DB0FHN

G8MNY  > TECH     15.03.05 22:51l 68 Lines 2851 Bytes #999 (0) @ WW
BID : 36891_GB7CIP
Read: DF5NK GUEST
Subj: 2m & 6m Band "Neptune" Aerial
Path: DB0FHN<DB0RGB<DB0MRW<OK0PPL<DB0RES<DK0WUE<SP7MGD<RZ6HXA<IK1ZNW<GB7CRV<
      GB7CIP
Sent: 050315/1907Z @:GB7CIP.#32.GBR.EU #:36891 [Caterham] $:36891_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To  : TECH@WW

This is a rough IBM hi-AScii drawing of the Neptune dual band antenna for those
without MS Excel, it is NOT to scale.

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

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