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G8MNY  > TECH     16.05.22 07:12z 69 Lines 2906 Bytes #30 (0) @ WW
BID : 21817_GB7CIP
Subj: 2m & 6m Band "Neptune" Aerial
Path: SP7YDD<SR1BSZ<IW0QNL<ON0AR<GB7CIP
Sent: 220516/0704Z @:GB7CIP.#32.GBR.EURO #:21817 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To  : TECH@WW

(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
This is a rough IBM hi-AScii drawing of the Neptune dual band antenna for those
without MS Excel, it is NOT to scale.

          - - - - - - -
                                            1.25" Stainless
                                         A   1.404m
                                         B   0.483m
                                         C   0.057m
                       A   2m 3/4 Wave    D   0.064m +/-
                                         E   2.837m
                                         F   1.460m
            - - - - -                    G   0.169m +/-
      C                               H   0.139m
               B     
          D        
   ͼ - - - - - - - - - - - -
                                
                                           22mm Copper
                                         A   1.424m
                                         B   0.497m
                                E         C   0.052m
                                         D   0.057m +/-
                                         E   2.862m
                                         F   1.494m
            - - - - - -                  G   0.169m +/-
                                      H   0.139m
     Hĺ                     
                             
                 F            
                             
          - - -             
            G                
 ͼ- - - - - - - - - - - -
             Not critical, set as
             required from mounting.
             - - - - - - -

50 Ohm coaxial cable fed up the inside of the centre tube is joined on outer to
the centre tube & inner to the stub, at the points shown as "G" for 6m & "D"
for 2m.  Dimensions H & C are the centre to centre spacing between both stubs &
the centre pole.

Tapping points G & D should be adjusted for best standing wave on each band.
Although the original words do not specify the precise construction, I suspect
the stainless design is mitre cut & welded, the copper version being
constructed from 90degree Yorkshire fittings, in that case (easiest for the
garage constructor) you need to calculate the lengths to allow for the
"Yorkshire" I've never seen a cruciform Yorkshire coupling, so how you organise
the centre of the tridents I don't know, maybe a TEE coupling, & drill out
the bottom?

Dimensions E + A form a 3/4 wave on 6m, dimension A forms a 3/4 wave on 2m

Do a DC test to make sure all 3 wired are not framing. Then do an Ohm test.

Drawn, by G8AMG with reference to the Excel picture by G0WEH.

This was used by G0WEH of the GB3PC/PD repeater group, but they no longer have
a web site with info on it.


Why Don't U send an interesting bul?

73 De John, G8MNY @ GB7CIP


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