Pat,
I did have one made by Van Gordon back in the '80's. Whatever the coax
length was (either 75 or 72) I don't recall any warning that this was an
important length. When I couldn't get it to load on 10 meters, a local
suggested changing the length of the coax. Since it's easier to add
than remove, I added a few feet and all worked well. Worked the world
and had a blast with it.
73, Steve KW3A
On 8/20/2012 8:54 AM, Pat Byrne wrote:
> 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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