Today's Message Index:
----------------------
1. 05:04 AM - Transponder antenna distance (Michael Lazarowicz)
2. 06:09 AM - Re: Transponder antenna distance (Tcwtech)
3. 07:01 AM - Re: Transponder antenna distance (Rene)
4. 07:08 AM - Re: Transponder antenna distance (Charlie England)
5. 07:22 AM - Re: Saggy bus voltage on Cessna 182 (Alec Myers)
6. 07:31 AM - Re: Transponder antenna distance (Michael Lazarowicz)
7. 09:16 AM - Re: Saggy bus voltage on Cessna 182 (Robert L. Nuckolls, III)
8. 12:30 PM - Re: Saggy bus voltage on Cessna 182 (Alec Myers)
9. 07:35 PM - Re: Saggy bus voltage on Cessna 182 (Alec Myers)
10. 08:36 PM - saggy bus voltage on Cessna 182 (Paul Millner)
Message 1
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| Subject: | Transponder antenna distance |
Just when I think I have thought of everything in my G3X installation
something else comes up. I have a GTX23ES transponder that is a a remote
mount. I decided to mount it in the tail section where the rear battery
mount is. It worked well there because of weight and balance and I figured
my cable run to the Antenna would be short and out of the way of everything
else. I missed a requirement in the Garmin Manual that says the Antenna
should be 3 feet from the unit. I plande to out eh antenna just behind
unit on the belly. I will also have a ADSB antenna on the rear belly and
know that it needs to be 3' from the T-ponder antenna according to gamin.
Am I correct in assuming that the same RF problem will exist with the ADSB
being to close to the transponder unit itself ?
I have found at least one Installer that has the transponder unit within a
foot of the antenna and has had no problems.
Trying to keep all the antennas separated on the RV8 is not easy.
Any thoughts on this are appreciated.
Message 2
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| Subject: | Re: Transponder antenna distance |
I have my navworx ads-b box about 12" from the antenna in my rv-10 located in the
tail cone. No issues, works well for 4 years now. A full metal enclosure
transceiver, properly terminated RG-400 cable, mounted inside an aluminum tailcone
is just about as good as it gets.
Bob Newman
TCW Technologies, LLC
> On Jun 3, 2016, at 8:02 AM, Michael Lazarowicz <tllaz330@gmail.com> wrote:
>
> Just when I think I have thought of everything in my G3X installation something
else comes up. I have a GTX23ES transponder that is a a remote mount. I decided
to mount it in the tail section where the rear battery mount is. It worked
well there because of weight and balance and I figured my cable run to the
Antenna would be short and out of the way of everything else. I missed a requirement
in the Garmin Manual that says the Antenna should be 3 feet from the
unit. I plande to out eh antenna just behind unit on the belly. I will also
have a ADSB antenna on the rear belly and know that it needs to be 3' from the
T-ponder antenna according to gamin.
>
> Am I correct in assuming that the same RF problem will exist with the ADSB being
to close to the transponder unit itself ?
> I have found at least one Installer that has the transponder unit within a foot
of the antenna and has had no problems.
>
> Trying to keep all the antennas separated on the RV8 is not easy.
>
>
> Any thoughts on this are appreciated.
Message 3
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| Subject: | Transponder antenna distance |
I wonder if that is a cable length requirement or a physical distance
requirement. In my past reading I remember minimum cable length
requirements for GPS antennas. Just an opinion, I really do not know
anything. Maybe Stein knows?
Rene'
801-721-6080
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Michael Lazarowicz
Sent: Friday, June 03, 2016 6:03 AM
Subject: AeroElectric-List: Transponder antenna distance
Just when I think I have thought of everything in my G3X installation
something else comes up. I have a GTX23ES transponder that is a a
remote mount. I decided to mount it in the tail section where the rear
battery mount is. It worked well there because of weight and balance
and I figured my cable run to the Antenna would be short and out of the
way of everything else. I missed a requirement in the Garmin Manual
that says the Antenna should be 3 feet from the unit. I plande to out
eh antenna just behind unit on the belly. I will also have a ADSB
antenna on the rear belly and know that it needs to be 3' from the
T-ponder antenna according to gamin.
Am I correct in assuming that the same RF problem will exist with the
ADSB being to close to the transponder unit itself ?
