---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 04/23/17: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 02:28 PM - 1.5DB??? (William Hunter) 2. 03:05 PM - Re: 1.5DB??? (Chuck Birdsall) 3. 04:53 PM - Re: 1.5DB??? (user9253) ________________________________ Message 1 _____________________________________ Time: 02:28:50 PM PST US From: William Hunter Subject: AeroElectric-List: 1.5DB??? Hi, I am installing a GTN-650 in my Velocity and the antenna location is only 2.0 feet from the unit itself. The Garmin instruction manual states that the cable loss needs to be between 1.5 and 6.5 DB. The manual also states that the calculated loss of a 6.5 foot cable with two BNC ends is 1.5 DB. I assume that this means that I need to run a 6.5 foot cable for my short run? If so, what is the minimum radius of the bends I would need to make in the cable to coil it up? Thanks for your kind help!!! Bill Hunter ________________________________ Message 2 _____________________________________ Time: 03:05:23 PM PST US From: Chuck Birdsall Subject: Re: AeroElectric-List: 1.5DB??? Bill, Yes, you need a minimum of 6.5 feet of cable length. The GPS antenna is an active antenna, having a pre-amplifier built into it that's powered by a bias voltage applied on the antenna center conductor (power comes from the GTN). The 1.5 dB of loss is to keep the receiver in the GPS unit from being over-driven and thus degrading the signal. The minimum 1-time bend radius from the RG400 spec is 1" - and the FAA spec from AC 43.13-1 is 10 times the diameter of the cable (which would make it just under a 2" radius). Both of these are a bit tight in my mind, and I would suggest a 3" radius (6" dia) or larger loop. That'll give about 19" of length per loop, which means three loops would get you what you need (or there about). Chuck ---- William Hunter wrote: > Hi, > > I am installing a GTN-650 in my Velocity and the antenna location is only > 2.0 feet from the unit itself. The Garmin instruction manual states that > the cable loss needs to be between 1.5 and 6.5 DB. The manual also states > that the calculated loss of a 6.5 foot cable with two BNC ends is 1.5 DB. > > I assume that this means that I need to run a 6.5 foot cable for my short > run? > > If so, what is the minimum radius of the bends I would need to make in the > cable to coil it up? > > > Thanks for your kind help!!! > > Bill Hunter ________________________________ Message 3 _____________________________________ Time: 04:53:43 PM PST US Subject: AeroElectric-List: Re: 1.5DB??? From: "user9253" In order to meet the minimum cable length requirement, I purchased a 10 foot RG400 cable with TNC connections from eBay for $12 with free shipping. Item number: 131817000902 -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=468711#468711 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-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/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-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.