K1, KX1, K2 antenna tuner high-impedance feed capabilites
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K1, KX1, K2 antenna tuner high-impedance feed capabilites
 
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I'm interested in using portable end-fed halfwave antennas when I'm
out camping. I have a Norcal BLT tuner that is a absorptive Z-match type, suitable for this type of high-impedance tuning and loading. I'm finishing my build of a K2 right now, just about to add an internal tuner to it, and I also plan to build a KX1 in the near future (and who knows, maybe a K1 as well?). I'm wondering whether I should add the tuner in, or just carry my BLT around with me? Since many of you are QRP buffs, and have possibly had occasion to use this type of antenna (and maybe even the BLT) in portable locations, could you tell me if the internal tuners in these rigs are capable of feeding this type of antenna successfully? I don't just mean to ask whether an L-match or T-match type of tuner will handle a high impedance load, but also whether the best power transfer is happening, such as what the BLT will do? Thanks in advance, Dave K7DAA http://www.k7daa.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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This post was updated on .
In reply to this post by Dave Andrus-3
My K1 with atu was just recently completed. Like you, I have plans for portable ops.
So far, I have only ventured out into the back yard with various wires flung over the trees, hung from the second floor balcony, etc. The antenna showing the best promise is the classic end-fed half wave Zepp. I've only made one so far - cut for 20 meters. It consists of a half wave radiator fed by a 1/4 electrical wave length of 300 ohm TV twin lead. One of the twinlead wires is connected to the half-wave radiator, and the other is unterminated. At the rig, both of the twinlead conductors are connected to the RF output via a BNC to binding post adapter. The 1/4 wave of twinlead serves to significantly reduce the feedpoint impedance, allowing the KAT1 to do its job without a balun, or an external tuner. Does a bang-up job on 20! I have also loaded this antenna up sucessfully on 40 and 30 meters. On 30 and 40 I tried it in various configurations - ground side of the twin lead disconnected, ground side of the twin lead disconnected and tied directly to earth ground, an additional semi-random length counterpoise added to the rig ground, etc. The K1 and KAT1 have so far managed to load up and produce good QSOs in every configuration. That chunk of twinlead is doing some genuine mojo. I have yet to make any defendable measurements of SWR, Impedance, etc. other than those provided by the KAT1. Frankly, the accuracy of the KAT1 SWR and power output indicator does not impress me as being of much value beyond a go or no-go status. Carl WA7CS |
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In reply to this post by Dave Andrus-3
Dave
The KAT2 ATU is an absolutely great accessory for the K2. It will load darned near anything. You won't regret having it. 73, Bob N6WG ----- Original Message ----- From: "Dave Andrus" <[hidden email]> To: <[hidden email]> Sent: Wednesday, February 20, 2008 10:36 PM Subject: [Elecraft] K1, KX1, K2 antenna tuner high-impedance feed capabilites > I'm interested in using portable end-fed halfwave antennas when I'm > out camping. I have a Norcal BLT tuner that is a absorptive Z-match > type, suitable for this type of high-impedance tuning and loading. > > I'm finishing my build of a K2 right now, just about to add an > internal tuner to it, and I also plan to build a KX1 in the near > future (and who knows, maybe a K1 as well?). I'm wondering whether I > should add the tuner in, or just carry my BLT around with me? > > Since many of you are QRP buffs, and have possibly had occasion to use > this type of antenna (and maybe even the BLT) in portable locations, > could you tell me if the internal tuners in these rigs are capable of > feeding this type of antenna successfully? I don't just mean to ask > whether an L-match or T-match type of tuner will handle a high > impedance load, but also whether the best power transfer is happening, > such as what the BLT will do? > > Thanks in advance, > > Dave K7DAA > > http://www.k7daa.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 AC7AC
I second this motion!~
