Re: power supply question
时间：04-08
整理：3721RD
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Hello,
Can anyone recommend what kind of power supply I can use for a 40M SSB transceiver. I have been using a battery eliminator I got from radio shack up until now. It seems to have a lot of noise on it above what I can measure with my O'scope. I'm not sure if it's a switcher or some form of linear type. I think that might be what is causing the L.O. to be very unstable. I am looking for an economical solution. Any suggestions?
George
Added after 45 minutes:
I used an LM317 to power the L.O., which is a Clapp oscillator, but I think perhaps the noise is getting through to it. Or perhaps the noise is caused by the length of wire that runs from the oscillator board to the air variable tuning cap which is used to adjust it, which is mounted on the chassis. The case of it is connected to one of the sets of plates. I am guessing that it is supposed to be connected to the chassis. There are no terminals for that side of the cap. But maybe I am supposed to isolate it from the chassis. That wouldn't seem unlikely, however. At this point I don't know what other things could be causing the oscillator frequency to fluctuate so much. May it's the bandwidth (too low a Q?). I'm not sure how to fix that. I used values for the resonant circuit of the oscillator that were recommended by a senior member of this forum and I am pretty sure he chose them for a good Q. I am hoping it is the power supply that is the problem. The wires from the oscillator board to the variable cap are as short as I could make them, but they're still a few inches. Maybe I should use coax (RG-174 I suppose). Any suggestions?
George
Can anyone recommend what kind of power supply I can use for a 40M SSB transceiver. I have been using a battery eliminator I got from radio shack up until now. It seems to have a lot of noise on it above what I can measure with my O'scope. I'm not sure if it's a switcher or some form of linear type. I think that might be what is causing the L.O. to be very unstable. I am looking for an economical solution. Any suggestions?
George
Added after 45 minutes:
I used an LM317 to power the L.O., which is a Clapp oscillator, but I think perhaps the noise is getting through to it. Or perhaps the noise is caused by the length of wire that runs from the oscillator board to the air variable tuning cap which is used to adjust it, which is mounted on the chassis. The case of it is connected to one of the sets of plates. I am guessing that it is supposed to be connected to the chassis. There are no terminals for that side of the cap. But maybe I am supposed to isolate it from the chassis. That wouldn't seem unlikely, however. At this point I don't know what other things could be causing the oscillator frequency to fluctuate so much. May it's the bandwidth (too low a Q?). I'm not sure how to fix that. I used values for the resonant circuit of the oscillator that were recommended by a senior member of this forum and I am pretty sure he chose them for a good Q. I am hoping it is the power supply that is the problem. The wires from the oscillator board to the variable cap are as short as I could make them, but they're still a few inches. Maybe I should use coax (RG-174 I suppose). Any suggestions?
George
One cheap solution is to add a gell cell across the supply output.
You didnt tell us the 2 most important factors, what is the transmitter power of the 40m tranceiver? and what current rating is the battery eliminator ?
it could be as simple as the B.E. cant supply the current needed by the radio
cheers
Dave
VK2TDN
let me know the voltage and current you are using now, with the power rating of the TX. wether it is a homebrew or a comercial one.
Cheers