[kiwinacol]

Hello all. I've been experimenting with a script for J2NT. It seems to me that a 2o1 pathway is often much more efficient even if the 4th + trump isn't promised. When do you tend to use Jacoby rather than a 2o1, and are there better uses for the 2NT bid?

One very economical sequence: 1S 2C; 2D 2S; (2C here is a good 4+ suit)

why would you go 1S 2NT instead, even if the bid does promise the trump support that makes slam investigation surer?

Even though it's descriptive I wouldn't fancy an auction like 1S 2NT; 4S. And especially if we also have a undisclosed double fit.

Thank you.

[steve2005]

If you don't raise opener with either Jacoby 2N or a splinter (or something else if using other conventions) then it is hard to show 4 card support latter especially if there is interference. The sequence you gave usually shows 3 card support. I guess you could play as 3+ with right follow-ups. You could play fit jumps which would help find double fits.
Jacoby 2N is generally considered a poor convention. A lot of times there is a jump to 4M really killing any slam try. There are better 2N raises out there, often where 2N is a limit+ raise.

[The_Badger]

A few years ago, I played against a Precision pair who used the J2NT bid as a low level Blackwood bid. But it obviously makes more sense with Precision as the opening hand is limited to 11-15. But it then left more space to highlight other features before committing to game or slam. To me, they did seem to bid a few more thin slams that other partnerships missed, but whether it was an effective tool long term I honestly cannot say.

[awm]

Here are a few advantages to Jacoby 2NT:

1. Opponents bid. Say the auction goes 1♥-Pass-2♣-4♠; you haven't shown a big heart fit yet, so you are quite a bit worse positioned than if you had started Jacoby 2NT. Clearly rare, but significant when it happens.
2. Responder has scattered values. Say ♠KQxx ♥AJx ♦Axxx ♣xx. If you bid 2♦ here, it will be hard for partner to evaluate that a singleton diamond is actually great, whereas a holding like Qxx is not necessarily so wonderful. Obviously the more your 2/1 sequences resemble relays (opener just describing his hand, responder's bids meaning little) the less this may cost you, but that's not how people usually play 2/1.
3. The 2/1 sequence is very nice when partner cooperates with a cheap call, but not so good when he raises your "suit." For example after 1♠-2♣-3♣-3♠ you have lost a whole level to Jacoby, and you still don't know partner's shortness (if any).

It's also worth noting that there are modified Jacoby structures which are much better, allowing you to include limit raises (for example) and avoiding the jump to 4M on a balanced minimum.

[bgm]

I agree with what Adam said, but personally I would also like to give up J2NT for other uses.

As many pairs did, and as OP mentioned, we can play 1M - 2♣ as club and BAL FG.
I think we can at least include the case with 4+M BAL FG case inside, or include any FG with 3+M without 5+ side suits.
Not sure if it is overloaded. If adopting this method,

 awm, on 2017-July-01, 05:38, said:

2. Responder has scattered values. Say ♠KQxx ♥AJx ♦Axxx ♣xx. If you bid 2♦ here, it will be hard for partner to evaluate that a singleton diamond is actually great, whereas a holding like Qxx is not necessarily so wonderful. Obviously the more your 2/1 sequences resemble relays (opener just describing his hand, responder's bids meaning little) the less this may cost you, but that's not how people usually play 2/1.
3. The 2/1 sequence is very nice when partner cooperates with a cheap call, but not so good when he raises your "suit." For example after 1♠-2♣-3♣-3♠ you have lost a whole level to Jacoby, and you still don't know partner's shortness (if any).

after suitable relay like Ambra or others, we can sort out the shortness below 3NT and knowing an approximate shape.
So I think it can be handled if the memory burden is not too high for the partnership.

 awm, on 2017-July-01, 05:38, said:

1. Opponents bid. Say the auction goes 1♥-Pass-2♣-4♠; you haven't shown a big heart fit yet, so you are quite a bit worse positioned than if you had started Jacoby 2NT. Clearly rare, but significant when it happens.

This is a very valid advantage. I would also like to add a point that after J2NT/Bergen raise, 4th seat seems tend to interfere more aggressively as you announced a big fit and not eager to penalize the opponent, compare to 1M - 2♣ where fit is not known yet and in many case it is BAL FG w/o fit targeting 3NT and the risk is also higher.

[Winstonm]

Nov 2007 issue of Bridge World has my article on Better Bergen Bidding which addresses major suit raises if anyone is interested.

[Zelandakh]

Most pairs use their forcing raise without a side suit source of tricks and 2/1 with one. This allows for more different hand types to be shown than always doing it a certain way. If you also play maxi-splinters, your 2NT response becomes in effect balanced or semi-balanced, which helps in terms of evaluating the hands for slam.

As others have mentioned there are also several alternative rebid structures to the original or "standard" J2NT ones, most of which are a considerable improvement. The version I use is (after 1♥ - 2NT): 3♣ = min + shortage; 3♦ = extras + shortage; 3♥ = min, no shortage; 3♠ = extras, no shortage; 3NT+ = max. More popular are methods in which the 3♣ rebid covers all minimum hands, allowing 2NT to cover limit raises as well as game-forcing ones. No doubt Winston's article has some further alternatives here.

The main point is to understand the differences and why they exist - a splinter auction is primarily showing your hand and expecting partner to be able to make an intelligent decision; a J2NT auction is primarily asking; while a 2/1 auction is showing as part of a dialogue. That line of thinking is usually sufficient to direct towards one path or another in cases where it is not clear which will be best.

[Vampyr]

 awm, on 2017-July-01, 05:38, said:

It's also worth noting that there are modified Jacoby structures which are much better, allowing you to include limit raises (for example) and avoiding the jump to 4M on a balanced minimum.

You don't need to do that just to avoid jumping to 4M on a balanced minimum. For example, I use 3♣ as a balanced non-minimum and 3NT as a balanced minimum when spades are opened, responses and rebids generally a step lower when hearts are opened.

[ggwhiz]

I use J2nt anytime I want to hear about a stiff such as with Axx in one side suit and my own stiff in another and a few other cases some of which are hands with very modest to no slam ambitions but I need to let partner know in case they have a big hand.

As for the jump to game after it screwing our slam bidding, we play that opener bids 3nt with modest extras including control rich minimums (AAK with a Q or a fitting JT is usually enough) and have never had a problem with that. The jump to game after J2nt is a certifiable dog.

Most slamish auctions that follow involve cue bidding rather than rkc which can be attractive to the initial responder who is thinking ahead.