---------------------------------------------------------- Avionics-List Digest Archive --- Total Messages Posted Fri 04/25/14: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 10:05 AM - Re: Garmin SL-30 poor VOR reception (Matt Dralle) ________________________________ Message 1 _____________________________________ Time: 10:05:31 AM PST US From: Matt Dralle Subject: Re: Avionics-List: Garmin SL-30 poor VOR reception I just went and measured the resistance between the center pin and the outside connector on my CI-158C and it too is basically a short, so that part seems "normal". I would do a similar test on your cable with both ends disconnected. That should be infinate resistance. Are you using "RG-58A" or "RG-58C/U"? "RG-58A" is really lossy. ""RG-58C/U" is better, but still not that great. I would strongly recommend RG-142 or RV-400 for that application. I have RG-142 installed in my RV-8 connected to an SL-30 and to a CI-158C antenna mounted in the top of my vertical stab and I get outstanding reception. Pull the RG-58 out, get some RG-142 and some high-quality BNC connectors (the crimp-on kind NOT the screw-on kind) and then see how things work. You may still have a problem with the NAV receiver on the SL-30, but upgrading your cable will go a long way in improving your reception in any case. Matt At 09:17 PM 4/24/2014 Thursday, you wrote: > >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 > > Matt G Dralle | Matronics | 581 Jeannie Way | Livermore | CA | 94550 925-606-1001 V | 925-606-6281 F | dralle@matronics.com Email http://www.matronics.com/ WWW | Featuring Products For Aircraft ------------------------------------------------------------------------------------- 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.