Milt, N5IA wrote: > > ----- Original Message ----- From: "Merv Schweigert" <k...@flex.com> > >> I started to try and find the problem and using another >> receiver I find the Astron SS-30 is generating all sorts of noise. >> I have used this supply for some time and have not noticed the noise >> before. > > Merv, > > For weight considerations, the SS-30 supplies were selected for the > Ducie Island expedition this past year. > > This problem you mention, or a very similar one, was evident during > the VP6DX expedition from the time that Robin started making tests > while underway on the Braveheart from ZL to FO. > > We added extra filtering internally. > > We grounded extensively. > > We cleaned the case cover screw holes both on the main chassis and on > the cover to improve bonding to the cover. We were never able to make > them clean. All supplies performed in the exact same manner. > > We were float charging small batteries to keep the K-3s and the > ancillary equipment running while the gensets were being refueled and > having oil changed. The extra capacitance of the battery helped with > the DC filtering but most of the stuff was of a frequency that the > battery and other filtering could not remove. And we couldn't keep it > inside the case. > > The fact remains that the harmonics of the switcher were a very real > problem for us, especially on the lower frequency bands. The most > annoying situation was the harmonic signal moving around, slowly up > and down the band such that we could not avoid it at times when we > were in the middle of a tough one on 160 and were trying to dig it out > of the noise floor. We had to wait until the birdie slowly slithered > on by or many times I just reached and turned the SS-30 off during a > difficult contact. > > 73 de Milt, N5IA The noise floor with the switchers has always been a problem, but the increase is what was bugging me, and happy to have it confirmed that they are somewhat incurable, thought it was just me, have done about all that Milt describes and still has noise. The past couple days its has just increased by 2 DB on the meter, in other words on 20 meters the K3 is hovering around s4 to s5 noise floor, compared to turning off the switchers and K3 and listening on a Ft-1000D it has a noise floor of S0. I guess its back to an old transformer supply, had been trying to stay away from that due to the shipping weight etc. Thanks for all the input. 73 Merv KH7C > >
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