I wholeheartedly endorse Don's comments. A good practice with any antenna installation is to check the SWR on each band for which it is used, and make a note of that. That can help determine whether an antenna problem is responsible for any sudden changes in behavior by simply rechecking the SWR. Alternatively (and more accurate) you can use your antenna analyzer and note the impedance at the feed point. If you live in an area with lots of moisture and snow, a check in mid-summer and another in mid-winter is useful. Significant differences can occur with a normally functioning antenna from winter to summer.
The 1/4 wave wires Don mentions can be in the shack. In similar situations I've run them along the baseboard in the shack, sometimes out under the door and down a hallway. Just be aware that the far end of that wire may have significant RF voltage present while transmitting. If you run several, you can run them in parallel for much of their length, then separate each one for the last several feet so its end is away from the longer 'radials'. Good luck. Isn't messing about with antennas fun? (And this is supposed to be done in mid-winter, don'cha' know? You get more RF mojo from fixing up the antenna in a snowstorm than on a nice summer day.) 73, Ron AC7AC -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Don Wilhelm Sent: Thursday, October 20, 2011 7:28 PM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] Now General RF Issue WAS 160m loop experiment a big failure Don, You MFJ259B can help you locate the fault. Look at the instructions for the 259B and in particular the Distance to Fault section. Yes, crushed coax can cause severe discontinuities, including actual shorts in the coax - not unlikely for coax being run over by heavy equipment. A shack on the second floor is always a problem for RF. A ground wire to a ground rod (hopefully also connected to the utility entrance ground rod) will provide a good path for AC Mains faults, and may also provide *some* lightning protection, it will not serve well for an RF ground point. The distance between the ground rod and the shack connection will have some reactance due to its length - if it is near a quarter wavelength, it will present a high impedance in the shack - to be effective, an RF Ground point should present a low impedance at the shack location. This may ba a case where the only good solution is he use of "counterpoise" wires. A quarter wavelength of wire on each frequency of interest will present a low RF impedance at the shack end and a high impedance at the far end of the wire. You may have to resort to this 1/4 wave wire as your best solution. Some experimentation may be required. 73, Don W3FPR On 10/20/2011 9:21 PM, gold...@charter.net wrote: > Dear Group, > > I apparently have a bigger problem with RF in the shack and it has > nothing to do with the loop. > > I have been running a successful shack on the second floor of my house > and as of Friday last week when I installed the loop I have had nothing > but RF problems. I thought on Saturday when I removed the ladder line > from the shack and coiled it up in the tree far away from the shack that > I would be ok and everything seemed to be ok. > > Anyway long story short, now with only the dipole (alpha delta trapped > dipole at 30 ft) connected in the shack I have terrible RF problems and > it can occur even barefoot at 100w so I am not pointing to the amp as of > yet. > > I have dropped the antenna and checked that the coax is tight, checked > to see if the coax is tight at the lighting arrestor, ran with and > without the tuner connected. I have rechecked the grounding that I > have in the shack, which after more research is not adequate, and I will > be addressing that this weekend. However, I don't think that this will > fix it. > > Right now I am thinking that I have a bad coax line outside of the > house. The reason for this is that I had a new propane tank installed > and they needed to back the truck up and had to drive over the buried > coax. I did put boards down to spread out the load and protect the lawn > and also the coax. However the problem has started since this incident. > > I pulled the coax out of the ground and it has bend marks at the edges > where the boards were which to means that it was deformed and maybe it > is now crushed. > > So other than doing a whole new ground setup with more ground rods > outside and adding more chokes to the coax, I want to check out the coax > that I have this weekend to determine if I have a "crushed" problem. Is > there a way I can check it out with my 259b or is it just replace it and > see what happens. > > Anyway, I am off the air until I get this sorted out. > > Basically now I have to start over, and frankly speaking I am a bit > overwhelmed right now so I just need a friendly group to lean on as I > really am frustrated right now as my favorite pastime is now no longer > possible due to some failure of some kind or another. > > Thanks in advance for your understanding in a non-elecraft post, but > this is the most friendly and knowledgeable group on the net that I > belong to so please help me get my K3 back on the air. > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
