RE: [Elecraft] Wire Antennas --apology
Rick: No need to apologize. Your comments are right on target for this reflector. If some feel otherwise, there is always the delete key, or they can unsubscribe. Keep them coming. Paul N8NOV Houston -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.441 / Virus Database: 268.18.3/697 - Release Date: 2/22/2007 11:55 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] Wire Antennas --apology
No need for anyone to apologize for discussing antennas on this reflector because they are the 'secret' to successful communications especially when doing QRP imho - 72 Bruce. 72/73 - Bruce ve5rc/ve5qrp - QRP-C#1, QRP-L#886, A1 Operator Enter QRP-Canada's RUN with RAC contest - details - http://www.qrp-canada.com -- I am using the free version of SPAMfighter for private users. It has removed 3726 spam emails to date. Paying users do not have this message in their emails. Get the free SPAMfighter here: http://www.spamfighter.com/len ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] Wire Antennas --apology
Paul Rubin wrote: Rick: No need to apologize. Your comments are right on target for this reflector. If some feel otherwise, there is always the delete key, or they can unsubscribe. Keep them coming. Paul N8NOV Houston I second Paul. I'll read any post about antennas that make my Elecraft radios more usable. After all, with QRP, it's all in the antennas. Fred K6DGW - Northern California Contest Club - CU in the 2007 CQP Oct 6-7 - www.cqp.org ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] Wire Antennas --apology
I third that! Antennas is the name of the game. And no need to apologize, you were right on topic! Ron, wb1hga Elmer the inquisitive Fred Jensen wrote: Paul Rubin wrote: Rick: No need to apologize. Your comments are right on target for this reflector. If some feel otherwise, there is always the delete key, or they can unsubscribe. I second Paul. I'll read any post about antennas that make my Elecraft radios more usable. After all, with QRP, it's all in the antennas. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
Yea, that is what has been keeping me away from 160m. I have several on going projects, and I can't start one of that magnitude now. Might have room for a dipole, so will just have to try that. Once I order some ladder line. David Wilburn [EMAIL PROTECTED] Don Wilhelm wrote: Dave, As far as switching your loop to a 160 top loaded vertical, yes you can do it remotely with relays and a matching network. If your goal is efficiency on 160 meters, the relay switching os only a small part of the equation - you must have a good RF ground for the vertical to work against, and that menas lots of wires in the ground, radiating from the base of the antenna. Some will tell you tht 120 radials will give optimum performance, but 16 or more will give great performance as well. If the radials are buried, the length is not critical, lots of short buried radials will do almost as good as a moderate number of long ones - see the 160 meter antenna simulation results that are outlined on L B Cebik's website www.cebik.com. More information on low band antennas can be found in ON4UN's Low Band DXing book - there are many possibilities. For best results, put the 160 meter matching network at the base of the antenna and match it to your feedline. Since there are many possibilities, make some decision even though it may be a compromise and you too can be successful on 'top-band'. 73, Don W3FPR -Original Message- I am very much enjoying reading the discussions on wire antennas. I have something I have been trying to figure out how to do for some time, and thought this might be a good place to ask. I have an 80m loop, up about 60 or 70 feet. Currently it is fed with 300 ohm line. All I could find at the time, as what I had left in 450 ohm line (after I helped my elderly neighbor get his antenna back up, and gave him some of the ladder line) was not long enough. Additionally, I went to the local hamfest this weekend and could not find a single vendor selling ladder line, but I digress. I have approximately 290 feet of wire in the air in a horizontal, triangular configuration, fed with (soon to be) ladder line, a balun (1:1) and then coax to the shack. Is it possible to switch this (seems possible from what I have read) to a 160m antenna by taking one side to ground at the balun and feeding the other side? If this is possible, is there a way to do this remotely? David Wilburn [EMAIL PROTECTED] K4DGW -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.441 / Virus Database: 268.18.3/694 - Release Date: 2/20/2007 1:44 PM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
Yes, and it doesn't work. This is the second 80m horizontal loop I have had, and they just do not like going low. David Wilburn [EMAIL PROTECTED] Don wrote: Have you tried using the antenna on 160 through a tuner just as it is? Chances are you can match it even on 160M and if you do you will not have to worry about the ground losses you would have feeding it against ground (unless using lots of radials). Don K7FJ - Original Message - From: David Wilburn [EMAIL PROTECTED] To: elecraft@mailman.qth.net Sent: Tuesday, February 20, 2007 8:07 PM Subject: Re: [Elecraft] wire antennas I am very much enjoying reading the discussions on wire antennas. I have something I have been trying to figure out how to do for some time, and thought this might be a good place to ask. I have an 80m loop, up about 60 or 70 feet. Currently it is fed with 300 ohm line. All I could find at the time, as what I had left in 450 ohm line (after I helped my elderly neighbor get his antenna back up, and gave him some of the ladder line) was not long enough. Additionally, I went to the local hamfest this weekend and could not find a single vendor selling ladder line, but I digress. I have approximately 290 feet of wire in the air in a horizontal, triangular configuration, fed with (soon to be) ladder line, a balun (1:1) and then coax to the shack. Is it possible to switch this (seems possible from what I have read) to a 160m antenna by taking one side to ground at the balun and feeding the other side? If this is possible, is there a way to do this remotely? David Wilburn [EMAIL PROTECTED] K4DGW ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
