would return to what I believe was its original
intent.
John K. Wayne
Message 2
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| Subject: | AEC9011 and other worries . . . |
>Hope your trip to Osh went well. I am still interested in the AEC9011
>module for the Z-19RB diagram. Can you give me an estimate as to when
>this module will be available? I will be using the Eggenfellner engine
>with an internally regulated alternator. Can you also give me design
>modifications to your schematic to suit this application? I wish I could
>use an externally regulated alternator, but at this time that isn t an
>option.
I'm not sure that's true. I'm told that Plane Power is
going to be offering an externally regulated alternator.
Check with them to see how long that will be.
Keep in mind that you don't need an alternator
installed on your airplane until time for first
flight. How far away are you from flying? I wouldn't
spend a LOT of time praying over present options especially
if a lack of understanding and knowledge may be
driving your anxiety levels upward.
>There surely is something I can include in my design to make this
>alternator application as safe as possible. Eggenfellner isn t offering
>any changes in alternator options. Your help would be greatly
>appreciated. I am working with Tim Hedding from B&C Electronics and
>purchasing all hardware from their supply if available. You might be more
>aware of what they stock and recommend something.
Beyond incorporation of ov protection there are
no SAFETY issues that should drive your alternator
selection. Many folks seem to feel that they're
flying around with a fused bomb that only waiting
for some opportune time to light up and ruin their
day. Alternators are indeed capable of extreme
and expensive misbehavior but they are never
a safety concern in a properly architectured,
adequately maintained system, only a cost-of-
ownership concern.
>Do I need a separate avionics master switch for the Z-19 design? Everyone
>seems to think about protecting the avionics, or is the 7A fuse to the
>E-bus built-in protection?
Go to the website front page and do a search on
"avionics master". If one were useful, it would have
appeared on the Z-figures.
> Can the (1-7) switch for the volt meter be exchanged for a (2-1)
> switch? This might give the option of continuous monitoring voltage on
> either battery.
Yes, you can adjust functionality of any Z-figure
to address your wants and desires. The Z-figures are
illustrations of architecture with some parts selection
and system fabrication details. But the primary value
of the Z-figures are to lay the ground-work for
a minimum-parts count, simplest-operation system to
achieve the desired operability.
If it's absolutely necessary that a decision be made
today, get a Plane Power alternator. Install the AEC9011
when it becomes available later this summer and you'll
be done.
If you can provide me with a set of Eggenflener's
drawings, perhaps I can tailor Z-19 to be a tad more
specific to this engine.
Bob . . .
Message 3
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| Subject: | BATTERY MASTER SWITCH |
Cheers,
I'm still searching for that elusive device - in an attempt to avoid
the cost of an ampere or two of contactor current - which will control a
primary battery source and another for secondary battery source.
I have found several which meet one criterion or another, but not
all:
[a] should carry as much current as a contactor for that job;
[b] needs to be an up-down rather than rotary type switch;
[c] should be on a remote(able) stalk so I can undo the connection to
remove the instrument panel ;
[d] cost less than the usual contactor - or at least be competitive.
I have devised a system to isolate the controls from wandering
fingers so am not fussy about security. I'm not sure what a "Kill switch" is
really.
Any help would be most appreciated.
Ferg
Classic 914 CS prop mono
PS: My server is down for the last 2 days, so my thanks will be
delayed.........
Message 4
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| Subject: | Re: Aero-Electric Chat Room |
At 09:53 AM 8/6/2007 -0400, you wrote:
>I have recently found the AeroElectric-List Digest
>Archive. Unfortunately, it appears to have become a chat room instead of
>a constructive exchange of useful information.
>
>I would hope that it would return to what I believe was its original intent.
This is a fundamental condition for every "wide open"
forum. This is why one needs to be adept at using the
search functions. You'll find that adjustment of search
terms and honing your scanning skills will offer a strong
filtering function for separating chaff from the good stuff.
The archives were never intended to be a short-cut, in
fact it may be a longer path to the answer sought than
to simply repeat the topic on today's postings. However,
the archives offer a greater depth of coverage than
you might get from a lick-and-a-promise exchange on
the current list.
