Re: [Elecraft] time for KPA1500 - but why no tubes?
Quite a few years ago I was running the comm's on one of the British Antarctic Survey bases (Adelaide Is). My main TX used a Racal amp with 3 x 4-400 in parallel (if I remember correctly). It used a Pi-L network. That network quite happily matched 20:1 SWR if necessary. The tuning was rather critical but in other respects all was normal as far as the tubes were concerned. The coax (RG-8 type) from the TX to the balun would run very warm in those circumstances and sag from the ceiling. Not desirable I admit but necessary to broadcast safety critical WX forecasts to remote sledging teams on a frequency in the 2MHz range that the antenna was never designed for and seldom used. Regards, Mike VP8NO On 21/02/2012 04:14, Ron D'Eau Claire wrote: Well, Don, it's been a number of years since I homebrewed an amp, but from what I recall a pi-net wouldn't meet the later FCC regs and a Pi-L network only sufficed over a fairly narrow matching range. By the 1970's I was counting on my outboard antenna tuner that matched my open wire feeders to provide the added spur suppression to meet FCC regs even though I was still using a tunable Pi-L network on the output of my homebrew rig. 73, Ron AC7AC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] time for KPA1500 - but why no tubes?
For CW, this might be easy. A single MRFE6VP61K25H is used now commercially for 2m: 2 W in 1 KW out. This is key down not pulse mode; see http://www.w6pql.com/parts_i_can_provide.htm Since W6PQL offers it for sale, he must have done lots of testing and determined good reliability. In CW, KPA500 with such a device perhaps could provide 800-900W due to increased efficiency (70 vs 45%). Two such modified KPA500 would easily make 1.5 KW on CW. Also can be driven by K3/10. SSB would be a different question. But Elecraft is innovative. Why not class B be with forward correction Ignacy, NO9E -- View this message in context: http://elecraft.365791.n2.nabble.com/time-for-KPA1500-but-why-no-tubes-tp7303191p7305113.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] time for KPA1500 - but why no tubes?
Quite right, Mike. A Pi-L will match a wide range of impedances. What I was saying was that, IIRC, the Pi-L provided the spurious signal rejection required by the FCC over only a narrow range of impedances. Ron AC7AC -Original Message- Quite a few years ago I was running the comm's on one of the British Antarctic Survey bases (Adelaide Is). My main TX used a Racal amp with 3 x 4-400 in parallel (if I remember correctly). It used a Pi-L network. That network quite happily matched 20:1 SWR if necessary. The tuning was rather critical but in other respects all was normal as far as the tubes were concerned. The coax (RG-8 type) from the TX to the balun would run very warm in those circumstances and sag from the ceiling. Not desirable I admit but necessary to broadcast safety critical WX forecasts to remote sledging teams on a frequency in the 2MHz range that the antenna was never designed for and seldom used. Regards, Mike VP8NO On 21/02/2012 04:14, Ron D'Eau Claire wrote: Well, Don, it's been a number of years since I homebrewed an amp, but from what I recall a pi-net wouldn't meet the later FCC regs and a Pi-L network only sufficed over a fairly narrow matching range. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
[Elecraft] time for KPA1500 - but why no tubes?
RE: memo below. Excuse me, but there were (are?) lots of no tune rigs that use tubes. I used one (an Alpha 78) over 25 years ago. Of course, since then, I've been a QRPer, so moot point for me. de Doug KR2Q Yes, it *has* to be solid state. It would be complete insanity for Elecraft Agreed - a new tube design would be moving in the opposite direction on the technological timeline. I operated the ARRL DX contest with K3/AL80BQ (QSK). Bandhopping was slowed by the need to tune the amp each time __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] time for KPA1500 - but why no tubes?
Note that No Tune means, simply, Fixed Tuned, set for a 50 ohm non-reactive load on each band. If we don't have an antenna reasonably flat across the whole band we add an Antenna Tuner to the output which is simply moving the tuning we used to do on the xmtr output to an outboard box! For example, when you add a KAT3 to the K3 it's all in one box, so we operate just like we did decades ago, tuning our rigs for the band/frequency in use. Only now the tuning is done automatically under digital control, so we don't need to look at meters except to confirm the automated circuits did their job correctly. It's the speed of the logic controlling the tuner that makes modern rigs so fast on the QSY, not any lack of need to tune them for a given load. There is a hidden advantage to all of this. The output filters are far more exotic than the simple Pi and Pi-L networks rigs used in the days when one dipped the finals and adjusted the loading. Those networks provide for superior rejection of spurious products. 73, Ron AC7AC -Original Message- RE: memo below. Excuse me, but there were (are?) lots of no tune rigs that use tubes. I used one (an Alpha 78) over 25 years ago. Of course, since then, I've been a QRPer, so moot point for me. de Doug KR2Q Yes, it *has* to be solid state. It would be complete insanity for Elecraft Agreed - a new tube design would be moving in the opposite direction on the technological timeline. I operated the ARRL DX contest with K3/AL80BQ (QSK). Bandhopping was slowed by the need to tune the amp each time __ __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] time for KPA1500 - but why no tubes?
