Strange radio problems
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Joined: Dec 2011
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I think the crackling was the sound of static charge, picked up by the aircraft as a whole, arcing across (flashing across) the non-conductive elevator bearings to the elevator, from which it escaped via the static wicks as normal.
That's my guess.
But yes it could have been the other way around i.e. static charge picked up by the elevator arcing across its bearings to the airframe, from which it got dissipated via the static wicks on the flaps, and the (somewhat less effective) static wicks on the ailerons.
The COM2 antenna is a lot closer to the elevator than the COM1 antenna, hence...
No idea. These radios are damn complicated digitally synthesised jobs.
That's my guess.
But yes it could have been the other way around i.e. static charge picked up by the elevator arcing across its bearings to the airframe, from which it got dissipated via the static wicks on the flaps, and the (somewhat less effective) static wicks on the ailerons.
The COM2 antenna is a lot closer to the elevator than the COM1 antenna, hence...
what about the 'only detectable when there's carrier' part
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From: Cilboldentune, Britannia
It's quite noticeable that the later PA28 types (Warriors/Archers) that I've come across recently (and with glass cockpits) seem to have many more bonding and static wicks than previous.
Joined: Jan 2010
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From: Texas and UK
I did see in the late 70's a 172 get hit by a lightening (hit the wing) on on short finals. The ailerons were welded solid on the side which took the strike. The only evidence of the strike (other than the welded aileron) was the small area of discolouration on the wing surface.
I guess no amount of bonding strap would have helped with that, but static discharge is a different mater.
Well done Peter
I guess no amount of bonding strap would have helped with that, but static discharge is a different mater.
Well done Peter
Joined: Feb 2006
Aviation Qualifications: LAME
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From: Falling off the end of the thread
I would make sure the jack plugs in the panel are tight and haven't worked loose, also clean your headset plugs, I use a little bit of fine scotchbright.
Joined: Nov 2007
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From: Too close to EASA
Hey Peter - good fix!
It seems like a British avionic engineer can actually diagnose a problem correctly (post 11) - I thought you believed only Americans could do anything right.
You know where we are when you finally want the PRNav upgrade - and not for £40K!
It seems like a British avionic engineer can actually diagnose a problem correctly (post 11) - I thought you believed only Americans could do anything right.
You know where we are when you finally want the PRNav upgrade - and not for £40K!
Thread Starter
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Interesting... how do conventional VHF aerials work on a wooden hull?
Surely they need a ground plane? At least around the aerial base.
Otherwise what you have is a length of coax whose screen suddenly ends in nothing, and the inner conductor goes to the base of the aerial. RF stuff was never my strong area (I used to build pirate ratio transmitters in the late 1960s, with a pair of 807s; we even considered powering it from the 700V DC train rail
) but this doesn't seem right. The cable screen needs to go to that ground plane.
Surely they need a ground plane? At least around the aerial base.
Otherwise what you have is a length of coax whose screen suddenly ends in nothing, and the inner conductor goes to the base of the aerial. RF stuff was never my strong area (I used to build pirate ratio transmitters in the late 1960s, with a pair of 807s; we even considered powering it from the 700V DC train rail
) but this doesn't seem right. The cable screen needs to go to that ground plane.
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From: Too close to EASA
On a wooden or composite airframe, the ground plane foe a uni-pole antenna is normally either metallic foil or mesh inside the fuselage. The ground plane should be at least 1/4 wavelength radius and the antenna should be centred to avoid becoming directional. The core of the co-ax goes to the antenna which is insulated from the ground plane and the screen connects to the ground plane. It's also possible to use a 1/2 wave dipole -typically a NAV antenna, or a Comm antenna inside the fin. In this case, the connection to the co-ax uses a matching balun cable and the co-ax core doesn't actually connect to either leg of the dipole.
Joined: Aug 2006
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From: Sth Bucks UK
What I know about radios can be written on the back of a fag packet using only two letters, one of them being "F".
For the antenna mounted inside the fuselage I used a self-manufactured aluminium ground plane of around 10"x8". For the externally mounted antenna I used the original aluminium ground plane which is about 1/4 of the size.
I would like to eventually return to having an out-of-sight solution but for the moment I have other priorities and am happy that at least the problem has been resolved, even if without any technical understanding.
For the antenna mounted inside the fuselage I used a self-manufactured aluminium ground plane of around 10"x8". For the externally mounted antenna I used the original aluminium ground plane which is about 1/4 of the size.
I would like to eventually return to having an out-of-sight solution but for the moment I have other priorities and am happy that at least the problem has been resolved, even if without any technical understanding.