I'm sorry my friend but education is never a simple,
time-frugal endeavor. If it were, everybody would be
smart.
I've attempted to condense the salient features of
some topics into articles on the website. I'll suggest
you being with a search at
http://aeroelectric.com
and expand the search if you don't get the needed help
there.
Bob . . .
Message 5
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| Subject: | Re: Intermittent vs. Continuous Duty Contactors (was |
batteries)...
Greg or Bob , I know that there is an electrical way of telling the two
apart in the Connection, but do you know if there is a way to tell them
apart visually? All mine as they came with the firewall from Lancair seem
to look alike, even to the stenciled numbers on them?
> **
>
--
John McMahon
Lancair Super ES, S/N 170, N9637M (Reserved)
Message 6
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| Subject: | Optimal bus voltage set point . . . |
>Comments/Questions: I plan on using a gell cell battery in my Glasair and
>have been told that I must set the charging voltage at a different level
>if I do not want to damage the battery. No one is able to tell me what
>voltage level I should use.So much for these self styled experts ,eh?
>Can you help?
>Stan
No special considerations. Set for 14.2 volts nominal.
There ARE "optimal" modes of operation for best life
in the lab . . . which are generally impractical in the
field and overshadowed by other, much more significant
stresses.
Install it, run it, check for capacity after first
year and replace when capacity drops below your
personally defined endurance minimums. The act of
"tweaking" nominal bus voltage for the purpose of
maximizing service life will be exceedingly difficult
to validate and probably not improve on service life
by more than a few percent.
Bob . . .
----------------------------------------
( IF one wishes to be "world class" at )
( anything, what ever you do must be )
( exercised EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
Message 7
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| Subject: | Re: Intermittent vs. Continuous Duty Contactors (was |
batteries)...
At 09:32 AM 8/6/2007 -0600, you wrote:
>Greg or Bob , I know that there is an electrical way of telling the two
>apart in the Connection, but do you know if there is a way to tell them
>apart visually? All mine as they came with the firewall from Lancair seem
>to look alike, even to the stenciled numbers on them?
No. Put an ohmmeter on them. A continuous duty contactor
will NEVER measure under 6 ohms while an intermittent
duty device is always under 6 ohms.
Or wire to battery and measure coil current. A tennis
ball sized contactor that dissipates more than 20 watts
is in deep doo-doo in a matter of minutes. 1.5 A draw
from a 12v battery is 18 watts . . . .
An intermittent duty device will draw 3-5 amps, 36 to
60 watts.
Bob . . .
----------------------------------------
( "Physics is like sex: sure, it may )
( give some practical results, but )
( that's not why we do it." )
( )
( Richard P. Feynman )
----------------------------------------
Message 8
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| Subject: | Strobe whoop whoop wine |
>
>
>> We have completed 130 flight hours with our Z-14 wired subaru now
>> without any nuisance OV trips. The only electrical issue is that I
>> recently purchased a comfortable David Clarke headset and with our
>> fairly quiet engine, I now hear weak but annoying strobe whine that I
>> couldn't hear in cruise with other headsets. I have already followed
>> most of your wiring recommendations so it may take me awhile to solve
>> this one especially since the strobes operate off a different
>> alternator and battery as the radio and intercom.
>
>
> Start with a test battery made up of a couple 6v
> lantern batteries to run the strobe supply with a
> short cable and batteries located right at the power
> supply. You need to deduce the propagation mode. I suspect
> it's conducted and a relatively simple filter at the
> power supply will fix it.
>
> Bob . . .
>
It is a pain to pull my wingtips to get at the aeroflash power supplies
and I have not done that yet. However I have powered the strobes from a
separate battery with their normal fuse pulled and I still hear the
noise faintly in the headset even with the engine, master switch,
intercom, and radio turned OFF. It is a bit louder with the intercom
powered up but I was not expecting to hear it with the intercom and
radio turned off. It is a metal airframe and the strobe power supplies,
the comm radio, and the intercom are all grounded to the airframe
because they are all internally grounded to their respective cases. The
headset jacks are insulated from the airframe (in a plastic box) and
wired with shielded wire. Thinking it could be a ground loop situation
I tried grounding the temporary battery to a screw on the wing spar but
it did not seem to make a difference. Adding some inductance to the
+power lead and some electrolytic capacitors made no diference.