I have found at least one Installer that has the transponder unit within
a foot of the antenna and has had no problems.
Trying to keep all the antennas separated on the RV8 is not easy.
Any thoughts on this are appreciated.
Message 4
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| Subject: | Re: Transponder antenna distance |
It's worth asking Garmin, but I'd bet what they really mean is 3' of
coax minimum; easy to do with a 'U' shaped run.
I'd hope that boxes intended to emit and/or receive RF energy would
contain and isolate it to the center of the coax connector. Otherwise,
you'd have issues with a lot of other 'stuff' in the plane.
Charlie
On 6/3/2016 8:07 AM, Tcwtech wrote:
>
> I have my navworx ads-b box about 12" from the antenna in my rv-10 located in
the tail cone. No issues, works well for 4 years now. A full metal enclosure
transceiver, properly terminated RG-400 cable, mounted inside an aluminum tailcone
is just about as good as it gets.
>
>
> Bob Newman
> TCW Technologies, LLC
>
>> On Jun 3, 2016, at 8:02 AM, Michael Lazarowicz <tllaz330@gmail.com> wrote:
>>
>> Just when I think I have thought of everything in my G3X installation something
else comes up. I have a GTX23ES transponder that is a a remote mount. I
decided to mount it in the tail section where the rear battery mount is. It worked
well there because of weight and balance and I figured my cable run to the
Antenna would be short and out of the way of everything else. I missed a requirement
in the Garmin Manual that says the Antenna should be 3 feet from the
unit. I plande to out eh antenna just behind unit on the belly. I will also
have a ADSB antenna on the rear belly and know that it needs to be 3' from the
T-ponder antenna according to gamin.
>>
>> Am I correct in assuming that the same RF problem will exist with the ADSB being
to close to the transponder unit itself ?
>> I have found at least one Installer that has the transponder unit within a foot
of the antenna and has had no problems.
>>
>> Trying to keep all the antennas separated on the RV8 is not easy.
>>
>>
>> Any thoughts on this are appreciated.
Message 5
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| Subject: | Re: Saggy bus voltage on Cessna 182 |
I started by looking at the voltage at the regulator terminals, which is a t
housand times easier to reach than the alternator. I took four measurements,
at idle RPM and 1600RPM, lights off and lights on.
idle (lights off/lights on)
V_bus 13.6 / 13.2
V_F 5.56 / 9.09
V_S 12.87 / 12.34
V_A 13.89 / 13.79
1600RPM (lights off/lights on)
V_bus 13.6 / 13.2
V_F 4.02 / 7.72
V_S 12.77 / 12.38
V_A 13.99 / 13.78
It's a 14v regulator.
Note: the bus voltage is displayed on the engine monitor, the others are mea
sured with my Fluke.
Does this shed any light?
On Jun 2, 2016, at 15:43, Robert L. Nuckolls, III <nuckolls.bob@aeroelectric
.com> wrote:
At 10:37 AM 6/2/2016, you wrote:
> On Thu, Jun 2, 2016 at 8:08 AM, Alec Myers <alec@alecmyers.com> wrote:
>
>
> Hello all,
>
> I wonder if I could get some ideas on fixing an electrical issue with my 1
975 Cessna 182.
>
> The issue is that the bus voltage sags under load. With the engine running
and no electrical load the voltage is approximately 13.8V, dropping to 13.2
V with daytime load (beacon, avionics, engine monitor, electrical TC, autopi
lot) and with night time lighting (add strobes, position lights, LED landing
and taxi lights, instrument lights) it drops to 12.8V
The factory spec set point for those regulators
is 14.2 +/- 0.2 volts . . . After engine start
and before turning on any additional loads, the
BUS voltage should be within those limits.
> .
>
> During flight the battery isn't fully charging and the engine start for th
e next flight I would describe as "reluctant". If I top off the battery from
a line voltage charger for a few hours the next engine start is "enthusiast
ic".
This observation rules out soggy battery. Given
the voltages you've reported, battery performance
sans external supports is understandable. A
battery will not accept significant energy
at bus voltages below 13.8 . . . and even at 13.8
it would take HOURS to top it off. This is why
the slightly excessive set-point is the legacy
value of 14.2 was selected for flooded lead-acid
batteries . . . 'slight' overcharge that quickly
tops off battery without serious 'damage'.
