Hi Folks I discovered PSK31 just before the sunspots faded out. I bought an interface and worked QRP on 14.070MHz. Had a really good time too, its a fantastic mode, especially for QRP and those who cant fit yagis into the homestead (like me). But a quick question to those more familiar with data modes. If I connect the interface to my desktop computer, it receives well, but I cant get clear transmit. It sends full scale white noise no matter how I adjust the mic gain or audio levels. If I connect up the laptop, same TX noise problem .... until I unplug the mains charger and run on batteries. Then its perfect. My laptop batteries last about 2 hours there days, so I'm limited to 2 hour long operation until I sort the problem or get a higher capacity battery. Any thoughts what's causing it? cheers Jack VK2CJC / MM0AXL FISTS #9666 CW Ops QRP Club #753 Mid North Coast Amateur Radio Group www.mncarg.org

Thanks for the input guys. I am using a Buxcomm rascal interface (I had forgotten the make, but have been reminded since), which apparently has excellent isolation. The problem occurs equally on all HF bands, so is not really frequency specific. If its a stray RF problem, which I am very willing to accept, I'm surprised that it effects two very differently designed computers in exactly the same way.

> Yeah, yeah, green-wire "protective ground", etc. etc. Well, > I don't see what exactly the "protection" here is doing, Well it will be double insulated so doesn't really need an earth at all. I'm surprised there was one. Jack

"Richard Crowley" <rcrowley@xp7rt.net> wrote in message news:13kkii43nphuk9b@corp.supernews.com... > "Alan WA4SCA" wrote ... >> One has to start somewhere, and the presence of ground loops can, and >> have, resulted in RF and not just audio problems. FWIW. > > This is a FAQ in the audio world. It is a very common problem with getting > audio into and out of laptops. Their "brick" power supplies are > notoriously noisy. At AF frequencies, and likely RF, as well. In the > audio world, we use full transformer isolation in and out. (Or else use > an inexpensive USB-powered audio interface. Likely cheaper than trying to > isolate the PSK31 interface.) > Since the problem is just on TX perhaps he has a hot sheild and his feedline needs decoupling from the antenna. Its also a shame many radio interface circuits are designed so poorly without proper isolation. On numerous occassions I have had to add isolation transformers and opto isolator circuits to get things to interface right. Im always on the lookout for good quality 600 ohm to 600 ohm transformers. Jimmie