Before I pull the wingtips I'd like to have a plan and any needed parts
on hand. I will look for some automotive radio power supply filters and
pick up some nylon bolts to insulate the power supply from the airframe.
Any other suggestions? Is there any point adding some capacitance to
the headphone audio circuit to try and bypass some of the higer
frequencies. This noise was not bothering me until I replaced one
headset with a DC H10-13.4.
thanks
Ken
Message 9
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| Subject: | Re: ...T-shirts.. |
Henador Titzoff a crit :
> They're talking about a nice song in French and Spanish...
Wait a minute...I'm French ;-)
Sorry, no moustache, no beret, no baguette...
Best regards,
--
Gilles
http://contrails.free.fr
Message 10
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| Subject: | Antenna for second com radio |
To get ready for the 2008 AirVenture Cup Race, I am conducting a drag reduction
program on my all metal Evo. I would like to eliminate one of the two external
surface com antennae from the belly.
Two options seem available, an antenna mounted in the cockpit behind the passenger
seat on the aft cockpit bulkhead, or a thin wire antenna taped to the windscreen
(not unlike the thin wire antennae found in windshields on automobiles.)
Any suggestions from the list members on how to proceed?
If I use the taped wire antenna on the windscreen, should I use the same system
as used on copper foil entennae on composite aircraft but substituting a thin
wire for the copper foil?
Thanks in advance for any help or suggestions!
Paul Siegel N4XU
Message 11
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| Subject: | Powering a Camcorder to Record Flight Tests |
I have an old analog Sony Handycam (CCD-FX310) that I'd like to mount in
the cockpit to record my upcoming flight tests. Batteries are expensive
and don't last long -- I'd like to use ship's power. It has a 110VAC to
7.5VDC power brick (Sony Model AC-V35) with a special adapter plate that
clicks into the place where the battery would go. The brick says the
output is 7.5VDC & 1.6A. I'd like to cut the cord between the brick and
the adapter plate, insert a set of connectors and make a pigtail with a
matching connector on one end and a cigarette lighter plug on the other.
Because of the voltage difference (14VDC - 7.5VDC), it looks like I'll
need about a 4 ohm resistor to drop the 6.5VDC. It looks like the power
consumption will be about 10.4 Watts. The closest thing I could find on
Radio Shack's website is either a 1 ohm or 10 ohm, 10 Amp, 10%
wire-wound power resistor (Catalog No. 271-131). There was no
indication how large they are physically. In theory, I could chain four
of the 1 ohm units together.
Is my thinking correct? All I want is to power the camcorder from
ship's power. Any recommendations on connectors and any critique on the
idea of simply putting a resistor (and a fuse) in the pigtail/circuit to
reduce the voltage? Is there any other power conditioning I should do?
Best regards,
Bob
Message 12
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| Subject: | Powering a Camcorder to Record Flight Tests |
Hi Bob,
Depending on how complicated you want to get. A LM2579 plus a few external
components (a schotty diode, a couple of caps / resistors and an inductor)
can provide a switched DC-DC step down supply <3A.
http://www.onsemi.com/pub/Collateral/LM2576-D.PDF
Total parts from digikey / mouser should be < $20 I would hope.
Regards,
Carl (working on a Canon DV camera power feed ;-)
--
ZK-VII - RV 7A QB - still finishing? - New Zealand
http://www.rvproject.gen.nz/
-----Original Message-----
From: r falstad [mailto:bobair8@msn.com]
Sent: Tuesday, 7 August 2007 1:13 p.m.
To: AEROELECTRIC LIST
Subject: AeroElectric-List: Powering a Camcorder to Record Flight Tests
I have an old analog Sony Handycam (CCD-FX310) that I'd like to mount in
the cockpit to record my upcoming flight tests. Batteries are expensive and
don't last long -- I'd like to use ship's power. It has a 110VAC to 7.5VDC
power brick (Sony Model AC-V35) with a special adapter plate that clicks
into the place where the battery would go. The brick says the output is
7.5VDC & 1.6A. I'd like to cut the cord between the brick and the adapter
plate, insert a set of connectors and make a pigtail with a matching
connector on one end and a cigarette lighter plug on the other.
