Topband: Inverted L with elevated radials for topband

[Grant Saviers]

comments in line

On 3/5/2020 10:02, Gabriel - EA6VQ via Topband wrote:
> I have some doubts about installing and inverted L with elevated radials for
> 160m.  I have been searching in Google and find some contradictory
> information, so I would appreciate very much if you can help me with your
> own experience.
> 
As noted by others, N6LF has a wealth of modeled and measured data on 
elevated radials.    antennasbyn6lf.com

> 
> The antenna would be supported by a 16 m (52.5 ft) high fiberglass pole
> placed on top of a 3m (10 ft) high small tower with the horizontal part of
> the L slopping down to a 5 m (16 ft) high mast about 23 m (75 ft) away.  Two
> to four tuned elevated radials can be placed, although they will have to be
> bent due to space restrictions.
> 
>
By "tuned" do you mean resonant 130ft +/-?  Again N6LF has data for 2 to 
16 elevated radials, and with more they can be shorter.
Also see his paper in Antenna Compendium 8 re inductively loading for 
shorter radials.  I had only 2 75ft radials on a 52' mast.
> 
> Now the doubts:
> 
>   
> 
> What impedance can I expect at the feed point with this configuration?
> 
Having the radials as high as possible will minimize ground losses and 
decease Z.  With 2x at 10ft plan on 25 to 30 ohms.
>   
> 
> How to match it in order to feed it with a 50 ohm cable?  Some pages say
> that no match is required, only a choke. Other pages say a hairpin is
> necessary as the impedance can be too low. So other say that a tuner at the
> base is required?    I am confused L
> 
> 
SWR losses on 160 are so low that a 2:1 doesn't cost many db's.  Too 
keep your amplifier happier I use a 50::25 ohm transmission line 
transformer.  make it or buy it.

A good choke is a must.  Make the K9YC 4" #31 choke.

> 
> What performance for DX can be achieved by this antenna?  Is it really good
> or do you have some better suggestion for a really small lot where no ground
> radials are possible?
> 
You won't do better with anything else.  More radials will improve it 
slightly.
>   
> 
> Would it be worth to use a higher fiberglass pole, let's say 4 m (13 ft)
> higher, in order to lengthen the vertical section of the L?  Would the
> difference be noticeable?
> 
> 
The taller the better but probably less than 1 db gain.

> 
> Anyone has real experience setting up this antenna with elevated radials?
> Most information I can find on Internet is related to ground mounted
> antennas.

Read all of what Rudy N6LF says, and you will be an expert.

Grant KZ1W


> 
>   
> 
> Thanks in advance!
> 
>   
> 
> 73. Gabriel - EA6VQ
> 
>   
> 
> _________________
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