[TowerTalk] VNA

[Paul Christensen]

>"I have a couple of 50KW BC stations nearby that I've measured at -3dBm on
my inverted-l.? As long as I start a sweep at 1.7 MHz or above I have no
issue with them."

I have a nearby 50KW AMBC station a few miles to the south of my remote
site.  With the Array 2180 and N2PK VNAs, it's possible to sweep a 160m "T"
right through the station's carrier and barely see the effect on the complex
impedance trace.   What appears on the trace is a tiny "blip" at the AMBC
carrier frequency and even that can be smoothed out in software.   A
combination of a very narrow detector bandwidth and moderately high output
power of +13 dBm makes this possible.

In about a month, I'll have a chance to compare AA-230-Zoom and 55-Zoom
vector impedance analyzers on a new 160m 4-square, then the result can be
compared with the Array and N2PK devices.  Although the 55-Zoom is limited
to 55 MHz, it's output power is 23 dB greater than the 230-Zoom.  The
55-Zoom is also less expensive and has a larger color LCD display area.
However, with its frequency limitation, TDR measurements are not as accurate
when compared to the 230-Zoom.

Paul, W9AC