[TowerTalk] Omnidirectional antenna for domestic contests

Tue Oct 6 05:02:25 EDT 2015

Just my thoughts:

Seems like I saw slopers mentioned.  I have several center fed, half 
wave slopers  on about a 45 degree angle for 75 and 40.  On 40 they are 
just OK state side, but work well for DX.  I'd not recommend them for 
state side unless you have enough to switch into for direction and 
distance.  For close in, broad side, or even 180 degrees might be 
preferable for close in, although IIRC they aren't a ball of fire off 
the back side

I'm in Southern MI about 25 MI W of the S end of Saginaw Bay, so I'm 
thinking we probably have similar propagation, although for state side 
contacts, it's pretty much 090 to 330.   From 90 to around 135 is pretty 
much short hop, or roughly 130 to roughly 5oo miles the rest is from 
roughly 120 to about 2500 miles  As I have one sq acre antennas favoring 
distances and direction are limited and definitely a compromise.

If I were serious about omni state side I'd probably go for a pair of 
inverted V fans at 70 to 80 feet at right angles to each other, but I 
don't think you have that height as an option.  It's a compromise, but I 
have the tower although the antenna anchored in the front yard would be 
definitely temporary.  Getting fan slopers would allow switching to 
which ever favored the direction and distance, but you'd need at least 
three of them, if not 4 and that's a lot of wire and feed lines.  It's 
unlikely you'll get full use of 75 or 40 without a tuner.

73 es good luck,

Roger (K8RI)

On 10/6/2015 3:02 AM, Jim Brown wrote:
> Hi Rudy,
>
> You've received some really "off the wall" replies to your question. 
> Some thoughts from the left coast, interspersed below.
>
> On Sun,10/4/2015 7:18 AM, Rudy Bakalov via TowerTalk wrote:
>> I need antennas for working the US and Canada on 20-15-10 from my VE3 
>> QTH.  I'd appreciate any and all suggestions.
>>
>> Currently considering 1) vertical dipoles and
>
> Verticals are pretty cool, but not much radiation above about 30-40 
> degrees, so you could be weak in W1/W2/W3/W8/W9.
>> 2) a curtain of 3 stacked dipoles (or inverted Vs) from 10' to 30'.
>
> There are serious misconceptions about the height of horizontal 
> antennas and their effectiveness at low angles. Low horizontal 
> antennas are NOT better for NVIS, they are worse for both short AND 
> long distances. The IDEAL NVIS antenna is about 3/8 wavelength high.
>
>
>> Anything else? Do keep in mind that from VE3 the US is from ~160 to 
>> ~330 degrees azimuth and I do not want to rotate the antenna.
>
> I strongly suggest that you STUDY 
> http://k9yc.com/VertOrHorizontal-Slides.pdf  (CAPS added for 
> emphasis).  There's "simple" and "too simple." Fan dipoles at a "good" 
> height could work really well for you -- 30-40 ft is a good starting 
> point -- but any good dipole has a null off the end, so you really 
> need two at right angles to work both S and W.  With dipoles, the only 
> thing that really matters is the nulls off the ends. Longest US DX for 
> you is CA, OR, WA, so I suggest that you try to be approximately 
> broadside to San Francisco with one fan and to MS with the other, then 
> a simple switch to go between them. The west fan will be killer from 
> KS to CA/OR/WA and will do fine in NTX, etc. The S fan will be great 
> from W1 to FL and TX. There are photos in this presentation
>
> http://k9yc.com/LimitedSpaceAntennasPPT.pdf
>
> of a fan dipole I used in Chicago on a small city lot. Very easy to 
> build -- the spacers are 1/2-in PVC conduit.  I used these antennas 
> here in CA before I found space to turn aluminum. :)
>
> 73, Jim K9YC
>
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-- 

73

Roger (K8RI)

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