Thanks to all who replied. The antenna is for transmission only. The receier has a 1/4 wave whip. There IS a ground plane on the opposite side of the board. Is that a bad thing? Thanks again, Shawn -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Vasile Surducan Sent: Thursday, September 08, 2005 5:24 AM To: Microcontroller discussion list - Public. Subject: Re: [EE:] Antenna Resonance A network analyzer will allow you to measure all the S parameters. These will show you how much from the incident power is reflected and how much is transmitted. You can't adapt by hand a PCB antenna if you didn't simulate it first just a little. The 1.5mm thick PCB epsilon is between 5.0 and 5.5 (ordinary pcb). This may help if you have a ground plane (hope not) to compute the antenna capacitance or the parasitic capacitance. As a homebrew solution try a grip-dip-meter. But you didn't say if the antenna is just for receiving or for transmision too. At 3dB input power with -1.5dB loss on antenna ( a very good situation) you'll not be able to transmit something. cheers, Vasile On 9/7/05, Shawn Yates wrote: > > I have a PCB with a loop trace (correct term?) antenna. That is, its > a track that's right around 1/2 wavelength long. I want to put a > variable cap on that and then be able to tune each pcb for optimum > resonance at my radios freq. What equipment would I need for that? A signal > injector? A network analyzer? The freq is 916Mhz fixed incase that > helps. The output power of the radio is about between 3 and -3 db, > very low power. If anyone can suggest equipment, including make and > model it would give me a starting point to do some shopping. or if > you can tell me some of the specs to look for that would be great. > > Any input is welcome and appreciated. > > Shawn > -- > http://www.piclist.com PIC/SX FAQ & list archive View/change your > membership options at http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist