[TowerTalk] 4 Sq array Dx or Hi Z

[Roger D Johnson]

If the current preamps are the same as the ones I purchased several years ago,
this is not true. There are jumper blocks that allow one to insert various L and C
combinations for various freq ranges but it is not required. I measured my preamps
on a VNA and found that putting a jumper in the L1MF position (220uH and 1000 Ohms)
from the input to ground increased the gain across 160m by approx 7 db. It caused a
faster rolloff through the BC band and gain above 160m dropped off to normal for 
80m.
I found the supplied 108in whips to have inadequate pickup on 160m and made 4
20ft elements out of old beam parts. With the longer elements, I no longer 
needed the
L1MF jumper in place.

Both the DXE and HiZ 4 square RX arrays use "crossfire phasing" as described by
W8JI on his site. This phasing method allows a unidirectional pattern over a large
frequency range.

I also have the HiZ 8 circle array which IS a single band array. It will receive 
over a
large frequency range but the pattern is not optimum.

Comparing the two arrays on Top Band was interesting. The 8 circle definitely hears
better due to the narrower beamwidth but this is also it's Achilles heel.  
Signals off the
side of the selected azimuth are often not heard unless strong. I usually use 
the 4 sq
for searching for that reason. I have recently put up a 500ft Beverage and it 
sometimes
hears better. I believe this to be due to it's having a higher angle pattern.

The old idea that you can't have too many antennas on 160m is true!!

73, Roger

On 9/6/2012 7:34 PM, Rick Karlquist wrote:
> One thing I am surprised no one has mentioned is that the
> DXE preamp requires the user to tune a front end filter to
> a particular frequency range.  This makes it into a 1 band
> solution.  A receive 4 square might be useful on more than
> one band and it is also useful to be able to receive WWV on
> 2.5 MHz for testing purposes.  Another disadvantage of the
> DXE front end filter is that component tolerances will result
> in phase differences between units that will degrade the
> pattern.
>
> The Hi Z preamp is truly broadbanded and is checked at the
> factory for phase matching.
>
> Rick N6RK
>
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