[600MRG] last nights results: fishing pole helical vertical

[Graham]

John,

Thanks for the thoughtful reply.

Yes please, more details when available. I am not yet ready to jump in 
but I need to give much thought to what I can do given my limited 
resources with respect to property size - barely wide enough to put up a 
full size 40M dipole.

cheers, Graham ve3gtc



On 14-02-01 04:03 PM, John Langridge wrote:
> Hi Graham,
>
> Sorry for the lack of details in my last system assessment.  I had a 
> number of plates spinning at the same time HI!
>
> So all of these experiments have been based around a 5 gallon plastic 
> bucket variometer with the outer coil wound with #14 and a small 
> rotating coil of 30 turns total, same wire.  I've wound these coils 
> before with many more turns on the rotating coil and I think after 
> these experiments I would go back to use maybe as many as 50 turns (my 
> main antenna ATU uses a rotating coil with 50 turns and it transitions 
> a much larger area with sharper tuning as expected).  Taps are on the 
> main coil about every 5 turns but I did not really count. carefully  
> Anyway, I wrote a document chronicling in detail the steps I went 
> through to make my original coil and can send you that directly if you 
> like. While i have been unable to measure the inductance on the vario 
> directly due to limitions with my metering, the calculated value seems 
> to be around 1800 uH total.  My advice would be to just wind it and 
> not worry about it.  This coil, with the help of a little additional 
> series inductance was able to successfully resonate a 102" "whip" in a 
> prior experiment so unless you are doing to load up something 
> extremely ridiculous, you should have plenty with the bucket alone for 
> most reasonable verticals.
>
> That coil was used to resonate 4 different "small" antennas so far 
> with some interesting results.  The fishing pole vertical seemed to be 
> a pretty good performer but was by no means the best during these 
> tests.  Perhaps under different conditions things might have been 
> different and I will revisit the fishing pole again once the wx 
> stabilizes again and I have fixed my analyzer and will add some top 
> loading wires as this is the most efficient configuration.
>
> The fishing pole was a 15 foot long telescoping and subsequently 
> tapering fiberglass design.  I simply wound about 30 long, tapered 
> turns down the length of the pole using wire ties to secure the wire 
> to the pole.  At the top, I allowed about an 8" tuft of wire to extend 
> beyond the tip of the pole.  The antenna wire feeds the HV side of the 
> vario.  In the case of the fishing pole and the 102" whip test, i 
> needed slightly more series inductance to resonate so I used a smaller 
> coil to accomplish this, connecting the smaller coil (6" diameter and 
> about 60 uH total) on the low voltage side of the bucket and tapping 
> with the coax feeder when I was near resonance but close enough to 
> adjust with the vario.
>
> using the MFJ analyzer, I measured the impedance from inside the shack 
> and was able to get it matched in about 4 trips out to the antenna.  
> You want to make this adjustment far away from the antenna because you 
> will couple to it.
>
> The radial system was an old existing radial system that I have not 
> maintained in many years and it has gone unused for a long time.  
> These tests suggest that many of the radials are probably in tact but 
> our average ground conditions here are above average  so its difficult 
> to assess.  Obvious as many  radials as you can get will be good.  
> Anecdotally, at the site of my first test 1 mile away from my normal 
> operating position, I used a 20m Inverted Vee fed with 25 feet of 450 
> ohm window line as a marconi with this coil against 4 radials, 3 were 
> 25-30 feet long and 1 was about 50 feet long and coiled around the 
> available space (worst case, i know).  That antenna proved to be the 
> best of these tested so far but again, good ground conditions may make 
> up for fewer radials.
>
> Some have asked about decoupling the coax as with few radials, that 
> coax tends to look like a radial and carry a lot of current sometime.  
> The tests here at my station have buried coax and grounding at the 
> feed point as well as at the entrance to the shack and this seemed 
> sufficient.  no bites or sparkies in the shack HI!  The first test 
> with the Vee at the site a mile away had the coax laying on the ground 
> and it definitely looked like a radial.  In fact initial tests left me 
> with a nice tingly feeling on my finger tips.  This was fixed with a 
> ground rod at the coax entrance tied to the shield.  Problem solved 
> and no more RF at the rig/amp.
>
> I'm leaving a lot out here but I am still organizing and going through 
> information as I prepare to write a bit and also put together some 
> presentations for this spring and summer.  As you can see, I did not 
> get too hung up on calculated or measured values.  That was 
> intentional.  You should be able to wind that bucket vario and find a 
> tap to load a G5RV that you might have on your property, or 80m 
> dipole, etc.  Obviously construction technique is important with the 
> antenna since it will have a lot higher voltage on it potentially then 
> normal but if you have a dipole with the feeder either in free space 
> or coming down an insulated support I would encourage you to try and 
> load it up. With the dipole wires acting like a top hat, it should be 
> more efficient than the straight fishing pole antenna alone (no 
> toploading wires).
>
> Performance of the fishing pole was really pretty good.  All of these 
> compromise antennas have been excellent performers on ground wave out 
> to at least 200 miles and there has been some skywave fun as well, 
> with many signal levels consistent with QSO quality signal levels 
> (Mike /12 in CO and I were just talking about this yesterday as he was 
> receiving me in the low teens during the 2nd night of my test).
>
> I'll be happy to send you some pics directly if you like and I will 
> certainly keep you posted as I develop more content. Hopefully in a 
> week or two i will be able to continue this parade of insanity in one 
> capacity or another.
>
> 73,
>
> John XIQ
>
>