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This blog is the replacement of the my preview Topband blog here http://topband.blog.cz/ because of an aggressive advertising and flash banners inserted by the blog provider. For older posts access You can visit the old blog link which will exist still... but it will not be updated anymore.
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Friday, November 29, 2013
Crappy Chinese cables in Your shack by Alan, N5NA
At the beginning of the ARRL 10M Contest a couple of weeks ago I noticed several "squalling" noises across the band. I had heard these before but hadn't investigated. I thought it was probably from the Ethernet cabling in my house I decided to see if I could do something about it.
First I disconnected the coax from my rig, the noise disappeared. I reconnected the coax and turned off my router and wireless internet radio. The noise was still there. Next I disconnected the coax from the remote sensor for my SWR meter. The noise was still there. Hmmm, that's strange. I disconnected the coax from the antenna from the back of my amp. The noise was still there. Next I disconnected the jumper from my rig from the back of the amp. The noise was still there. At this point the only thing connected to my rig was a 6' coax jumper. I disconnected it and the noise disappeared!
That coax jumper was factory assembled with molded strain relief at the PL-259's. I replaced that cable with a homemade cable and the noise stayed gone.
I cut open the factory cable and found the coax had maybe 10% coverage, if you could call it coverage. It was junk. If I'm not mistaken I bought that cable from one of the large dealers at Hamcom. Below are a couple of pictures. It looks pretty until you cut it open.
A few months ago I was getting ready for the Texas QSO Party. I was testing a USB>Serial adapter that uses a separate USB cable. When I connected the adapter there was a noticeable noise increase in my Elecraft K3. Again, I tracked that noise down to the USB cable, which was a piece of junk from China. After replacing the USB cable with a Belden cable I didn't hear any noise from the adapter.
Moral of the story, beware of crappy cables from China!
73 - de Alan, N5NA.
Inspired by Alan and his article I started to check all of my coaxial cables in the shack. Well because of tons of cables over here it's not the "one evening project" but some strange results are available even now...
I found that after changing some of the cables for high quality one I noticed the SWR changes on LF/HF bands and also I noticed some noise improvement. It not solved my noise issue completely of course but even just noticable changes in the noise level seems that cables was not good and put me in troubles with weak signal reception over here.
I am going to check all of my cables !
73 - Petr, OK1RP