K3 and Alpha 87A SWR
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Using the suggested 72" length of coax between my K3 and my 87A the SWR is
one bar on 20 and 15 meters, 2 bars on 40 meters, 3 bars on 160 and 10 but on 80 meters it is 6+ bars (about 2.5 to 1) which seems quite a bit high. I think I have gotten the display of "Hi SWR" at one point. I have tried other coax lengths and when 80 was ok then 10 meters was high. Anyone see the same thing and/or have any solutions/suggestions? Thanks, Mike W9RE ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3 and Alpha 87A SWR
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Hello Mike
I also notice that on my Drake L7. When amp is ON the SWR on the K3 is high, instead on my wattmeter/SWR the SWR is as always I don´t know what´s wrong, I use to turn on the K3 ATU, but the idea is to don´t have this high SWR on the K3 73, Jorge CX6VM/CW5W -----Mensaje original----- De: [hidden email] [mailto:[hidden email]] En nombre de Mike Wetzel Enviado el: miércoles, 22 de agosto de 2012 13:28 Para: [hidden email] Asunto: [Elecraft] K3 and Alpha 87A SWR Using the suggested 72" length of coax between my K3 and my 87A the SWR is one bar on 20 and 15 meters, 2 bars on 40 meters, 3 bars on 160 and 10 but on 80 meters it is 6+ bars (about 2.5 to 1) which seems quite a bit high. I think I have gotten the display of "Hi SWR" at one point. I have tried other coax lengths and when 80 was ok then 10 meters was high. Anyone see the same thing and/or have any solutions/suggestions? Thanks, Mike W9RE ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by W9RE
On 8/22/2012 9:28 AM, Mike Wetzel wrote:
> Anyone see the same thing and/or have any solutions/suggestions? I mostly drive Ten Tec Titans or a KPA500, and rarely see this. You might try engaging the auto tuner in the K3 if you have one. I've done that occasionally when driving an amp and it worked to reduce the mismatch. You might also look for something funky in the input circuitry of the amp. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Jorge Diez - CX6VM-2
84" works well for many including myself.
-----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Jorge Diez - CX6VM Sent: Thursday, 23 August 2012 2:34 AM To: [hidden email] Subject: Re: [Elecraft] K3 and Alpha 87A SWR Hello Mike I also notice that on my Drake L7. When amp is ON the SWR on the K3 is high, instead on my wattmeter/SWR the SWR is as always I don´t know what´s wrong, I use to turn on the K3 ATU, but the idea is to don´t have this high SWR on the K3 73, Jorge CX6VM/CW5W -----Mensaje original----- De: [hidden email] [mailto:[hidden email]] En nombre de Mike Wetzel Enviado el: miércoles, 22 de agosto de 2012 13:28 Para: [hidden email] Asunto: [Elecraft] K3 and Alpha 87A SWR Using the suggested 72" length of coax between my K3 and my 87A the SWR is one bar on 20 and 15 meters, 2 bars on 40 meters, 3 bars on 160 and 10 but on 80 meters it is 6+ bars (about 2.5 to 1) which seems quite a bit high. I think I have gotten the display of "Hi SWR" at one point. I have tried other coax lengths and when 80 was ok then 10 meters was high. Anyone see the same thing and/or have any solutions/suggestions? Thanks, Mike W9RE ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] 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:[hidden email] 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3 and Alpha 87A SWR
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In reply to this post by Jim Brown-10
On Aug 22, 2012, at 1:01 PM, Jim Brown <[hidden email]> wrote:
> You > might try engaging the auto tuner in the K3 if you have one. Be aware that both the Alpha 87A and 99 manuals tell you "NEVER use an automatic antenna tuner into or through the [87A or 99]. This will cause damage to the Input Wattmeter & Input Relay." It's largely because of this prohibition that I don't even have a KAT3 in my K3. Bud, W2RU ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Hi,
Something is not right here. VSWR is not supposed to vary up and down a coax a few feet in length, particularly not on low frequencies as 80 and 160m. 8' or 96" is less than 1/10 of a wavelength on 80m. Is this happening with amp operating into a dummy load? If it is, something is wrong with the instrumentation, if not, the real problem is RF in the shack. AB2TC - Knut
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Read down thru this thread on eHam
