[TowerTalk] Heliax acting strangely: Help?

[Grant Saviers]

A TDR scan would identify where a fault might be, so that would be the 
next test I would try.  The AIM, VNWA, SARK and others have that 
capability, I scanned all my Heliax (used) before putting it on the 
tower.   I had to use 3 x 120' runs of new AVA5 7/8" and found the DIN 
connector fitting to the shield much more difficult than LDF5. The AVA 
unique tools are really helpful.

Grant KZ1W

On 8/27/2017 4:25 AM, kr2q at optimum.net wrote:
> I put out a 160 foot run of 7 eights heliax last year.  Worked great.  Last time I was
> QRV was end of January, 2017.
> I recently put some RF out (100 watts...HP for me) and was surprised to see an SWR in the
> shack of about 3:1.
>
> Setup:
> Outdoor antenna switch box just outside the shack.
> >From there, very short run of RG8 (under 4 feet) to "start" of Heliax.
> 160 foot run of Heliax to "back" tower.
> Then another "short run" of RG8 to about 80 feet of RG217, which goes "up" my crankup tower.
>
> What I have done:
> Put a dummy load at the rig: shows 1:1 SWR.
>
> Put the dummy load at the "far end" of the heliax by "breaking" the connection from the
> Heliax to the short run of RG8.  SWR in the shack still 3:1 (all HF bands).
>
> Put the dummy load at the end of the short run of RG8 coming from the antenna switch box.
> SWR in the shack shows 1:1 (dummy working, coax to that point working).
>
> OK, so seems like something is wrong with the Heliax.
>
> I disconnected the Heliax at both ends.  If I short inner to outer, it shows dead short at
> the "other" end.  I know, DC is not RF.
>
> I measure the resistance between center conductor and outer shield of the Heliax.  I expected
> "infinite," but using my crappy RS ohmeter, it shows about 500k ohms.  I measured other runs
> I have RG217 (nothing connected at either end, about same length), and the crappy RS meter
> shows infinite, as expected.
>
> So what could go "wrong" with my 7 eights inch Heliax?  It is above (on) ground for the entire length.
>
> I walked it yesterday, picking it up about every 10 feet.  Looked "normal" to me.
>
> Any help/suggestions?
>
> Thanks,
> de Doug KR2Q
>
>
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