Ok, has anybody tried retrofitting the stock 3/16" solid LL wires in a F-12
340N [3 el 40m yagi] with coils ??
On paper, this looks fairly straight forward. To save weight, and still keep
the UN loaded Q of the coils high,
I was thinking of either 3/16" or 1/4" AL wound coils. Per K6STI's coil
software, a typ coil for a 40m yagi,
using 3/16" AL tubing [ all air wound] has an UN loaded Q of aprx 767.
IF the same 3/16" coil was made from
CU tubing, the Un loaded Q would be aprx 1200. If the coil was made from
1/4" AL tubing, the UN loaded
Q would still be sky high, [ > 1250]... but a lot lighter than 3/16" CU tubing.
My concern is... where will the 40m yagi resonate on it's aprx 3rd harmonic ??
As is, stock, the F-12 340N
does NOT resonate on 15m. Rather it resonates at aprx 24.3 mhz. [which
screws up 12m]. I don't operate
10+12 m..so that is not an issue. However I do operate 17 +15m. The only
thing I can think of, is to try
retrofitting just the DE... and install it at a reasonable height...and see if
resonates any where near 15m.
The thought here is... stock, the REF-DE-DIR are all different tip to tip
lengths..ranging from 51' to 53' to 59'.
IE: the resonant point on each ele is done by tweaking the tip lengths. That
being the case, if coils are retrofitted,
all 6 x coils would have identical uh. The ele lengths would still be
Has anybody done a similar retrofit ? I dunno if it would buy much..since
the ele's are pretty long anyway to start with.
The stock LL consists of aprx 52" long x 3/16" solid al rods. They start at
the solid 1" fiberglass insulator..and then extend
OUT towards the tips, then across 10", then back 48" to the other side of
the same insulator. Any coil would not weigh
any more than the existing 9' of solid rod. The replacement coils would just
straddle the existing insulator. It looks
'doable'..... but has anybody 'done it' ? If AL coils are used, then no
dissimilar metal problems either. Each end of the
AL coil could be flattened, and then bolted to some thick AL bar stock, that is
then in turn, bolted to the AL ele...with
1/4-20 SS bolts and SS nylocks.
Tnx....... Jim VE7RF
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