http://www.eham.net/ehamforum/smf/index.php?topic=79974.15 Chuck, KE9UW Sent from my iPad On Aug 22, 2012, at 3:54 PM, "ab2tc" <[hidden email]> wrote: > Hi, > > Something is not right here. VSWR is not supposed to vary up and down a coax > a few feet in length, particularly not on low frequencies as 80 and 160m. 8' > or 96" is less than 1/10 of a wavelength on 80m. Is this happening with amp > operating into a dummy load? If it is, something is wrong with the > instrumentation, if not, the real problem is RF in the shack. > > AB2TC - Knut > > > W2RU - Bud Hippisley wrote >> >> On Aug 22, 2012, at 1:01 PM, Jim Brown <jim@> wrote: >> >>> You >>> might try engaging the auto tuner in the K3 if you have one. >> >> Be aware that both the Alpha 87A and 99 manuals tell you "NEVER use an >> automatic antenna tuner into or through the [87A or 99]. This will cause >> damage to the Input Wattmeter & Input Relay." >> >> It's largely because of this prohibition that I don't even have a KAT3 in >> my K3. >> >> Bud, W2RU >> ______________________________________________________________ >> > > > > > -- > View this message in context: http://elecraft.365791.n2.nabble.com/K3-and-Alpha-87A-SWR-tp7561478p7561493.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:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Chuck, KE9UW
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In reply to this post by W9RE
Alpha shipped a 6ft length of coax to use between the exciter and the 87A. With new tubes, the input SWR on all bands should be 1.5 or less. As the 3CX800A7s hours add up, the tubes gradually require more RF drive for the same output. Alpha recommends keeping the grid current between 20 and 50 ma. Brand new tubes will require between in the low 40s to high 30s (watts) at 35 ma of grid current for full output depending upon band.
Go ahead and use the K3 ATU inline. It's not a problem. But do watch for the gradually increasing drive and grid current demands of the 87A over time. If that means keeping the drive down as the tubes age, 1200 vs 1500 watts output will never be noticed. With very heavy use, a pair of 3CX800A7s can last 10-12 years. YMWV. 73 - Steve WB6RSE On Aug 22, 2012, at 9:28 AM, Mike Wetzel wrote: 80 meters it is 6+ bars (about 2.5 to 1) which seems quite a bit high. I have tried other coax lengths and when 80 was ok then 10 meters was high. Anyone see the same thing and/or have any solutions/suggestions? ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by W2RU - Bud Hippisley
I use a 99 with the K3 and any length coax works just fine, it there is
SWR on the line there is a problem someplace, have never had to cut a coax to any particular length. If theres SWR its either a ground differential problem between the amp and radio chassis or the tuned input is not correct, or the amps input resistor has been cooked. Merv K9FD/KH6 > On Aug 22, 2012, at 1:01 PM, Jim Brown<[hidden email]> wrote: > > >> You >> might try engaging the auto tuner in the K3 if you have one. >> > Be aware that both the Alpha 87A and 99 manuals tell you "NEVER use an automatic antenna tuner into or through the [87A or 99]. This will cause damage to the Input Wattmeter& Input Relay." > > It's largely because of this prohibition that I don't even have a KAT3 in my K3. > > Bud, W2RU > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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I've been following this thread with interest.
I have a K3 and an Alpha 8100. The 8100 uses a pair of Pentodes fed through a swamped grid. I believe the Alpha 99 does as well. I think this is why Merv and I have never seen issues involving the coax length. For the record, the Alpha manual for the 8100 does state to NOT use a tuner in the exciter. On 8/22/2012 7:10 PM, Merv Schweigert wrote: > I use a 99 with the K3 and any length coax works just fine, it there is > SWR on the > line there is a problem someplace, have never had to cut a coax to any > particular > length. > If theres SWR its either a ground differential problem between the amp > and radio chassis or the > tuned input is not correct, or the amps input resistor has been cooked. > Merv K9FD/KH6 >> On Aug 22, 2012, at 1:01 PM, Jim Brown<[hidden email]> wrote: >> >> >>> You >>> might try engaging the auto tuner in the K3 if you have one. >>> >> Be aware that both the Alpha 87A and 99 manuals tell you "NEVER use an automatic antenna tuner into or through the [87A or 99]. This will cause damage to the Input Wattmeter& Input Relay." >> >> It's largely because of this prohibition that I don't even have a KAT3 in my K3. >> >> Bud, W2RU >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[hidden email] >> >> 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:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > -- 73, Gary K9GS Greater Milwaukee DX Association: http://www.gmdxa.org Society of Midwest Contesters: http://www.w9smc.com CW Ops #1032 http://www.cwops.org ************************************************ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Merv Schweigert
I've been running a K3 into an Alpha 87A for years, and SWR is just fine.
