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
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.