If I disconnected one side of the loop from balun, at that point (at least from what I have looked at on the web) it is similar to an inverted L with the wire wondering around instead of going off in one direction like it should. At that point, an inverted L would need radials. Problem is, this is right at the back side of my house, there is a deck and then an above ground pool. So looking at it from above, I could only get radials on about a 90 degree portion. Seems like a lot of trouble to go to for such a small foot print. I had originally hoped to put enough wire in the air for a 160m loop, but my best estimates put me about 100 ft too short. David Wilburn [EMAIL PROTECTED] Dale Putnam wrote: I would be wanting to try to utilize it as a top loaded vertical, tie the twinlead feeder together, then treat it as a vertical on 160. The loop as a loop presents tuff to match situation for most tuners. They just run out of capability at that low end. You might try moving the length of feedline with a set of coils, one in each lead, you may be able to move the match enough using the length of feedline to help the tuner get into a working situation. Worth the effort tho. That should work nicely and let you hear well too. --... ...-- Dale - WC7S in Wy Discover the new Windows Vista Learn more! http://search.msn.com/results.aspx?q=windows+vistamkt=en-USform=QBRE ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
Not sure where you are suggesting I open it. I was considering disconnecting the feedline on one side where it connected to the balun. Is this what you mean. My apologies if it is a silly question. David Wilburn [EMAIL PROTECTED] Rick Hiller wrote: Dave, Another possibility for 160 -- Don't know to what extent/effort you want to go to get on 160, but here is an easy way, although, a bit of a compromise. Simply open the loop at one of the 80 meter voltage loops (also a current node). The 80 meter standing wave current distribution /performance will not change, but it will force the wire to be an off center fed 1/2 wavelength for 160. Although not quite resonant within the 160 meter band, if you feed it with open wire and run it thru the appropriate matching network, you should be right. Quite possibly, if you adjust your overall length you might be able to find a length that is 1 wl on 80 where you need it and 1/2 wl on 160 close to where you want to work. Have a look at this in EZNEC to see how it will work for you in your particular situation. I use this method to run 80 on my 40 meter delta loop. It is a lot easier than relays and switches, but Don's good suggestion might be the preferred solution for you. GL...Rick -- W5RH Date: Tue, 20 Feb 2007 23:47:33 -0500 From: Don Wilhelm [EMAIL PROTECTED] Subject: RE: [Elecraft] wire antennas To: David Wilburn [EMAIL PROTECTED], elecraft@mailman.qth.net Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=iso-8859-1 Dave, As far as switching your loop to a 160 top loaded vertical, yes you can do it remotely with relays and a matching network. If your goal is efficiency on 160 meters, the relay switching os only a small part of the equation - you must have a good RF ground for the vertical to work against, and that menas lots of wires in the ground, radiating from the base of the antenna. Some will tell you tht 120 radials will give optimum performance, but 16 or more will give great performance as well. If the radials are buried, the length is not critical, lots of short buried radials will do almost as good as a moderate number of long ones - see the 160 meter antenna simulation results that are outlined on L B Cebik's website www.cebik.com. More information on low band antennas can be found in ON4UN's Low Band DXing book - there are many possibilities. For best results, put the 160 meter matching network at the base of the antenna and match it to your feedline. Since there are many possibilities, make some decision even though it may be a compromise and you too can be successful on 'top-band'. 73, Don W3FPR -Original Message- I am very much enjoying reading the discussions on wire antennas. I have something I have been trying to figure out how to do for some time, and thought this might be a good place to ask. I have an 80m loop, up about 60 or 70 feet. Currently it is fed with 300 ohm line. All I could find at the time, as what I had left in 450 ohm line (after I helped my elderly neighbor get his antenna back up, and gave him some of the ladder line) was not long enough. Additionally, I went to the local hamfest this weekend and could not find a single vendor selling ladder line, but I digress. I have approximately 290 feet of wire in the air in a horizontal, triangular configuration, fed with (soon to be) ladder line, a balun (1:1) and then coax to the shack. Is it possible to switch this (seems possible from what I have read) to a 160m antenna by taking one side to ground at the balun and feeding the other side? If this is possible, is there a way to do this remotely? David Wilburn [EMAIL PROTECTED] K4DGW -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.441 / Virus Database: 268.18.3/694 - Release Date: 2/20/2007 1:44 PM -- Message: 2 Date: Tue, 20 Feb 2007 23:46:42 -0500 From: Matthew D. Pitts [EMAIL PROTECTED] Subject: Re: [Elecraft] Custom K2? To: Bob Nielsen [EMAIL PROTECTED] Cc: Elecraft elecraft@mailman.qth.net Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=ISO-8859-1; format=flowed So tempting... I haven't fiddled with Linux in a few years and might be able to scrounge up a PC to run it on (I think all I'm missing for a working system amongst the parts I have is a power supply). Bob Nielsen wrote: On Feb 20, 2007, at 3:32 PM, Ian Stirling wrote: On Tuesday 20 February 2007 18:19, you wrote: Rig control software for people who use real computers (Fedora Core here). http://www.hamsoftware.org/ Haven't used it, but saw your comment and did a quick google. This is the first one I ran across, may be others. Are you on Mac or Linux? Because there were quite a few choices for Mac also. Multiplexing myself between my kubuntu/gnu/linux computer and cooking cream of scallion soup. I've recently switched to kubuntu from FreeBSD 6.1. There are a lot of good ham apps suitable
Re: [Elecraft] wire antennas
