W1 and QRN

[jperelst]

I recently built the W1 Wattmeter/SWR Bridge to use in tuning my antenna.  

I've noticed that whenever I have it in-line between my K1 and the antenna, I hear a dramatic increase in receiver noise level.  The S-meter on the K1 goes from 2 bars to 4 bars.  This happens whether I have the W1 turned on or turned off, and happens on both 20 and 40 meters.

The noise level is lower when the antenna is out of tune (it's a manual trap antenna that requires me to manually change a wander lead and change the length of a counterpoise when I switch bands).  When I first switch bands, the noise is down at 2-3 bars.  Once I tune up the antenna with the wander lead and counterpoise, the noise is back up to 4 bars.  I believe (but can't measure) that the level of actual transmissions is higher with the W1 in the circuit than with the W1 not in the circuit.

The noise itself sounds like broad atmospheric QRN -- it's nothing specific, just loud crackling as opposed to a hum or ignition noise or a specific tone.

The only other thing I can say is that I have the W1 connected to the K1 by a 3' BNC to BNC cable.  The cable is coiled to sit on my desk.  I have tried stretching out the cable, but it has not reduced the noise.  Similarly, I have tried moving the W1 to various locations on my desk and off the desk without any noticeable improvement.

My antenna is not that far from power lines, telephone lines, and cable lines (about 10' at closest point, but positioned so that it can't fall on any of the lines), and the W1 is not that much further away from the antenna (the antenna is mounted to the house just outside the window of my shack).

Any thoughts as to why the noise level would be dramatically louder with the W1 in the line?  Could I have done something wrong in building the W1?  It seems to be working correctly.

Obviously, I can just take the W1 out of the antenna line to eliminate the noise, but I'm curious as to why I would be getting this effect.

Thanks.


     
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[Darwin, Keith]

Do you have a BNC coupler such that you could remove the W1 while still
leaving all the BNC cables in place?  Have you tried placing the W1
between the rig and a dummy load to see if the noise level comes up
compared to the dummy load alone?

- Keith N1AS -
- K3 711 -

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Jon Perelstein
Sent: Wednesday, July 09, 2008 7:45 AM
To: [hidden email]
Subject: [Elecraft] W1 and QRN

I recently built the W1 Wattmeter/SWR Bridge to use in tuning my
antenna.  

I've noticed that whenever I have it in-line between my K1 and the
antenna, I hear a dramatic increase in receiver noise level.  The
S-meter on the K1 goes from 2 bars to 4 bars.  This happens whether I
have the W1 turned on or turned off, and happens on both 20 and 40
meters.

The only other thing I can say is that I have the W1 connected to the K1
by a 3' BNC to BNC cable.  The cable is coiled to sit on my desk.  I
have tried stretching out the cable, but it has not reduced the noise.
Similarly, I have tried moving the W1 to various locations on my desk
and off the desk without any noticeable improvement.

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[cc1865]

Jon,

I can't help you much other than the fact that mine does not do this.

My setup is the same as yours.

K1-- about 18 inches of cable --- W1  --- 18 inches of cable--- ant. tuner.

I replaced the W1 with a coupler and no change. Try swapping out cables or a coupler as previously posted. I can't see any reason the the W1 would pick up white noise on or off.

Note: I only checked my on 40 meters.

HTH, Chris, KE6GS /XE3

K1 - #2481
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