Steve,
A friend pointed me at the G5RV probably twenty-five years ago and
the specs. he had said at least seventy feet of coax. So the urban
legend has been around at least that long!
I had that antenna mounted off the side of my tower at nearly fifty
feet in an inverted fashion, not the most recommended and that
antenna did such a great job!!
So you do all you can to get it right and fudge on some of it and
probably the antenna is going to do just fine. And when you've done
your best and plug the coax in to the transmitter, what happens happens!!
Pat, K9JAUAt 07:05 AM 8/20/2012, you wrote:
>Just a guess on my part, but one of the ARRL books lists 76 feet as a
>non resonant length for guy wires. Maybe the antenna guys are trying to
> hit a "good" length for the coax. Maybe not to improve anything, but
>to prevent a problem on a particular band.
>
>I know from my own experience (and that of others) that adding a short
>coax jumper to increase the length a bit will make a finicky band tune
>better.
>
>
>Or it just may be that's how much coax he had laying around the first
>time, and since it worked , that became the length. Or it was just
>considered enough to get from point A to point B.
>
>
>73, Steve KW3A
>
>
>
>On 8/20/2012 7:23 AM, Lou Kolb wrote:
> > Colin,
> >
> > The minimum 70 feet is a specification from W8AMZ, whose version
> of the G5RV
> > Howard and I are using. I have no idea where that comes from nor
> do I think
> > it's meant to be a universal spec for all G5RV's. I imagine he has his
> > reasons for such a spec but I haven't seen them listed anywhere. When I
> > bought the coax for mine, I just happened to get a 75 foot run to make sure
> > I'd have enough. Then, when I bought his version, I saw his
> requirement and
> > just left the coax in tact even though I don't need that much. Lou WA3MIX
> > Lou Kolb
> > Voice-over Artist:
> > Radio/TV Ads, Video narrations
> > Messages On-hold:
> > www.loukolb.com
> > ----- Original Message -----
> > From: "Colin McDonald" <[log in to unmask]>
> > To: <[log in to unmask]>
> > Sent: Monday, August 20, 2012 12:09 AM
> > Subject: Re: Tom's G 5 R V
> >
> >
> >> granted, the recommendation for using 75 feet of 50 ohm coax is something
> >> your antenna designer stated.
> >> However, most antennas based on the G5RV design do not specify a certain
> >> length of 50 ohm coax to feed it.
> >> Where does the magic number of 75 feet come from? it's not a quarter wave,
> >> or a half wave on any of the frequencies the G5RV style antenna covers...
> >> I've now seen several installations where a short pig tail, or any various
> >> length of 50 ohm coax is used and the antenna plays perfectly fine.
> >> does the extra long length of coax somehow reduce swr or increase
> >> bandwidth
> >> or make the antenna more efficient? I would think any gain in efficiency
> >> would be off set by loss in the coax over 75 feet.
> >> those are just my thoughts.
> >> But if you have a technical explanation as to why they work better with 75
> >> feet of coax, please explain if you would.
> >> I'm curious to know why.
> >>
> >> 73
> >> Colin, V A6BKX
> >> ----- Original Message -----
> >> From: "Howard, W A 9 Y B W" <[log in to unmask]>
> >> To: <[log in to unmask]>
> >> Sent: Sunday, August 19, 2012 7:51 PM
> >> Subject: Tom's G 5 R V
> >>
> >>
> >>> I have been out of town until about an hour ago. I just read all the =
> >>> posts in regard to your antenna Tom.
> >>>
> >>> For the antenna to work properly you need about 75 feet of coax between =
> >>> the window line and your radio. The excess coax can just be coiled up =
> >>> in your shack or outside the RV at a convenient place.
> >>>
> >>> I know you really don't need to buy a new antenna, however, the G 5 R =
> >>> V's from W 8 A M Z are made very well. The connections at the top where =
> >>> the window line connect to the two legs of the antenna are sealed in =
> >>> epoxy. The bottom end of the window line is terminated in an S o 239 =
> >>> connector which is also sealed in epoxy therefore all the connection =
> >>> points will not get any moisture in them. The 450 ohm window line is =
> >>> copper coated steel wire which is insulated and will not break from =
> >>> movement in the wind.
> >>>
> >>> I own one of these and I feel it is of high quality. The regular size =
> >>> is about $70.
> >>>
> >>> Get the wire off the ladder, cut the P L 259 connector off the coax =
> >>> pigtail check for continuity. If there is still a short, cut the =
> >>> pigtail completely off the window line and make a new pigtail and =
> >>> install it be sure to water proof all connections.
> >>>
> >>> Again, 75 feet of coax between window line and radio, a must!!!
> >>>
> >>> In general, it seems like most agree on what you should do.
> >>>
> >>> 73
> >>>
> >>> Howard #3
> >
> >
> >
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