The EX card's segment is resolved as an absolute segment number — the tag field is ignored — so any deck whose feed is not on the first wire is silently excited at the wrong point. LD's tag mapping is correct (verified separately with a two-wire discriminator deck), so this is specific to the excitation path.
Minimal reproduction
Three collinear 25-segment wires forming one 10 m dipole, fed at the true center (tag 2, its segment 13 = absolute segment 38):
CE 3-wire chain, fed middle of tag 2
GW 1 25 0 -5 10 0 -1.6666 10 1e-3
GW 2 25 0 -1.6666 10 0 1.6666 10 1e-3
GW 3 25 0 1.6666 10 0 5 10 1e-3
GE 0
FR 0 1 0 0 14 0
EX 0 2 13 0 1 0
XQ
EN
| deck |
onec (b58c4ad) |
nec2c 1.3 |
EX 0 2 13 (center feed) |
184.811 −199.602j |
64.123 −55.120j |
EX 0 1 13 (off-center feed) |
184.811 −199.602j |
184.810 −199.600j |
onec returns the off-center answer for both — and its ANTENNA INPUT PARAMETERS row prints TAG 1 SEG 13 for the tag-2 request:
TAG SEG.
1 13 1.00000E+00 ... 1.84811E+02-1.99602E+02
i.e. the source landed on absolute segment 13 instead of tag 2 / segment 13.
Impact
Any multi-wire deck fed via a tag other than the first wire silently produces wrong results with no diagnostic. In the LD-corpus sweep for #11 this accounts for essentially all of the 258/447 diverging decks — split-element models (e.g. Cebik tutorial decks with a fed 1-segment bridge, EX 0 3 1) come out 100×+ off; driven-element beams ~2× off. Together with #16, a wild deck currently needs XQ and a feed on wire 1 to be trustworthy.
A golden deck with a tag-2 feed in the #15 CI matrix would pin this permanently.
The
EXcard's segment is resolved as an absolute segment number — the tag field is ignored — so any deck whose feed is not on the first wire is silently excited at the wrong point. LD's tag mapping is correct (verified separately with a two-wire discriminator deck), so this is specific to the excitation path.Minimal reproduction
Three collinear 25-segment wires forming one 10 m dipole, fed at the true center (tag 2, its segment 13 = absolute segment 38):
EX 0 2 13(center feed)EX 0 1 13(off-center feed)onec returns the off-center answer for both — and its ANTENNA INPUT PARAMETERS row prints
TAG 1 SEG 13for the tag-2 request:i.e. the source landed on absolute segment 13 instead of tag 2 / segment 13.
Impact
Any multi-wire deck fed via a tag other than the first wire silently produces wrong results with no diagnostic. In the LD-corpus sweep for #11 this accounts for essentially all of the 258/447 diverging decks — split-element models (e.g. Cebik tutorial decks with a fed 1-segment bridge,
EX 0 3 1) come out 100×+ off; driven-element beams ~2× off. Together with #16, a wild deck currently needsXQand a feed on wire 1 to be trustworthy.A golden deck with a tag-2 feed in the #15 CI matrix would pin this permanently.