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Old 02-04-2014, 08:39   #1
GWB
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Laptop loses coms with pactor modem

When trying to send email on low frequencies (3-7 mhz) the modem will initiate the connection but after about 3 seconds I will get a message in RMS express that communication has been lost with the modem. I assume that this is because there is RF interference getting back to the laptop usb port.
There are ferrites on all the cables between modem and HF radio, and modem and laptop. The installation is per Farralon electronics.
Is it because I'm putting too much power out on these lower frequencies in digital mode? If so, how do I reduce power? I'm using RMS express....
Thanks for any help
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Old 02-04-2014, 10:10   #2
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Re: Laptop loses coms with pactor modem

I've found that when RMS Express works, it works great; however, I'm having similar issues with it locking up when going through the initialize, connect, send, .... sequence. It does seem to be on lower frequencies. It doesn't seem to recover from dropped connections and timeouts very well. I've often had to reboot the laptop and recycle the modem.

I do have an RFI problem that I'm chasing down. I'm experimenting with different ferrites and grounding.

I'm still experimenting with my configuration. I've had better luck with Win2K, through I prefer RMS Express as far as its user interface. Haven't decided which program I'll use - I think it depends on which one ultimately works best.

Good luck!
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Old 02-04-2014, 17:16   #3
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Re: Laptop loses coms with pactor modem

As a followup, I managed to block the RFI causing high-voltage across my laptop mouse pad. I used 1/4" ferrites, with 4 wraps around the serial cable, going from the modem to the USB-Serial adapter, plugged into the laptop. With the ferrites close to the modem, I didn't need additional on the USB-Serial cable. I'm happy that this is resolved. Good luck with your RFI issues and RMS Express.
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Old 06-04-2014, 08:21   #4
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Re: Laptop loses coms with pactor modem

Thanks for the feedback Don. I'll try more ferrites at the modem
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Old 06-04-2014, 10:01   #5
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Re: Laptop loses coms with pactor modem

You should have ferrites on all the cables that are attached to the laptop. They can all act as antennas and inject signal into the USB connection and controller.
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Old 06-04-2014, 10:46   #6
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Re: Laptop loses coms with pactor modem

Remember, all ferrites are not created equal. Most of the ones you see are designed to work well at VHF frequencies, and aren't as effective at HF (SSB) frequencies. Using more of them, and running more turns through the core will help, but if you can you should use a ferrite designed for a lower frequency range. Here's a link to a presentation I gave that includes some info about some appropriate ferrites: http://sailvalis.com/presentations/S...ons%202012.pdf (see page 14).

Here's a link to a good ferrite clamp-on core at Mouser Electronics (electronics distributor): 0431164181 Fair-Rite | Mouser
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Old 06-04-2014, 11:34   #7
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Re: Laptop loses coms with pactor modem

The key that I learned, in my case, the single pass small ferrite beads didn't suppress the RF interference on my laptop. It took the larger (1/4" ferrites) with 3 wraps of wire through the core (you can see this is Paul's presentation, page 14). The other interesting thing, I only need the ferrites on the serial cable running from the modem to USB adapter.

It is interesting how the high-voltage found its way into the laptop and actually caused little burns on my fingers.

Here's my earlier thread on this subject,
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