---------------------------------------------------------- Avionics-List Digest Archive --- Total Messages Posted Thu 04/24/14: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 09:18 PM - Garmin SL-30 poor VOR reception (DEAN PSIROPOULOS) ________________________________ Message 1 _____________________________________ Time: 09:18:02 PM PST US From: "DEAN PSIROPOULOS" Subject: Avionics-List: Garmin 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. Thanks for the help Dean Psiropoulos RV-6A N197DM 200+ hours since 2008 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message avionics-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Avionics-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/avionics-list Browse Digests http://www.matronics.com/digest/avionics-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.