Re: [Elecraft] HPS-1a Gamma Hybrid,Communications Power Supply
output resistance to pull the output below the clamping level. Don't know what fuse you are using: say it's an ordinary "fast" blow 20A, then you will need >40A for 30s to blow it by which time the transient has long gone. The clamping voltage also depends on the current drawn and could be as high as 21.2V according to the spec. I would have to draw a load line to find out how that would perform with the supply but that would be only static conditions. Agree with all your statements. I tested the circuit ahead of time with a variable switching supply and a 25A fast-acting fuse (a value I am currently using with the K3). At about 15.5V the diode clamped, the fuse blew and the circuit opened up as intended. The diode remained good after that fault event. Now, how fast did the fuse blow? According to the info I've gathered from the Littelfuse and Bussman 3AG fuse datasheets, not fast enough to ensure 100% protection. Also agree that some switching designs will limit current ahead of the zener device and that may preclude the fuse blowing. I don't particularly care as I still want that fuse there for safety purposes. Again, all this may be trivial in the grand scheme of things if the Gamma OVP design actually works. But consider this: as long as the diode is clamping, even if we're waiting for the fuse to blow or the current of the supply to self-limit, the diode should still be performing a reasonably fast protection function. OTOH, if the diode fails while we're waiting for the fuse to open or the circuit to self-limit, all bets are off on the usefulness of the diode. A fast-acting circuit breaker may be better -- or not. I need to research the available types of CBs a bit more, including the Airpax types. Paul, W9AC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] HPS-1a Gamma Hybrid,Communications Power Supply
Paul I'm always a little wary of this scheme since using it myself a while ago and not getting the results I expected. I would call it a limiter not a crowbar. I'm guessing these supplies have a relatively high (compared to conventional linear regulator) output resistance and when I've done this with other supplies it doesn't actually blow the fuse. I'm sure it would still protect your rig, but simply act as a peak limiter using the fuse and holder and output resistance to pull the output below the clamping level. Don't know what fuse you are using: say it's an ordinary "fast" blow 20A, then you will need >40A for 30s to blow it by which time the transient has long gone. The clamping voltage also depends on the current drawn and could be as high as 21.2V according to the spec. I would have to draw a load line to find out how that would perform with the supply but that would be only static conditions. David G3UNA I'm a bit leery of the over-voltage protection circuits built into these small supplies. I added a Vishay 1.5KE15A 15-volt transient suppressor, reverse-based across the DC output (Mouser P/N 625-1.5KE15A). The diode is in parallel with the DC output terminals but a series fuse is inserted just ahead of the diode. This is essentially a zener crowbar device that upon reaching 15 VDC will conduct and blow the DC fuse before any damage is done to the rig (or one hopes!) > Paul, W9AC . ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] HPS-1a Gamma Hybrid,Communications Power Supply
It works at 100W SSB with 10-20dB compression. For CW at 20WPM you need to go down to 70W or so. I've been testing the Gamma supply with my K3 on CW. It works very well at 95W down to about 15 WPM. I rarely send below 20WPM and at that speed, the rig's full 100W can be expected. Even with this limitation, it's a remarkable device, given its size. I'm a bit leery of the over-voltage protection circuits built into these small supplies. I added a Vishay 1.5KE15A 15-volt transient suppressor, reverse-based across the DC output (Mouser P/N 625-1.5KE15A). The diode is in parallel with the DC output terminals but a series fuse is inserted just ahead of the diode. This is essentially a zener crowbar device that upon reaching 15 VDC will conduct and blow the DC fuse before any damage is done to the rig (or one hopes!) My only nit with the supply is that the AC line cord is hard-wired into the unit. An IEC receptacle would have been a nice addition. But in all fairness to the designer, there's almost zero room inside the enclosure for the receptacle. One alternative is to cut the line cord ~ 6-inches from the cabinet and add an IEC pig-tail. This offers the benefit of being able to use an IEC RFI/EMI filter as part of a disconnecting pig-tail assembly. Paul, W9AC . ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] HPS-1a Gamma Hybrid,Communications Power Supply
I use one with my K3/10. 73 jim ab3cv ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] HPS-1a Gamma Hybrid,Communications Power Supply
I have one for casual portable operation. I hear it just a little bit, so I wouldn't use it at home where a full-sized linear supply is available. Dick, K6KR -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Doug Phillips Sent: Saturday, December 06, 2008 3:48 PM To: elecraft@mailman.qth.net Subject: [Elecraft] HPS-1a Gamma Hybrid,Communications Power Supply Is anyone using the HPS-1a with their K3? 73, Doug W7RDP K3 1937 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] HPS-1a Gamma Hybrid,Communications Power Supply
It works at 100W SSB with 10-20dB compression. For CW at 20WPM you need to go down to 70W or so. It would not be good for RTTY or MFSK or other 100% duty cycle modes past 20W or so. Think of it as a 5A switching supply if you're usign 100% duty cycle. Leigh/WA5ZNU Is anyone using the HPS-1a with their K3? 73, Doug W7RDP K3 1937 _ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] HPS-1a Gamma Hybrid,Communications Power Supply
Is anyone using the HPS-1a with their K3? 73, Doug W7RDP K3 1937 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
