gszes, on 2012-June-13, 10:48, said:
x 3 card support extra values
3s invitational (unsure what competitive means by others) p is around
the 8-10 range for 2s bid so 3s is asking if they are at or close to 10.
If we are too weak to invite we can pass and leave further competing
up to partner.
3h natural too strong for overcall virtually game forcing
I totally agree with this analysis.
Think about the action that advancer took and what wasn't done.
Advancer didn't cue bid 2
♦ guaranteeing something like an opening hand. But advancer did bid 2
♠ showing probably 8+ points. It is possible that advancer has made that call on a decent 4 card
♠ suit. Advancer might also have bid 2
♠ holding 4-4 in the majors in order to facilitate showing both majors.
So it's important for doubler to be able to identify the value of his/her hand AND the extent of the spade support held. Doubler shows extras by making a free bid or call directly after opener's rebid. Since Doubler guarantees at least 3 cards in each unbid suit and can't possibly hold a penalty double hand -- double must be extras with 3 card
♠ support. 3
♠ then shows extras and 4 card
♠ support.
Advancer then has some idea how to proceed if opener makes a call.
With the equivalent of a minimum opener, doubler can pass over 3
♦ and let advancer decide what to do. If advancer has 5+
♠, he/she can compete to 3
♠. If advancer has only a 4 card
♠ suit and maximum values, he/she can double or and bid a new suit.