-Original Message- From: [EMAIL PROTECTED] If I disconnected one side of the loop from balun, at that point (at least from what I have looked at on the web) it is similar to an inverted L with the wire wondering around instead of going off in one direction like it should. At that point, an inverted L would need radials. Problem is, this is right at the back side of my house, there is a deck and then an above ground pool. So looking at it from above, I could only get radials on about a 90 degree portion. Seems like a lot of trouble to go to for such a small foot print. --- Sounds to me like the loop is up in the air and the feedline drops down to near the ground, right outside the house. It then goes into a balun, and coax runs from the balun into the shack. Hope that's right. If so, what I would do is this: 1) Disconnect *both* wires of the feedline from the balun. Tie them together. 2) Disconnect coax from balun 3) Connect an unbalanced tuner (simple L network?) between balun and the two feedline wires which are tied together. 4) Connect ground system to tuner 5) Adjust tuner for minimum SWR In such a system the vertical feedline does much of the radiating. The loop does some, and also acts as a sort of top-hat loading. The main benefit is the feedpoint Z Of course you need a ground system, and the pool/deck are in the way. So run the wires and rods that you can. Better than nothing. If it were me, I'd try this out temporarily (wires on top of ground, tuner in a plastic bag to keep the weather off, etc.) just to see how it works. If it seemed OK, then I'd do a permanent system with relays, remote-control tuner, buried radials, etc., when the weather improves. 73 de Jim, N2EY Check out the new AOL. Most comprehensive set of free safety and security tools, free access to millions of high-quality videos from across the web, free AOL Mail and more. =0 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
Dave, Open it at the point 180 degrees (midway around) from the feedpoint. If your existing loop is a full wavelength on 80 meters, opening it will turn the loop into a folded back 1/2 wave dipole on 160 meters - not as good as straight out, but it should work since you are feeding the line with a tuner anyway. In fact, you may be able to make it automatic by using a trap tuned to 160 meters - that will electrically open the loop on 160 and only add some inductnce on the other bands. 73, Don W3FPR -Original Message- Not sure where you are suggesting I open it. I was considering disconnecting the feedline on one side where it connected to the balun. Is this what you mean. My apologies if it is a silly question. David Wilburn [EMAIL PROTECTED] Rick Hiller wrote: Dave, Another possibility for 160 -- Don't know to what extent/effort you want to go to get on 160, but here is an easy way, although, a bit of a compromise. Simply open the loop at one of the 80 meter voltage loops (also a current node). The 80 meter standing wave current distribution /performance will not change, but it will force the wire to be an off center fed 1/2 wavelength for 160. Although not quite resonant within the 160 meter band, if you feed it with open wire and run it thru the appropriate matching network, you should be right. -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.441 / Virus Database: 268.18.3/694 - Release Date: 2/20/2007 1:44 PM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
That is definitely getting interesting. So I want to block 160m from going through, but pass 80m and above. Does that sound do able? With the number of people that run horizontal loops you would think this would be going on more. David Wilburn [EMAIL PROTECTED] Don Wilhelm wrote: Dave, Open it at the point 180 degrees (midway around) from the feedpoint. If your existing loop is a full wavelength on 80 meters, opening it will turn the loop into a folded back 1/2 wave dipole on 160 meters - not as good as straight out, but it should work since you are feeding the line with a tuner anyway. In fact, you may be able to make it automatic by using a trap tuned to 160 meters - that will electrically open the loop on 160 and only add some inductnce on the other bands. 73, Don W3FPR -Original Message- Not sure where you are suggesting I open it. I was considering disconnecting the feedline on one side where it connected to the balun. Is this what you mean. My apologies if it is a silly question. David Wilburn [EMAIL PROTECTED] Rick Hiller wrote: Dave, Another possibility for 160 -- Don't know to what extent/effort you want to go to get on 160, but here is an easy way, although, a bit of a compromise. Simply open the loop at one of the 80 meter voltage loops (also a current node). The 80 meter standing wave current distribution /performance will not change, but it will force the wire to be an off center fed 1/2 wavelength for 160. Although not quite resonant within the 160 meter band, if you feed it with open wire and run it thru the appropriate matching network, you should be right. -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.441 / Virus Database: 268.18.3/694 - Release Date: 2/20/2007 1:44 PM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
How low did you have your horizontal loop? We always use a 2 wave or so one for field day, (80m), but mostly use it on 40m and up to 15m. It is always only 20 feet high, as that is the limit of reach of our portable ladder. We get great signal reports, and work all over the country from the Central Southwest. I have seen an 80m loop work less well than a dipole when low to a roof containing a metal edging, which we put off to detuning and coupling issues. We feed our loops with parallel lines, either 300 ohm window or 450 ohm window line. Stuart K5KVH ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
Mike and the group, I am currently routing heavy duty 300 ohm twin lead from a 5/8 leg 20m antenna, thru a slot cut into some foam pipe insulation that acts as a panel in the bottom of a aluminum sash window. The window has aluminum sill, and frame, and individual panes of glass with aluminum sub frames. Cross the metal at right angle does not affect the normal operation of my BW tuner, and I am using the internal balun of this tuner and getting normal loading, and good signal reports with only 20 watts SSB, from the rig I use. If you cross at right angles and twist the feeder outside along its run, interaction with conductors is minimized and balance is preserved adequately for use with the tuner. Stuart K5KVH ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
