Home |
Search |
Today's Posts |
#16
|
|||
|
|||
swr goes up on antenna
On 12/19/2014 10:14 AM, Jerry Stuckle wrote:
On 12/19/2014 2:33 AM, Jeff wrote: By changing the length of the coax you can make the antenna appear as being resonant or non resonant, even though the antenna may or may not be a perfect 50 ohm load. Incorrect, changing the length of the feeder will not change the SWR beyond any extra loss in the cable. It will change the phase of the mismatch that is all; (rotate around a constant VSWR circle on a Smith Chart). Jeff Incorrect. The basic VSWR meter measures the voltage, not the power. And if the SWR is other than 1:1, this voltage will change depending on the distance to the mismatch. Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms). But a shorted 1/4 wavelength coax shows an open (infinite impedance). Somewhere in between (I'm not going to bother to figure out exactly where because it's not that important) it will show an effective 50 ohm impedance. With a short, an open, or with what kind of load? Coax length is unimportant when you have a 1:1 SWR, but if you don't, the coax will act as a matching network. And length will affect the overall system. |
Thread Tools | Search this Thread |
Display Modes | |
|
|