I was so concerned with trying to match the antenna on more than one
band that I forgot to address the basic issue of how the antenna will
perform.
On 160 meters for low angle signals, in its best direction it should be
down about 5 dB from a full size vertical with a good ground system. In
its worst direction it should be down somewhere around 10 dB. It is
basically a cloud warmer antenna, so receive noise should be high.
On 80 meters it is also a cloud warmer antenna. Compared to a full size
vertical, for low angles it should be down 5 to 8 dB in all directions.
Jerry, K4SAV
K4SAV wrote:
>Here is a quick simulation. This may not be exactly what you are
>thinking because I don't know how high the ends of your vee will be off
>the ground, but it should give you an idea of what to expect. I assumed
>the ends were at 15 ft, and set the antenna for resonance at 1.8 MHz
>(resonance at the antenna, not at the end of the feedline). With 65 ft
>of 600 ohm line, and a 4 to 1 balun, the SWR at the switch box would be:
>1.8MHz = 24.7, 3.6 MHz = 3.5, 7MHz = 7.9, 10.1MHz = 12.2, 14MHz = 4.5,
>18.1MHz = 5, 21MHz = 3.3, 24.9MHz = 9.2, 28.1MHz = 9.6. Probably not
>what you are looking for.
>
>There is a basic problem with trying match a 160M inv vee to get a
>reasonable SWR on 80M. On 80 meters it is very high impedance. One
>solution would be to use the feedline as a tuner. This would require
>that you switch feedline lengths for each band. For example for this
>antenna, you would need 260 ft of 600 ohm feedline for 1.8 MHz and 200
>ft for 3.5 MHz. This can become a real switching nightmare for more than
>about 2 bands. You would not need the 4 to 1 balun, but you would need a
>good common mode choke balun at the end of the feedline. If you are
>interested in this approach see:
>http://www.qsl.net/w5dxp/notuner.htm
>
>You can also use 450 ohm ladder line instead of the 600 ohm line, but
>the required lengths will be a little different.
>
>Probably a simpler approach is to convert your inv vee into a fan
>dipole, with an element for 160M and another for 80M.
>
>Jerry, K4SAV
>
>
>Gary.Stone@med.va.gov wrote:
>
>
>
>>Hi,
>>
>>
>>
>>I am thinking of putting up an antenna and would like your input please? I
>>am thinking of putting up an inverted vee configuration and then feed it
>>with 600 ladder line so that it would be tunable on 160 thru 10 meters. I
>>am thinking the apex would be at about 70 feet on the tower and the two legs
>>would be about long enough to allow tuning for 160 meters (about 120 feet or
>>even a little more on each leg). I would like to take the 600 ohm feedline
>>down to the rat pak (PL259) switch box on the tower - mounted at about 5
>>feet up from the ground. So, it would have about 65 feet of 600 ohm ladder
>>line. From my rat pak to the shack is 50 ohm LMR400. I would also consider
>>using twin lead (easy to buy in rural North Texas) but also want to run 600
>>watt amp if desired. I am thinking I would need to use a 4-1 balun at the
>>bottom end of the ladder line and then connect a short coax jumper to the
>>rat pak.
>>
>>
>>
>>I now have an alpha delta sloper (DX-A) with the apex at about 60 feet. I
>>am hoping to improve my signal on 80 and 160 with the added plus of being
>>able to load up easily on other bands (hence the ladder line feed line).
>>
>>
>>
>>Ideas? And how far do I need to put the feedline away from the tower - is a
>>couple feet ok? Thanks in advance for any tips and critique.
>>
>>
>>
>>Gary, N5PHT
>>
>>
>>
>>
>>
>>_______________________________________________
>>
>>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
>>questions and ask for Sherman, W2FLA.
>>
>>_______________________________________________
>>TowerTalk mailing list
>>TowerTalk@contesting.com
>>http://lists.contesting.com/mailman/listinfo/towertalk
>>
>>
>>
>>
>>
>_______________________________________________
>
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
>questions and ask for Sherman, W2FLA.
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
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