After contemplating it a bit, I would say that it is 75 to 80 feet up. I had a similar one at my previous house up about 90 feet. It worked great. I broke more than one pileup while barefoot. I'm hoping this one works better after I get some 450 ohm ladder line on it. The both have tuned very well on the major bands, and with a bit of a struggle on some like 30m. The automatic antenna tuners in the my rigs has always worked pretty well tuning them up. David Wilburn [EMAIL PROTECTED] Stuart Rohre wrote: How low did you have your horizontal loop? We always use a 2 wave or so one for field day, (80m), but mostly use it on 40m and up to 15m. It is always only 20 feet high, as that is the limit of reach of our portable ladder. We get great signal reports, and work all over the country from the Central Southwest. I have seen an 80m loop work less well than a dipole when low to a roof containing a metal edging, which we put off to detuning and coupling issues. We feed our loops with parallel lines, either 300 ohm window or 450 ohm window line. Stuart K5KVH ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
Stuart wrote: Even simpler is a 80m dipole fed with balanced line to a tuner for all band use. The window line is less costly than coax. A good quality tuner is less lossy in multiband use than coax/ tuner balun, etc.. Balanced antennas have fewer problems than off center feeds. Balanced line to dipole does not need a balun at the antenna. That's always seemed the ideal approach to me. You can go anywhere with it with very low resulting losses, which is also very useful for MARS/CAP/SHARES work on those odd HF military frequencies. The only real problem seems to be routing the balanced line from the antenna into the shack without it having much interaction with nearby materials. A second problem is the lack of real balanced-line antenna tuners. Unbalanced tuners with that small output balun are problematic. I bought an old Johnson Matchbox just because it is one of the few true balanced tuners can can still be found. I know that MFJ has a couple of non-balun tuners design for balanced line, but I've never investivated their technical details, nor read reports on how well they perform. Obviously, these would not serve the gotta swap bands in five seconds contest crowd, but that's not me. I never trusted those resistor-terminated folding dipoles. Every analysis of them that I've ever read over the past 30 years has been basically unfavorable, as one would expect, with performance at best very much below that of a simple dipole. It is similar to a broad-band antenna design using any length of center-fed non-folded dipole fed with coax, with a hefty 50-ohm resistor across the coax leads at the connection to the dipole. You'd get good VSWR with that from 1.8 to 30 MHz! Come to think of it, about 25 years ago some outfit was hawking something just like that to hams at high cost. Yet, I'm sure you could make some contacts with it, just like you can with a resistor-terminated folded dipole. What these types of antennas show is that, no matter how bad an antenna design is, it'll work sometimes. TANSTAAFL! Mike / KK5F ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
I always advise using a non-resonant length for a multi-band doublet with tuner combination. There's a magic figure: multiples of 44ft, 88ft... that Cebik came up with which is a good compromise with impedance matching, ie not horrendously high or low X and R. I notice no-one has mentioned the G5RV and its derivatives, yet. David G3UNA - Original Message - From: Mike Morrow [EMAIL PROTECTED] To: elecraft@mailman.qth.net Sent: Tuesday, February 20, 2007 11:50 PM Subject: Re: [Elecraft] wire antennas Stuart wrote: Even simpler is a 80m dipole fed with balanced line to a tuner for all band use. The window line is less costly than coax. A good quality tuner is less lossy in multiband use than coax/ tuner balun, etc.. Balanced antennas have fewer problems than off center feeds. Balanced line to dipole does not need a balun at the antenna. That's always seemed the ideal approach to me. You can go anywhere with it with very low resulting losses, which is also very useful for MARS/CAP/SHARES work on those odd HF military frequencies. The only real problem seems to be routing the balanced line from the antenna into the shack without it having much interaction with nearby materials. A second problem is the lack of real balanced-line antenna tuners. Unbalanced tuners with that small output balun are problematic. I bought an old Johnson Matchbox just because it is one of the few true balanced tuners can can still be found. I know that MFJ has a couple of non-balun tuners design for balanced line, but I've never investivated their technical details, nor read reports on how well they perform. Obviously, these would not serve the gotta swap bands in five seconds contest crowd, but that's not me. I never trusted those resistor-terminated folding dipoles. Every analysis of them that I've ever read over the past 30 years has been basically unfavorable, as one would expect, with performance at best very much below that of a simple dipole. It is similar to a broad-band antenna design using any length of center-fed non-folded dipole fed with coax, with a hefty 50-ohm resistor across the coax leads at the connection to the dipole. You'd get good VSWR with that from 1.8 to 30 MHz! Come to think of it, about 25 years ago some outfit was hawking something just like that to hams at high cost. Yet, I'm sure you could make some contacts with it, just like you can with a resistor-terminated folded dipole. What these types of antennas show is that, no matter how bad an antenna design is, it'll work sometimes. TANSTAAFL! Mike / KK5F ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
Mike Morrow wrote: What these types of antennas show is that, no matter how bad an antenna design is, it'll work sometimes. TANSTAAFL! Has anyone seen the Illuminator from Tom Schiller, N6BT, of Force 12 fame? Fred K6DGW - Northern California Contest Club - CU in the 2007 CQP Oct 6-7 - www.cqp.org ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
