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cardinalnsb(at)aol.com
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 Posted: Thu Mar 28, 2019 11:21 pm Post subject: Quick transponder cavity tube test |
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I inherited 6 older transponders, from someone not known to collect junk. I understand that if the cavity tube is bad, it is junk. Is there a cheap easy way to verify if the cavity tube is bad? thanks in advance, Skip
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nuckolls.bob(at)aeroelect
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| Posted: Fri Mar 29, 2019 4:46 am Post subject: Quick transponder cavity tube test |
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At 02:10 AM 3/29/2019, you wrote:
| Quote: | I inherited 6 older transponders, from someone not known to collect junk. I understand that if the cavity tube is bad, it is junk. Is there a cheap easy way to verify if the cavity tube is bad? thanks in advance, Skip
|
That takes some pretty sophisticated bench test
equipment . . . I'm not sure that contemporary
shops would even know how to test them
much less have the equipment.
Bob . . .
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alec(at)alecmyers.com
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| Posted: Fri Mar 29, 2019 6:18 am Post subject: Quick transponder cavity tube test |
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Every time I get my static system rectified (24 months) my avionics guy sets up a little antenna on a stand next to the airplane, connects it to his yellow box, and checks the transponder’s working and outputting the right mode C codes for the pressure in the pitot system. You don’t get a power measurement but his box does check the output frequency.
So that sort of test would give you a go/no-go for the tube.
The text box might have a transmitted power measurement too, if you cable the transponder directly into it. I’m not sure. So worth enquiring at an avionics place.
On Mar 29, 2019, at 8:46 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:
At 02:10 AM 3/29/2019, you wrote:
| Quote: | I inherited 6 older transponders, from someone not known to collect junk. I understand that if the cavity tube is bad, it is junk. Is there a cheap easy way to verify if the cavity tube is bad? thanks in advance, Skip
|
That takes some pretty sophisticated bench test
equipment . . . I'm not sure that contemporary
shops would even know how to test them
much less have the equipment.
Bob . . .
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
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| Posted: Fri Mar 29, 2019 9:04 am Post subject: Quick transponder cavity tube test |
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Unless they have disposed of transponder bench check units, most
avionics shops can test on the bench for power output and frequency
accuracy/waveform. Until a couple years ago, when I sold airplane, I had
a Narco AT50 with good cavity tube..ie still putting out rated power.
That is a 50 year old design. I would think that most would consider
cavity tube ok if it puts out 90 % of rated power, but I don't know what
the standard is.
On 3/29/2019 7:07 AM, Alec Myers wrote:
| Quote: |
Every time I get my static system rectified (24 months) my avionics guy sets up a little antenna on a stand next to the airplane, connects it to his yellow box, and checks the transponder’s working and outputting the right mode C codes for the pressure in the pitot system. You don’t get a power measurement but his box does check the output frequency.
So that sort of test would give you a go/no-go for the tube.
The text box might have a transmitted power measurement too, if you cable the transponder directly into it. I’m not sure. So worth enquiring at an avionics place.
On Mar 29, 2019, at 8:46 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:
At 02:10 AM 3/29/2019, you wrote:
> I inherited 6 older transponders, from someone not known to collect junk. I understand that if the cavity tube is bad, it is junk. Is there a cheap easy way to verify if the cavity tube is bad? thanks in advance, Skip
>
That takes some pretty sophisticated bench test
equipment . . . I'm not sure that contemporary
shops would even know how to test them
much less have the equipment.
Bob . . .
|
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Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
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cluros(at)gmail.com
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| Posted: Fri Mar 29, 2019 9:18 am Post subject: Quick transponder cavity tube test |
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I'm sure that if your avionics guy is certifying your transponder he is checking the power output at some point. Either on the bench or with his yellow box.Appendix F to Part 43—ATC Transponder Tests and Inspections
https://www.ecfr.gov/cgi-bin/text-idx?SID=5829ce2954d4be54fdd72f9a80db6781&mc=true&node=pt14.1.43&rgn=div5#ap14.1.43_117.f
(1) Verify that the transponder RF output power is within specifications for the class of transponder. Use the same conditions as described in (c)(1)(i), (ii), and (iii) above.(i) For Class 1A and 2A ATCRBS transponders, verify that the minimum RF peak output power is at least 21.0 dbw (125 watts).
On Fri, Mar 29, 2019 at 7:24 AM Alec Myers <alec(at)alecmyers.com (alec(at)alecmyers.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: Alec Myers <alec(at)alecmyers.com (alec(at)alecmyers.com)>
Every time I get my static system rectified (24 months) my avionics guy sets up a little antenna on a stand next to the airplane, connects it to his yellow box, and checks the transponder’s working and outputting the right mode C codes for the pressure in the pitot system. You don’t get a power measurement but his box does check the output frequency.
So that sort of test would give you a go/no-go for the tube.
The text box might have a transmitted power measurement too, if you cable the transponder directly into it. I’m not sure. So worth enquiring at an avionics place.
On Mar 29, 2019, at 8:46 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
At 02:10 AM 3/29/2019, you wrote:
> I inherited 6 older transponders, from someone not known to collect junk. I understand that if the cavity tube is bad, it is junk. Is there a cheap easy way to verify if the cavity tube is bad? thanks in advance, Skip
>
That takes some pretty sophisticated bench test
equipment . . . I'm not sure that contemporary
shops would even know how to test them
much less have the equipment.
Bob . . .
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cluros(at)gmail.com
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| Posted: Fri Mar 29, 2019 9:18 am Post subject: Quick transponder cavity tube test |
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"I would think that most would consider cavity tube ok if it puts out 90 % of rated power, but I don't know what the standard is. "
125 W, and you're allowed 3db loss in the cable to the antenna.
On Fri, Mar 29, 2019 at 10:15 AM Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>
Unless they have disposed of transponder bench check units, most
avionics shops can test on the bench for power output and frequency
accuracy/waveform. Until a couple years ago, when I sold airplane, I had
a Narco AT50 with good cavity tube..ie still putting out rated power.
That is a 50 year old design. I would think that most would consider
cavity tube ok if it puts out 90 % of rated power, but I don't know what
the standard is.
On 3/29/2019 7:07 AM, Alec Myers wrote:
> --> AeroElectric-List message posted by: Alec Myers <alec(at)alecmyers.com (alec(at)alecmyers.com)>
>
> Every time I get my static system rectified (24 months) my avionics guy sets up a little antenna on a stand next to the airplane, connects it to his yellow box, and checks the transponder’s working and outputting the right mode C codes for the pressure in the pitot system. You don’t get a power measurement but his box does check the output frequency.
>
> So that sort of test would give you a go/no-go for the tube.
>
> The text box might have a transmitted power measurement too, if you cable the transponder directly into it. I’m not sure. So worth enquiring at an avionics place.
>
>
>
>
> On Mar 29, 2019, at 8:46 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
>
> At 02:10 AM 3/29/2019, you wrote:
>> I inherited 6 older transponders, from someone not known to collect junk. I understand that if the cavity tube is bad, it is junk. Is there a cheap easy way to verify if the cavity tube is bad? thanks in advance, Skip
>>
>
> That takes some pretty sophisticated bench test
> equipment . . . I'm not sure that contemporary
> shops would even know how to test them
> much less have the equipment.
>
> Bob . . .
>
>
>
>
>
>
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rel="noreferrer" target="_blank">http://www.matronics.com/contribution
===========
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