Because of the voltage difference (14VDC - 7.5VDC), it looks like I'll
need about a 4 ohm resistor to drop the 6.5VDC. It looks like the power
consumption will be about 10.4 Watts. The closest thing I could find on
Radio Shack's website is either a 1 ohm or 10 ohm, 10 Amp, 10% wire-wound
power resistor (Catalog No. 271-131). There was no indication how large
they are physically. In theory, I could chain four of the 1 ohm units
together.
Is my thinking correct? All I want is to power the camcorder from ship's
power. Any recommendations on connectors and any critique on the idea of
simply putting a resistor (and a fuse) in the pigtail/circuit to reduce the
voltage? Is there any other power conditioning I should do?
Best regards,
Bob
Message 13
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| Subject: | Re: Powering a Camcorder to Record Flight Tests |
Your calculations on how to do this show why it isn't usually done with resistors.
Resistors also presume constant load, which in general is not often true.
If you had to do this in a hurry you could simply wire a 6V lamp in series. But
the right way to do it is a linear regulator chip like the LM350.
See: http://www.national.com/mpf/LM/LM350.html. The LM317 can be used, but is 1.5A. The LM350 is the same part at 3A.
"Don't worry about people stealing an idea. If it's original, you will have to
ram it down their throats."
-- Howard Aiken
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones@charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=127880#127880
Message 14
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| Subject: | Re: Powering a Camcorder to Record Flight Tests |
r falstad wrote:
> I have an old analog Sony Handycam (CCD-FX310) that I'd like to mount in the
cockpit to record my upcoming flight tests. Batteries are expensive and don't
last long -- I'd like to use ship's power. It has a 110VAC to 7.5VDC power brick
(Sony Model AC-V35) with a special adapter plate that clicks into the place
where the battery would go. The brick says the output is 7.5VDC & 1.6A. I'd
like to cut the cord between the brick and the adapter plate, insert a set
of connectors and make a pigtail with a matching connector on one end and a cigarette
lighter plug on the other.
>
> Because of the voltage difference (14VDC - 7.5VDC), it looks like I'll need about
a 4 ohm resistor to drop the 6.5VDC. It looks like the power consumption
will be about 10.4 Watts. The closest thing I could find on Radio Shack's website
is either a 1 ohm or 10 ohm, 10 Amp, 10% wire-wound power resistor (Catalog
No. 271-131). There was no indication how large they are physically. In
theory, I could chain four of the 1 ohm units together.
>
> Is my thinking correct? All I want is to power the camcorder from ship's power.
Any recommendations on connectors and any critique on the idea of simply
putting a resistor (and a fuse) in the pigtail/circuit to reduce the voltage?
Is there any other power conditioning I should do?
>
> Best regards,
>
> Bob
>
>
Seems to be a lot of work for a temporary use that could be holding up
your flight tests. You can get a 70watt inverter for about $20 that
will plug into the cigarette lighter jack. Then you can use your
adapter plate as-is, don't have to worry that you got all the
electronics modified correctly, and won't regret cutting the cord at
some point in the future.
--
"Life is not a journey to the grave with the intention of arriving safely in
a pretty and well preserved body, but rather to skid in broadside,
thoroughly used up, totally worn out, with chocolate in one hand and wine in
the other, loudly proclaiming 'WOO HOO What a Ride!'"
--Unknown
Message 15
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| Subject: | Re: Powering a Camcorder to Record Flight Tests |
Bob;
One of the shortcomings of doing it with a simple resistor is that the
Camcorder's current draw will vary as you record, or go to standby,
zoom, or turn it on/off etc. (It's not constant at that 1.6 Amp figure,
that's just a max) Therefore the voltage you're applying to it will vary
(perhaps drastically, all the way up to the supply voltage) and the
camcorder may not like that. (As the current requirement falls so does
the voltage drop across your resistor and therefore a greater voltage is
applied to your camcorder than you planned for)
Bob McC
----- Original Message -----
From: r falstad
To: AEROELECTRIC LIST
Sent: Monday, August 06, 2007 9:13 PM
Subject: AeroElectric-List: Powering a Camcorder to Record Flight
Tests
I have an old analog Sony Handycam (CCD-FX310) that I'd like to mount
in the cockpit to record my upcoming flight tests. Batteries are
expensive and don't last long -- I'd like to use ship's power. It has a
110VAC to 7.5VDC power brick (Sony Model AC-V35) with a special adapter
plate that clicks into the place where the battery would go. The brick
says the output is 7.5VDC & 1.6A. I'd like to cut the cord between the
brick and the adapter plate, insert a set of connectors and make a
pigtail with a matching connector on one end and a cigarette lighter
plug on the other.
