[RFI] FW: Quiet Switching Power Supply?

[Howard Lester]

> On Aug 4, 2016, at 1:40 PM, Jim Brown <jim at audiosystemsgroup.com> wrote:

You're asking the right questions, Paul. And balance is determined by the entire antenna system, not only the feedline and the transmitter (tuner). Most REAL antennas are unbalanced by their surroundings, and most REAL parallel-wire feedlines are unbalanced by their surroundings -- we have to get them through walls, for example.
 
When I bought my FT-950 4+ years ago I bought it with an Astron switching supply. I wanted a lightweight “desktop” supply. I don’t remember what kind of noises I heard from it, nor the exact spacing, but whatever I did hear, maybe every 50 KHz, it sure was annoying. (At the time, I didn’t know it was the power supply that created the noise.) I phoned the dealer who sold it all to me. “What kind of transmission line are you using?” he asked. (I was surprised at the seemingly irrelevant question, and hesitated.) “450-ohm window line,” was my reply. He  then said, “You need a linear power supply." I sent back the switcher and got an Astron RS-35M (that weighs a ton) and have had no noise. 

No way is my 140’ inverted-V balanced, and I knew this; as far as I know, it’s “unbalanceable." The apex is at 33’, and each leg is over different terrain that is of different heights. One leg now even goes through extended branches of a tree! (I can’t stop it from growing.) The antenna support pole is about 50 feet from the shack. The window line, with a few twists to it, drops straight down for about 27’, then heads for the house, suspended above the lawn, also with a number of twists. But there are a few splices along the way, and a dual banana plug and jack quick-disconnect I devised. 

The window line attaches to a Balun Designs 1171 current balun outside the shack. From the balun an 8’ length of RG8 runs through the wall to the Palstar transmatch. A balanced system? I don’t think so. Regardless, I’m pleased with the antenna’s performance 80 - 10 and I have fun with it. Isn’t that the point? 

Howard N7SO