flex 6700 swr in 50 Mhz

on5po

on5po

WK2Y

Mike-VA3MW

The 6700 has an actual SWR meter in the radio.  Let's see if I can remember this correctly from school.  If I don't have it correct, please take the time to correct me.

Along a 50 ohm feedline unless the Antenna is a 50 ohm resistive load the SWR will vary along the feedline depending on where you measure it and that is based on wavelength.  If you want to do this test, make up a bunch of RF patch cables, 1/4 wave, 1/2 wave and 3/4 wave long and measure the SWR in those points.  That was an experiment I had to do in College and I spent 3 days making patch cables accounting for velocity factor and connectors.  

A simple calibration test is to use either a 25 ohm (2 dummy loads in parallel) or a 100 ohm dummy load and see if you measure 2:1 as that is a calibration point.   If you don't see that on your SWR bridge it out of calibration.

Mike

on5po

Mike-VA3MW

Hi Janny

Can you check both devices on a 25 ohm resistive load please.  You should measure 2:1.

73

HCampbell WB4IVF

on5po

HCampbell WB4IVF

Flex radios decrease output power automatically when reflected power exceeds 25 watts, regardless of SWR, so you are safe. 

Luis del MOlino

When you get different readins on a SWR meter placed in different places on your transmission line (one placed inside the flex and another outside) it is ALWAYS due to RF circulating outside the coaxial cable, because there is no ANY balun at the antenna connection. The SWR readings on a coaxial cable with RF currents well iquilibrated (thans to a balun) if they are identical and opposed  in the central conductor and in the braid , always are the same in ANY PLACE of the cable, because they only deppend of the rate between the impedance Zo of the cable and de Z presented by the antenna.

But this is not true if there is a common mode RF current circulating outside the asimetrical coaxial cable. This common mode current have to be elimnated with a tension  or a current balun.

73 Luis EA3OG

Gary Ashdown

Just a quick note about the 50mhz swr reading on a flex signature seriies 6700. I raised a ticket some time ago about this very issue - end result - the radio has to be returned for realignment.

I tested numerous other radios into the same feedline/antenna (injected at the same point) and only the flex shows a higher swr.

At the end of the day, it was not worth the time or the money to return the radio for this single issue as the swr reading on all hf bands is correct.

regards

Gary

VK8AW