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Author Topic: Navigator Interface RFI Susceptibility  (Read 143 times)

W2MV

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Navigator Interface RFI Susceptibility
« on: July 15, 2020, 11:48:16 AM »

I have an older (Made by US Interface, Not Timewave) Navigator attached to my Icom 7610 and Dell PC.
It experiences problems related to RF intrusion only on 20 meters. I'm running a KW to an X7 antenna which seems reasonably matched.

When I transmit, the normally green power LED turns a different color and I lose the COM port connection to the PC running N1MM. The rig connection using a different COM port for HRD seems to not be affected.

I've wrapped each end of the cables around 2.4 I.D. toroids. Seems not to have helped.
There is no "ground" lug on this unit or I would have tried that too.
I have a common ground bar which most of my equipment is connected to, connected to several ground rods located close by.

Has anyone else experienced this problem?

Thanks
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K0UA

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Re: Navigator Interface RFI Susceptibility
« Reply #1 on: July 15, 2020, 02:29:19 PM »

What was the mix of the torroids you used and how many wraps?
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73  James K0UA

AA4PB

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Re: Navigator Interface RFI Susceptibility
« Reply #2 on: July 15, 2020, 04:13:33 PM »

You might try a USB cable that has ferrite beads on each end. I use a tripp-lite model U023-006 that I purchased from Amazon. You might also try connecting a ground strap to the metal case on Navigator and
to your ground bar.
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Bob  AA4PB
Garrisonville, VA

W2MV

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Re: Navigator Interface RFI Susceptibility
« Reply #3 on: July 15, 2020, 05:43:07 PM »

Thanks for the responses.

The ferrite is #77 mix about 6 turns around each one.

Re: a ground strap to the Navigator case...after calling Timewave, the gentlemen suggested a ground connection to the circuit board ground, which he stated was where one of the external jacks was grounded to. I tried that...a ground wire from there to my ground bus. Did not help :(

On my common coax line I have a Balun Designs 1:1 choke.
There's also a toroid on the cable to the DB25 connector on the Navigator.

Will keep trying...73
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W2MB

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Re: Navigator Interface RFI Susceptibility
« Reply #4 on: July 15, 2020, 08:46:03 PM »

Try to determine which cable is bringing the RF into the device. If it’s not the USB cable it may require trying to isolate and bypass the interconnection used by the various services that the Navigator is providing such as CAT control, PTT, Sound Card services or FSK and CW keying if you are using it for that. Once you’ve determined how the RF is getting into it you will be able to choke it off effectively by experimenting with your torroids. I don’t think that grounding will be the solution.

Good luck! QRO is nice but it comes with headaches. It took me forever to address all the devices in my house that would lose their mind when I ran power.

Some say that a high quality balun  at the antenna’s feed point works wonders, but in my case, due to the complexity and hi-q of my Pro-67B’s feed point installing a balun wasn’t practical.
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W9IQ

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Re: Navigator Interface RFI Susceptibility
« Reply #5 on: July 16, 2020, 03:52:05 AM »

For 20 meter RFI, type 31 ferrite would be a better choice. Get a large enough toroid so that you can put several turns of the cable around it.

You may also see an improvement by adding another 1:1 choking balun to your antenna system so that you have one near the antenna feed point and one near the shack. A little common mode current becomes a lot of common mode current when running QRO so extra measures are often warranted.

Also note that matching an antenna and SWR has nothing to do with common mode current

- Glenn W9IQ
« Last Edit: July 16, 2020, 03:55:23 AM by W9IQ »
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

AD0AR

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Re: Navigator Interface RFI Susceptibility
« Reply #6 on: July 16, 2020, 08:32:02 AM »

Sometimes a ground loop can occur on the chassis of the PC if it is not grounded to the same ground as the radio chassis. 
I had this happen on my IC-7600 and host PC.  After I grounded to the same reference point my RFI issues were resolved.
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WB4SPT

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Re: Navigator Interface RFI Susceptibility
« Reply #7 on: July 16, 2020, 10:30:58 AM »

Thanks for the responses.

The ferrite is #77 mix about 6 turns around each one.



77 works well at the lower HF freqs but realize that the core is quite conductive!  Use insulated wire. 
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