That's interesting. I have a RM 70 that has been turned on for over 15 years with no problems and a RS-35 for 10 years w/o a problem. Rock Solid.
Phil Philip LaMarche LaMarche Enterprises, Inc [email protected] www.LaMarcheEnterprises.com 727-944-3226 727-937-8834 Fax 727-510-5038 Cell www.w9dvm.com K3 #1605 CCA 98-00827 CRA 1701 W9DVM -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of george fritkin Sent: Wednesday, August 18, 2010 12:45 PM To: [email protected] Subject: Re: [Elecraft] K3 - small power supply 110-240VAC I have several of the MFJ-4125 supplies and several of the ASTRON 20 and 35 amp models. The only ones I have trouble with have been the ASTRONs. Random failures even when not under load. Go figure. MFJs....rock solid. George, W6GF --- On Wed, 8/18/10, [email protected] <[email protected]> wrote: From: [email protected] <[email protected]> Subject: Re: [Elecraft] K3 - small power supply 110-240VAC To: Date: Wednesday, August 18, 2010, 9:37 AM I've used the Gamma on PSK at 30 watts and CW at 100w and no one complained (I realize that only means no one complained). I may have been pushing the envelope but the Gamma met my needs for a small lightweight portable supply. I wouldn't use it full time in the shack when there are other more robust choices. Buck k4ia K3 #101 In a message dated 8/18/2010 11:57:34 A.M. Eastern Daylight Time, [email protected] writes: > *Gamma Research further hedges their rating by adding a footnote to > their spex that "Output power should be limited to 25 or 300 watts > during tune-up or other prolonged key-down operation." At > 13.8 VDC that means the supply should not be expected to provide more > than 2A continuous! With a less than 50% DC to RF efficiency for most solid state rigs (K3 is 36% based on 20A @13.8V for 100 W output), 25 or 30 Watts output would be close to 5 Amps @ 13.8V assuming 40% efficiency. 73, ... Joe, W4TV On 8/18/2010 11:39 AM, Ron D'Eau Claire wrote: > Quite true Joe, and that's why it's important to note how the supply > is rated. > > If you're talking about the Gamma HPS1a, it's rated at only 5 amps > continuous* and they do not offer an ICAS rating. Instead they say it will > handle 22 amps peak at 25% duty/sec., which I interpret to mean no > more than > 22 amps for up to 250 milliseconds during any 1 second interval. > Clearly that's useless for supplying anything but SSB voice > modulation, and I'd be > concerned with using it with any degree of compression at that. I'd > never expect it to support RTTY or FM with the K3 above 10 watts RF > output where > the current demand exceeds the 5 amp rating of the HPS1a. > > By comparison the MFJ-4125 with its 22A continuous, 25 A peak rating should > allow you to put a brick on the key at 100 watts with *most* K3s > feeding a > low SWR. K3's can be well with in factory spec's and show a variation > in current demand of a few amps at 100W RF out from rig to rig and > band to band > and, of course, the SWR has a big effect on the current needed. > > As I noted, with my K3 if I were to run a 100% duty cycle mode like > RTTY or > FM and planned to transmit more than 5 minutes at a time, I might > dial back > the RF output power 1 or 2 dB to keep the Astron 20A within its CCS rating. > > Ron AC7AC > > *Gamma Research further hedges their rating by adding a footnote to > their spex that "Output power should be limited to 25 or 30 watts > during tune-up > or other prolonged key-down operation." At 13.8 VDC that means the > supply should not be expected to provide more than 2A continuous! > > -----Original Message----- > > I run my K3 from an Astron 20A with no problems at all. The 20A > > is rated at 20A Intermittent Commercial and Amateur Service >(ICAS) > > and 16A continuous commercial service (CCS). > > Ah, but there is a significant difference in the rating between a > linear supply (your Astron RS-20) and a switching supply like the > MFJ-4125 or similar. The Astron is rated for average current and > duty cycle ... it can almost certainly provide more than 20A on short > peaks ... the 20A rating is based on heating of the transformer and > regulator transistors. > > A switching supply is generally rated for CCS with peak current > rating based on the energy storage in the capacitors (how much > current can be drawn before the output drops too low) and the average > current based on the capacity of the switching circuit to keep the > capacitor charged (current rating of the inductor, transformer, and > switching devices). > > A prime example of the peak/average issue is the Gamma supply. > It does not even tolerate full power CW well at slow speeds and falls > apart completely at 100 W (even 50 W) RTTY because of the > "continuous" current limitations. > > The K3 is quite happy with a 25A peak / 20-22A continuous switching > supply. Since a linear supply generally has sufficient energy > storage in the filter cap because of the need to work with a much > lower ripple voltage than a switcher, a "20A" linear supply can > usually supply the same brief 25A peaks (dynamic load) within the > heating limits of 20A (average) ICAS service depending on the design > of the regulator (current limiting). > > 73, > > ... Joe, W4TV > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net Please help support this > email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