When I lived in the city for years, I could never put up a decent 80 meter antenna. I don't work the "high bands" much and don't like BIG beams. Too easily damaged by high winds, lightning, etc. Also a big maintenance problem, as I don't REALLY like climbing towers! nowadays I'm too damned old for that foolishness! I used a short "L" end fed antenna about 125' long on all bands. When you run 500-1000 watts out, this makes for a very strong RF field in the shack. I had a very extensive grounding system using several ground rods in mucky, very wet/high water table in the New Orleans area. Connections were all made using 3" wide copper flashing strip, which we commonly used in marine installations. Regular wire, 10 guage stranded, or "old coax. braid" or regular 3/4" tinned braid (now prohibitively expensive in 1" or wider sizes!) usually didn't "cut it". The flashing is easy to get under a window as well. SOLDERING ALL connections is recommended, especially if exposed to the weather. Don't rely on "clamped" connections whenever possible. Anyway the flashing system clears up the "stray RF" problem except in VERY stubborn cases. Nowadays, all this digitally controlled stuff has a tendency to go "bananas" with stray RF floating around. If you have any "control cables" to other devices associated with your transmitter, run a strip of flashing on the wall, between the devices, tied to the main ground buss and run your cables on top of the flat flashing. This seems to equalize the RF potential on both ends and enroute. Some of the last digital GMDSS stuff I installed years ago refused to work properly until this was done due to "stray RF" problems. The whole idea is to get all the chassis/cabling at least at the same rf potential, even if there is still some RF voltage being induced in the system. Anyuway, I had pretty good luck with the "voltage fed" antenna even though it was kind of in a bad location on a small city lot! 73, Sandy W5TVW ----- Original Message ----- From: "Ron D'Eau Claire" <[hidden email]> To: "'Dave Andrus'" <[hidden email]>; <[hidden email]> Sent: Thursday, February 21, 2008 1:25 AM Subject: RE: [Elecraft] K1, KX1,K2 antenna tuner high-impedance feed capabilites I've used an end fed dipole (i.e. half wave wire) a lot. I'm currently using an end fed 80 meter dipole in my fixed-station setup. Such an antenna presents quite a high impedance at the end, of course. That impedance is outside the range of the KX1, and probably the K2, although I haven't tried it on the KAT2 tuner for the K2. However, you don't have to be very far off of exactly 1/2 wavelength for the tuner to find a match. Normally, I use a link-coupled tuner when feeding such antennas. As you probably know, the closer you can get the antenna to exactly 1/2 wavelength at the operating frequency, the lower the ground return losses. Indeed, at 1/2 wavelength long it doesn't really need a ground except that without an RF ground the rig will tend to "float" up to the high impedance so you will have "rf on the rig". For that reason, it's a very good idea to plan on some sort of ground: 1/4 wave counterpoise, etc. The antenna is efficient without it, but the ground will help hold down the RF voltage on the rig. The KX1 tuner has the most limited range of all the Elecraft tuners to date. That's because of the very small space available for coil/capacitor combinations on the tiny board inside the KX1 case. Ron AC7AC -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Dave Andrus Sent: Wednesday, February 20, 2008 10:36 PM To: [hidden email] Subject: [Elecraft] K1, KX1, K2 antenna tuner high-impedance feed capabilites I'm interested in using portable end-fed halfwave antennas when I'm out camping. I have a Norcal BLT tuner that is a absorptive Z-match type, suitable for this type of high-impedance tuning and loading. I'm finishing my build of a K2 right now, just about to add an internal tuner to it, and I also plan to build a KX1 in the near future (and who knows, maybe a K1 as well?). I'm wondering whether I should add the tuner in, or just carry my BLT around with me? Since many of you are QRP buffs, and have possibly had occasion to use this type of antenna (and maybe even the BLT) in portable locations, could you tell me if the internal tuners in these rigs are capable of feeding this type of antenna successfully? I don't just mean to ask whether an L-match or T-match type of tuner will handle a high impedance load, but also whether the best power transfer is happening, such as what the BLT will do? Thanks in advance, Dave K7DAA http://www.k7daa.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 -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.20.9/1291 - Release Date: 2/21/2008 11:05 AM _______________________________________________ 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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