Today's Message Index:
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1. 02:49 PM - Re: warning lights for engine T&Ps (Sacha)
2. 04:21 PM - Re: warning lights for engine T&Ps (Robert L. Nuckolls, III)
3. 09:25 PM - SL-30 Poor VOR reception (DEAN PSIROPOULOS)
Message 1
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| Subject: | Re: warning lights for engine T&Ps |
>
> The device you linked seems like
> it should do the job. You may have a wiring error...
I tested the circuit on the bench by simulating the senders with a bunch of 1k
ohm potentiometers wired in parallel (the resistance range of interest is 30-230
ohms approx in the case of the Rotax senders).
Turns out I had indeed made a wiring error.
The circuit I linked does the job perfectly as it's designed to measure resistance
so it's output is pretty much independent of bus voltage, so there was no
need for the dc-dc voltage regulator upstream.
I calibrated them by simulating the senders with the 1k pots and connecting them
to the gauges and the tri-color LED circuit. The sensitivity can be very finely
adjusted with the two 33-turn pots that are on the (approx 1x2 inch) circuit
board.
I also managed to adapt the circuit to measure absolute bus voltage (for the high/low
voltage light) by wiring a 7805 5v regulator thingy with three legs to
get a fixed reference voltage.
All in all I'm very satisfied with the results!
Message 2
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| Subject: | Re: warning lights for engine T&Ps |
At 04:45 PM 4/24/2014, you wrote:
>
> >
> > The device you linked seems like
> > it should do the job. You may have a wiring error...
>
>I tested the circuit on the bench by simulating the senders with a
>bunch of 1k ohm potentiometers wired in parallel (the resistance
>range of interest is 30-230 ohms approx in the case of the Rotax senders).
>Turns out I had indeed made a wiring error.
>
>The circuit I linked does the job perfectly as it's designed to
>measure resistance so it's output is pretty much independent of bus
>voltage, so there was no need for the dc-dc voltage regulator upstream.
>
>I calibrated them by simulating the senders with the 1k pots and
>connecting them to the gauges and the tri-color LED circuit. The
>sensitivity can be very finely adjusted with the two 33-turn pots
>that are on the (approx 1x2 inch) circuit board.
>
>I also managed to adapt the circuit to measure absolute bus voltage
>(for the high/low voltage light) by wiring a 7805 5v regulator
>thingy with three legs to get a fixed reference voltage.
>
>All in all I'm very satisfied with the results!
Good for you sir . . .
Bob . . .
Message 3
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| Subject: | SL-30 Poor VOR reception |
Hello listers:
I have an RV-6A that I've been flying for a few years. When I first started
flying the airplane I did some rough VOR range reception checks with the
SL-30 and I had to get within 20 miles of a VOR station to get the receiver
to lock on and the OBS indicator to stabilize with no flag displayed. I
continued with the flight test regimen and getting familiar with the
airplane and enjoying it. Since flights have been in VFR conditions around
the busy Tampa (Florida) airspace I used the panel mounted moving map
(GPS/Comm) to make sure I stayed out of the Class B, there was no need to
have good VOR reception. The Com portion was the only thing I was using on
the SL-30 and that worked very well. Then, a couple months ago I turned on
the SL-30 and, nothing, no display or Com so I returned the unit to Garmin
for repair. In the meantime I'd been talking to a CFII about working on
my instrument proficiency to get back up to FAA standards after a long
hiatus. When the SL-30 was repaired and back in the instrument panel I took
off on a flight to Ocala to check it out. I climbed up to 4500 feet and
watched the OBS and listened for the ID code as I entered the 40 mile radius
of the Ocala VOR. Nothing so I kept going on a course straight for the
station. Around 20-25 miles out I started getting activity on the indicator
but the flags were intermittent and the radio could not maintain a lock.
Finally about 15 miles out the indicators stabilized and the flags stayed
off, obviously something is amiss.
I'm using a Comant CI-159 VOR/ILS antenna. This unit consists of a phenolic
"puck" with a BNC connector cast into it for the coax connection. There are
two fiberglas elements (thin rods about 18 inches long) that screw into the
puck to form a "V" shaped antenna. I have it mounted on the bottom of the
fuselage in the back of the airplane under the horizontal stabilizer. The
BNC sticks through a hole in the belly and appx 25 foot length of RG-58 coax
runs inside the aircraft up to the SL-30 receiver. No gasket was supplied
with the antenna so I just bolted the puck to the aluminum using the two
bolt holes. After the Ocala flight I removed the puck and elements for
closer inspection and checked the connector on the coax cable at the antenna
end. Nothing wrong that I could tell just by looking at the equipment.
There was a bit of engine oil (from the exhaust) on the puck surface facing
the skin. I cleaned it off and made a gasket to go between the puck and the
skin to minimize the oil build up again. I have not flown the airplane
since but I doubt that lack of a gasket was causing the poor reception,
maybe someone here can tell me. The other thing I checked was the
resistance between the center pin and outside barrel of the BNC connector on
the antenna. Resistance was showing basically a dead short (less than 1
ohm, same reading as touching the meter probes together). I'm not an
antenna designer so I don't know if this is what the reading should be or
not. Aircraft Spruce has the following description for this antenna: " "V"
Dipole VOR/Glide Slope Antenna with detachable elements is similar to the CI
158C-3 with the exception of offering 2-hole mount instead of a 4-hole
mount. This V Dipole encompasses reduced static capability with the use of
P-Stat paint. Integral ferrite balun provides for higher radiation
efficiency." . I don't know if the construction of the antenna would cause
the meter to show such a low resistance, maybe some here could shed some
light on that.
Any ideas, experiences with poor VOR reception here on the list? Since the
radio has been repaired and tested by the factory I'd say it's not the
radio. I checked the connector at the back of the radio tray and it appears
secure so I'm not sure what else to do. Since VORs are being decommissioned
there is going to be less and less need for VOR reception but if I have to
use victor airways during instrument operations I need to have good
reception at the expected range or I won't be able to comply with ATC
clearances. On an side note, a fellow RV-9 builder who is using a simple
flat metal antenna in the wingtip, has no problem receiving the VOR 40 miles
out, and he didn't pay anywhere near what I did for his antenna. Thanks for
the help
Dean Psiropoulos
RV-6A N197DM
200+ hours since 2008
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