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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