Re: [Elecraft] OT: K3 and antenna questions
It's temporary, but works fine for now. I drilled 2 holes in the bedroom wall and slid 2 lengths of nylon tube therein, they stick out a few inches outside. A piece of 450 ladder line about 3 ft or so goes from the PL in the rig to a connector block on the inside wall and the 2 wires from outside feed thro to that. Height above ground is about 15ft at this point. One wire goes to the bottom of the garden about 3ft up, then thro a rt angle for about 6ft rising to 4ft or so. The other wire bends at about 80deg and drops to 8ft at the garage barge board, then thro rt angle down between the houses to a tree at the front, about 6ft up. Wire is 20swg SnCu used on several projects. BTW no rf or any other kind of earth on rig. Occasionally hear US 80m ssb early morning. No balun; after initial tuning the K3 remembers its settings and changes instantly on band change. I think I asked it to fine tune on a couple of freqs but can't remember which. I'll try this for the cubscouts with longer feeder for JOTA and see how it works inverted V style. David G3UNA - Original Message - From: "Jim Wiley" <[EMAIL PROTECTED]> To: Sent: Thursday, July 03, 2008 6:44 PM Subject: Re: [Elecraft] OT: K3 and antenna questions David - How high is it? What kind of feed-line are you using? How long is the feed-line? Do you use a balun at the antenna or at the transmitter end? Does the K3 auto-coupler show any symptoms of having trouble matching one or more bands (long tuning time)? - Jim, KL7CC David Cutter wrote: I run a 2 x 88ft doublet straight into my K3 and it matches top to 10 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 ___ 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] OT: K3 and antenna questions
David - How high is it? What kind of feed-line are you using? How long is the feed-line? Do you use a balun at the antenna or at the transmitter end? Does the K3 auto-coupler show any symptoms of having trouble matching one or more bands (long tuning time)? - Jim, KL7CC David Cutter wrote: I run a 2 x 88ft doublet straight into my K3 and it matches top to 10 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 ___ 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] OT: K3 and antenna questions
I run a 2 x 88ft doublet straight into my K3 and it matches top to 10 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] OT: K3 and antenna questions
Hi Dave, I know I should also model this thing in EZNEC, but have not taken the time to learn how to use it yet. Seems a little daunting when I look at it. When you do have the time to try EZNEC you will find that it is quite easy to use. Transmission line programs are also very useful because once ENZEC gives you the value of the feedpoint impedance of an antenna at some frequency, you can enter this value into the transmission line program as a load, along with the characteristics or type of feeder, and read off the values of resistance and reactance at any point along the length of feeder. The results are reasonably accurate and can save a lot of time otherwise spent cutting off lengths of feeder to obtain a suitable load for a balun or matching unit. One program that I use is TLW which came with the ARRL Antenna Handbook 20th edition. Plus, I'm a little confused as to how it seemed to work so well in that configuration. Probably just dumb luck on my part ;-) Both the resonant frequency and the feedpoint impedance at the resonant frequency of an Inverted V change quite rapidly as the included angle between its legs is decreased. With decreasing angle the resonant frequency increases and the feedpoint impedance at the resonant frequency decreases IIRC, so the load that your balun or tuner saw in the first antenna configuration could be very different from that seen in the second if the included angle between their legs is different. The height of the top is another factor as is the length of feeder. Yesterday, I was tuning around 40m when I heard a station calling CQ - QRP on 7.059. He was a 479 here so I thought I would give him a call back. He answered and gave me a report of 359. After the initial exchange, he stated he could not copy me - we tried a couple more times and then signed off. He was a definite solid copy on my end with the S-meter hitting S1-3 at times with some QSB. It was like this the whole time. - with all the great receiver reports I've read on the K3 - could it be that I was simply hearing him better with my K3 than whatever he was using (unfortunately I don't know what he used as we never got that far in the QSO)? Assuming that he was not having trouble with QRN nor QRM (which you could not hear due to skip conditions), this could be a instance where the law of reciprocity is not obeyed - quite common on 40m especially during the summer on East-West paths. One reason for this is that the path followed by a signal going from A to B can be different from the path B to A. After sorting out the feeder etc it takes time to evaluate properly the performance of an antenna! 73, Geoff GM4ESD ___ 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] OT: K3 and antenna questions
