I've got one of those as well. Put the response public. I'm sure other people care too.
Ray_pilot New Orleans Ok, here is one of the responses I got off net. Name has been removed to protect his smartness. Paul, Receiving ONLY antennas do not need a RF choke, which is what those things really do when installed. They are used on transmitting coax to keep reflected RF energy (standing waves) from feeding back down the coax into the transmitter and usually ruining the output transistor(s). Sort of like an electronic check valve. RST engineering is still in business, and they sell kits of stuff to make antennas - which included's 20 ferrite toroids. Check it out at http://www.rst-engr.com/ I don't know what the diameter of RG-400 is, so if you can tell me I would appreciate it. Have a good 4th weekend xxxxxxxxxxx Thanks for the response. The RG-400 diameter is .200" What you said is my understanding. But on RST front page they have a picture of a VHF Nav antana. It looks like it has toroids. This is were I'm confused Paul - Right you are - I just looked and sure enough, there seem to be toroids in that picture. Now I'm not sure whether he used the wrong picture or the wrong description, or whether he really does use toroids on receiving antennas. I can see no reason to have them . . . but read on. That pictured antenna is a dipole, and I have used dipoles with no balun in ham radio - and believe me, they receive fine for VOI CE reception. Whether or not a NAV signal is that much different I do not know, or whether there is something about it that would make a difference. I don't think so, but could sure be wrong. One thing I have noticed about NAV antennas (OMNI?) on planes is that they are vee shaped, usually pointing the open end of the vee toward the front of the plane, but sometimes toward the rear. Maybe that makes a difference as well so there are not blank spots in receiving NAV signals. I guess I should not really have commented without absolutely being positive about the toroids on NAV antennas, but for what it's worth, it is true that for other uses RECEIVING antennas do not need a balun or RF choke to function well. Could you experiment on the ground with a temporary setup to prove the proper reception, or would it have to be done in the air to be able to receive a signal where you are ? I don't have a nav receiver and indicator here to test with, or I would. As I learned many, many years ago with ham radio, experimenting in that field is as much fun and pain as doing it with airplanes. :-) If you find out what the answer to the toroid question is, please let me know sometime. I can always learn something new. Thanks for the coax diameter info. That helps me. xxxxxxxxx
