Topband: DX Engineering Receiver 4 Square using W8JI PassiveElements

[Lee K7TJR]

    There is no doubt that the W8JI shortened verticals work well in a 
160 meter array. However in the tests that I have made I would
 recommend a minimum of 8 radials at the base of the elements.
I have measured phase shifts between elements in the output
 phase of an actual received signal. These errant shifts can be
 minimized at a level of 8 radials.
     This phase shift is particularily important if you have a close spaced
 array. I cant explain the exact mechanism for the phase shifts with
 application of radials but I have actually measured this in the field.
I do not think it is all just tuning of the element. There is some
 reflection from the radials to the element as well. If memory serves
 me I think W8JI recommends 8 radials as well.
       Although it is claimed you can move your array closer to your
 transmitting array with these elements it is not only noise you may
 pick up but you can have a severely distorted pattern as a result of
 the interaction. This can result in lowered RDF and front to back ratio.
 A quick look with Eznec should be performed for each contemplated
 array and its surroundings. Less than 200 feet separation is almost
 guaranteed pattern distortion with a resonant TX vertical.
     Also moving the array closer to the TX vertical will induce some
 pretty high levels of RF into the receiver input during transmit. More
 so with a passive system than one with electronics that simply
 saturate limiting the RF into the receiver. Of course this can be
 mitigated with electronics or other techniques but certainly a big
 concern for some systems and transceivers. Some rigs will lock up
 with too much RF into an RX antenna port.
     And lastly Victor K1LT has changed from the loaded elements to
 Hi-Z amplifiers in his arrays. I was hoping he would chime in here
 with his opinions as well. Might have been just the ease of not
 having to deal with radials or top loading on so many elements?
     I have an Eznec model of a loaded element 4-square if any one
 needs it just send me a private e-mail.

Lee  K7TJR   OR