[TowerTalk] 2 Element Parasitic Vertical

[Stan Stockton]

Thanks to everyone for the responses to my question.  There were posts to boith Topband and Towertalk as well as several sent just to me.

The responses ranged from you will probably never make it work or you need to drive both elements to it will work according to the computer model.  Many had suggestions as to how I should proceed in tuning it, cautions regarding the ground system, etc.  All the responses were thoughtful and had information that was useful.

I played with it a little bit last night in the dark.  I switched the parasitic element in and out while listening to W1AW and it was difficult to see whether there was any difference in the forward direction.  I had no signal source to the Southwest so worked with what I had.  I then shortened the element by some amount (perhaps five feet or so) and checked again.  This time I could see a difference and W1AW was best in the Omni directional state indicating to me the parasitic element was now a director.  Then I added back about ten feet or so and W1AW was better with the parasitic element switched in.  Now I am getting somewhere.  When I got up this morning I went out and disconnected the shunt feed on the tower and used an MFJ analyzer to see what that wire element looked like.  It looked like it would show least reactance a little below the lowest frequency the analyzer would tune - maybe 1750 or so.  I took a couple feet off and it now shows a small amount of reactance and about 28 ohms at 1785.  Does this give any indication of how adequate the ground system may be?  I didn't measure anything but think the element is probably 2-3 feet longer than it originally was.  

The F/B is insignificant and is of no interest to me since I am going to listen on Beverages.  Maximizing the F/B would only be useful if it would correspond to highest forward gain or if it were known to be say 30 Khz above the point at which maximum gain would occur so I could trim or add accordingly. With the tools I have available I think it would be difficult for me to see a small difference in forward gain from one frequency to another.  It may only vary a small fraction of a dB over 20 khz.  The computer model would not indicate major changes in what little F/B there is over that range either.  

I am thinking that if the element shows to be resonant somewhere between 1775 and 1790 and I can see a small but noticeable movement up in the S meter reading on NE stations when I switch the element in, I have done about all I can do unless someone has a practical suggestion as to how I can quickly squeeze our that last dB of gain that may be available somewhere between 1800 and 1900 and move it to 1830.

Thank you for the suggestions.  Since I posted to both reflectors, perhaps the best thing would be to send a response just to me in case this is boring to some.

73...Stan, K5GO