Today's Message Index:
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1. 08:37 AM - Re: OT-potting with RTV silicone (Jeff Page)
2. 11:57 AM - Re: Re: OT-potting with RTV silicone (Robert L. Nuckolls, III)
3. 01:08 PM - Dimmers (jonlaury)
4. 06:09 PM - Re: Dimmers (Robert L. Nuckolls, III)
5. 07:04 PM - Comm Antenna & SWR: Grounding Issue (Bob Falstad)
Message 1
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| Subject: | Re: OT-potting with RTV silicone |
You can buy silicone without acetic acid at the pet store - used for
sealing aquariums. I haven't tried it for potting though.
Jeff Page
Dream Aircraft Tundra #10
Message 2
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| Subject: | Re: OT-potting with RTV silicone |
At 10:30 AM 1/30/2011, you wrote:
>
>You can buy silicone without acetic acid at the pet store - used for
>sealing aquariums. I haven't tried it for potting though.
Thank you! I'd forgotten about that. I think the
same grade of RTV is approved for situations that
come into contact with food.
I'm pretty sure this stuff would do the job if applied
in several layers of 1/4" or less and allowed to cure
before more is added.
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
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I used one of these http://www.ledlightsworld.com/12v-inline-led-dimmer-switch-with-rotary-knob-2a-24w-p-191.html to control some LED lights in my panel by cannibalizing the innards for a panel mount w/knob.
Could this also be used to control incandescent lamps in my rocker switches?
Thanks,
John
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=329010#329010
Message 4
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At 03:04 PM 1/30/2011, you wrote:
>
>I used one of these
>http://www.ledlightsworld.com/12v-inline-led-dimmer-switch-with-rotary-knob-2a-24w-p-191.html
>to control some LED lights in my panel by cannibalizing the innards
>for a panel mount w/knob.
>Could this also be used to control incandescent lamps in my rocker switches?
Sure. Both LED and incandescent lamps are friendly
to duty-cycle dimming. It's illumination systems with
ELECTRONICS between the ship's power and the light
emitting devices that are problematic. This includes
but is not limited to flourescent and electro-luminescent
lamps.
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
Message 5
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| Subject: | Comm Antenna & SWR: Grounding Issue |
Bob N., et al,
I have run a bunch of additional tests of my antennas in various configurations
to see what effect they had on VSWR readings. The raw data and VSWR results
are pretty variable (to my eyes) and not very encouraging.
But my immediate issue is the one that Bob N. focused on shortly after my original
post -- the quality of the ground between my antenna base and my ground plane.
At the time I did the original tests, it tested out at ~0.1 Ohms on my digital
VOM.
But I dug out the four-wire ohmmeter that I build years ago based on Bob N's directions
in the AeroElectric Connection and soldered in a fresh "D Cell" battery.
The meters (especially the voltmeter) fluctuated quite rapidly and over quite
a range so I'm not sure my data are accurate (although it did come close
to the calculated resistance of a hunk of 18 AWG wire that I used to check the
four-wire ohmmeter for accuracy).
As best I can tell, the resistance between my antenna mounting screws and the ground
plane are in the 250 milli-Ohm range. This seems to be way too high. Is
it? I believe you said that resistance should be in the very low milli-Ohm
or even micro-Ohm range.
I've got one of your newer low resistance testers on order and as soon as I get
it, I'll measure the resistance again.
I'll probably just have to pull the ground plane and re-do the mechanical mounting
again and hope I get a lower resistance.
Would it make sense to get some conductive epoxy and bond a ground strap from the
antenna base to the ground plane? I know soldering copper to aluminum doesn't
work and corrodes almost immediately. I've seen some silver-filled epoxies
rated as low as 0.001 Ohm-cm but that stuff is expensive. Could I solder a
small ground strap to the antenna's metal base without damaging the antenna?
I've got room in the hole for the BNC connector to run a small ground strap up
from the antenna base to a ring terminal that I could clamp under one of the
mounting screws. Would conductive gel under the hardware help?
Since I've got a glass skin between the antenna base and the washer stack that
leads to the ground plane, I didn't "brighten" the underside of the ground plane
-- just the top under each of the four machine screws. I'm thinking if I brightened
up both sides of the ground plane, there might be some improvement because
of the additional contact between the hardware stack, the machine screws
and the underside of the ground plane.
All comments and thoughts are welcome.
Best regards,
Bob Falstad
GlaStar N248BF
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