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[TowerTalk] NCC-1 and ARAV2-1P verticals observations

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Subject: [TowerTalk] NCC-1 and ARAV2-1P verticals observations
From: "Tod -ID" <>
Date: Sun, 21 Oct 2007 16:02:09 -0500
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I posted this for the Top band reflector and it occurred to me there may be
some folks on this reflector who might be interested as well.


In the recent [yesterday] Stew Perry warm-up I used my newly installed NCC-1
and a pair of ARAV2-1P active RX verticals. 

At my location with the installation parameters I used I found that there is
a significant signal at 1850 kHz where I can hear the AM content the local
stations at 590 kHz and 1260 kHz. This was of no concern during the Stew
Perry warm-up since it was much above the recommended CW section of the 160
meter band plan for the US. There are much weaker spurs every 10 kHz across
the 160 meter band but they are present below the band as well so I am
suspicious that they are from something generated by me or a close neighbor.
Their source remains undetermined.

The active whips were installed on a line running NE-SW 27 degrees East of
North. They are separated by 120 feet. The feedines to the active whips are
approximately 220 feet long and buried starting about 35 feet from the whip.
The whips are mounted on 3/4" copper pipe sunk into the ground about 5 feet
and the whip portion is six inches above the actual earth. There are no
additional radials. The earth itself is 'standard' potato farm dirt [very
fine particles] in a layer about 36 inches deep above a layer of river
stones several feet deep deposited sometime during the past 500,000 years by
the nearby Snake River as its main channel varied over time.

The feedlines go the NCC-1 and the power for the active whips is derived
from the NC-1 power supply. The output from the NCC-1 goes to a preamp and
from the preamp into the RX antenna input of my FT1000MP. The jumper
settings in the AVA matching unit for the ARAV2's were the default setting
from the factory. When I injected a signal through a 20 pF capacitor into
the AVA matching unit with these default settings I found that the output
was -7.8 dB relative to the input signal. The input impedance is about 4000
ohms and the output impedance is about 75 ohms so there is power gain. The
gain profile changed when I used the L1MF jumper or the L1HF jumper but I
decided to try the default settings since that gain  profile was essentially
constant from 1.8 MHz to above 7 MHz.

The first significant listening with the system was two periods during the
Stew Perry warm-up. The initial period was from 0145Z to 0600Z. The second
period was from 1200Z to 1400Z which covered the Sunrise here in Idaho.

Most of the time the phased verticals had better S/N than the TX antenna [a
top loaded vertical]. Almost always though, the signal level from the
NCC-1/phased whips was lower than the signal level from the TX antenna --
even with the 15 dB of pre-amplification for the NCC-1 output. In the
pre-dawn and during the Sunrise Time here in Idaho I found I could adjust
the NCC-1 so that the signal levels were essentially the same from either
antenna. During that period the phased active verticals definitely had
better S/N than the TX vertical. It may be that I had learned how to use the
NCC-1 by the time of the second period and it might have been possible to
adjust things for equal signal strength during period #1 if I had known how.

There were times when the TX vertical produced better RX results because the
signal was noticeably stronger than I was able to adjust the NCC-1 to
produce. This 'extra' signal made it possible to pull out the information
although sometimes it took several repeats. It may be that this was entirely
attributable to 'pilot error' since this was my very first training session.

I worked slightly more than 100 stations in the SP warm-up. That included
N1BUG and a number of W2's in the NE US and KL7RA plus KH6BZ and KH6LC. I
heard but did not work KV4FZ. I did not hear any JA's or EU's or any other
Caribbean stations. I did not work any FL stations. Since this was the
'warm-up' it may be that stations from the Southeastern edges of the US were
not active or it may have simply been propagation. Most of the stations I
worked were 4,5 or 6 pointers but that is because there are so few stations
close by my grid square. [For those not familiar with SP scoring 4 points
implies the station is between 1500-2000 km from your station, 5 points =>
2000-2500 km, 6 pts => 2500-3000 km].

I still have not figured out just what direction is enhanced by the various
settings of the NCC-1 for the two active whips I have installed. 

I would be happy to hear from others who may be running similar experiments
with the NCC-1 at their locations.

Tod, K0TO


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