[Elecraft] Antenna question

[Walter Underwood]

In a dry climate, ladder line is fine, but good coax has low losses, too, and is less fussy about being run next to the gutters.

It is rare for a dipole to be perfectly balanced (thanks to near field objects like houses), so a high-quality current balun at the antenna can really help reject common mode noise. I recommend Balun Designs. Mine dropped the noise by 6dB.

Also consider the “loop skywire”. A loop often fits into the same space as a dipole and lots of people like them.

For pre-built dipoles, I’m happy with my Hy Power Antenna: http://www.hypowerantenna.com/

wunder
K6WRU
CM87wj
http://observer.wunderwood.org/

On Oct 17, 2014, at 6:35 PM, James Bennett <w6jhb at me.com> wrote:

> Fred is right about the 450-ohm stuff getting funky in wet weather. Cause my tuners to do the clicky-click dance whenever it rains here, although we've been pretty dry the past few years. Because of this, I plan on replacing my 450-ohm line with 600-ohm ladder line in a couple weeks.  I had the 600-ohm stuff on that doublet initially but a change in roofing materials made me change. Long story.  Anyway, as you probably know, antennas work much better when built or adjusted when the weather is horrible!!!
> 
> Jim / W6JHB
> 
> 
>> On Oct 17, 2014, at 4:57 PM, Fred Jensen <k6dgw at foothill.net> wrote:
>> 
>> Don pretty much described my low band antenna.  Full Disclosure: I live on 5 acres and have a 70' tower.  That said, it is a Sloping V [I'd call it an inverted V except is isn't resonant on any band], about 210' on a side from the top of the tower.  450 ohm window line to the bottom of the tower, DXE 4:1 balun, and coax into the house.  I have chokes on the coax at the balun and at the weatherhead entrance, but I've never had any problems with RFITS [RF In The Shack] with or without the chokes.
>> 
>> It works well on 80-40-30, requires a tuner of course [KAT500].  Works on 160 but warms the clouds and worms, I use an Inv-L for top band.  It also works on all the bands up from 30 but the pattern gets fairly complex and squirts my RF in a lot of non-productive directions because it's so big.
>> 
>> My experience is that an 88 ft doublet, center-fed, works really well on 40 and up in frequency, often used by those activating summits in Summits On The Air.  Shorter doublets are also effective, and not being resonant doesn't really matter [in some cases, it helps].  Neither does what you do with the ends.  Most of the radiation comes from the center, high current sections.
>> 
>> 450 ohm window line is sensitive to moisture ... if you set up your tuner for dry conditions and it's now raining, things will need retuning.
>> 
>> Keep in mind the wisdom of Tom, N6BT, "Anything conductive will radiate if you get power into it."
>> 
>> 73,
>> 
>> Fred K6DGW
>> - Northern California Contest Club
>> - CU in the 2015 Cal QSO Party 3-4 Oct 2015
>> - www.cqp.org
>> 
>>> On 10/17/2014 3:54 PM, Don Wilhelm wrote:
>>> 
>>> Make it a balanced dipole antenna (equal lengths on either side of the
>>> feedpoint) for best efforts in keeping RF off the feedline.  The actual
>>> length does not matter a lot, but it should be greater than 80% of the
>>> half wavelength for the lowest band of interest.
>>> 
>>> Use open wire line or 450 ohm ladder line to feed it down to the point
>>> where it enters the shack - hopefully you can run the feedline
>>> perpendicular from the radiator for at least 1/4 wavelength on the
>>> lowest frequency of interest for lowest radiator to feedline pickup. Put
>>> a good 1:1 current mod choke at that point.  See page 29 of K9YC's RFI
>>> tutorial http://www.audiosystemsgroup.com/RFI-Ham.pdf
>>> for instructions on how to construct a very effective current mode choke
>>> - note: a good balun *is* a current mode choke, but many fail to perform
>>> as well as the ones tested by K9YC.
>>> 
>>> You will need a tuner, and any Elecraft tuner should do the job nicely.
>>> If it does not, then you may have to make some adjustments in the length
>>> of the parallel feedline to see if you can achieve success on all bands
>>> of interest.
>>> 
>>> You may want to take a look at the Antenna and Transmission Line article
>>> on my website www.w3fpr.com for a bit on non-math theory on antennas.
>> 
>> 
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