I use a traditional wide-range balanced tuner - the same circuit Cebik shows and that has been a Hamshack staple item among some of us since Marconi was around. Center link, split stator variable, and feeders tapped onto the coil. With that tuner feedline length has never been an issue at all. It matches easily values from a few ohms up to several thousand ohms: the highest impedance one might expect with typical antenna geometries. It uses a large coil with heavy wire to avoid ohmic losses at the low impedance end and wide-spaced transmitting cap to handle the very large RF voltages present feeding high impedance loads. It's not automatic, so it's not fast, but I can change bands in about 15 seconds. And it's flexible, handling unbalanced loads like an end fed wire or coax line with equal ease. My normal feedline is high-efficiency open wire line. My open wire line is made of #14 electrical wire separated by high-quality ceramic insulators at long intervals to minimize dielectric and ohmic losses. My antenna of choice has always been the doublet, since I've not had the space for a rhombic or other traveling wave type or the room for a tower and beam. As long as the doublet is at least 1/4 wavelength long, end to end, it's virtually as effective as a half wave. So a 66 foot doublet does a very good job on 80 and a 130 foot doublet does a good job on 160. The big issue on the lower bands is usually height, especially enough height for good low angle radiation from a horizontal antenna. That requires a height of at least 3/8 wave and 1/2 wave is better. On 160 meters it needs to be close to 100 feet up: 130 feet would be ideal G. I count myself lucky to get the wire 50 feet up. That provides low angles for DX on 40 meters and up. On 80 or 160 it's an omni-directional NVIS or short skip antenna providing excellent coverage out to about 1,000 miles or so on 80; a little less, typically, on 160. Where the wire is well over 1/2 wave long, it shows significant gain as the pattern breaks up into many lobes. In spite of the antenna patterns one finds in books, a real world antenna does not have zero radiation in any direction. It's a matter of having lobes that produce a superior signal in various directions. I've never noticed any deleterious effects from the lobes and long ago quit thinking much about trying to align the antenna for specific coverage. Ron AC7AC -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of David Cutter Sent: Tuesday, February 20, 2007 4:14 PM To: Mike Morrow; elecraft@mailman.qth.net Subject: Re: [Elecraft] wire antennas I always advise using a non-resonant length for a multi-band doublet with tuner combination. There's a magic figure: multiples of 44ft, 88ft... that Cebik came up with which is a good compromise with impedance matching, ie not horrendously high or low X and R. I notice no-one has mentioned the G5RV and its derivatives, yet. David G3UNA ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
I am very much enjoying reading the discussions on wire antennas. I have something I have been trying to figure out how to do for some time, and thought this might be a good place to ask. I have an 80m loop, up about 60 or 70 feet. Currently it is fed with 300 ohm line. All I could find at the time, as what I had left in 450 ohm line (after I helped my elderly neighbor get his antenna back up, and gave him some of the ladder line) was not long enough. Additionally, I went to the local hamfest this weekend and could not find a single vendor selling ladder line, but I digress. I have approximately 290 feet of wire in the air in a horizontal, triangular configuration, fed with (soon to be) ladder line, a balun (1:1) and then coax to the shack. Is it possible to switch this (seems possible from what I have read) to a 160m antenna by taking one side to ground at the balun and feeding the other side? If this is possible, is there a way to do this remotely? David Wilburn [EMAIL PROTECTED] K4DGW ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
Dave, As far as switching your loop to a 160 top loaded vertical, yes you can do it remotely with relays and a matching network. If your goal is efficiency on 160 meters, the relay switching os only a small part of the equation - you must have a good RF ground for the vertical to work against, and that menas lots of wires in the ground, radiating from the base of the antenna. Some will tell you tht 120 radials will give optimum performance, but 16 or more will give great performance as well. If the radials are buried, the length is not critical, lots of short buried radials will do almost as good as a moderate number of long ones - see the 160 meter antenna simulation results that are outlined on L B Cebik's website www.cebik.com. More information on low band antennas can be found in ON4UN's Low Band DXing book - there are many possibilities. For best results, put the 160 meter matching network at the base of the antenna and match it to your feedline. Since there are many possibilities, make some decision even though it may be a compromise and you too can be successful on 'top-band'. 73, Don W3FPR -Original Message- I am very much enjoying reading the discussions on wire antennas. I have something I have been trying to figure out how to do for some time, and thought this might be a good place to ask. I have an 80m loop, up about 60 or 70 feet. Currently it is fed with 300 ohm line. All I could find at the time, as what I had left in 450 ohm line (after I helped my elderly neighbor get his antenna back up, and gave him some of the ladder line) was not long enough. Additionally, I went to the local hamfest this weekend and could not find a single vendor selling ladder line, but I digress. I have approximately 290 feet of wire in the air in a horizontal, triangular configuration, fed with (soon to be) ladder line, a balun (1:1) and then coax to the shack. Is it possible to switch this (seems possible from what I have read) to a 160m antenna by taking one side to ground at the balun and feeding the other side? If this is possible, is there a way to do this remotely? David Wilburn [EMAIL PROTECTED] K4DGW -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.441 / Virus Database: 268.18.3/694 - Release Date: 2/20/2007 1:44 PM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
Have you tried using the antenna on 160 through a tuner just as it is? Chances are you can match it even on 160M and if you do you will not have to worry about the ground losses you would have feeding it against ground (unless using lots of radials). Don K7FJ - Original Message - From: David Wilburn [EMAIL PROTECTED] To: elecraft@mailman.qth.net Sent: Tuesday, February 20, 2007 8:07 PM Subject: Re: [Elecraft] wire antennas I am very much enjoying reading the discussions on wire antennas. I have something I have been trying to figure out how to do for some time, and thought this might be a good place to ask. I have an 80m loop, up about 60 or 70 feet. Currently it is fed with 300 ohm line. All I could find at the time, as what I had left in 450 ohm line (after I helped my elderly neighbor get his antenna back up, and gave him some of the ladder line) was not long enough. Additionally, I went to the local hamfest this weekend and could not find a single vendor selling ladder line, but I digress. I have approximately 290 feet of wire in the air in a horizontal, triangular configuration, fed with (soon to be) ladder line, a balun (1:1) and then coax to the shack. Is it possible to switch this (seems possible from what I have read) to a 160m antenna by taking one side to ground at the balun and feeding the other side? If this is possible, is there a way to do this remotely? David Wilburn [EMAIL PROTECTED] K4DGW ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