Because of the voltage difference (14VDC - 7.5VDC), it looks like I'll
need about a 4 ohm resistor to drop the 6.5VDC. It looks like the power
consumption will be about 10.4 Watts. The closest thing I could find on
Radio Shack's website is either a 1 ohm or 10 ohm, 10 Amp, 10%
wire-wound power resistor (Catalog No. 271-131). There was no
indication how large they are physically. In theory, I could chain four
of the 1 ohm units together.
Is my thinking correct? All I want is to power the camcorder from
ship's power. Any recommendations on connectors and any critique on the
idea of simply putting a resistor (and a fuse) in the pigtail/circuit to
reduce the voltage? Is there any other power conditioning I should do?
Best regards,
Bob
Message 16
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| Subject: | Re: Powering a Camcorder to Record Flight Tests |
At 19:13 8/6/2007, you wrote:
>Seems to be a lot of work for a temporary use that could be holding
>up your flight tests. You can get a 70watt inverter for about $20
>that will plug into the cigarette lighter jack. Then you can use
>your adapter plate as-is, don't have to worry that you got all the
>electronics modified correctly, and won't regret cutting the cord at
>some point in the future.
Or just <horrors> purchase a car-cord for the unit...
http://www.ebuybatteries.com/product/models/2_Sony-NP-77-AC-charger_Sony+CCD-FX310.htm
http://www.dc-battery.com.au/sony-np77-battery-charger-p-1330.html
Message 17
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| Subject: | Powering a Camcorder to Record Flight Tests |
Bob,
Th other guys are correct about using a resistor to drop the voltage.
It
will have varying voltage at the load, as it draws varying current. Not
a
good way to go.
You need a voltage regulator. Someone earlier suggested that you need a
linear voltage regulator. The problem with this solution is that it
will
dissipate (not consume) 6.5V*1.6A = 10.4W. That's a lot of power, and
you
will have to heat sink it very heftily. It does have the advantage of
providing the cleanest output, though, if you can handle the heat
sinking.
Another solution is to go with a packaged switching voltage regulator.
Digi-Key has the TI PT78HT208H (Digi-Key pn 296-20250-ND) in stock for
USD
$16.20. It outputs 8.0V at 2.0A all day long. Can you handle 8.0V =B1
2%?
Can you handle output voltage ripple of =B11% (0.08V)? If you can, this
may
be the way to go. This part comes in an EFA package, which is about 1
inch
X .90 inch X .31 inch.
Unfortunately, it needs a 1 uF ceramic capacitor C1 at the input and a
100
uF electrolytic capacitor C2 at the output. Here are some examples:
Digi-Key pn493-1283-ND
100 uF, 16V, electrolytic, radial, 20%, general purpose, min buy
1,
price USD $0.14 each
Digi-Key pn 478-4504-ND
1 uF, 50V, ceramic, 10%, radial, general purpose, min buy 1,
price
USD $9.02 each
All parts above are RoHS, so soldering will be about the same temp.
Since Digi-Key has a USD $5 handling charge for orders less than USD
$25,
you can throw these caps into the same order to get it above $25. I
would
strongly advise you looking at the datasheets to know what you are
getting
into, but I believe that this combo of parts would suit your
requirements,
if you can handle 8 VDC =B1 the tolerances above.
