Birmingham - - - G3UPA - - - IO92dm

Here are some notes on the Inverted L and the G5RV that I am currently using.

Although I can tune all bands using the original 180 feet L with the remote controlled L match at the base of the vertical, band changing could sometimes take around 2 minutes, waiting for the capacitor and inductor to move from one end to the other. I decided, therefore, to add the G5RV slung underneath the top wire, which allows me to use any band from 160m to 10m without any re-tuning.
I can switch the L match output to the 30ft vertical pole rather than the inverted L.
Both ends of the top 120ft wire are held up via insulators and pulleys so that the whole thing can be on the ground in less than 10 minutes.
Some observations on my G5RV:-
There are literally dozens of articles about the G5RV available on Google but here's what I found.
My G5RV has a 102ft top and 29'6" of 300 ohm window ladder line. The ladder line came from Nevada Communications and is high quality, low loss stuff. I have a 25ft fibre-glass fishing pole at the centre to help reduce the droop.
Originally I used 300R TV twin, since I never run more than 100 watts, but it was several years old and getting a bit battered and it has absolutely no physical strength at all. The system got stuck in a nearby tree during a gale and I pulled on the feeder to get it down. It broke, in two places. Hence the change to the heavy duty stuff. The length of the feed changed from 31ft with the TV cable to 29' 6" with the new stuff.
My current G5RV is slung below the centre of my Inverted L, as per the above picture.
Below are the actual readings taken from the current setup.

VSWR readings taken on my G5RV

Frequency3.5003.6003.7003.800
VSWR2.91.61.42.7
Frequency5.2005.3005.400 
VSWR5.05.05.0 
Frequency7.0007.1007.200 
VSWR1.82.22.7 
Frequency10.10010.15010.200 
VSWR4.64.44.0 
Frequency14.00014.10014.20014.300
VSWR2.02.73.03.3
Frequency18.00018.10018.200 
VSWR2.01.91.9 
Frequency21.00021.10021.20021.300
VSWR2.12.12.12.1
Frequency24.80024.85024.90024.950
VSWR3.23.43.53.5
Frequency28.00028.50029.00029.500
VSWR2.82.22.73.0

As you can see, I can use the G5RV on all bands from 80m up, with the exception of 60m and 30m perhaps, despite the ex'sperts opinions telling you it will only work, poorly, on half the bands. Plus all the EzNEC simulations showing a VSWR of 80+ on some bands.
.At present the only tuner that I use is the one in the rig. The readings above are without any tuner. With the tuner it shows 1:1 on all except 60mtrs.
The proof of the pudding is in the eating, as they say!
On most of the bands the G5RV, compared to the Inverted L, produces about 1 to 2 S-points improvement in received signal strength and on all bands it usually shows between 1 and 2 S-points lower noise.
As you can see from the figures 80m is a bit high in frequency, based on my preference for CW, but if I increase the top length to improve 80m operation it puts 40m & 20m way below the bands. They already have minimum VSWR below the bands as it is.
I intend to try a separate run of low loss 75 ohm co-ax feed to the bottom of the 300 ohm twin, in the not too distant future.
During my initial construction and tests I anchored the ends of the top wires to the fence posts via another length of insulated wire simply tied onto the ends. This caused me more than a whole day of grief. The system went up and down like a yoyo with bits trimmed off/added to both the top wires and the feeder with very little effect on the readings. Just before I hung myself from the mast, I found that the far end anchor wire had become part of the system. Even at 50 watts max. the insulation had completely broken down and the anchor wire had become welded to the top wire, making one side 62ft long. The other end showed no sign of overheating/melting at all, suggesting that my system is not very well balanced, but it may just be that the earth leakage was much greater at the far end. All future work was carried out with dog-bone insulators at both ends.
No more problems with breakdown since. Maybe I should have used nylon rope instead of insulated cable but none was handy at the time.
G3UPA said that......