[SCCC] Antenna Challenge

[Michael Tope]

This is a longshot, Mark, but I wonder if LDG is trying to match your 
antenna at a harmonic of the input frequency. Do you happen to have a 
standalone impedance analyzer (e.g. an MFJ-269) that you could use to 
sweep the input of the LDG after it tunes up (with the IC-7600 driving 
it) and indicates the 1.3:1 VSWR across 160 meters?

You mentioned putting ferrites on the lines going to the rig. What about 
the line carrying the +12V power going to the LDG?

How is the connection between the tuner and the antenna (i.e. shorted 
twinlead) and the ground radials configured? Do you have a short piece 
of coax running to the feedpoint where the radials and the shorted 
twinlead come together? Is there a current balun (i.e. RF choke) on that 
coax to help keep the coax outer conductor and tuner chassis from 
becoming part of the radial system?

73, Mike W4EF................

On 1/23/2019 8:57 PM, Mark Schoonover wrote:
> Good evening,
>
> Hoping the collective of SCCC can give me some assistance. I'm looking
> at participating in the ARRL 160M contest this weekend. The antenna is
> a 33' of shorted ladder line with a 40M full wave loop at the top
> antenna. I put down as many radials as I could, some are close to 1/4
> wave on 160 but most are lucky to be 1/4 on 40.
>
> I have an IC-7600 attached to a LDG 1000proII tuner. I can get a good
> match all across 160M <1.3:1 on the tuner's built-in SWR meter but the
> meter on the rig is >3:1 and power folds back. I have the tuner right
> next to the rig with RG-213 from DXE between the two. There's 1" braid
> from tuner->rig->ground rod outside. When I take the LDG out of line
> and use the rig's built-in tuner, I can get 1.4:1 across the band.
>
> I initially thought it was RFI getting back into the rig because the
> antenna is about 5' from the radio desk. I put mix 43 chokes on every
> cable entering the rig. No luck on that front but it sure did reduce
> RFI.
>
> So any ideas what this could be? I'm scratching my head on this one...
>
> Thanks for reading!
>
> 73! Mark KA6WKE
>
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