The sealed vented lead-acid (SLVA) likes to be
charged more aggressively . . . excerpts from
the Hawker data says:
<ea42f08.jpg>
This fact drives the B&C policy decision to factory
set their regulators to 14.6 volts.
> I have had the alternator serviced, and I have replaced the regulator. I h
ave put a 'scope on the bus with the engine running and I see steady dc with
about 50mV pp of ripple. I have a photograph of the scope trace, not sure h
ow best to make it visible to list readers, but the ripple looks like a rect
ified AC waveform with no gaps (gaps I think would indicate a failed diode).
>
> Can anyone suggest where I could look next?
Yes . . . and it is simple . . . just not easy. You need
to get a voltmeter reading at the "S" and "F" terminals
of your regulator with the engine running. "VS" should
be the 14.2 +/- 0.2 volt value (or what ever is presently
presented on the regulator's name-plate) and "VF" should
be substantially larger than zero but NOT pegged against
the bus . . . if it is pegged, then increase RPM to see
if the voltage comes off the peg.
I have had the alternator serviced, and I have replaced the regulator. I hav
e put a 'scope on the bus with the engine running and I see steady dc with a
bout 50mV pp of ripple. I have a photograph of the scope trace, not sure how
best to make it visible to list readers, but the ripple looks like a rectif
ied AC waveform with no gaps (gaps I think would indicate a failed diode).
This reading is WAAaayyy low. It should be on the order
of 1.5 volts pk-pk. 3 phase rectified DC is predicted
to have an RMS ripple voltage on the order of 4% of the DC
output. Hence 14 X 0.04 = 560 mVrms and approx 3x that
pk-pk.
If the bus voltage is that 'clean' then I think you're going
to find that the field voltage is essentially zero. Depending
on what you fine for "VS", there's probably a wiring disconnect
somewhere along the path from Bus through the alternator switch
to the OV sensor, out to the regulator and on to the alternator
"F" terminal.
Having the voltage measurements I suggested will 'divide' the
enemy in the battle toward submission.
Finally, once the stock regulator is working, you may want
to consider a more modern ADJUSTABLE device that can be
set to accommodate the special needs of SVLA batteries.
Bob . . .
Message 6
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| Subject: | Re: Transponder antenna distance |
Well I asked Garmin. and they indicated that in a mental airplane is was
probably ot going to be an issue. The manual says distance from Unit , not
cable length. The guy I talked with said this is really a bigger issue on
composite AC than on mental ones. He also noted that I could switch the
ADSB antenna with the Transponder Antenna locations since the ADSB is in
only. Fortunately I have enough Coax to do that. I will have close to 3
feet and the Coax will be at least 3 feet long from the transponder to the
antenna.
On Fri, Jun 3, 2016 at 10:10 AM, Charlie England <ceengland7@gmail.com>
wrote:
> ceengland7@gmail.com>
>
> It's worth asking Garmin, but I'd bet what they really mean is 3' of coax
> minimum; easy to do with a 'U' shaped run.
>
> I'd hope that boxes intended to emit and/or receive RF energy would
> contain and isolate it to the center of the coax connector. Otherwise,
> you'd have issues with a lot of other 'stuff' in the plane.
>
> Charlie
>
> On 6/3/2016 8:07 AM, Tcwtech wrote:
>
>>
>> I have my navworx ads-b box about 12" from the antenna in my rv-10
>> located in the tail cone. No issues, works well for 4 years now. A full
>> metal enclosure transceiver, properly terminated RG-400 cable, mounted
>> inside an aluminum tailcone is just about as good as it gets.
>>
>>
>> Bob Newman
>> TCW Technologies, LLC
>>
>> On Jun 3, 2016, at 8:02 AM, Michael Lazarowicz <tllaz330@gmail.com>
>>> wrote:
>>>
>>> Just when I think I have thought of everything in my G3X installation
>>> something else comes up. I have a GTX23ES transponder that is a a remote
>>> mount. I decided to mount it in the tail section where the rear battery
>>> mount is. It worked well there because of weight and balance and I figured
>>> my cable run to the Antenna would be short and out of the way of everything
>>> else. I missed a requirement in the Garmin Manual that says the Antenna
>>> should be 3 feet from the unit. I plande to out eh antenna just behind
>>> unit on the belly. I will also have a ADSB antenna on the rear belly and
>>> know that it needs to be 3' from the T-ponder antenna according to gamin.
