[TowerTalk] [Bulk] Mosley (Antenna Gain)

[Grant Saviers]

An NEC4 analysis shows a 5+5 20m stack beats a dipole at the same max 
height (125') in absolute gain by 10db (7.6dbi to 17.6dbi). This 5+5 owa 
is <1.25:1 swr band edge to edge.  The dipole has several -1 to -3db 
high angle lobes to pick up local QRM/QRN so the stack has another big 
advantage for working DX.  There are many bigger stacks out there that 
do better.

Re the other assertions, you may want to check out what designers using 
computer analysis have produced for very good multiband interlaced 
antenna designs.  These interlaced designs tend to be on shorter booms 
because it is easier to do, and that is where the market is.   Putting 5 
bands on one 48' boom has been done, but it is pretty complex.

Grant KZ1W

On 2/19/2015 11:05 PM, Chuck Smallhouse wrote:
>
> "Since the 70s,  at least a dozen times we have helped swap a Mosely 
> TA-33 jr to
> something else, usually a Hy-gain 204BA.   The difference on 20m is the
> usual 10 db".
>
> You really must have drunk a lot of the CC Kool Aid.  There is no HF 
> yagi antenna that has anywhere close to 10 dBD gain, let alone that 
> difference over another !  Even a stacked monobander system doesn't 
> come close to 10 dBD gain .
>
> In my opinion, no multiband yagi has anywhere close to optimum gain, 
> they are all compromises.   To meet the current needs of SS xmtrs and 
> PAs (no manually tune pi networks) they are designed to be broad band 
> and thus compromise gain.    The more elements (more bands) the 
> greater the compromise.
>
> The tunable SteppIR that supposedly can be optimized at all 
> frequencies across a band, might be better, even though the element 
> spacing remains the same for all bands and frequencies. However 
> monoband yagis, with good gain, can be designed with element spacing 
> of < 0.1 WL to > 0.3 WL.  I assume that SteppIR's S/W takes this into 
> account, therefor essentially making them a muti-band set of monoband 
> yagis.
>
> No I don't have one - just a fairly new design, broadband tribander.
>
> Chuck,  W7CS
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>