[TenTec] bill orr article

Sun Feb 1 15:18:20 EST 2009

If bringing twin lead, either ladder or window type, into the shack is 
an issue, it is possible to mount a 1:1 balun just outside and run coax 
into the building. The swr on the coax will be high, depending on band, 
antenna length, and feedline length, but if the coax is kept short and 
is of good quality, the losses will be low, certainly much lower than 
the  68-70 feet of RG-8X or RG-58, commonly used with G5RV antennas.

			73,

			Bob WB2VUF

Bob McGraw - K4TAX wrote:
> Bob is correct on this and I fully agree.  The G5RV works well for a wire 
> antenna on 20M.  As to other bands, it is compromised to a very compromised 
> antenna.  I know lots of hams have used one and think it is a very good 
> antenna.  Perhaps it is due to space limitations not being able to put up 
> 135 ft of wire to operate 80M - 10M or the desire to have a "all band" 
> antenna without using a tuner.  My experience indicates that a tuner is 
> still really needed with the G5RV for most applications.  The high SWR at 
> the balanced to unbalanced transition through the balun and the loss in the 
> coax make the antenna appear to have a low SWR at the radio.
> 
> One good approach to an antenna is put up what ever length of wire you can 
> support, feed it in the center with a balanced feed system, connect it to 
> the tuner that one used for the G5RV, but use the balanced output, and enjoy 
> a new world of ham radio.  Balanced wire feed is really not that difficult 
> to install and use.  Just keep it about 6" to 10" away from parallel runs of 
> metal towers, masts, downspouts and such and it works just fine.  As to 
> getting it through the window, walls or floor or ceiling, no Herculean 
> effort is required.  Actually MFJ makes a panel to do just that.  As to 
> lightning protection, The Wireman make a static discharge device to use 
> outside of the house that addresses that concern.  It makes no difference if 
> you use the true open wire line, although a bit more of a challenge to 
> handle or if you use the covered web type line.  I would comment that the 
> covered web type line is more prone change tuning with rain, snow and ice, 
> but the tuner takes care of that nicely. As to using 300 ohm line, 450 ohm 
> line or 600 ohm line, take your choice.  I have a beautiful folded dipole 
> for 75M made totally out of the 300 ohm web type line.  Works great and 
> stayed up through 2 Winters of snow and ice.
> 
> As to concerns of RFI or TVI, if you have these problems then you have an 
> installation problem.  It is not a fault of the balance feed-line, so don't 
> blame that.  I use a balanced feed on my 256 ft center fed wire, bring the 
> balanced feed from the top of the tower on 12" PVC stand-offs that I made, 
> then through the wooden attic eve vent, under the roof rafters and it drops 
> down through the ceiling via a 1" slot direct behind the tuner.  The TV 
> antenna and its coax is on the same tower along with the DSS antenna and 
> there is NO RFI or TVI issues at legal limit power, any band, any mode.  Oh, 
> the only ground for the station is via 3rd pin safety ground supplied via 
> dedicated 230 volt 20 amp service direct from the breaker panel to the 
> operating position.  I'm on the 2nd floor and in the middle of a wood frame 
> house so any ground is 50 or so ft away.  My lightening protection system is 
> mounted on the tower at the point the balanced feed enters the house.  The 
> tower has driven grounds at its base and it is BONDED back to the main AC 
> ground, all outside of the house.
> 
> 73
> Bob, K4TAX
> 
> 
> 
> 
> ----- Original Message ----- 
> From: "Bwana Bob" <wb2vuf at gti.net>
> To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
> Sent: Friday, January 30, 2009 10:11 AM
> Subject: Re: [TenTec] bill orr article
> 
> 
>> Yes, The G5RV is optimized only for 20 meters, where it is a 3/2
>> wavelength.  The 30 feet of twin lead is a matching section cut for 20
>> meters.  At the end of the twin lead on all other bands the swr will be
>> high.  Th secret to the wide bandwidth and low swr on all bands that
>> some claim is the fact that most G5RV designs specify 70 feet of coax
>> connected to the twin lead. The resulting high losses in the coax due to
>> normal loss plus high swr has the effect of smoothing out the swr.
>>
>> Years ago I used a G5RV rigged as an inverted V (not the best
>> configuration, but the only way it would fit in the back yard). It
>> worked OK on 80, 40 and 20, but was terrible on 15 and 10.  On 10
>> meters, a dipole in the attic out performed it. I took it down when I
>> discovered that a simple 1/4 wave inverted L was better on 80.
>>
>> Check out Walt Maxwell's (W2DU) site.  It has a good discussion of the
>> G5RV vs the merits of a dipole with twin lead, window line, or ladder
>> line running to the shack.
>>
>>
>> 73,
>>
>> Bob WB2VUF
>>
>> Bob McGraw - K4TAX wrote:
>>> Do a Google search for G5RV.  You'll find a bountiful amount of info. 
>>> Lots
>>> of test data, construction techniques and design information.
>>>
>>> >From my use of a G5RV some years ago, I'd say if that's the only antenna 
>>>> one
>>> can put up, it's better than no antenna at all, but not much.  There are
>>> much better antenna configurations, antennas that are more efficient, 
>>> more
>>> reliable and work quite well.  All much simpler and easier to build.  Try
>>> the 135 ft center fed wire fed with a balanced feed system.  And oh yes, 
>>> the
>>> balanced feed system is much much easier to install and keep in the air 
>>> than
>>> 90% of the hams understand.  It will always have lower loss than any coax
>>> fed antenna too.
>>>
>>> 73
>>> Bob, K4TAX
>>>
>>>
>>> ----- Original Message ----- 
>>> From: "Verne Smith" <vernew7grn at cascadeaccess.com>
>>> To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
>>> Sent: Thursday, January 29, 2009 8:10 PM
>>> Subject: [TenTec] bill orr article
>>>
>>>
>>>> bill orr has a book on antennas in which he covered g5rv i believe it is
>>>> available from arrl
>>>>
>>>> verne
>>>> w7grn
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>>>
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> 
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