[Elecraft] Now General RF Issue WAS 160m loop experiment a big failure

[Don Wilhelm]

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, goldtr8 at 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.
>
>