Dene, you should be able to use your CB radio SWR meter for VHF as well. These things work by coupling a conductor parallel to the RF cable (they are not connected) and through a diode setup you switch the measurement between forward power and reflected power. The total amount of power that couples into the meter depends on frequency, but the coupling factor is the same for forward and reflected power, and since you only want to measure the ratio between the two it does not matter. It might be, though, that you are not able to tune to a full 100% in the forward setting, in which case you need to adjust the reading for the reflected power.
If you want to measure the actual power going to the antenna, then you need to have a tuned meter, such as the Bird Wattmeter with a respective insert. Greetings from the still cold Western Pennsylvania, Wolfgang N1YM -----Original Message----- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On Behalf Of AVLEC Sent: Monday, February 26, 2007 4:35 PM To: KRnet Subject: KR> antennae tuning Hi KR radio heads This one is for the radio literate. I have just installed an antennae into an aircraft made from coax only. I left the radiator and counterpoise too long on purpose so that I could tune it to length in the aircraft using a SWR meter and a handheld radio. Here is where my confusion starts. I have in the past built a number of antennae for CB radio and have tuned them with one of two SWR meters that I have and they worked fine. Today I spoke to a guy that has built a few airband antennae and he says that the SWR meters suitable for CB radio freq are not suitablr for airband?? As far as I know all a SWR meter is is a voltmeter so why should the freq make any difference? He also told me that a handheld radio does not put out enough power to be able to get reliable readings??? Sounds really obsurd to me. Comments from those in the know would be very much appreciated. Regards Dene Collett KR2SRT builder South africa Whisper assembler See: www.whisperaircraft.com mailto: av...@telkomsa.net _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net Post photos, introductions, and For Sale items to http://www.kr2forum.com/phpBB2/index.php please see other KRnet info at http://www.krnet.org/info.html __________ NOD32 2083 (20070227) Information __________ This message was checked by NOD32 antivirus system. http://www.eset.com
