[TowerTalk] Verticals above chain Link fence

Joe Subich, W4TV lists at subich.com
Wed Oct 2 15:28:13 EDT 2019


On 2019-10-02 12:41 PM, Mark - N5OT wrote:
> Actually if it was me, given that you only need two resonant radials
> to make a complete system when they are above ground, and from what
> I understand this works when the two radials are symmetric about the 
> feedpoint, I would not be able to stop myself from digging out some 
> ribbon cable and cutting it so that I had one wire in the ribbon
> cable per band per side that was the right length. then I would have 
> everything I need in a single assembly with a single attachment point
> at each end, per each side of the feedpoint.
If you do that, be sure to pull back about 18-24" at the end of each
wire and let it hang down.  Otherwise the shorter wires will "disappear"
due to the capacitive coupling.  I learned that the hard way when
trying to make a cheap multiband dipole for 80/40 (15)/20/10 meters
using the old 4-wire rotor cable shortly after upgrading from novice.

Now I prefer individual wires spaced 12-18" using schedule 120 (very
light) 1/2" PVC.

 > On 10/1/2019 9:52 PM, ed_richardson at shaw.ca wrote:
>> I was then planning on using 2-3 resonant radials on each band
>> (40/30/20/15 forget about 10m).
You should only need three wires.  30 will work on 10 meters, 40 will
work on 15 meters if you tweak the antenna length slightly.

 >> I was considering mounting the antenna about 13-15 above the ground
 >> and above a 7 foot high chain link fence.

I would not go any higher than necessary (say 9') as the take off angle
will rise on the higher bands until you get a couple wavelengths above
ground (high enough to lose the ground reflection).   I know 10/15 are
probably not very useful given the current solar conditions but you
don't want to handicap yourself any more than necessary.

73,

    ... Joe, W4TV


On 2019-10-02 12:41 PM, Mark - N5OT wrote:
> Hi Ed,
> 
> Do I understand correctly that you have two antennas and you are asking 
> about making changes to one of them?  If the other antenna does not 
> change, then you could compare the new unusual design to the other 
> design that has not changed, and you would know the answer.  If it was 
> me, I might be inclined to "put it up and see what happens" but be 
> advised that this approach is slovenly and without merit to some, which 
> could open you to disparaging public comment, regardless of how loud 
> your signal becomes because of the new antenna.
> 
> For the humor impaired, that was a little bit of a joke really.
> 
> Actually if it was me, given that you only need two resonant radials to 
> make a complete system when they are above ground, and from what I 
> understand this works when the two radials are symmetric about the 
> feedpoint, I would not be able to stop myself from digging out some 
> ribbon cable and cutting it so that I had one wire in the ribbon cable 
> per band per side that was the right length.  then I would have 
> everything I need in a single assembly with a single attachment point at 
> each end, per each side of the feedpoint.
> 
> Then, I would mount it so that the radials were also symmetric about the 
> fence.
> 
> Some wax poetic about tuning the radials for resonance, but I, being 
> confident the system was symmetric, would not look back at that, I would 
> cut the radials to approximate a resonant dipole, feed the whole thing 
> with a matching network located for my personal convenience, I would 
> make the radio happy with a swell SWR, and get on the air and work other 
> radio operators.  Comparing it to the other antenna could yield 
> confidence or concern, a not-inappropriate currency in my way of looking 
> at it.
> 
> Bear in mind, it's possible the exact ribbon cable one uses might turn 
> out to be too small.  This is easily determined without math as 
> follows:  Put it up.  Use it.  If the ribbon cable heats up, it is too 
> small.  If the ribbon cable does not heat up, it is not too small. 
> Flames could be an indication too.  Watch the SWR while doing the 
> experiment.
> 
> You might be able to do it differently than I have described and achieve 
> what some would call "better" results, which would be an arguable 
> statement, and then the argument about the results and how to measure 
> them (seasoned with comments about engineering practices), would occupy 
> the posts of this email reflector in the grand style to which we have 
> become accustomed.
> 
> Or, you could do what I have described and get on the air and enjoy 
> radio contacts from your warm cozy shack during the cold winter that 
> will soon be upon us.
> 
> And thanks for getting me thinking.  I might have to go outside and try 
> that.
> 
> 73 - Mark N5OT
> 
> 
> 
> 
> 
> On 10/1/2019 9:52 PM, ed_richardson at shaw.ca wrote:
>> Getting ready for another contesting season from my Postage stamp size 
>> City Lot.  In previous years I have installed a winter antenna 
>> (Steppir Vertical) in the rear yard as a second antenna to the tower 
>> mounted beams. In the past I have had had so-so success laying out 
>> 50-60 radials around the base of the antenna.. The problem is there is 
>> a lot of ground clutter such as trees and wooden fence in close 
>> proximity to the antenna.
>>
>> I was considering mounting the antenna about 13-15 above the ground 
>> and above a 7 foot high chain link fence. I was then planning on using 
>> 2-3 resonant radials on each band (40/30/20/15 forget about 10m).
>>
>> Has anyone had any experience with a similar configuration? Obviously 
>> keeping the radials away from the fence would be important.
>>
>> Thanks for the bandwidth!
>>
>> Ed VE4VT
>>
>>
>>
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