SWR
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When do you know if you need an ATU (KAT3). I just installed my Big SteppIR Vert.
On 6m my swr is 1.9, 17m,20m,80m a swr of 1.6. Thanks Chris W7CTH ______________________________________________________________ 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 Chris W7CTH
Hi Chris:
I have a K3 and a BigIR. The problem with using a tuner with any SteppIR antenna is that you want want to change the SteppIR controller frequency to match your transmitter frequency which then changes the length of the antenna. As you know, this is how SteppIR maintains good SWR over the entire band. This happens automatically if you have the transceiver tracking option with your SteppIR. You do it manually if you don't have tracking So what next, do you then activate the ATU tune function on the K3 to readjust the internal tuner? It's just a little bit of additional complexity. This procedure would be especially troublesome on 80 meters where the antenna makes substantial length adjustments every 10KHz. With the 80 meter coil option on the BigIR, you could see higher SWRs on 15 through 6 meters in the normal 1/4 wave mode. SteppIR recommends using the 3/4 wave mode for those bands. This may help. Before my K3, I had a FT1000D. I saw power rollbacks on 17 and 30 meters where my BigIR SWR is 2.0:1 and 1.6:1 respectively. So I used the tuner on those bands. I don't see any power rollback with my K3 so I don't use the tuner on those bands anymore. 73, Mike K2MK
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> With the 80 meter coil option on the BigIR, you could see higher SWRs on
> 15 > through 6 meters in the normal 1/4 wave mode. SteppIR recommends using > the > 3/4 wave mode for those bands. This may help. .........with everything but wave angle........ :-) ______________________________________________________________ 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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On all other bands, increasing the power level goes in 0.1W steps up 12watts
and then in one watt steps above this. I'm sure this used to happen on 50MHz as well. However, now the power increases in 0.1W steps to 8 watts and then jumps to 13W before increasing in 1W steps. So I can't set an output level between 8 and 13 watts, which is just what I need for the amplifier!!!! Any ideas as to what I can have done to achieve this "feature" ? TIA Roger - G4BVY ______________________________________________________________ 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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That characteristic has been discussed here Roger. The driver generates spurious signals between 8 and 13 watts, so the software makes the level skip these powers until the 100 watt final kicks in at 13 W.
Willis 'Cookie' Cooke K5EWJ ________________________________ From: Roger Dixon <[hidden email]> To: [hidden email] Sent: Fri, June 11, 2010 9:59:44 AM Subject: [Elecraft] Power control on 50MHz On all other bands, increasing the power level goes in 0.1W steps up 12watts and then in one watt steps above this. I'm sure this used to happen on 50MHz as well. However, now the power increases in 0.1W steps to 8 watts and then jumps to 13W before increasing in 1W steps. So I can't set an output level between 8 and 13 watts, which is just what I need for the amplifier!!!! Any ideas as to what I can have done to achieve this "feature" ? TIA Roger - G4BVY ______________________________________________________________ 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 G4BVY
Roger,
That is "the way it is" - at least for the time being. The Low Power amplifier is limited to 8 watts on 6 meters, as I recall because of IMD performance. Wayne has said he will do something to allow the KPA3 to begin above 8 watts on 6 meters, but I have no idea about the schedule for that change. 73, Don W3FPR Roger Dixon wrote: > On all other bands, increasing the power level goes in 0.1W steps up 12watts > and then in one watt steps above this. > > I'm sure this used to happen on 50MHz as well. However, now the power > increases in 0.1W steps to 8 watts and then jumps to 13W before increasing > in 1W steps. So I can't set an output level between 8 and 13 watts, which > is just what I need for the amplifier!!!! > > Any ideas as to what I can have done to achieve this "feature" ? > > TIA > Roger - G4BVY > > 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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The IMD of my LPA is quite bad on 10m as well, at least if my KK7UQ PSK IMD meter is to be believed. It's worse at 5W than it is at 13W which leads me to believe it is the LPA that is at fault. I have no way of measuring it accurately, unfortunately. Have there been any mods to the LPA since my early S/N #222 that might improve this? I would really, really like the option to disable this switching out of the 100W PA altogether. It seems to be an utterly pointless extra complication. I never use my K3 portable so the extra current draw is nothing to worry about.
