[TowerTalk] F12 340N tuning + m2 40m yagi notes.

[Jim Thomson]

When tweaking the  F12 340N  REF tips, the manual sez to open circuit the DE.   However the manual doesn’t say whether to open circuit the DIR.
Ditto when tweaking the DIR, no mention if the REF has to be open circuited.   Does anybody know for sure ? 

(It does appear that when the DE is tweaked, and or the hairpin is tweaked, the shorting strap for both the REF + DIR must be in place per the manual).

On a related note, has anybody modeled  the 340N  on eznec ?   Is the gain fairly flat across the band or does it drop off towards the top
of the band ?    I would expect that the FB ratio is only good for aprx 150 khz, or aprx 7000-7150..or 7050-7200, etc.  

I note that both the 4-el M2 40m dual DE yagi....and also the 4-el, dual DE 40M yagi from optibeam both have good FB across only 150 khz.
The M2 has low swr across the entire band.  I believe the low swr on the M2 is more a function of the dual DE,,which also have staggered tip lengths. 
The gain on all 3 of these yagis is the same, aprx 5-5.2 dbd.    M2 has both an all band option, as well as an enhanced lower end  40m option. 
Interesting to note that the lower end option has less gain at the bottom of the band vs the all band option !    The only thing the lower enhanced 
tuning option provides is better FB at the bottom of the band, and better swr at the bottom of the band.  

Other than flatter swr, I don’t think the  m2 or optibeam is really much better than the 340N.   I did build a relay box for the 340N DE feedpoint. 
Consist of 3 x G2  gigavac relays in a f12 nema box... + 2 x silver plated flat strap coils.  The strap is 1 inch wide, and  coil assy has a 1.5 inch ID. 
4 turns used on each coil.   1st coil is tapped at the one third point and shorted out if required with vac relay #1.  Vac relay #2 used to short out
the remaining two thirds, if required.    Vac relay #3 is used to short out coil #2, if required.   I end up with 7 x segments.  The DE will either have its tips
shortened, or the LL rods shortened.  The 1:1 swr segments will end up at  7000-7050-7100-7150-7200-7250-7300.   I know its probably  gross overkill
but I had a half doz new G2 vac relays on hand..and loads of strap in various widths.  1 inch wide strap is easy to wind, and zero stray C between
turns, looks like knife edges facing each other, then they can be closer wound if required.  1 inch strap is the eq of  .637 inch OD tubing.  Tubing
eats up a lot more space than flat strap coils, and harder to wind and work with. 
    
Tnx... Jim  VE7RF