Simon Ramirez, Aerocanard Builder
Flying LEZ
Copyright =A9 2007
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of r
falstad
Sent: Monday, August 06, 2007 9:13 PM
Subject: AeroElectric-List: Powering a Camcorder to Record Flight Tests
I have an old analog Sony Handycam (CCD-FX310) that I'd like to mount in
the
cockpit to record my upcoming flight tests. Batteries are expensive and
don't last long -- I'd like to use ship's power. It has a 110VAC to
7.5VDC
power brick (Sony Model AC-V35) with a special adapter plate that clicks
into the place where the battery would go. The brick says the output is
7.5VDC & 1.6A. I'd like to cut the cord between the brick and the
adapter
plate, insert a set of connectors and make a pigtail with a matching
connector on one end and a cigarette lighter plug on the other.
Because of the voltage difference (14VDC - 7.5VDC), it looks like I'll
need
about a 4 ohm resistor to drop the 6.5VDC. It looks like the power
consumption will be about 10.4 Watts. The closest thing I could find on
Radio Shack's website is either a 1 ohm or 10 ohm, 10 Amp, 10%
wire-wound
power resistor (Catalog No. 271-131). There was no indication how large
they are physically. In theory, I could chain four of the 1 ohm units
together.
Is my thinking correct? All I want is to power the camcorder from
ship's
power. Any recommendations on connectors and any critique on the idea
of
simply putting a resistor (and a fuse) in the pigtail/circuit to reduce
the
voltage? Is there any other power conditioning I should do?
Best regards,
Bob
7.5.476 /
Message 18
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| Subject: | Re: Homemade Aviation Headset |
Getting ready to do the same, and have all the parts and an old headset
to gut for the mic, cords, and plugs.
A couple simple Q's:
1) And the most basic of questions - if I build a stereo headset, is
there any problem with a stereo plug in a mono intercom system jack? I
assume I will just hear monaural sound.
2) One builder put in pots and another just added resistors to adjust
the ear speakers to match other headsets (in case someone flying with
you uses a different headset) - has anyone built one without these? I
guess I will need to experiment, and it will depend on the sensitivity
of the in-ear speakers. I did get the Comply headset with their
proprietary tips that are wonderful. The set looks to be the same from
TrickAudio. Haven't tested in the air, but cuts out the wife and kids
nicely...I mean excessive noises. After two hours in the ear, the
comfort is wonderful - really don't notice the tips. The set is nice
enough that I will have it jack separately into the project box so I can
use them elsewhere besides the plane.
http://www.canardzone.com/members/nickugolini/CuplessHeadet/cupless_headset.htm
http://www.cozy1200.com/geeklog/index.php
http://www.trickearphones.com/index.htm
Carl
Message 19
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| Subject: | Re: Homemade Aviation Headset |
and if you run two such headsets at the same time, the 1000 ohms falls to
500 ohms, a much better match?
Bill
----- Original Message -----
From: "Bob White" <bob@bob-white.com>
Sent: Monday, August 06, 2007 2:02 AM
Subject: Re: AeroElectric-List: Homemade Aviation Headset
>
> On Sun, 5 Aug 2007 10:16:47 -0400
> "Bill Bradburry" <bbradburry@bellsouth.net> wrote:
>
>> <bbradburry@bellsouth.net>
>>
>> I am considering trying to make a headset as is described in the link
>> below:
>>
>> http://www.cozy1200.com/geeklog/article.php?story 070427102533266
>>
>> I am confused by the fact that the transformer he suggests to use from
>> Radio
>> Shack is 1000 ohm input/8 ohm output. The plane system is going to be
>> looking for a 600 ohm input???
>>
>> What will this 1000 ohm transformer do to the plane system? Will it harm
>> it? Will the system output be louder or softer with the 1000 ohm than it
>> would have been with a 600 ohm transformer?
>>
>> If I knew what I was doing here I would probably afraid to proceed. As
>> it
>> is I am fearless....:>)
>>
>> Thanks for your assistance.
>>
>> Bill B
>
> Hi Bill,
>
> The 1000 ohm transformer will not load a 600 ohm circuit quite as
> much. In audio circuits, you need to match impedance to maximize power
> transfer. If you don't need maximum power transfer, and you probably
> don't, it should work just fine.
>
> Bob W.
>
> --
> N93BD - Rotary Powered BD-4 - http://www.bob-white.com
> 3.8 Hours Total Time and holding
> Cables for your rotary installation - http://www.roblinphoto.com/shop/
>
>
>
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