The coax between the K3 and amp happens to be 15-20 feet, but that length is just what was necessary for the run between the shack and an equipment closet in the basement where the amp is located. I have found in the past, however, that it's best if the coax is at least 6' long, as recommended by Alpha. High input SWR on some bands most likely means something is wrong in the input circuit, such as bad contacts on the wafer switch, burned out resistors or inductors, etc. You can also get high SWR if the contacts on the large band switch aren't properly aligned. The alignment is set by the factory and stored in program memory. There's a simple procedure for re-aligning the band switch and storing the new stepper motor position in memory. I suggest you contact RF Concepts and ask them for help. 73, Dick WC1M > -----Original Message----- > From: Merv Schweigert [mailto:[hidden email]] > Sent: Wednesday, August 22, 2012 8:10 PM > To: [hidden email] > Subject: Re: [Elecraft] K3 and Alpha 87A SWR > > I use a 99 with the K3 and any length coax works just fine, it there is > SWR on the > line there is a problem someplace, have never had to cut a coax to any > particular > length. > If theres SWR its either a ground differential problem between the amp > and radio chassis or the tuned input is not correct, or the amps input > resistor has been cooked. > Merv K9FD/KH6 > > On Aug 22, 2012, at 1:01 PM, Jim Brown<[hidden email]> > wrote: > > > > > >> You > >> might try engaging the auto tuner in the K3 if you have one. > >> > > Be aware that both the Alpha 87A and 99 manuals tell you "NEVER use an > automatic antenna tuner into or through the [87A or 99]. This will > cause damage to the Input Wattmeter& Input Relay." > > > > It's largely because of this prohibition that I don't even have a KAT3 > in my K3. > > > > Bud, W2RU > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:[hidden email] > > > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Gary K9GS
Whoops...make Pentode=Tetrode
On 8/22/2012 8:26 PM, Gary K9GS wrote: > I've been following this thread with interest. > > I have a K3 and an Alpha 8100. The 8100 uses a pair of Pentodes fed > through a swamped grid. I believe the Alpha 99 does as well. I think > this is why Merv and I have never seen issues involving the coax length. > > For the record, the Alpha manual for the 8100 does state to NOT use a > tuner in the exciter. > > > On 8/22/2012 7:10 PM, Merv Schweigert wrote: >> I use a 99 with the K3 and any length coax works just fine, it there is >> SWR on the >> line there is a problem someplace, have never had to cut a coax to any >> particular >> length. >> If theres SWR its either a ground differential problem between the amp >> and radio chassis or the >> tuned input is not correct, or the amps input resistor has been cooked. >> Merv K9FD/KH6 >>> On Aug 22, 2012, at 1:01 PM, Jim Brown<[hidden email]> wrote: >>> >>> >>>> You >>>> might try engaging the auto tuner in the K3 if you have one. >>>> >>> Be aware that both the Alpha 87A and 99 manuals tell you "NEVER use an automatic antenna tuner into or through the [87A or 99]. This will cause damage to the Input Wattmeter& Input Relay." >>> >>> It's largely because of this prohibition that I don't even have a KAT3 in my K3. >>> >>> Bud, W2RU >>> ______________________________________________________________ >>> Elecraft mailing list >>> Home: http://mailman.qth.net/mailman/listinfo/elecraft >>> Help: http://mailman.qth.net/mmfaq.htm >>> Post: mailto:[hidden email] >>> >>> 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:[hidden email] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> -- 73, Gary K9GS Greater Milwaukee DX Association: http://www.gmdxa.org Society of Midwest Contesters: http://www.w9smc.com CW Ops #1032 http://www.cwops.org ************************************************ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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