I know that lots of factors come into play in swr measurement,
especially when dealing with the full band of amateur frequencies being
read by one meter. But I have noticed while experimenting that my noise
bridge (a new Palomar PT-340 tuner-tuner) and Autek WM-1 SWR meter are
not in agreement, especially on 10 meters (not that this is perhaps
unusual).
I have noticed the following readings:
A. PT-340 noise bridge noise nulled by antenna tuner
Transceiver IC = 15 amps
WM-1 SWR = 1.9:1
SWR meter in my Ten-Tec 238 antenna tuner = 1.5:1
Output = 96+ watts
B. Ten-Tec 238 antenna tuner adjusted to read 1:1 SWR on its meter
Transceiver IC = 16 amps
WM-1 SWR = 1.5:1
PT-340 = not at noise null
Output = 93 watts
C. Antenna tuner adjusted so WM-1 reads 1:1 SWR
Transceiver IC = 20 amps
Ten-Tec 238 Antenna tuner = 1:1 SWR
PT-340 = Quite a ways from noise null
Output = 90 watts
The transceiver is a Ten-Tec Omni V and the antenna is a GAP Titan
vertical. The readings are all on 10 meters. I notice that all three
read much more closely on the lower bands...... in fact the noise bridge
and Autek WM-1 agree on 40 meters..... the noise null then is where the
meter reads 1:1
Which is generally more accurate ...... a noise bridge like the PT-340
or a decent SWR meter like the Autek WM-1 ? My vote is for the noise
bridge.......
--
Michael Melland, W9WIS
Winneconne, Wisconsin, USA
FISTS #4387, 10-10 #69281, QRP-L #1656,
QRP-ARCI #9875, AK/QRP #478, NorCal,
NJ-QRP #214, SOC #142, Cheeseheads QRP Club
CW, SSB, and Electronics
List Administrator: grundig@qth.net
http://www.qsl.net/w9wis
--
FAQ on WWW: http://www.contesting.com/tentecfaq.htm
Submissions: tentec@contesting.com
Administrative requests: tentec-REQUEST@contesting.com
Problems: owner-tentec@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|