On the 27 I spent most of the day trying out a new antenna which is a dipole 45 meters long each way and at 15:00 I got it to work happily on the Frequency from 1.951 to 1.990 at 30 meters long each way at about 17:30 I started to call CQ on 1.990 then had a contact, this time 57 both ways which was a lot better because last time it was 33 both ways then a bit later on G3WFK came in 57 but no contact maybe next time I will make a two way contact in to G. maybe 80 meters soon.
You say you were using a dipole â45 metres long each wayâ, and then â30 metres long each wayâ. I assume these are the lengths of wire per leg of the dipole. Neither of these lengths would be anywhere near resonance on the 160m or 80m bands, so for it to work properly you would need to use an Antenna Tuning Unit (ATU).
Are you using an ATU, and what kind of feedline are you using? Presumably not coax?
so for it to work properly you would need to use an Antenna Tuning Unit (ATU).
Or a âboat-anchorâ, peaking and dipping!
Just for reference, I have had a number of successful chases on Top Band with a G5RV set up as a doublet and tuned by an MFJ-949E, the G5RV is as usual just over 31 metres long.
I listened on all bands on Saturday, hoping for a s2s with you, from GW/NW-062 Hope Mountain but heard nothing. Having said this, I was unable to work Barry or Karen on GW/NW-057 but did manage a 2m contact with them on GW/NW-074.
Pardon? I suppose you are referring to what was known as a âpi networkâ in the old days. Yes, that was standard practice in the days when valve output stages were the norm.
Just for reference, I have had a number of successful chases on Top
Band with a G5RV set up as a doublet and tuned by an MFJ-949E, the
G5RV is as usual just over 31 metres long.
A G5RV is a G5RV. A doublet is a doublet. I assume when you say âa G5RV set up as a doubletâ you mean it is without the coax ⌠i.e. using balanced feeder all the way down to the ATU? That is exactly what I use at home; a doublet with 102 ft top and 300 ohm slotted twin feeder terminating on an MFJ ATU. No coax. That works on all bands from 160m to 10m, including the WARC bands.
A G5RV is a G5RV. A doublet is a doublet. I assume when you say âa
G5RV set up as a doubletâ you mean it is without the coax ⌠i.e.
using balanced feeder all the way down to the ATU? That is exactly
what I use at home; a doublet with 102 ft top and 300 ohm slotted twin
feeder terminating on an MFJ ATU. No coax. That works on all bands
from 160m to 10m, including the WARC bands.
73,
Walt (G3NYY)
A common misconception, Walt. I refer you to Louis Varneyâs article in Radcom, July 1984, p572-575: âBy far the most efficient feeder is the open wire type. A suitable length of such can be constructed in the same manner as that described for the open-wire matching section. If this form is used, almost any length may be used from the centre of the antenna to the matching network (balanced) output terminals.â What defines a G5RV as far as its inventor is concerned is not the feeder arrangement, but that it is a 1.5 wave antenna on twenty metres with four lobes in its horizontal polar diagram. As you and I both know, as a doublet its a damâ fine all-band antenna - even on six metres thoâ only the Good Lord knows where the lobes are pointing!
A common misconception, Walt. I refer you to Louis Varneyâs article in
Radcom, July 1984, p572-575: âBy far the most efficient feeder is the
open wire type. A suitable length of such can be constructed in the
same manner as that described for the open-wire matching section. If
this form is used, almost any length may be used from the centre of
the antenna to the matching network (balanced) output terminals.â What
defines a G5RV as far as its inventor is concerned is not the feeder
arrangement, but that it is a 1.5 wave antenna on twenty metres with
four lobes in its horizontal polar diagram.
That was the case AFTER he updated his antenna design in the July 1984 issue of Radcom.
The original G5RV design was published in 1946. It consisted of a 102 ft top and a 34 ft matching section of open wire feeder, which had attached to its lower end an unspecified length of either 75 ohm impedance twin lead or 80 ohm coaxial cable. This configuration could be made to work (just) on all bands without an ATU, because it presented a low-ish impedance on the bands available at the time, which was within the impedance range of early amateur radio transmitters with pi-network outputs. However, the match to the coaxial or twin feeder at the lower end of the matching section is only good on 14 MHz and 24 MHz. Therefore, even when 75 ohm or 80 ohm feeder is used, on other bands it is really essential to use an ATU between the low impedance feeder and the transceiver. This will enable the transceiver to âseeâ a correct matching impedance of about 50 ohms, but there will be a considerable mismatch in the system and standing waves along the feeder.
By 1984, G5RV had come to accept this (stressing in his 1984 article that an ATU IS necessary) and concluded that if you were going to use an ATU anyway, it was more sensible to dispense with the low impedance feeder altogether and use balanced feeder all the way to the shack. Furthermore, if balanced feeder is used throughout, there is no longer any need for the top to be 102 feet long. It can be any convenient length to fit into the space available and will still provide high-performance, all-band working.
On the rare occasions where I describe my antenna, I call it a âG5RV doubletâ!
Before I converted it to a doublet I used semi-air spaced coax to the matching section and could tune the six bands on a TS-520S and all bands to 6 metres on an FT-817 with a home-brew Z-match, but I was worried about losses due to standing waves in the coax and spliced on extra 300 ohm window ribbon after hunting out the Radcom article I referred to.
To be argumentative, though, I still think that the defining feature is that 1.5 wave on 20 metres and the resulting four-leaf clover polar diagram, hence I do not believe that the âhalf-sizeâ and the âdouble-sizeâ variations deserve the distinction of Louis Varneyâs callsign!
My transceiver is an Icom 703. These are equipped with automatic tuners.
To explain a little better, my experiments were with two lengths of wire, each 45 metres long and connected with a length of coaxial feeder cable. By adjusting the lengths using the standard method used by the military I found that it would tune according to my needs and with minimum s.w.r.
In reply to MW6GWR:
Hi Ricky
By âBy adjusting the lengths using the standard method used by the militaryâ - do you mean 'by folding the outer ends back along the wire of the dipole?
How high off the ground are the wires?
73 Ken
GM0AXY
maybe next time I will make a two way contact in to G. maybe 80 meters soon.
