Comparing Cross Needle SWR Meter and SWR Meter of FT-710

Connected my cross needle SWR meter to the SO239 connector of my FT-710 radio with a patch cable. In fact there are two patch cables, one with PL259 at one end and SO239 at other end and 50 cm long, meant for protecting the SO239 on the radio and another one with PL259 at both ends, which is 1m long, for connecting the SWR meter. The SWR meter on my FT-710 gives only the SWR while the cross needle SWR meter gives forward power and reflected power in addition to the SWR, which is indicated by the point where the two needles cross each other. In FT-710 there is an option to change the meter display to power instead of SWR, which I use occasionally. But I have not seen a way to check the reflected power. After tuning with the automatic antenna tuner in FT-710, the built-in SWR meter will show the tuned low SWR while the external SWR meter will continue to show the elevated SWR in the feedline as can be seen very well in this short video clip taken during a test CW transmission.

Now I am testing SWR on my zig-zag linear loaded, off center-fed inverted V dipole 80m antenna which is under construction, with low power in the radio. Built-in SWR meter of the radio shows HI-SWR indication in red colour and the needle is almost at the region of infinity. The crossing point of the needles in the cross needle SWR meter is also in the region of infinity. So it tallies with the measurement in the radio. Forward power noted in the black scale is around 5 watts. Reflected power in the blue scale seems to be beyond the maximum of 5 watts! So there is no chance of using this antenna at all in the current status.

This test was on the lower end of 30m band and SWR is just above 3 in both meters. Both forward power and reflected power seems to be a bit above the range chosen. It was only later that I recognized that the option chosen in the SWR meter was Peak Envelope Power or PEP and not the average power.

Tested again at the middle of 30m amateur radio band and got similar results for SWR, forward power and reflected power.

Similar results were obtained at the upper end of 30m band as well. After all, 30m band is a narrow band.

This test is after tuning with the built-in automatic antenna tuner of FT-710. You can see that the radio shows a very good SWR of nearly 1, while the SWR meter shows the elevated SWR in the feed line. If it was a remote antenna tuner at the antenna feedpoint, then the SWR in the feedline would also have become 1. Remote antenna tuner is quite expensive and requires additional power supply line to the antenna feedpoint or a T-bias power supply option through the feedline. Remote antenna tuners have to be weatherproof as well.