T1 tuner issue
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Hello All,
I just got my SW-20+ working, and I ran into an antenna question. Currently, I don't have a 20 meter antenna, so I thought I would try to use my 40 meter dipole with it and just use my Elecraft T1 to tune it to 20m. It it didn't work too well...I got an SWR around 2.5. Is this to be expected, or could there be an issue with the T1? The T1 sure sounds like it is working hard to get to the 2.5 (relays are busy). My antenna ignorance is probably showing, but since 20 is a direct multiple of 40, I thought the T1 wouldn't have a problem matching. So I guess my question is: Is something wrong with my T1, or do I just need to put up a 20meter antenna? 72, Kurt - ae6uj __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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Avoid to have odd multiple. A 40M antenna could be used on 15M, like the Alpha Delta DX-CC, but not on 20M without high SWR.
On Tuesday, October 25, 2005, at 03:57PM, Kurt Loken <[hidden email]> wrote: >Hello All, > >I just got my SW-20+ working, and I ran into an >antenna question. Currently, I don't have a 20 meter >antenna, so I thought I would try to use my 40 meter >dipole with it and just use my Elecraft T1 to tune it >to 20m. > >It it didn't work too well...I got an SWR around 2.5. >Is this to be expected, or could there be an issue >with the T1? The T1 sure sounds like it is working >hard to get to the 2.5 (relays are busy). My antenna >ignorance is probably showing, but since 20 is a >direct multiple of 40, I thought the T1 wouldn't have >a problem matching. > >So I guess my question is: Is something wrong with my >T1, or do I just need to put up a 20meter antenna? > >72, > >Kurt - ae6uj > > > > >__________________________________ >Yahoo! Mail - PC Magazine Editors' Choice 2005 >http://mail.yahoo.com >_______________________________________________ >Elecraft mailing list >Post to: [hidden email] >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 > > ========================================== /¯\/¯\/¯\/¯\/¯\/¯\ JEAN-FRANCOIS MENARD V A 2 V Y Z [hidden email] \_/\_/\_/\_/\_/\_/ Elecraft K2 #4130 Elecraft KX1 #999 http://homepage.mac.com/jfmenard ========================================== _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by Kurt Loken
That is just about the worst matching challenge you could try. At 20 meters
*each* side of the dipole is a half wave and presents a very high impedance to the feedline. The actual impedance presented to the tuner depends on feedline length and type of feedline so results are unpredictable. Inserting 20 meter traps and adjusting overall antenna length accordingly may be the way to go ... or just hang a 20 meter sloping Vee off the center, or something like that. A lot of us started our 'antenna' careers by just trying this or that ... but eventually broke down and studied the subject to reduce the wasted effort outside by expending a little effort inside where it is more comfortable. Grab a handbook .. and good luck. Don K7FJ > Hello All, > > I just got my SW-20+ working, and I ran into an > antenna question. Currently, I don't have a 20 meter > antenna, so I thought I would try to use my 40 meter > dipole with it and just use my Elecraft T1 to tune it > to 20m. > > It it didn't work too well...I got an SWR around 2.5. > Is this to be expected, or could there be an issue > with the T1? The T1 sure sounds like it is working > hard to get to the 2.5 (relays are busy). My antenna > ignorance is probably showing, but since 20 is a > direct multiple of 40, I thought the T1 wouldn't have > a problem matching. > > So I guess my question is: Is something wrong with my > T1, or do I just need to put up a 20meter antenna? > > 72, > > Kurt - ae6uj > > > > > __________________________________ > Yahoo! Mail - PC Magazine Editors' Choice 2005 > http://mail.yahoo.com > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > 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: [hidden email] 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 |
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In reply to this post by Kurt Loken
Kurt:
Feed the same antenna with either 300 twin lead or 450 Ohm ladder line. Connect a 4 to 1 balun at the shack end of the feed line, then connect the other end of the balun to the output terminal of the tuner. It will then tune and radiate RF quite well! 73, Don WA9TGT / Donnie Garrett / Muncie, IN ARCI #6447, ARS #1717, AmQRP, ECI-QRP #001 (Indiana) Drake 2B, R4A, R4B, K2 #3186, K1 #1806 LDG Z-11 Auto Tuner, 102' CF Zepp using glass doobies! www.wa9tgt.com _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by Kurt Loken
Kurt,
It all depends on the feedline length (in electrical wavelengths). If your feedline is anywhere near a multiple of a half wavelength at 20 meters, that behavior is not unusual. The T1 tuner (and most similar tuners) do not work well if the impedance presented at the shack end of the feedline is quite high. If you add or subtract a bit of feedline length (1/8 wavelength at a time is my suggestion), you will likely see better results. I will go into all the reasons why should you ask, but try changing the feedline length and see if it improves things. 73, Don W3FPR > -----Original Message----- > > Hello All, > > I just got my SW-20+ working, and I ran into an > antenna question. Currently, I don't have a 20 meter > antenna, so I thought I would try to use my 40 meter > dipole with it and just use my Elecraft T1 to tune it > to 20m. > > It it didn't work too well...I got an SWR around 2.5. > Is this to be expected, or could there be an issue > with the T1? The T1 sure sounds like it is working > hard to get to the 2.5 (relays are busy). My antenna > ignorance is probably showing, but since 20 is a > direct multiple of 40, I thought the T1 wouldn't have > a problem matching. > > So I guess my question is: Is something wrong with my > T1, or do I just need to put up a 20meter antenna? > > 72, > > Kurt - ae6uj > > _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