>>>
>>> Am I correct in assuming that the same RF problem will exist with the
>>> ADSB being to close to the transponder unit itself ?
>>> I have found at least one Installer that has the transponder unit within
>>> a foot of the antenna and has had no problems.
>>>
>>> Trying to keep all the antennas separated on the RV8 is not easy.
>>>
>>>
>>> Any thoughts on this are appreciated.
>>>
>>
>
>
Message 7
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| Subject: | Re: Saggy bus voltage on Cessna 182 |
At 09:21 AM 6/3/2016, you wrote:
I started by looking at the voltage at the regulator terminals, which
is a thousand times easier to reach than the alternator. I took four
measurements, at idle RPM and 1600RPM, lights off and lights on.
idle (lights off/lights on)
V_bus 13.6 / 13.2
V_F 5.56 / 9.09
V_S 12.87 / 12.34
V_A 13.89 / 13.79
1600RPM (lights off/lights on)
V_bus 13.6 / 13.2
V_F 4.02 / 7.72
V_S 12.77 / 12.38
V_A 13.99 / 13.78
It's a 14v regulator.
Interesting . . .
Okay, the fact that your field voltages are responding
to load changes and not 'stuck on a rail' says the
regulator is actively controlling alternator behavior.
Voltage behaviors for loads-off/on suggest that the
alternator is shouldering the loads albeit at magnitudes
less than ideal.
If I recall correctly, Vs comes through the ov
protection module which explains the approx
1 volt lower value than Va which comes directly from
the bus.
Va and Bus voltages should be closer together,
You might get a reading of bus voltage with
the Fluke to compare with what's displayed
on the engine monitor . . . but the difference
doesn't explain the chief complaint.
The fact that your Va value (bus sense to
the regulator) is so close to 14.0 (lower limit
of spec) suggests that this regulator may
have passed acceptance testing at the factory
but given that it IS low yet actively controlling
the alternator suggests that it's simply set
too low . . . but not as low as bus volts reading
on your engine monitor suggests.
Do you have the service manual for this airplane
hence, access to the applicable alternator wiring
diagram? My recollections are 40+ years old
and may indeed be in error. If you don't have
the applicable wiring diagram, I can call my
'mole' at Textron and get the drawing. It would
also be useful to get the part number off the
regulator.
I'm puzzled by the 'scope readings you cited but
again, given the values you collected above,
the ripple numbers are not germane to the
chief complaint either.
Given that this is a new regulator, I'm not
ready to jump on the defective regulator diagnosis
quite yet but the numbers sure do point in
that direction . . .
How old is your battery and what type . . .
flooded or RG? What is the s/n of the
airplane?
Bob . . .
Message 8
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| Subject: | Re: Saggy bus voltage on Cessna 182 |
I'm going to look for a high impedance connection between the A terminal of t
he alternator and the bus: the regulator is seeing 13.8V at A, but with the l
oad current flowing from A to the bus the bus voltage is 0.6v lower, at the o
ther end of a thick cable and 60A breaker.
On Jun 3, 2016, at 12:13, Robert L. Nuckolls, III <nuckolls.bob@aeroelectric
.com> wrote:
At 09:21 AM 6/3/2016, you wrote:
I started by looking at the voltage at the regulator terminals, which is a t
housand times easier to reach than the alternator. I took four measurements,
at idle RPM and 1600RPM, lights off and lights on.
idle (lights off/lights on)
V_bus 13.6 / 13.2
V_F 5.56 / 9.09
V_S 12.87 / 12.34
V_A 13.89 / 13.79
1600RPM (lights off/lights on)
V_bus 13.6 / 13.2
V_F 4.02 / 7.72
V_S 12.77 / 12.38
V_A 13.99 / 13.78
It's a 14v regulator.
Interesting . . .
Okay, the fact that your field voltages are responding
to load changes and not 'stuck on a rail' says the
regulator is actively controlling alternator behavior.
Voltage behaviors for loads-off/on suggest that the
alternator is shouldering the loads albeit at magnitudes
less than ideal.
If I recall correctly, Vs comes through the ov
protection module which explains the approx
1 volt lower value than Va which comes directly from
the bus.
