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rparigor(at)suffolk.lib.n
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 Posted: Tue Nov 11, 2008 2:25 pm Post subject: Antenna routing without effecting pitch trim indicator |
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Was wondering specifics on wiring, how not to have radio transmission
effect pitch trim indicator?
Use of twisted Steinair servo wire?
Use shielded signal wire for indicator perhaps? Where to get or how to
make?
RG400 versus RG58?
Will have a Bob Archer antenna in rudder.
Thx. in advance.
Ron Parigoris
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rampil
Joined: 04 May 2007
Posts: 870
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| Posted: Tue Nov 11, 2008 2:56 pm Post subject: Re: Antenna routing without effecting pitch trim indicator |
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I never noticed any RFI on my trim indicator even though I have
rg58u bundled all the way out past the trim motor/sensor.
Keep in mind Ron that the trim motor runs slowly and seldom will
you need to watch it move on the indicator while transmitting.
I use the trim indicator mostly to set takeoff trim, and feel to set
trim in flight.
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frans(at)paardnatuurlijk.
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| Posted: Wed Nov 12, 2008 11:21 am Post subject: Antenna routing without effecting pitch trim indicator |
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rparigor(at)suffolk.lib.ny.us wrote:
| Quote: |
Was wondering specifics on wiring, how not to have radio transmission
effect pitch trim indicator?
Use of twisted Steinair servo wire?
Use shielded signal wire for indicator perhaps? Where to get or how to
make?
RG400 versus RG58?
|
Most important factor is not to have RF on the shield. That is,
sometimes the shield of the coax is behaving as if it is part of the
radiating part of the antenna. In many setups, the shield is connected
directly to one half of the dipole antenna. If this is the case, the
shield starts radiating as well (the electrical current has no way to
determine where the antenna ends and the coax begins), creating heavoc
with all other conducters in its near environment.
It is common practice for radio engineers to use some kind of
transformer between the antenna and the coax. Apart from transforming
the impedance, it also converts from balanced (the dipole) to unbalanced
(the coax). You might search on google for "balun", which describes
precisely such a transformer, which can be built with coax or other
easily available materials. Alternatively, you can coil up part of the
RG-58 as close as possible near the antenna. Some people use toroids
over the antenna cable, but the effect is highly dependable on the kind
of torroids used. Best bet is to use some kind of transformer.
The aim is to make the shield of the coax radio-neutral.
If the shield is neutral, there will be still substantial radiation from
the antenna, but it is further away from other wires, and in our Europa
setup, the field is almost 90 degrees offset compared to the other
wires, so they won't pick up very much. For some sensitive equipment
though, it may be still too much. You can loop these wires through a
toroid, or just coil them up in a tight loop at their ends, so the radio
signal doesn't enter either the source or destination of these wires.
| Quote: | Will have a Bob Archer antenna in rudder.
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This antenna won't be better than just an ordinairy dipole in the
rudder, whether it be the Europa dipole, a homemade dipole, or a big $$$
dipole. Physics (and interference) remains the same for all brands.
Also, RG-58 is the best cable, if you balance costs and performance.
Best regards,
Frans Veldman
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