Yes, you CAN put multiple dipoles on one feedline. It's commonly done in the government and/or commercial world. It's often referred to as a fan dipole. The feedline can be either coax or open wire/TV twinlead. Picture two telephone poles (or towers) with the support points for the individual dipoles several feet apart vertically along the two poles/towers. Such an arrangement is sometimes seen at a National Guard armory or Civil Defense center. The dipoles -DO- interact and will need length adjustment, one at a time 73! Ken Kopp - K0PP [EMAIL PROTECTED] or [EMAIL PROTECTED] ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
I happen to have pictures of just such a beast at http://www.craigr.com/coppermine/thumbnails.php?album=35. It's cut for 40/20/10 meters and works nicely on 15 of course. The KAT100 tuner makes it work on the WARC bands and even on 80m though not very well. Craig NZ0R K2/100 #4941 K1 #1966 KX1 #1499 -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ken Kopp Sent: Monday, February 19, 2007 4:41 PM To: [EMAIL PROTECTED]; elecraft@mailman.qth.net Subject: Re: [Elecraft] wire antennas Yes, you CAN put multiple dipoles on one feedline. It's commonly done in the government and/or commercial world. It's often referred to as a fan dipole. The feedline can be either coax or open wire/TV twinlead. Picture two telephone poles (or towers) with the support points for the individual dipoles several feet apart vertically along the two poles/towers. Such an arrangement is sometimes seen at a National Guard armory or Civil Defense center. The dipoles -DO- interact and will need length adjustment, one at a time 73! Ken Kopp - K0PP [EMAIL PROTECTED] or [EMAIL PROTECTED] ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
Scott, I use 'fanned dipoles' fed with a common coax - yes a balun is highly recommended. The secret to fanned dipoles is to get the ends as far apart as possible so they do not interact. Expect some interaction in any case, and tune them from the lowest band first. I have tried 5 bands - in a word, DON'T, unless you are willing to drive yourself crazy cutting and pruning due to the interaction. 3 bands is about my limit. One other point - do not try to combind bands that are close to the 3rd harmonic of the lower one on the same coax - that too will drive you crazy trying to tune them because the 3rd harminic frequency antenna will also present a low impedance feedpoint. In other words, stay away from combining 80 and 30 meters or 40 meter and 15 meters. I successfully use an 80/40 meter combination, a 20/15/10 combination and a 30/17/12 combination - 3 feedlines to cover 8 bands. Some are dipoles and others are inverted VEE. 73, Don W3FPR -Original Message- Hi This is a little off topic, but I don't know of a better place to find someone that would know the answer to my question. Many years ago I used one coax to feed three different inverted V antennas all for different bands. At the time I thought they worked just fine. Worked all kinds of dx with the setup. I have been told lately that the unused antennas on the setup would pick up additional noise. Has anyone ever done any testing with multiple antennas on one feedline to see if they really do pick up extra noise? I'm thinking about putting up new inverted V antennas on 160, 80, and 40 meters and feeding them with one coax. Sure beats antenna switching and it always seem to me that the signal would go to the resonate antenna. I always used a coaxial balun in the feedline. Any ideas would be appreciated. Thanks Scott N5SM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: 7.5.441 / Virus Database: 268.18.2/692 - Release Date: 2/18/2007 4:35 PM -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.441 / Virus Database: 268.18.2/692 - Release Date: 2/18/2007 4:35 PM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
On Mon, 19 Feb 2007 22:41:24 -, Ken Kopp wrote: Picture two telephone poles (or towers) with the support points for the individual dipoles several feet apart vertically along the two poles/towers. Such an arrangement is sometimes seen at a National Guard armory or Civil Defense center. A lot of them have been replaced by the now-ubiquitous BW All Band Folded Dipole - the same antenna that I use in an open-V configuration. It works equally flat over the HF (1.8-30 MHz) spectrum. -- 73 de K2ASP - Phil Kane Elecraft K2/100 s/n 5402 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
[EMAIL PROTECTED] wrote: Has anyone ever done any testing with multiple antennas on one feedline to see if they really do pick up extra noise? Hm, nobody answered this. My feeling (and it's not based on experiments) is that it would normally not be a problem. For example, if you have an 80 and 160 meter dipole on one feedline, then the unused antenna would be just as likely to pick up additional signals on the desired band as it would noise. So while it might have a tiny bit more gain, the s/n ratio wouldn't change. Having said that, the total signal and noise voltage delivered to the receiver front end would be greater, since the bandwidth of the combination of antennas would be wider. If the receiver's dynamic range characteristics were inadequate, there might be spurious signals generated in the receiver. For example, if you lived in Europe where there are enormous SWBC signals around 40 meters at night, then you probably wouldn't want a 40 meter dipole in parallel with your 80 meter one. -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
