[Hi-zreceivingarraydiscussions] Grounds for 4 square

[contact at hizantennas.com]

   Hi-Z Group,
 With all due respect to the TDR,(I have a Tektronix one) there is another
way to test the verticals and amplifiers with the Hi-Z 4, 4-8P, and 8A
arrays.
  You simply remove one end of each of the delay lines. Tune in a strong
constant signal like WWV on 2.5 MHz. As you then turn the direction control
you will test a single antenna/amp for each direction. In the 8A you
actually test two. For the 4 and 4-8P arrays the direction control will
point toward the antenna that is active. As you rotate the direction control
each antenna/amp should produce exactly the same signal at the RX meter.
There can be a couple dB difference due to propagation affects. The station
tuned in should be at least 50 miles away. For the 8A array the two antennas
active with the delay lines disconnected on one end are the East and West
antennas when the direction control points North. As you rotate the
direction control to NE the SE and the NW antennas will be active. This
continues around the control with the perpendicular antennas active to the
direction selected.
   This test can point out shorted elements, bad cables,  and bad amplifiers
very easily without disconnecting and testing each element/amp.

Lee K7TJR
Hi-Z Antennas


>>
Paul (K5ESW) and all,

To do my impedance measurements on the verticals, I disconnected the
feedpoint amplifier and connected the antenna and ground leads directly to
the AIM-4170 input port.  At 1.8 MHz, the radiation resistance of a short
vertical is essentially zero, so all the resistance that is measured is
assumed to be ground resistance.  

I measured two of the verticals in my 8 circle and got very similar results.
At that point I didn't bother measuring the rest of the verticals because I
assumed the results would also be similar.  

W3LPL uses passive (non-amplified) receiving verticals.  In his
multi-transmitter operations, the extremely strong RF from the transmitters
would cause serious blockage or intermods in any active electronics at the
array when another receiver is trying to listen through them.   That's why
he uses the passive approach but it also means his verticals are very
narrowband because they have to be resonated (with inductance).  I'm not
sure what kind of combiner he is using and I don't know exactly how he is
doing his TDR measurements.  However, I am guessing he is checking for
feedline discontinuities or faults that would produce reflections back to
the TDR.  The TDR would help him pinpoint the location of the faults.

With the Hi-Z system, which uses active electronics, I'm not sure what you
could learn about the verticals from a TDR in the shack.

73, John W1FV

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