[TowerTalk] 2 Element Parasitic Vertical for 160M

[Dennis OConnor]

An interesting thread...
First, on the reflector - Make it resonant just below the band edge... 
I consider this the best point for the trade off between forward gain and FB ratio...

 e.g. for operation with the driven matched to 1825, 
with 100 foot spacing for the reflector, 
shooting for the FB ratio of 10dB and gain at 5.36 dBi, (Mininec ground)
 you will get these numbers with the reflector adjusted to resonance at 1790...  
It has been my experience with my arrays that these numbers work in the real world...

Use either a noise bridge or drag a rig out to the base of the reflector and use an SWR meter, to trim the reflector to frequency (remember, resonant is 30-34 ohms, not 50) - with the shunt to the tower disconnected to move the tower off resonance... 
 As much as I love my MFJ259, broadcast AM stations overpower the diode detector when hooked to a full size 160 antenna...

A comment on the comment that' . . .  the end of an antenna is infinite impedance and SWR . . . '... This is not so in the real world...
I am currently playing with some half wave verticals, bottom fed, and worked against elevated radials...   For instance on the 20 meter I worked on last night... Modeling indicated the feed point to be ~2500 + j -570 ohms... 
A matching network was made up and resonated out on the antenna... Then the matching network was moved inside to the bench and a 2.2K resistor in series with a 39 pF cap was inserted on the antenna terminals and the match checked...  The match was not perfect but close enough to indicate the modeled value was in the ball park...  When I have time I will refine the numbers, but CQWW approaches and working antennas trump intellectual curiosity...

denny / k8do

denny / k8do