Re: SWR cable or ant problem?


High Ryan,

Welcome to the strange world of RF...  Sometimes (maybe all the time...) it can do weird stuff and give you strange results.  And not always repeatable..

Lou is right.  The higher the frequency, the harder it is to reliably measure SWR.  I almost always use an external SWR Meter for VHF/UHF frequencies, rather than the 7100's internal metering.

Your antenna system includes the coax, the antenna and anything else in-line (or sometimes beside) the feedline between the radio and the final radiating element of the antenna.  So your next setup is to isolate the different parts of the feedline and check them one at a time...  Invest in a simple SWR/Power meter and a small dummy load.  They are not that expensive and will pay for themselves many times over...

Some equipment examples below.

Digital SWR/Power Meter:

Dummy Load:


On 06/28/19 15:08, Lou Giliberto (KD7HCW) via Groups.Io wrote:
The 7100 swr meter is flaky at the higher frequencies. Icom quietly put a note regarding that in the advanced manual. For non HF use an external swr meter.

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-------- Original Message --------
On Jun 28, 2019, 2:48 PM, Ryan - KJ7GIE < rsm@...> wrote:

I am now the happy owner of an IC-7100. Thanks much to Tom for his very nice overview during field day it convinced me to go get me one. I'm also now the unhappy owner of some odd SWR numbers since the 7100 has an internal SWR meter. I also now hate PL-259/SO-239 connectors.

But back to my odd SWR numbers. Here they are:
144.100 SWR tested: 1.5
147.5 SWR tested: 2.1
432.5 SWR tested: 3.0
446.2 SWR tested: 1.1 / 1.0
The IC-7100 sweeps a couple steps below and above that exact frequency and SWR numbers are average result.
3.0 is basically off the chart.

The middle of both bands is 1.5 or less. The reading of 2.1 on 2m seems high but being at the edge of the band I'm not so concerned. My main concern is that the edge of 70cm is off the chart. I'm using LMR400 from a 2/70 dual-band Arrow Antenna which is _supposed_ to be 1.5 or less across the entirety of both bands. I suspect if I had a loose connection I'd _not_ be able to achieve 1.0 anywhere in the band and that held true this morning when I wasn't achieving better than 2.0 anywhere and found a loose connection. I've gone back and checked everything again except for the antenna connection (ladder deployment pending). Based on the design of this antenna maybe I need to adjust the 70cm element? Loosen a screw? All suggestions welcome. Maybe my understanding of coax is incorrect and this is a coax issue? How many times must I retry screwing in those * connectors?

I don't have a dummy load or external meter. That's probably my next step huh? Verify the coax?
Would someone be willing to lend me their meter and dummy load this weekend? Would be much appreciated. At least our repeater at 441.8 is is working great.

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