160M on G5RV & tuning

Submitted by M6YBM on Sun, 27/11/2016 - 22:36

Spent a fair bit of time today looking into the following issues on 160M on G5RV & tuning :

Problems intermittently on FT857 - Tuned well, Tx & receive good, the auto tuner kicks in & upsets SWR. Sometimes helped by joining the 2 halves of the T, sometimes not.

Problems most of time on 817 resulting in V low signal

Test setup & results:

used the 817 as the issues are worst there. 

Connected UHF cheapo SWR meter & manual tuner

Signal results

Manual explains power output very poorly for 817.

Basically L +il| = 2.5W

               L +il = 1W

               L +i = 0.5W

               Square = 5W

With manual tuner max outputs (on AM) as seen on low level reading on SWR=

FT857 - Set to 5W gave 0.75units

               ..       10W       1.5 units

FT817    ..        2W         0.1units

               ..       5W         0.2units

Next I checked the O/P of both in same way on higher bands & there was no similar problem.

Seems like the mismatch on the antenna is too great for the 817 impedance? 

So focusing on the 160M I attached the auto tuner with the manual tuner before the antenna. Results in much improved tuning & 817 power outputs much increased to about 80% of the rated values! 

(I also checked the voltage form battery unit & tried connected to main PSU with no changes) 

Hope this may be of some use to others :-)


Thanks to M0XAN, G0FYX & G4RGO and many others for help on the 160M net. I'll bring tuner & 817 on Friday but looks like I have a solution.