[TenTec] PC generated noise & the pegasus serial cable

[Bill Miner]

Guy,

There is a signal ground pin AND a shield ground pin  in a  standard
serial cable configuration.  Some commercial cables do not even have a
shield! Make up your own cables and you will be happier.

73, Bill - K6WLM 

Guy Zebrick wrote:
> 
> Hey all - I found a problem, and then the solution, to a noise issue I discovered on 15 and 40 meters. I was doing some testing on my Pegasus the other night, and when I was on the dummy load, I found I had a S-5+ noise level on 15 and 40 meters. the other bands were quiet. Turning off the connected laptop PC eliminated the noise.
> 
> I have an ICOM 740 (now resting in a comfortable retirement mode) right next to the Peg, and it was NOT effected by the noise at all.
> 
> Turning on the laptop again, the noise returned to the Pegasus, BUT when I disconnected the serial cable, the noise went away again. I should also note that I have been battling a cracking noise coming into the accessory input when running PSK or SSTV using the speaker-out on the laptop.
> 
> The noise was coming in through the cables, not 'over the air'!
> 
> The solution was simple. I ran a ground wire from my grounding post on the back of the Peg to one of the  screw terminals on back of the laptop that is used to secure a parallel port cable. This eliminated the crud on 15 and 40 meters, as well as the crud on the speaker output. Seems that I may have had some sort of ground loop going.
> 
> Funny thing is I am using a commercial RS232 cable to connect the laptop to the serial port on the Pegasus, so I thought the grounds would be common through the 9-pin cable.. but I guess not.
> 
> Anyway, just wanted to share. Still think the Pegasus is one of the best bargains in Ham Radio along with Carl's N4PY's software.
> 
> 73's
> WD5ACP
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec