[1000mp] YAGI 4 elements long boom for 10mtb

[Bud Ansley]

HELLO FERDY .
            I have built many many yagi's over the years . They all work
, Some work better
than others . This is caused by several things , The most important
thing to remember is
the performance of the yagi is controlled by the element lengths and
spacing . I have
found most any spacing will work if you use a accurate taper schedule
for the element
lengths . I recently built a 4 element wide spaced 10 meter yagi . I
wanted it to be very
light ( weight ) , No U bolts or heavy hardware . The boom is 22 feet of
1 1/2 inch tubing
with out a top guy . I made thru boom insulators for attaching the
elements to the boom .
The elements are thin wall aluminum tubing , 1/2 inch , 3/8 inch and 1/4
inch tips . It
required much longer overall lengths due to the taper schedule . 
            Remember the antenna must be resonant at the operating
frequency . The feeding
of the antenna is a different issue . On 10 meters I have found the
coaxial gamma to be
useless , This is caused by the gamma rod being to short to provide
enough capacity . The
old rule of thumb is use 7 x the frequency in meters for the gamma
capacity . ( 7 x 10 =
70 pf ) I would use about 100 pf variable cap . 
            If you open most any hand book to the antenna section , Find
a parasitic beam
design and use the graph to find the element spacing and lengths , Then
apply the correct
taper schedule It will work very well . Matching it is easy if the above
is applied .

 HAVE FUN  REGARDS  

 de  BUD / W6VH

"De Martin, Ferdy" wrote:
> 
> Hello, I know that my question is not directly connected with the 1000mp
> but...
> 
> I would like to build a 4 element long boom monoband Yagi for 10mtb (28500)
> 
> (I already have aluminium tubes and hardware from old yagi)
> 
> Is anyone having a good drawing or an adresse on internet where I can find
> this info?
> 
> Thank you very much in advance
> 
> Best 73's
> 
> Ferdy
> [HB9DSP]
> www.gtoevolution.ch/hb9dsp
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