In a message dated 2/19/07 4:45:23 PM Eastern Standard Time, [EMAIL PROTECTED] writes: have been told lately that the unused antennas on the setup would pick up additional noise. If so, it will also pick up additional signal. Has anyone ever done any testing with multiple antennas on one feedline to see if they really do pick up extra noise? I haven't done any scientific testing, but in actual operation (FD), I have not found any difference from a regular dipole. The principle of multiple parallel dipoles is that the nonresonant dipoles present a high impedance, so almost all of the power goes to the resonant dipole. That principle works the other way, too, when receiving. I'm thinking about putting up new inverted V antennas on 160, 80, and 40 meters and feeding them with one coax. Sure beats antenna switching and it always seem to me that the signal would go to the resonate antenna. I always used a coaxial balun in the feedline. Works for me! How high of a center support do you have? 73 de Jim, N2EY ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
Scott: I use several fan dipoles. Both use two elements. One operates on 40 and 30 meters (and I get 15 meters, 3rd harmonic of 40, free into the bargain, but the SWR is a bit above 2 on 15 m, and I must use tuner to match it to the K2. ). The other antenna operates on 80 and 20 meters (and I get 17/12 meters, 3rd and 5th harmonic of 80 meters free into the bargain, but the SWR is a bit above 8 on 12/17 m. I must use tuner to match it to the K2 on 17/12. However, the line losses are acceptable, and the antenna is very effective on all four bands. ) Several gotchas. The elements do interact. The shorter element will be non-trivially off from the 468 formula. The longer element is pulled much less noticeably. However, if you're looking for low SWRs of both bands, be prepared to do a lot of tweaking. I agree with other posted comments. If you use more than 2 elements, be prepared to do a very great deal of very frustrating of tweaking. Very important: Construct your antenna in such a way that the short element cannot wrap around the long one. If it does wrap, it will pull your painstakingly tuned antenna way off the desired resonant frequency. Other caution: Do not suppose that you can simulate a fan dipole on EZNEC. The condition of two parallel elements of unequal length very close together is one place where the computer model departs from reality. I do not use baluns, and it does not seem to have caused me any trouble. Good luck, Steve AA4AK At 04:44 PM 2/19/2007, [EMAIL PROTECTED] wrote: Hi This is a little off topic, but I don't know of a better place to find someone that would know the answer to my question. Many years ago I used one coax to feed three different inverted V antennas all for different bands. At the time I thought they worked just fine. Worked all kinds of dx with the setup. I have been told lately that the unused antennas on the setup would pick up additional noise. Has anyone ever done any testing with multiple antennas on one feedline to see if they really do pick up extra noise? I'm thinking about putting up new inverted V antennas on 160, 80, and 40 meters and feeding them with one coax. Sure beats antenna switching and it always seem to me that the signal would go to the resonate antenna. I always used a coaxial balun in the feedline. Any ideas would be appreciated. Thanks Scott N5SM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
In a message dated 2/19/07 7:00:22 PM Eastern Standard Time, [EMAIL PROTECTED] writes: A fan dipole is a single-band affair. It's is a way of broadening the bandwidth of a single-band dipole by simulating a fat wire using multiple wires. Typically the wires join at an apex at the center and spread or fan out at the far end with cross-wires connecting the ends. That forms larger effective radiator diameter that reduces the Q of the antenna; hence the bandwidth is increased. That's what I think of when someone uses the term fan dipole. It's not a commonly-used antenna because a simple wire dipole usually has adequate bandwidth on 40 meters and up, and in practice even a large fan doesn't broaden the bandwidth all that much; not enough to cover the 3.5 - 4 MHz range with a low SWR, for example. I disagree! Way back in the 1980s, WA3UZI and I did some tests on an 80/75 meter fan dipole. We used four equal-length wires with spreaders at the ends, making a sort of giant bow tie. The far ends were not connected, they just terminated at the spreaders. The spreaders were horizontal and the whole thing was up about 50 feet, fed with 50 ohm coax. IIRC, if the ends were spread about six feet, the antenna had an SWR well under 2:1 from 3.5 to 4.0 MHz. The wires were a lot shorter than one would expect from the formula - about 57 feet or so. It was built so that one antenna could cover 80 CW and 75 phone on Field Day without need of a tuner, since the rigs we used could handle 2:1 SWR with no problem at all. It took a bit of pruning and testing to get the wire and spreader lengths right. It worked as well as a regular halfwave dipole. However, like any fat radiator dipole, the resonant length is shortened a bit, which can be a help in limited space. Yup. Another approach is a cage dipole - multiple wires of the same length all in parallel, spaced around a circle throughout their lengths. I've not tried one because of the mechanical complexity compared to simple fan. Calculations (which I have not tried) predict that a cage of three feet in diameter is needed to get 2:1 SWR from 3.5 to 4.0 MHz. The big problem with such antennas is that they are heavier, more mechanically complex, and have much more wind/ice loading than a regular single wire. We had good supports at the old FD site, and the antenna only had to last a weekend. Even so, we only used it one year. Cebik has a good write-up on fan dipoles and their close cousin, the bow tie antenna, at www.cebik.com as part of his discussion of small beams. I suppose the best description of our antenna is a bow tie. 73 de Jim, N2EY ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] wire antennas
On Mon, 19 Feb 2007 17:54:25 -0500, Don Wilhelm wrote: 3 bands is about my limit. Yes -- beyond that, they get both electrically and mechanically unwieldy. One other point - do not try to combind bands that are close to the 3rd harmonic of the lower one on the same coax - that too will drive you crazy trying to tune them because the 3rd harminic frequency antenna will also present a low impedance feedpoint. In other words, stay away from combining 80 and 30 meters or 40 meter and 15 meters. This is also very good advice. W2DU has an excellent discussion of this on his website. Google to find it. It's in one of the chapters of his book. I successfully use an 80/40 meter combination, a 20/15/10 combination Agreed. I also have an 80/40 fan that has loading coils at the ends of the 80 meter element to allow it load on 160 (and, of course, the 40 meter element works fine on 15. That antenna also works quite well (and it's a 4-band antenna!). The loading coils are from HyPower Antenna Co. Google to find them -- they're a good solution for antennas on small lots. I also have a 40/30/20 that works, but is not as well behaved as the harmonically related ones, for the reasons noted. 73, Jim Brown K9YC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] Wire Antennas and feedline for the KX1