Va and Bus voltages should be closer together,
You might get a reading of bus voltage with
the Fluke to compare with what's displayed
on the engine monitor . . . but the difference
doesn't explain the chief complaint.
The fact that your Va value (bus sense to
the regulator) is so close to 14.0 (lower limit
of spec) suggests that this regulator may
have passed acceptance testing at the factory
but given that it IS low yet actively controlling
the alternator suggests that it's simply set
too low . . . but not as low as bus volts reading
on your engine monitor suggests.
Do you have the service manual for this airplane
hence, access to the applicable alternator wiring
diagram? My recollections are 40+ years old
and may indeed be in error. If you don't have
the applicable wiring diagram, I can call my
'mole' at Textron and get the drawing. It would
also be useful to get the part number off the
regulator.
I'm puzzled by the 'scope readings you cited but
again, given the values you collected above,
the ripple numbers are not germane to the
chief complaint either.
Given that this is a new regulator, I'm not
ready to jump on the defective regulator diagnosis
quite yet but the numbers sure do point in
that direction . . .
How old is your battery and what type . . .
flooded or RG? What is the s/n of the
airplane?
Bob . . .
Message 9
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| Subject: | Re: Saggy bus voltage on Cessna 182 |
I worked through the wiring from the B lead post on the alternator. The wiring
goes from the alternator post, to some kind of filter bolted to the engine side
of the firewall (which doesn't appear in the Cessna service manual wiring diagrams)
then to the 60 amp alternator CB, then to the bus.
The voltage on the alternator B lead post is the same 13.9V (13.8V with heavier
load) that I see on the A terminal of the regulator.
I looked at the voltage drop along the B current path: it's about 100mV per terminal
- there doesn't appear to be one connection that's any worse than the others.
There's also about 150-200mV drop across the 60 amp CB, when the bus is loaded
up. The terminal screw also gets hot - nearly too hot to touch. Is this expected?
It's a thermal-type breaker but I don't know how warm they are intended to
get, outside an overload condition.
I'm stumped on two questions:
Why, although the regulator field terminal voltage is well within normal operating
range (4-7v), the regulated voltage is low at 13.8 to 13.9V. This is the case
with two different regulators.
Secondly why I'm losing 0.6V, distributed equally across four crimp terminals and
a CB. I'm going to estimate the current at 20 amps, including LED landing and
taxi lights, halogen position and beacon lights, strobes, pitot heat and full
avionics bus, and recharging the battery soon after cranking. Is this to be
expected?
On 2Jun2016, at 11:37 AM, Charlie England <ceengland7@gmail.com> wrote:
Can you get voltmeter probes *directly on* the alternator B lead post & case? Not
on the bolts, clamps etc, but directly on the post. Measure voltage there with
the engine running & loads off, then on.
Sounds like the alternator is supplying ~the right voltage (possibly just a bit
low). But if you have high resistance connections anywhere between the alternator
and the loads (on the B+ side *or* the ground side paths), the loads may
not be seeing the full alternator voltage. If you have an issue with high resistance
connections, the voltage from alternator B terminal to case will still
be at 13.8 but your bus (and battery) voltage will be lower, due to voltage drops
in the high resistance connections.
Secondary possibility would be the same issue, but in the field circuit from regulator
to field terminal on the alt.
Charlie
Message 10
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| Subject: | saggy bus voltage on Cessna 182 |
>> to some kind of filter bolted to the engine side of the firewall
(which doesn't appear in the Cessna service manual wiring diagrams)
Cessna only installed that filter on airplanes that had the "avionics"
package... so the filter is found in the "Avionics" manual for your year
range of airplane. The Avionics manuals were typically for the entire
100 series (150/152, 172, 177/RG and 182). Some manuals covered two or
three model years. There are free scans online, include lots of little
details you won't find elsewhere.
>> There's also about 150-200mV drop across the 60 amp CB, when the bus
is loaded up. The terminal screw also gets hot - nearly too hot to
touch. Is this expected?
Nope... sure sign of resistance there. You can start by breaking both
connections to the breaker, cleaning them up to shiny, and reassembling
them wetted with ACF50 or CorrosionX. But the breaker itself may be
developing high resistance, and needs replacement. There's a series of
service bulletins on that breaker... it was a problem. Aircraft Spruce
and others have aftermarket breakers for that service.
Paul
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