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Power Supplies
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I am wondering what others are using for power supplies. I have received signal reports of weak signal, and there was a comment that it might be a lack of power during transmission. I am using a wall wart, rated at 12V, 1.65 amps. I went to the thrift store and got a laptop power supply, rated at 20V, 2.25 amps. I measured 20.6V at no load. This power supply is now connected to PA power.? I have replaced the heat sink with one about twice the mass, 13 grams vs. 6 grams, and not quite twice the size of the original.? It seems to pass the initial smoke test. I am hoping that this combination of two power supplies resolves the weak signal problem.? There are other options, such as a lead acid battery on a charger, or my big 20 amp 12V power supply. |
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I use 3 PSU total I use a WII power supply to power the radio itself and I use 2 xbox 360 power bricks in series for 24 Volts to the PA.? The WII PSU is 10 amps rated and the xbox supplies are 16 amps each so 32 amps total.? I get about 15-20 watts out on 40 and and 30 watts out on 80 and 10 watts out on 30M.? Antenna Antenna Antenna.? What are you using for an antenna?? I often hear about Hams buying $1000+ radios and Kw amps but if your antenna is garage it's just a waste, the antenna should be one of the largest investments in a station. On Mon, May 1, 2017 at 9:52 AM, KC8WBK via Groups.Io <cruisenewsnet@...> wrote:
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LOL I actually use a computer heatsink from a CPU it's like 3x2 and has 20 or so fins and I have a cpu fan attached to it's back.? I have push this thing to the max and the hottest I have had it on JT65 was 60c and was plenty cool by next TX. On Mon, May 1, 2017 at 10:52 AM, KC8WBK via Groups.Io <cruisenewsnet@...> wrote: What type of heat sink are you using? |
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I'd ?say 60C at the heatsink is dangerously hot. ?Time to stock up an extra IRF510's, you will likely need them. The transfer of heat from die to tab is not very efficient on the IRF510, it is spec'd at 3.5 degrees C per Watt. ?Assume you are transmitting 20 Watts at 50% efficiency. ?So the IRF510 die is dissipating 20 Watts, and the die itself is 60C + 3.5*20 ?= ?130C. ? That's assuming the tab of the IRF510 has perfect heat transfer to the heatsink where you mesured your 60C. ? Jerry, KE7ER /g/BITX20/message/24339 On Mon, May 1, 2017 at 07:59 am, Steve Greer wrote:
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That was on the face of the fet and they are rated 170c I have a few extras we don't learn limits without a little black smoke. On Mon, May 1, 2017 at 1:57 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
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Also, that 130C calculation assumes you have been transmitting that 20 Watts long enough for things to reach equilibrium. ?If the tab is still slowly heating beyond 60C, that means the die is much hotter than 130C. The IRF510 is spec'd for a junction operating temp of 175C max, but ?I think you might be pushing dangerously close to that. ?Heatsink shouldn't get much more than lukewarm. ?Those insisting on lots of power might do well to borrow the design of the uBitx final: ?? ? building just the push-pull 2n2219 and IRF510 stages. ?The two single npn stages preceding that in the uBitx design can be adapted from the existing Bitx40 stages. On Mon, May 1, 2017 at 10:57 am, Jerry Gaffke wrote:
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Funny you mentioned that because I started a thread about that exact subject and looking for some input about it.? I think it would be rather easy to do.? Please see other thread On Mon, May 1, 2017 at 2:09 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
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/g/BITX20/message/25933 Here is the thread I started On Mon, May 1, 2017 at 2:09 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
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Running 20 V on the PA jack, I had a short 1 minute transmit QSO. The report was that the signal was strong but with some audio distortion. I touched the heat sink and it was hot to the touch. My unreliable swr power meter shows normal speaking power at about 6W peaking to over 10W. With 12V on the PA jack it is about 2W or 3W during normal speaking, peaking to about 6W. |
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Have you upped the size of the heatsink more power=more heat you need a good radiator to keep it as cool as possible. I have a cpu heatsink and fan on mine at 24 volts I get 15-20 depends on the band I'm on. On Tue, May 2, 2017 at 9:55 AM, KC8WBK via Groups.Io <cruisenewsnet@...> wrote:
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Jack Purdum
So, what's going to fill that hole in the mobile version? Jack, W8TEE From: KC8WBK via Groups.Io <cruisenewsnet@...> To: [email protected] Sent: Tuesday, May 2, 2017 11:23 AM Subject: Re: [BITX20] Power Supplies Here are some pics: https://www.qrz.com/db/KC8WBK
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LOL very kewl that heatsink needs to be about 3 or more times that size.? ? |
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oled display./w DDS On Tue, May 2, 2017 at 12:30 PM, KC8WBK via Groups.Io <cruisenewsnet@...> wrote: I was looking for an ammeter that would fill the hole. I'm not sure what to do with it. |
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Jack Purdum
...or the attached... From: Larry Acklin <acklin@...> To: [email protected] Sent: Tuesday, May 2, 2017 12:31 PM Subject: Re: [BITX20] Power Supplies oled display./w DDS On Tue, May 2, 2017 at 12:30 PM, KC8WBK via Groups.Io <cruisenewsnet@...> wrote: I was looking for an ammeter that would fill the hole. I'm not sure what to do with it. |
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I like that s-meter! I found another old pc power supply that puts out 16.2V.? I connected the 16.2V to the PA jack and called CQ for a minute.? The heatsink was warm but not hot.? I did not get a signal report, the band was dead at the time. I would say that it peaked out just over 10W but it is really difficult to read the meter, it moves very fast and it all depends on how loud I yell into the mike. I think that I will stick with the 16.2V PA power supply for a while and see what kind of signal reports I get.? I will report it as a 10W power output and that still qualifies for SSB QRP, which I like. |
