---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 03/31/13: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 09:30 AM - Can Antenna problems damage a com transmitter? (user9253) 2. 01:34 PM - Re: Can Antenna problems damage a com transmitter? (Tim Andres) 3. 03:50 PM - Re: Can Antenna problems damage a com transmitter? (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 09:30:10 AM PST US Subject: AeroElectric-List: Can Antenna problems damage a com transmitter? From: "user9253" I intend to do some experimenting with homemade com antennas connected to my IC-A200. Is there a danger of damaging the transmitter if the antenna is either open or short circuited or otherwise unsuitable? Thanks, Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=397423#397423 ________________________________ Message 2 _____________________________________ Time: 01:34:02 PM PST US Subject: Re: AeroElectric-List: Can Antenna problems damage a com transmitter? From: Tim Andres Hi Joe, yes there is the possibility of damage if not built correctly. I assume you are building a 1/2 wave dipole or 1/4 wave vertical according to some published plans and if so, and the elements are cut to the correct length and it should be ok. Just make sure you have continuity at the radio connector, from the coax connector center conductor to the individual correct element and from the connector shield out the the other element. Also ensure you have NO conductivity between the elements. Then try the receiver, then the transmitter. The SWR of the antenna can also be influenced by proximity to other stuff, like you or your airplane. To be safe, buy yourself a SWR meter or borrow one. Then you will know you are presenting a suitable impedance to the radio. Good luck Tim Sent from my iPad On Mar 31, 2013, at 9:28 AM, "user9253" wrote: > > I intend to do some experimenting with homemade com antennas connected to my IC-A200. > Is there a danger of damaging the transmitter if the antenna is either open or short circuited or otherwise unsuitable? > Thanks, > Joe > > -------- > Joe Gores > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=397423#397423 > > > > > > > > > > ________________________________ Message 3 _____________________________________ Time: 03:50:15 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Can Antenna problems damage a com transmitter? At 11:28 AM 3/31/2013, you wrote: > >I intend to do some experimenting with homemade com antennas >connected to my IC-A200. >Is there a danger of damaging the transmitter if the antenna is >either open or short circuited or otherwise unsuitable? >Thanks, >Joe The very first solid state VHF transmitter I crossed paths with was indeed vulnerable to high SWR loading. But that was 1968 and the transistors were germanium PNP devices. A lot of improvements have been made over the years not only in the efficiency of transistors suited to the task but in their relative ruggedness as well. Nowadays, it is so easy to build a reflectometer right into a transceiver. The reflected power function is used to reduce drive to the transmitter's final amplifiers such that the transceiver is self protecting in extreme SWR situations (shorted or open coax). When using your transceiver for exploratory measurements, look at SWR first and excited the test setup for only long enough to see that your SWR readings are not really out of whack. The IC-A200 manual allows normal operations at SWR as high as 3:1 but is silent as to any cautions for still higher numbers. Open and shorted coaxes are part and parcel of living in the real world. Your transceiver is not at risk for the short duration measurements you're needing to accomplish. When ever we needed to make extended tests on a transmission line/antenna combo with high SWR, we would stick a 6 db attenuator in the line (100 feet of RG-58 coax works good too. The losses through the attenuator/coax are so great that TERRIBLE swr at the far end has no great effect on the energy source. The attenuator would keep the transmitter's auto-power down circuit happy. Bob . . . ------------------------------------------------------------------------------------- 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.