On Mon, Feb 20, 2012 at 8:18 PM, Ron D'Eau Claire r...@cobi.biz wrote: Note that No Tune means, simply, Fixed Tuned, set for a 50 ohm non-reactive load on each band. If we don't have an antenna reasonably flat across the whole band we add an Antenna Tuner to the output which is simply moving the tuning we used to do on the xmtr output to an outboard box! Not exactly. My No Tune ACOM 2000A will automatically handle up to 3:1 SWR on all bands except 160 where the limit is 2:1. Sometimes output power is reduced, and sometimes an external tuner is helpful. but for the ACOM at least, No Tune does not mean Fixed Tune. 73, Hank, W6SX Mammoth Lakes, California Elevation 8083 feet in John Muir's Range of Light __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] time for KPA1500 - but why no tubes?
WOW, I do not understand the distinction - there must be some harmonic suppression circuits that reduce the 2nd harmonic emissions from an amplifier (40 dBc if I recall), so whether that is done using a fixed tune output circuit, or whether that is achieved by the use of an external antenna tuner is a moot point. The bottom line is that somewhere in the path between the PA tubes (transistors, MOSFETs), there must be a path from the grid(, base, plate) to ground that will afford a transition to 50 ohms (and X - j0) solution that will yield greater than 5 watts on all bands (or in the case of the K3, 6 meters). So use whatever tuner matching section between the amplifier and the antenna is a good and prudent challenge. The inductance at the highest frequency will be greater than 3 times the 'oscilloscope oscilloscope and probe - 73, Don W3FPR On 2/20/2012 11:34 PM, Hank Garretson wrote: On Mon, Feb 20, 2012 at 8:18 PM, Ron D'Eau Clairer...@cobi.biz wrote: Note that No Tune means, simply, Fixed Tuned, set for a 50 ohm non-reactive load on each band. If we don't have an antenna reasonably flat across the whole band we add an Antenna Tuner to the output which is simply moving the tuning we used to do on the xmtr output to an outboard box! Not exactly. My No Tune ACOM 2000A will automatically handle up to 3:1 SWR on all bands except 160 where the limit is 2:1. Sometimes output power is reduced, and sometimes an external tuner is helpful. but for the ACOM at least, No Tune does not mean Fixed Tune. 73, Hank, W6SX Mammoth Lakes, California Elevation 8083 feet in John Muir's Range of Light __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] time for KPA1500 - but why no tubes?
i don't know how you get the idea that it isn't fixed tune. Just because it can handle a 3:1 SWR without self-destructing does not mean it isn't fixed tune. What tuning parameters do you think are changing? Dave AB7E On 2/20/2012 9:34 PM, Hank Garretson wrote: On Mon, Feb 20, 2012 at 8:18 PM, Ron D'Eau Clairer...@cobi.biz wrote: Note that No Tune means, simply, Fixed Tuned, set for a 50 ohm non-reactive load on each band. If we don't have an antenna reasonably flat across the whole band we add an Antenna Tuner to the output which is simply moving the tuning we used to do on the xmtr output to an outboard box! Not exactly. My No Tune ACOM 2000A will automatically handle up to 3:1 SWR on all bands except 160 where the limit is 2:1. Sometimes output power is reduced, and sometimes an external tuner is helpful. but for the ACOM at least, No Tune does not mean Fixed Tune. 73, Hank, W6SX Mammoth Lakes, California Elevation 8083 feet in John Muir's Range of Light __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] time for KPA1500 - but why no tubes?
Quite true Hank. Some amps have a fairly large tolerance of mismatch. But it's still fixed tune = you don't need to adjust anything. My point was that when the load exceeds what the fixed tuned output will handle, we now use an ATU to handle the tuning. P.S. I envy your elevation but, from my QTH on the edge of the continent just above the tsunami line, I enjoy lots of 599 reports from Oceania. 73, Ron AC7AC -Original Message- On Mon, Feb 20, 2012 at 8:18 PM, Ron D'Eau Claire r...@cobi.biz wrote: Note that No Tune means, simply, Fixed Tuned, set for a 50 ohm non-reactive load on each band. If we don't have an antenna reasonably flat across the whole band we add an Antenna Tuner to the output which is simply moving the tuning we used to do on the xmtr output to an outboard box! Not exactly. My No Tune ACOM 2000A will automatically handle up to 3:1 SWR on all bands except 160 where the limit is 2:1. Sometimes output power is reduced, and sometimes an external tuner is helpful. but for the ACOM at least, No Tune does not mean Fixed Tune. 73, Hank, W6SX Mammoth Lakes, California Elevation 8083 feet in John Muir's Range of Light __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] time for KPA1500 - but why no tubes?
Well, Don, it's been a number of years since I homebrewed an amp, but from what I recall a pi-net wouldn't meet the later FCC regs and a Pi-L network only sufficed over a fairly narrow matching range. By the 1970's I was counting on my outboard antenna tuner that matched my open wire feeders to provide the added spur suppression to meet FCC regs even though I was still using a tunable Pi-L network on the output of my homebrew rig. 73, Ron AC7AC -Original Message- WOW, I do not understand the distinction - there must be some harmonic suppression circuits that reduce the 2nd harmonic emissions from an amplifier (40 dBc if I recall), so whether that is done using a fixed tune output circuit, or whether that is achieved by the use of an external antenna tuner is a moot point. The bottom line is that somewhere in the path between the PA tubes (transistors, MOSFETs), there must be a path from the grid(, base, plate) to ground that will afford a transition to 50 ohms (and X - j0) solution that will yield greater than 5 watts on all bands (or in the case of the K3, 6 meters). So use whatever tuner matching section between the amplifier and the antenna is a good and prudent challenge. The inductance at the highest frequency will be greater than 3 times the 'oscilloscope oscilloscope and probe - 73, Don W3FPR __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
