This was addressed in a previous thread which had a link to a simple circuit to emulate an autotuner connected to the 705. Apparently, this then allowed the wfview tune button to force a 10 watt output for tuning purposes without swr foldback. Unfortunately, the image links no longer work. Can anyone provide that info again? Any other comments about this process are also welcome.
tnx,
Ross ve6ars
Maybe this?
https://sm7iun.se/station/ic705/
The 705 apparently tunes at maximum power (around 5-10 watts).
Im sorry Elliot, I should have just used the same topic. Maybe the same pics as from sm7iun? I wasnt sure if your father had changed the design slightly
I use sgc-230 and 10 watts is ok but the 705 normally folds back power before tuning is complete.
The discussion shows two options. One is a box that has audio recordings of tones at different levels.
The other is the Icom AH-4 interface button which makes it key up at tuning level.
Neither of these solutions have the ability to stop the radio from folding back power due to a poor match. This is usually a very low level circuit within the radio. On 100W radios, the threshold is usually high enough that 10W is no problem. But on the 705, I would estimate that it will not reliably make its maximum rated power into a mismatched load.
I have an SGC SG-230 ATU here and an SGC SG-2000. The 2000 was a tough radio and it would blast 60-150 watts into the 230 (even at significant mismatch), which would get it tuning just fine. That’s what the 230 is designed for and if I am not mistaken it will not even tune with 5 watts — it really wants 10 or more.
I don’t mean to dissuade you but the 705 is quite the opposite of the SG-2000, and it may be difficult to get it happy with that ATU. I have heard others mention that the 230 was hard if not impossible to use with a QRP setup.
Maybe try a different ATU or even make one using small parts. At these low power levels jr should be ok.
—E
de W6EL
Ok on the sgc-230, I have 3 of them. If the sensing diodes are not damaged, 10 watts can work ok. My Elad Duo works fine with them but it must have a more forgiving foldback mechanism. I also have an Elecraft T1 and MFJ-929 so not stuck for options.
Making the wfview tune button work at all with one of them is my biggest hurdle to move forward so I will play with the various circuits out there.
Congrats on the latest wfview, I just compiled it on 22.04 and seems fine.
I kind of suspect the SG-230 would happily tune at even lower power if a few laps were added to the secondary of the RF sample transformers. There are several versions of the 230, but the schematics I looked at seem like one could scale the detection.
If you are on linux, you should run the build script with “creator-widgets” as the first argument. Then you can try version 2!
Thanks,
–E
de W6EL
This 230 seems to have been scared into submission as its happily tuning with unmodified 705 at 10 watts, for today anyways. My 230’s are all older thru-hole designs yet still have major undocumented differences. Good point on the sensor windings.
Tried the creator-widgets build and its great! Lots of little fiddles to fix but has most of what I was hoping for. TNX to the developers! I will use a different topic for anything regarding the new builds.
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