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davidjoyce(at)doctors.org
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 Posted: Mon Oct 23, 2017 6:37 am Post subject: Nav antenna - The Answer |
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Just in case anyone else gets confused by this question, I discover that both my Comant nav antenna and a brand new certified one have a resistance from core to sheath (or indeed measured simply between the two metal limbs of the antenna) of just 0.4 ohms, quite distinct from Com antennae which have very high resistance. It had struck me that a short in the connectors or the coaxial cabling might be what is troubling the nav bit of my GNC255 but it is not so - clearly the two sections of the nav dipole are connected by some low resistance structure.
Regards, David Joyce, GXSDJ
On 2017-10-22 18:39, Alan Burrill wrote: | Quote: | The are horizontal dipoles and should effectively be open circuit.
Alan
Sent from my iPad
On 22 Oct 2017, at 18:01, davidjoyce(at)doctors.org.uk (davidjoyce(at)doctors.org.uk) wrote:
| Quote: |
Does anyone have a nav antenna (of VOR/Glide slope/Loc variety) conveniently to hand so that they could measure the resistance across the pin to sheath, or maybe is clever enough to know what it should be? Am pursuing a glitch and find that my nav antenna has a very low resistance unlike Com & Transistor antennae.
Regards, David Joyce, GXSDJ
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Burrilla
Joined: 25 Apr 2015
Posts: 182
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| Posted: Mon Oct 23, 2017 6:53 am Post subject: Nav antenna - The Answer |
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Interesting. The only antennae I have come across with low dc resistance is an end fed dipole or a folded dipole where for balancing the impedance a coil is used.
Looking at the picture in Mendelssohn catalogue for the Corment VOR Antenna I would not have expected any balancing coils to be used.
Live and learn, sorry if I misled you.
Alan
Sent from my iPad
On 23 Oct 2017, at 15:35, davidjoyce(at)doctors.org.uk (davidjoyce(at)doctors.org.uk) wrote:
| Quote: |
Just in case anyone else gets confused by this question, I discover that both my Comant nav antenna and a brand new certified one have a resistance from core to sheath (or indeed measured simply between the two metal limbs of the antenna) of just 0.4 ohms, quite distinct from Com antennae which have very high resistance. It had struck me that a short in the connectors or the coaxial cabling might be what is troubling the nav bit of my GNC255 but it is not so - clearly the two sections of the nav dipole are connected by some low resistance structure.
Regards, David Joyce, GXSDJ
On 2017-10-22 18:39, Alan Burrill wrote: | Quote: | The are horizontal dipoles and should effectively be open circuit.
Alan
Sent from my iPad
On 22 Oct 2017, at 18:01, davidjoyce(at)doctors.org.uk (davidjoyce(at)doctors.org.uk) wrote:
| Quote: |
Does anyone have a nav antenna (of VOR/Glide slope/Loc variety) conveniently to hand so that they could measure the resistance across the pin to sheath, or maybe is clever enough to know what it should be? Am pursuing a glitch and find that my nav antenna has a very low resistance unlike Com & Transistor antennae.
Regards, David Joyce, GXSDJ
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| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
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