An OCF (Off Center Fed) antenna works much better. Feed with coax. Low SWR
on all bands. Good reports. I'm using one. Jim N4BE
http://hamcall.net/7bandocf.html
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of Bob McGraw - K4TAX
Sent: Monday, February 02, 2009 12:38 AM
To: wb2vuf@arrl.net; Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] bill orr article
That will work, but will always be somewhat of a compromise. One must
consider the rating of the balun and subsequent loss.
73
Bob, K4TAX
----- Original Message -----
From: "Bwana Bob" <wb2vuf@gti.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Cc: <wb2vuf@arrl.net>
Sent: Sunday, February 01, 2009 2:18 PM
Subject: Re: [TenTec] bill orr article
> 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@gti.net>
>> To: "Discussion of Ten-Tec Equipment" <tentec@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@cascadeaccess.com>
>>>> To: "Discussion of Ten-Tec Equipment" <tentec@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
>>>>> _______________________________________________
>>>>> TenTec mailing list
>>>>> TenTec@contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/tentec
>>>>>
>>>>
>>>> _______________________________________________
>>>> TenTec mailing list
>>>> TenTec@contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/tentec
>>>>
>>>>
>>> _______________________________________________
>>> TenTec mailing list
>>> TenTec@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/tentec
>>>
>>
>>
>> _______________________________________________
>> TenTec mailing list
>> TenTec@contesting.com
>> http://lists.contesting.com/mailman/listinfo/tentec
>>
>>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|