T1 tuner issue: try shorting the feedline, working against ground
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Administrator
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Kurt,
The impedance of your 40 m dipole on 20 m is probably sky-high; 2.5:1 may be the best you can hope for. This probably won't hurt the rig, and the power loss due to the high SWR is probably less than a dB assuming the rig doesn't roll back power (or clip the voltage at the collector of its PA). Another thing you can try is to short the coax center connector to its shield. This is an old trick for extending the matching range of an antenna. Connect this to the T1's hot lead, then connect the T1's ground to a ground counterpoise. The impedance will likely be very different, giving the ATU a chance to match it. It will be slightly noisier than a dipole, and the directivity will change, but you may not mind. 73, Wayne N6KR --- http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] 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: T1 tuner issue: try shorting the feedline, working against ground
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A variation on the idea proposed by Wayne is to add an inductor or capacitor
in series with the center wire in the feeder. That will change the impedance presented to the tuner. You may need to experiment a bit to find a value that the ATU can match - as indicated by a low SWR - but you won't have to fiddle with a separate ground system. You whatever you have handy - a 20 to 50 pf cap or a dozen turns of hook-up wire around a 35 mm plastic film container. You aren't looking for any exact value, just enough reactance to move the impedance into a range the T1 can match. Ron AC7AC -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of wayne burdick Sent: Tuesday, October 25, 2005 4:32 PM Cc: Elecraft Reflector; QRP-L; Kurt Loken Subject: [Elecraft] T1 tuner issue: try shorting the feedline,working against ground Kurt, The impedance of your 40 m dipole on 20 m is probably sky-high; 2.5:1 may be the best you can hope for. This probably won't hurt the rig, and the power loss due to the high SWR is probably less than a dB assuming the rig doesn't roll back power (or clip the voltage at the collector of its PA). Another thing you can try is to short the coax center connector to its shield. This is an old trick for extending the matching range of an antenna. Connect this to the T1's hot lead, then connect the T1's ground to a ground counterpoise. The impedance will likely be very different, giving the ATU a chance to match it. It will be slightly noisier than a dipole, and the directivity will change, but you may not mind. 73, Wayne N6KR --- http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] 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: [hidden email] 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 |
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In reply to this post by wayne burdick
Hello All,
Thanks to everyone who responded. I received a lot of interesting suggestions that should be fun to experiment on. My final solution will probably be to add some additional elements on my current dipole for 20m...but it might be fun to fool around with the feed lines a bit before then. Thanks for the education. I think it is time for me to crack and antenna book and read it though. Regards, Kurt - ae6uj __________________________________ Yahoo! FareChase: Search multiple travel sites in one click. http://farechase.yahoo.com _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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One other thing worth noting Kurt is that when you use a tuner at the tx
end of a coaxial (unbalanced) feedline, then the feedline itself becomes a radiating part of the antenna system. The ATU will hopefully reduce the SWR on the line between the transmitter and the ATU, but it will not change the SWR present on the feedline. If you use a balanced feeder such as twin or preferably open wire, then although the SWR on the feeder may be high, it is balanced and in a perfect world the feeder will not radiate. The likely outcome when using an ATU at the tx end of the feeder is: Coax Possible high SWR on feeder, feeder is unbalanced and will radiate and also receive unwanted signals (any rf generating device in the house). Possible TVI/BCI. Altered radiation pattern (usually for the worse) Open wire Possible high SWR on feeder, feeder is balanced and radiation (incoming or outgoing) will be minimised reducing unwanted interference both ways. Pattern remains predictable within usual constraints. Your RF gets to where it is needed most, up in the air :-) My advice is to leave the top section of your dipole as it is and to replace the feeder with open wire or at least twin. It should be an improvement on all bands. HTH Trev G3ZYY In message <[hidden email]>, Kurt Loken <[hidden email]> writes >Hello All, > >Thanks to everyone who responded. I received a lot of >interesting suggestions that should be fun to >experiment on. My final solution will probably be to >add some additional elements on my current dipole for >20m...but it might be fun to fool around with the feed >lines a bit before then. > >Thanks for the education. I think it is time for me >to crack and antenna book and read it though. > >Regards, > >Kurt - ae6uj > > > >__________________________________ >Yahoo! FareChase: Search multiple travel sites in one click. >http://farechase.yahoo.com >_______________________________________________ >Elecraft mailing list >Post to: [hidden email] >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 > -- Trevor Day UKSMG #217 www.uksmg.org _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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