G8MNY  > TECH     19.04.25 08:45z 79 Lines 2574 Bytes #180 (0) @ WW
BID : 30615_GB7CIP
Read: GUEST
Subj: Using a G5RV on 160M
Path: ED1ZAC<ED1ZAC<IZ3LSV<IK6IHL<IK7NXU<HB9ON<DK0WUE<DK0WUE<F1UBL<K7EK<
      VE3CGR<VK2RZ<GB7CIP
Sent: 250419/0831Z @:GB7CIP.#32.GBR.EURO #:30615 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To  : TECH@WW

By G8MNY                               (New Aug 13)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

To use a G5RV or any HF dipole/doublet conveniently to a Marconi T aerial on
topband you will need..

1/ A good earth
2/ A matching coil
3/ Double Pole Relay/switch
4/ Outdoor Box

AERIAL
Tree                                     2nd
Supports                                Support
- -oÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÒÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄo- -
Insulator            º
             Balancedº
               Feederº
                     º
                     º
                     º
                     º
                 Switched===================Coax to shack
                 Matching  ³Earth
                    Box    ³stakes
                           ³
SWITCHED MATCHING BOX
This has to house the relay or manual double pole high voltage switch with the
loading coil.

  Balanced
   Feeder 
   ³    ³           
   ³  oÄÁÄÂÄÄÄÄÄÄÄ(((()
RL1³_/o   o RL2   L /³\
      ³   o\_________³
      ³   ³_         ³
      ³   ³/|        ³
      ³  === C       ³         ___
      ³  /³          ÀÄÄÄÄÄÄÄÄ)___Shack
      ÀÄÄÄÁÄÄÄÂÄÄÄÄÄÄÄÄÂÄÄÄÄÄÂÙ   Coax
            Earth   ÚÄÄÁÄÄ¿ _³_
            Stakes  ³Relay³ \_/
                    ÀÄÄÂÄÄÙ  ³    Select
                       ÀÄÄÄÄÄÁÄÄÄ<160M

This circuit is with no HF balun for use on a G5RV or half sized G5RV. If a
dipole is used with then a switched balun & more complex switching is needed.

With the relay released L is shorted out & the feeder is connected to the coax
in the normal way.
With the relay operated the feeder is shorted together & connected to the coax
via the L & a SWR triming cap C. The voltages can be very high (1kV) so a relay
or switch with good contact separation & contacts to spacing is need.

TUNING
Generally a series L (tapped 60 turns on a 3cm dia former) is all that is
needed to get the resonated Z down to near 50/75ê with most aerials. But if the
SWR is still to high at resonance the C across the coax (via RL2 contact) of
100-2000pF should bring the Z to an exact match.

BOX
A black plastic box is best. Hermetically sealed boxes really don't seal that
well outdoors. A better approach is to leave a breathing hole in the bottom
(lowest point) so that any water can drain way, but put a fine mesh over it to
stop insects. Paint up & spray all parts with a light oil to resist rusting.

Grease up well, all screws & connectors use outside so any water has no where
to go.


Why Don't U send an interesting bul?

73 de G8MNY @ GB7CIP



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