Topband: 160M ant advice

[Herbert Schoenbohm]

It is important to realize that a cage just hung of the side of a steel 
tower has some drawbacks. The pattern when modeled is somewhat 
asymmetrical to a slight degree. In a properly designed cage feed it is 
the cage that does the radiating and not the tower. (Above the cage is 
mainly the voltage part of the radiator.)  This is also important 
because the tower downwind of the cage may interact.  With a symmetrical 
cage around the tower that is not the case.  Also another advantage of 
the symmetrical cage is the reduction of RF pickup on rotor wires, coax 
feed lines to other antennas, and certain control lines for switching.   
Jeff's intentions were good in pioneering the "easy cage"idea.  But one 
thing that may influence some people are the aesthetics of a beautiful 
four wire symmetrical cage to something hanging of the side of your 
tower.    But for me the most impressive was the ease of installation as 
compared to the list of material required in the asymmetrical cage.  
There may also be a slight increase of bandwidth with a symmetrical 
cage  as claimed by some.


Herb Schoenbohm, KV4FZ

On 12/18/2015 1:44 PM, Robert Harmon wrote:
> Gene,
>
> The cage design sounds very interesting.  I just ordered the book :-)
>
> thanks Gene,
> Bob
> K6UJ
>
>
>
>
> On 12/18/15 9:27 AM, Gene Smar wrote:
>> Bob:
>>         I built my shunt feed wire cage based on the design in Jeff 
>> Bigg's K1ZM book "DXing on the Edge..."  I bought it from the ARRL 
>> bookstore but you might be able to find it on Amazon, etc.  I used 
>> two widely-spaced wires whereas he used three in a triangular form 
>> held off the side of his tower with PVC pipe.  I was surprised at how 
>> well it seems to work for me ( I always get through and receive good 
>> reports.)  Good luck.
>>     73 de
>> Gene Smar  AD3F
>>
>>
>>
>> On 12/18/15, Robert Harmon wrote:
>>
>> Stan,
>>
>> With shunt feed I would gain the 18 foot mast with the yagis, the total
>> overall height is 108 feet.
>> I haven't really considered shunt feeding. I see your point of the
>> wires with an L in proximity to other
>> antennas. That was a worry I had with the 40 meter yagi and the L. I
>> will look into shunt feeding. I have ON4UN's book, probably should
>> start there to bone up. Any other resources to learn abut shunt 
>> feeding ?
>> The top band archives probably has a lot of discussions about shunt
>> feeding also.
>>
>> thanks Stan,
>> Bob
>> K6UJ
>>
>>
>>
>> On 12/18/15 1:36 AM, Stan Stockton wrote:
>>> Bob,
>>>
>>> There is no reason I can think of to not shunt feed the tower as it 
>>> is with either ground radials or elevated radials. An inverted L 
>>> isn't as good as a vertical for DX and you would just be adding 
>>> clutter and horizontal wires in proximity to your other antennas. 
>>> Shunt feeding a tower is very, very simple.
>>>
>>> 73... Stan, K5GO
>>>
>>>> On Dec 17, 2015, at 8:06 PM, Robert Harmon k6uj at pacbell.net> wrote:
>>>>
>>>> I am planning an install of a 160M inverted L and would like 
>>>> critique from you top banders.
>>>> I was originally planning a separate tower for 160 but my XYL has 
>>>> squashed the idea :-)
>>>> My tower is 90 feet fully extended with a 18 foot mast currently 
>>>> used for a Force 12 WARC plus 10/15 beam
>>>> on top and a N6BT DXU-32, 2EL 40 and 3EL 20 12 feet below.
>>>> At the top of the top section I have a 10 foot fiberglass pole I 
>>>> plan to extend out to support the vertical, so it will be 10 feet 
>>>> away from the tower.
>>>> I am thinking of feeding the vertical and having 4 elevated radials 
>>>> at the 14 foot level.
>>>> So the vertical wire will about 76 feet long.
>>>>
>>>> I am wondering if I would be better lowering the feedpoint & radial 
>>>> tie ins down from 14 feet say to 8 feet and have more length in the 
>>>> vertical portion of the L or better to have the 14 feet elevation 
>>>> for the radials ?
>>>>
>>>> Also the horizontal leg of the L on top will be about 5 feet below 
>>>> the 40/20 yagi only 10 feet out from the tower,
>>>> do you think this is OK as far as interaction between the yagi and 
>>>> the 160 L ? Anything else I should consider ?
>>>> I have never had a decent 160 antenna, just hoping I can work 
>>>> something out with my existing situation
>>>>
>>>> thanks in advance,
>>>>
>>>> Bob
>>>> K6UJ
>>>>
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