Due to my customizing two MFJ-1026 units I ran some tests on one today.
A Fluke 96B Scopemeter provided the readings and a Wavetek 3000
Service Monitor served as a signal generator for a RF signal on
1830 kHz. A 160 meter bandpass filter followed the Wavetek to better
clean up its output at that frequency.
Adjustment of the PHASE control had a negligible effect on the
amplitude of the the source whose phase was being adjusted. I didn't
write down numbers since the worse change was less 0.5 dB.
The reason for the test was more to observe the effects of the phase
control adjustment. I wanted to have a better understanding of how
the lobe center and nulls were being effected on my phased Beverages
by phase adjustment. I "normalized" the effect of the readings so
that 0º phase shift is shown with the PHASE control at "0" with the
PHASE switch in the "NORMAL" position. My wiring used did not
accurately reflect the phase relationship in this position. However,
the amount of phase change per control movement is accurate as well
as the effect of the invert switch. Those shifts probably would
have been even more in agreement if they weren't made after changing
the switch and readjusting the control. The figures below show the
amount of phase change due to the control adjustment and the effects
of the PHASE switch:
PHASE PHASE PHASE
CONTROL SWITCH: SWITCH:
SETTING NORMAL INVERT
0 0º 184º
1 2º 187º
2 7º 192º
3 12º 198º
4 16º 202º
5 21º 204º
6 28º 210º
7 39º 221º
8 61º 243º
9 105º 293º
10 162º 348º
I knew that there was a reason why I rarely had the PHASE control
setting between 0 and 5...
To answer AA4NC's question, IF THE NOISE IS FROM A POINT SOURCE,
the nulling of the noise will be similar to those figures that I
recently quoted for local AM broadcast stations (excellent). If a
power line is acting as an antenna for the noise source, the nulling
may not be nearly as good. Appropriately "matched" antennas are also
needed for good nulling. Fairly recent archive reflector messages
deal with this in more detail...
73, Bill K0HA
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