Thank you Don (W3FPR), Jack (K8ZOA) and Larry (N8LP) for
your interesting comments on this thread last week and for taking the
trouble to set them down so clearly.
My technical expertise in this area is no match for yours although I did
make my first, fairly unsophisticated, indicator of forward
A wattmeter built around a directional coupler always has to deal with
finite coupler directivity. Making the problem more difficult is that we
expect a wattmeter to be accurate over a rather wide frequency range,
1.8 to 30 or even 50 MHz. This places an even greater burden upon the
Several interesting topics have arisen in this discussion. Here are a couple
comments...
1) Most wattmeters use a diode peak detector for each of the coupler ports
(FWD, REF). The forward voltage drop of the diodes becomes an increasing
source of error as power is lowered. The means than for
Take any SWR meter and insert it at different locations along the length of
the feeder
and you will get different readings.
Other than SWR reduction due to cable loss, the SWR meter should read the
same SWR regardless of where it is on the coax. Picture the constant SWR
circles on a Smith
...@tx.rr.com
To: elecraft@mailman.qth.net
Sent: Monday, May 04, 2009 7:43 AM
Subject: Re: [Elecraft] K3 - SWR Indication
Take any SWR meter and insert it at different locations along the length
of
the feeder
and you will get different readings.
Other than SWR reduction due to cable loss, the SWR
- Original Message -
From: Steve Ellington n...@carolina.rr.com
It appears that your coax does not exactly match the impedance of your
dipole (It rarely does)
-
Thank you Steve for your comments. I fully accept about a probable mismatch
between
To: elecraft@mailman.qth.net
Subject: [Elecraft] K3 - SWR Indication
In the past week I've been tuning and pruning an inverted V dipole I've put
up for 40m, fed with coax. The job isn't finished yet but I'm noticing
significant differences between SWR readings on my K3 and an external
LP100A
Other than SWR reduction due to cable loss, the SWR meter should read the
same SWR regardless of where it is on the coax.
Some reasons for changes in indicated VSWR as measured at different points
along the line:
1) Line loss. As line loss increases, VSWR will show a better reading
closer
@mailman.qth.net
Sent: Monday, May 04, 2009 10:14 AM
Subject: Re: [Elecraft] K3 - SWR Indication
- Original Message -
From: Steve Ellington n...@carolina.rr.com
It appears that your coax does not exactly match the impedance of your
dipole (It rarely does
- Original Message -
From: Steve Ellington n...@carolina.rr.com
Geoff
Try putting a 50 ohm dummy load in line and see if the K3 and your ext.
meters read the same swr. This will take reactance and inbalance out of
the picture.
Thanks Steve. I did try that and with a 50 ohm dummy
Hello Geoff,
Which bands were you making the comparison on?
Bob, N6CM
On Mon, May 4, 2009 at 9:48 AM, Geoffrey Downs
geoff...@downs.globalnet.co.uk wrote:
- Original Message -
From: Steve Ellington n...@carolina.rr.com
Geoff
Try putting a 50 ohm dummy load in line and see if the
Geoff,
That test at 50 ohms substantiates that the wattmeters are properly
balanced for a 50 ohm system, and nothing more - read on if you are
interested in more skepticism.
Contrary to several statements made, it is quite possible that *all*
those wattmeters can be wrong when reporting SWR
In the past week I've been tuning and pruning an inverted V dipole I've put
up for 40m, fed with coax. The job isn't finished yet but I'm noticing
significant differences between SWR readings on my K3 and an external
LP100A.
For example: At 7.000 MHz the K3 currently shows 1.2:1 and the LP100A
!
Steve Ellington N4LQ
n...@carolina.rr.com
- Original Message -
From: Geoffrey Downs geoff...@downs.globalnet.co.uk
To: elecraft@mailman.qth.net
Sent: Sunday, May 03, 2009 7:12 PM
Subject: [Elecraft] K3 - SWR Indication
In the past week I've been tuning and pruning an inverted V dipole I've
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