Julian, G4ILO. K2 #392 K3 #222 KX3 #110
* G4ILO's Shack - http://www.g4ilo.com * KComm - http://www.g4ilo.com/kcomm.html * KTune - http://www.g4ilo.com/ktune.html |
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I also would like to see this option! As solid state amps become more prevalent,
more folks will be wanting to be able to adjust the power in that range to make sure they do not overdrive their amplifiers. VY 73, Lance On 6/11/2010 4:26 PM, Julian, G4ILO wrote: > I would really, really like the option to disable this switching out of the > 100W PA altogether. It seems to be an utterly pointless extra complication. > I never use my K3 portable so the extra current draw is nothing to worry > about. > > ----- > Julian, G4ILO. K2 #392 K3 #222. > * G4ILO's Shack - http://www.g4ilo.com > * KComm - http://www.g4ilo.com/kcomm.html > * KTune - http://www.g4ilo.com/ktune.html > -- Lance Collister, W7GJ (ex: WN3GPL, WA3GPL, WA1JXN, WA1JXN/C6A, ZF2OC/ZF8, E51SIX) P.O. Box 73 Frenchtown, MT 59834 USA QTH: DN27UB TEL: (406) 626-5728 URL: http://www.bigskyspaces.com/w7gj 2m DXCC #11/6m DXCC #815 Interested in 6m EME? Ask me about subscribing to the MAGIC BAND EME email reflector! ______________________________________________________________ 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 Julian, G4ILO
> I would really, really like the option to disable this switching out of the > 100W PA altogether. It seems to be an utterly pointless extra complication. Part of the point is that the DAC used to create the signal at 15 kHz, which is upconverted, is using fewer bits at lower output levels. While the gin scaling is very coarse, switching the HPA out at power levels which can be safely handled by the LPA improves the IMD of the signal being amplified by the Tx chain. iI is partly for this reason that there is a switchable attenuator in the Tx chain as well. 73, Lyle KK7P ______________________________________________________________ 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 Julian, G4ILO
Hi Julian,
We switch the KPA3 out at lower power levels to optimize the drive, ensuring a high carrier-to-noise ratio at lower-level stages. In any case, IMD should be quite respectable on 6 m even with the LPA by itself. If it isn't, we'd be happy to swap LPAs with you so we can see what's up. Just contact support. 73, Wayne N6KR On Jun 11, 2010, at 9:26 AM, Julian, G4ILO wrote: > > > Don Wilhelm-4 wrote: >> >> That is "the way it is" - at least for the time being. The Low Power >> amplifier is limited to 8 watts on 6 meters, as I recall because >> of IMD >> performance. >> ______________________________________________________________ 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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Wayne wrote:
> >We switch the KPA3 out at lower power levels to optimize the drive, >ensuring a high carrier-to-noise ratio at lower-level stages. > >In any case, IMD should be quite respectable on 6 m even with the LPA >by itself. Understood; but the simple term "IMD" covers a wide range of issues. It isn't all about 3rd order IMD; the overall width of the signal is determined by how rapidly the higher orders die away. Comparing the LPA near its maximum output and the HPA near its minimum (say 11W versus 15W) the LPA gives more 3rd-order IMD, but the higher-order IMD products taper away more quickly so the signal overall is narrower. There is also the issue of cooling; for example, with intensive RTTY or WSJT modes, 10W output would be pushing the passively cooled LPA close to its thermal limits. In such a case, it would be better to switch in the HPA so that both amplifiers are operating well within their thermal limits. The best solution to meet the wide range of possible user needs would be a configurable breakpoint between the LPA and the HPA. If the breakpoint could be adjusted between say 6W and 12W (configurable and stored per band), that would cover a wide range of practical user needs without affecting the SNR of the transmitted signal by more than 3dB. Then there is W7GJ's point about the gap in available power output on 50MHz: >As solid state amps become more prevalent, more folks will be wanting >to be able to adjust the power in that range to make sure they do not >overdrive their amplifiers. As well as the wide range of possible power amplifiers, there is also a wide range of legal power limits around the world. With my particular 50MHz PA, the gap in drive level available from the K3 makes it impossible to set the PA output to our 400W legal limit - the level jumps from 290W to 470W. It is truly bizarre that output levels between 8W and 13W are not available on 50MHz. This issue is as old as the K3 itself, and it really does need to be fixed! However, a complete solution would also include the configurable breakpoint between the LPA and the HPA as identified above. -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek ______________________________________________________________ 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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