Message 24643 in TECH.WW
From: G8MNY
Date: Wed, 24 Jun 26 07:58:00 Z
Newsgroups: TECH.WW
Subject: Using a G5RV on 160M
Message-ID: <63256_GB7CIP>
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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
Switched===================Coax to shack
SWITCHED MATCHING BOX
This has to house the relay or manual double pole high voltage switch with the
loading coil.
Balanced
Feeder
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 and more complex switching is needed.
With the relay released L is shorted out and the feeder is connected to the
coax in the normal way.
With the relay operated the feeder is shorted together and connected to the
coax via the L and a SWR triming cap C. The voltages can be very high (1kV) so
a relay or switch with good contact separation and 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 50/75R 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 and spray all parts with a light oil to resist rusting.
Grease up well, all screws and 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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