[TowerTalk] Unique Inv L...Help!

[K4SAV]

One more note about feeding the Cobra as a T on 160.  To do this you 
will probably need two sets of feedlines, and a switch box out by the 
radial system.  You could use open wire to feed the Cobra, and a coax 
line to feed it as a T.  The switch box is necessary to do the 
switching.  You will need relays with a lot of voltage standoff for the 
open wire.  I would not feed the T antenna with open wire.  You will be 
back into the rfi and noise situation again (although not as bad as what 
you have now).  You will also incur more ground loss doing that because 
the feedline will radiate.

And don't be tempted to tie the two open wires together at your tuner.

Another option if you run low power is a remote tuner out at the radials.

Jerry, K4SAV

K4SAV wrote:

>If you think about it for a moment, you should be able to see why you 
>have the rfi problem and why the antenna is noisy.  One half of your 
>antenna is up in the tree.  The other half of your antenna is whatever 
>is attached to your house ground system.  That includes ac wiring, TV 
>cables, telephone cables, and computer cables.  The best way to pick up 
>signals from electronic devices, or to give them rfi, is to connect your 
>antenna directly to the device.  You did that.
>
> From your description of your LW, you must have about 160 feet of 
>antenna horizontal and about 100 feet vertical.  That's a total of about 
>a half wave on 160, a very bad length to try and match.  It also doesn't 
>put out a very good pattern on 160.  I don't think it will beat a dipole 
>at 100 ft, except off the ends of the dipole.  If you could shorten the 
>top wire to about 50 ft, it would be much easier to match.  All you 
>would need would be a series cap.  It should then beat the dipole for 
>elevation angles less than about 18 degrees, and also beat the dipole 
>off the ends of the dipole for even higher angles.
>
>Another option is to connect both feedline wires together to your Cobra 
>and feed it as a T on 160.  This will require a different matching 
>network because the feedpoint impedance should be close to 100 ohms.
>
>For both of these you need a good set of ground radials.  If you don't 
>have that, the dipole will probably beat both of these.
>
>Jerry, K4SAV
>
>Edward Sylvester wrote:
>
>  
>
>>What a great group!  I have one more antenna curiosity for my second QTH....I work up north during the week and stay in my RV...I have the good fortune of having access to the tall pine trees (>100' tall).  I installed two antennas....
>>
>>The first is a Cobra Ultralite Senior (140' linear loaded, fed with open wire line).  This rivals some of the best antennas I have ever had.  Tunes 6-160m.
>>
>>Because the span between trees is about 300', I decided to add a second antenna in series to take advantage of the set up.  This second antenna is a LW with a total length of 300' or so.
>>
>>I have compared the two and I prefer the dipole.  The LW couples into anything electronic and I hesitate to use it because it causes interference.  It's also noisier and is virtually the same as the dipole, in terms of signal output.
>>
>>Hence, it's somewhat of a disappointment.  Plus, my signal on 160m is anemic.  Thinking I can convert this into an Inverted L for a better DX antenna.
>>
>>This would not be a resonant antenna for any specific band, as I don't know the exact length and I don't have access to the horizontal portion for pruning.
>>
>>I had to hire a tree climber to install these!!  I just want to work with what I have...
>>
>>Here are my thoughts....Why not bring the vertical portion of the LW to ground level (about 100') and attach to non resonant radials?
>>
>>I can feed it with 450 ohm ladderline and terminate with 4:1 balun before feeding it to a wideband tuner.  
>>
>>My question is, would I maintain the valuable characteristics of an Inv L and would this be killer on 160m?  
>>
>>I currently feed this same LW into a remote balun, with an effective counterpoise on the other terminal lug.  Only thing is that it's not a ground level and I have no radials, per se.
>>
>>Thanks for the bandwidth.  As always, your thoughts are appreciated.
>>
>>73 and Happy New Year!
>>
>>Ed NI6S
>>
>>
>>
>>     
>> 
>>
>>    
>>
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