G5RV Jr problem

[ok bowhunter]

This is my first post after finding this great forum.

New ham expermiting with a G5RV Jr and having problems tuning in 12M and 17M, 40M, 10m, and 20M works ok, but the other bands will not even get close to a usable SWR. The antenna is mounted flat on the peak of my roof 19 feet off the ground and I am using a MJF Versa Tuner and feeding the antenna to the twin lead with about 25 feet of coax. My first question how should the twin lead line be mounted? Does it need to be 90 degrees to the antenna wire? Do I need to get the antenna wire off the roof? I read somewhere that you need at least 50 feet of coax to properly connect to the twin lead. Do I really need 50 feet of coax all I need is about half that to reach my radio.

Thanks for the help.

 

[Captain Kilowatt]

You really should get the antenna up off the roof for a variety of reasons only one of which is performance. Any antenna in the clear of surrounding objects will work better than one that is not. The other is possible fire hazard due to high voltages developing on the ends of the wire arcing to the roof especially if it is wet or damp.

As for not working well on 12 and 17m all I can say is, sorry but it likely won't. Amateur bands are harmonically related but 12 and 17m as well as 30m are odd balls in relation to the other bands. The G5RV was designed long before 12 and 17m were amateur bands and the antenna was never meant to work on those bands. In fact it was designed as a 20m monoband antenna but it just happens to offer a somewhat half decent SWR on the other bands as well except for what are known as the WARC bands, 12m, 17, and 30m.

 

[Moleculo]

The antenna is mounted flat on the peak of my roof 19 feet off the ground and I am using a MJF Versa Tuner and feeding the antenna to the twin lead with about 25 feet of coax. My first question how should the twin lead line be mounted? Does it need to be 90 degrees to the antenna wire? Do I need to get the antenna wire off the roof?

You need to get it off the roof (as CK already said). Mount it as an inverted V or flat, but it needs to be off the roof. The G5RV is also designed to have the ladder line hang straight down from the feedpoint - it's part of the antenna and acts as an impedance transformer on certain bands. Do this stuff first and you should see some improvement. I bet you will even be able to get it to load up on 12 and 17

G5RV Multi-Band Antenna by Louis Varney

 

[BJ radionut]

This is my first post after finding this great forum.

New ham experimenting with a G5RV Jr and having problems tuning in 12M and 17M, 40M, 10m, and 20M works ok, but the other bands will not even get close to a usable SWR. The antenna is mounted flat on the peak of my roof 19 feet off the ground and I am using a MJF Versa Tuner and feeding the antenna to the twin lead with about 25 feet of coax. My first question how should the twin lead line be mounted? Does it need to be 90 degrees to the antenna wire? Yes... Do I need to get the antenna wire off the roof? It would certainly help...
I read somewhere that you need at least 50 feet of coax to properly connect to the twin lead....Never heard that one before!...Well just read the info from couple suppliers...The junior version requires 35ft min...length of RG8 coax....I am not sure I like that...means the're using the coax as a "matching stub" Do I really need 50 feet of coax all I need is about half that to reach my radio.

I would prefer "Myself" to extend the 300 or 450 line all the way to the tuner...make sure the tuner is grounded well and do it like a Doublet Antenna and I think you would have better preformance...(IMHO)
Lifting the "Legs" even 3 or 4 ft above the roof and stretching the 450 line down the side of the house on Old style twin lead stand-offs a few inches long( staying away from metal) if possible will make a big difference in how "she tunes" and preforms....
You might give us some additional info on your working conditions in regards to your lot and what your "acceptable" antenna configuration is...
Welcome to Ham Radio and the forum!

The G5RV is best used in "open space" with the twin lead running 90 deg's to the rest of the antenna....It is part of the antenna (not just feedline)
A G5RV needs to have that 450 feed line and the "flat top' section in as "much open space" as "possible" to work at it's best preformance....Google the antenna and see what has worked well for others...
All the Best
BJ

 

[Mudfoot]

Greetings and Salutations.