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On Tue, Jan 24, 2023 at 03:23 PM, Ken K wrote:

From my reading by default it's prevented so high voltage and damage won't happen.

It's suppose to allow slightly more or less capacitance and inductance
than what's available by default.

I run low power and wanted to find out if either more or less cap/Ind would
help with some tuning.
I have read the manual a few times and I am still a bit confused
how you extend the range.

I approved your post for today's date, a follow-up of this post, but it hasn't yet appeared on the GIO site nor in my inbox, so I'll just respond here.? ? ??

I'm replying from the group site, but often, when I do so, the formatting goes kaput and all the text gets run together with no paragraph breaks. Hopefully this will remain formatted. If it doesn't, my apologies. I'll leave a few extra spaces between paragraphs just in case.? ? ??

The group is what the members make of it. There are 133 members, some of whom have this tuner (I have one myself). No one person, or even several persons, can make a group work out well for the rest of the members. More time will tell if this group was not going to be a group worthy of being here. If the group doesn't work out, it can be "recycled" to a different ham radio group for a different purpose, something that will be useful to it's members. We're not there yet, though. It takes a few years to see how things work out. The Icom group I started at first didn't seem to be picking up steam, but it gathered momentum and I believe it's now a useful resource to Icom radio and equipment owners. This group is a little newer so let's give it another year or so. (Yes, it does take some time to get a group to be well-established.) I am glad I took some time to attempt to answer your question because I learned a few things about my 993B tuner that I didn't know were there before. I bought mine refurbished at Hamvention in Xenia, OH, a few years ago. (I saved about $100 buying it refurbished.) I will be changing the power limit to 150W now to get a larger range of SWRs that it can match.

Of those (probably several) members here who have this tuner, I would guess that none of them have ever tried to override the default chosen C and L values. In your case, I can see where you might benefit from doing so, but this tuner requires 10-20 watts for "maximum SWR tuning accuracy" (Page 1 of the manual), so it's not really intended to be a QRP tuner. The minimum power required to get any tuning is 2 Watts (page 1).? ? ? ??
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I can see where you might be confused in the wording of the manual about increasing the C and L limits, but I think I might be able to clear up some of the matter. On page 20, it says that you can change the maximum C and/or L value(s) as long as that doesn't go outside the limit for the power and frequency. So let's say that the tuner finds an SWR match of 1.4:1 and it stops there. You can fiddle with the L and C values to get a lower SWR (or a higher one, if you really cared to do so), as long as the final value(s) are within the limits that protect against arcing from too high of a voltage in the matching circuit. So you bump up the C value but try to go over the limit, and it won't let you. Of course, that's by design.?? ? ??

Now, on page 20, which also explains some of the above on the limits of C and L values, explains that the upper values of L and C are factory-limited according to power and frequency. So if you are using more than 150 W (up to the maximum of 300 W), it will restrict you more than if you are using 150W or less. For under 300W, it will match 6 to 3200 Ohms impedance, while over 300W, it will match 6 to 1600 Ohms. That translates to an SWR maximum of 64:1 and 32:1 respectively.

The factory default power setting is for 300W. If you haven't changed it from that, you're limiting yourself to a much narrower range of potential SWR matches than if you change that setting. The way to do that is under Power Level Menu on page 17. You can also change the target SWR (page 17) and the auto tune SWR threshold (page 18).?

As I read it in the manual, the best you can do is to set your 993B power level to the 150W limit, and perhaps make it more sensitive to when it will try to tune for a lower SWR in the auto tuner threshold and set the target SWR to just under the SWR limit set by the radio manufacturer, so that you're not trying to tune down to a 1:1 SWR when it's not necessary. Unless the radio is folding back power to compensate for a high SWR, you're not gaining much (if anything) by going for a perfect match. (If you want to discuss this sort of thing further, may I suggest starting a new thread in the ham-antennas group:???and discussing it there. Now, if you are dealing with a transmitter that doesn't have fold-back SWR protection, then you may have something to gain by aiming for close to perfection. Otherwise, in the time it takes to fiddle and diddle to manually tweak the SWR to make it better, you may have missed making that rare contact you were hoping to have a QSO with.?

One section I don't completely understand is about the Intellitune Menu on page 19. It says you can turn off the Intellitune algorithm. It doesn't specify if that means you can go full manual with the L and C values or not. I would interpret it to mean that you can use it as a full manual push-button tuner. You should be able to verify that quite easily by turning off the algorithm and seeing if it does, indeed, allow you to change the L and C values manually once you've done that. If you do this, please let us know. Someone else might be interested in this information.

(BTW--I still haven't seen the follow-up message by the original poster on the group site or in my inbox.)

Donald KX8K