Chuck, K2CG wrote: I enjoy putting together and playing with simple wire antennas for field operations. I have also been fortunate to enjoy moderate success with my efforts. However I am looking to refine my approach in an effort to make my systems more efficient. My approach in the past has been to follow designs and dimensions for established dipole's and doublets, then check my effort by using an MFJ-259 to verify that they fall within acceptable limits for my tuner and desired frequency range. I am not looking to build an antenna that will give me 1:1.0 SWR but rather try to change the feed-line impedance to produce a better load transfer. Currently I am using a 135' doublet with 50' of 450 ohm ladder line, but I am looking at trying an 88' Doublet and different types of balanced transmission lines to vary the input impedance, by using 300 ohm, 450 ohm ladder line or even trying some home built 650 ohm ladder line. - In truth, there isn't much to it! That's why simple antennas aren't belabored in the literature. It only gets complicated when you want passive antenna systems that show a low SWR on many bands or which has a lot of directivity, etc. The first requirement for an efficient antenna is low reactance at the connection to the transmitter. Low reactance is required for maximum power transfer. Almost 200 years ago Heinrich Hertz discovered that a wire that is electrically 1/2 wave long is naturally resonant; that is, it shows minimum reactance to the signal applied. That's the shortest length of antenna that is naturally or self resonant when operated independently (e.g. free space). Marconi had a huge problem as he started tinkering with antennas. To be self-resonant at the frequencies he was using in his early work - perhaps 50 or 100 kHz and probably less - he'd need an antenna at least 40,000 feet long. Even Gugliemo's mom must have balked at that idea! (He was still living at home.) He tinkered and worked out that if he connected one end of his antenna system to the earth, it would resonate at half the length of a Hertzian antenna. Well, that did save 20,000 feet of wire! (Now, I confess I'm telling tall tales here. It's not likely Heinrich or Gugliemo really understood resonance or, as Gugliemo like to call it 'synchronicity'. But as we better understood the effects of reactance on an antenna system in later years, what Heinrich and Gugliemo were doing by trial and error became evident.) When an antenna is longer than its natural resonant length, it'll have inductive reactance. If it's shorter, it'll have capacitive reactance. If it's not convenient to make the antenna the right length, we can add suitable inductance or capacitance and bring the system to resonance. Our antenna tuners will do that for us, if they have the required range to match our antenna at the frequency we want. That's one of the two things a tuner must do. We'll touch on the other in a moment. With the right amount of inductive or capacitive reactance, you could, on paper, have an antenna 1 inch long that would radiate as well as any wire ever launched into space, except for one problem: resistance. Here's why resistance is a problem. A resonant antenna looks like a resistor to the transmitter. If it has zero losses, that resistance is a fictional amount representing the RF that is radiated as electromagnetic waves. Since we're dealing with alternating currents here (at RF frequencies) we don't say resistance but impedance. Since the antenna is resonant (no reactance) the impedance is equal to the resistance. The value of that impedance varies according to the length of the antenna. If the antenna is 1/2 wave long, the value of that impedance at the end may be several thousand ohms. At the center it's about 75 ohms if the antenna is in free space. (Getting it close to the earth were most of us have to put them brings it down closer to 50 ohms). But, as you make the antenna shorter than 1/2 wave the impedance drops. At 1/4 wave (the length Marconi used) it's 35 ohms. As you go shorter the impedance plummets like a lead garden gnome dropped from that 90-foot tower you dream of owning. Many short antennas, like mobile antennas, have an impedance of less than 1 ohm, sometimes down in the range of 0.1 or even 0.01 ohms! That alone isn't a problem except for the fact that the antenna wire and the wire in any inductors we use to make it resonant also have resistance. The power is shared between the resistance of the wire and the radiation resistance. And don't forget that the RF resistance of a wire is much greater than the DC resistance because RF only flows along the skin of conductors. (That's why some RF conductors are silver plated for best efficiency.) Also, your feed line is part of that antenna system, so if it has a very high SWR it'll show high ohmic losses at the points where the RF currents are high. Even open wire line will do that under extreme conditions. I
Re: [Elecraft] Wire Antennas and feedline for the KX1
[EMAIL PROTECTED] wrote: ... I have read several articles and books on antenna building but have missed anything that addresses this aspect of antenna construction. That is not to say that it hasn’t been discussed only that I have not seen it. You might benefit from a visit to the DX Engineering web site (http://www.dxengineering.com/) where your path to Nirvana is Base Station Antennas - Multi-Band Dipoles. These guys do a great job of explaining the reasons for certain designs, choices of antenna lengths, feed-line types and lengths, the use of suitable choke-type baluns, and so on. And they sell great hardware. Their prices indicate that they are proud of their products, as they should be, but I'm happy that I purchased some of the critical components of my 80-10 meter doublet from them. Good luck with your antenna system, Gus Hansen KB0YH ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