Hi Ron, As I replied to Don, I had a slightly different setup last year and did indeed eliminate the balun and feed it directly with my K2 (at the urging of both you and Don BTW). And it seemed to work great. This year, I moved the antenna slightly higher and after researching some things on L.B. Cebik's site, I realized the feedline length of 33' put me at the half wave point for 40m. Since I had to lengthen it anyway, I went with the recommended 43' which was supposed to make it more of a multi-band use feed length. I'm kind of time strapped right now, but I would like to try this current config with my K2 and see if there is any difference in the way it tunes up. And then I guess I should play with different feed lengths to see if I can eliminate that balun. As I told Don, I should model this thing in EZNEC but I just haven't spent enough time with it to be comfortable with any results ;-) Thanks for the great info Ron. 73, Dave W8FGU > -Original Message- > From: Ron D'Eau Claire [mailto:[EMAIL PROTECTED] > Sent: Wednesday, July 02, 2008 1:02 PM > To: 'Dave Van Wallaghen'; elecraft@mailman.qth.net > Subject: RE: [Elecraft] OT: K3 and antenna questions > > No apologies needed Dave. Based on the posts here over the past decade, > your > question is *very* list-appropriate. > > Don's comments are "right on" as always. Any warming of the balun is RF > energy that was never radiated. At low powers, any noticeable heating is > likely a big chunk of your power. > > And a balun is completely unnecessary in most cases. > > About the reciprocity issue, keep in mind that almost *any* receiver has > plenty of gain to make up for poor antennas, where your transmit "gain" > (rf > power) is strictly limited. So almost any antenna will seem to "hear" much > better than it transmits. That's why on-ground and even underground > antennas > often do very well for receiving but are abysmal transmitting antennas. > > The big issue with receiving is usually signal-to-noise ratio. Your > transmitted signal is quite unaffected by local QRN, but your received > signal is terribly affected by such noise. (Again, that's why some use > on-ground or underground antennas for receiving. Local QRN is usually > attenuated much more at ground level than the signals arriving from > overhead, so such an antenna, while not providing as loud signals as a > true > "skywire" will often provide superior signal-to-noise ratios. The receiver > makes up for the overall lower gain and so often you hear signals much > better than with a skywire.) > > Ron AC7AC > ___ 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] OT: K3 and antenna questions
Hey Don, Thanks for the reply. I forgot to mention in the first post that I used this last year in a slightly different spot and it was fed with 33' of open feedline. I fed it directly from my K2 without a balun and it tuned up great 80m - 10m. To get 1:1 SWR on 20m I added 6' of feedline. After doing some reading on the L.B. Cebik site, I realized that the 33' feedline would put me at the half wave mark on 40m. So, I attached another 10' for a total of 43' as recommended. The K3 had a hard time tuning this up so I attached the balun to help things out and it did from a SWR standpoint. I was not very happy with that since I know that baluns can be quite lossy. Not to mention I was able to get the previous incarnation to tune up with my K2 without a balun. Unfortunately, it is vacation season around here and I'm working a lot of extra shifts, so my time is limited over the next few weeks. I would like to try this same config with my K2 just for a good comparison. Plus, I'm a little confused as to how it seemed to work so well in that configuration. Probably just dumb luck on my part ;-) I know I should also model this thing in EZNEC, but have not taken the time to learn how to use it yet. Seems a little daunting when I look at it. Thanks again Don, Dave W8FGU > Dave, > > Yes, the law of reciprocity applies on both TX and RX, but the K3 has a > better receiver, so it is entirely possible for you to hear ones that > you cannot work. His signal report to you indicates that is likely the > case. > > Try your antenna without the balun - you should not notice heating at 5 > watts unless there is considerable loss (maybe it was the sun shining on > the balun :-) ). Usually in multi-band QRP field operations, a slightly > unbalanced antenna radiation pattern is not a problem. If you end up > with hot RF on the chassis, you can alter the feedline length to bring > the impedance down and make the antenna easier to feed. Your current > radiator plus feedline might have a high impedance at the rig end on 40 > meters and up (the total feedline plus one leg of the antenna is near a > half wave on 40m). > > 73, > Don W3FPR > ___ 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] OT: K3 and antenna questions
A half-wave doublet center-fed with a quarter-wave of hi-Z feedline is a worst case scenario. A 66' doublet would be close to a resonant antenna on 7.0 MHz. Accounting for the thin wire, would expect a 70 ohm center-feed impedance, even at that height. It would appear that the length of the feedline would be approaching 30 feet if not over. Without calculating this exactly, given the thin wire and 3" spacing, the feedline characteristic Z would be over 600 ohms, perhaps as much as 800. The feedline will be very close to a 1/4 wave transmission-line transformer, given some velocity factor adjustment. The worst case of this scenario is to raise the feed impedance at the K3 end of the feedline to 800 squared divided by 70, or 9000 ohms, an enormous mismatch to the design 200 ohms on the antenna side of the balun. At 5 watts, the antenna tuner/balun combination would have to generate 212 volts on the feedline to match 9000 ohms. Even with moderation due to not being exactly at the worst case points, you could have had a 10:1 or worse mismatch at the OUTPUT of the balun, taking it way out of design parameters and efficient operation. In this case the rf path would have been taking any old alternative way to induce current, including capacitance of the rig to the ground below and dissipation in pure heat. The reason your balun was hot was that a lot of the transmitting power was being dissipated in the core. For forty meters using the open feedline you would try 66' of wire and the feedline off-center at 22' from either end, or the feedline at the end of a 43' wire. Your open wire feed will ENABLE these lengths. I assume you have the auto-tuner in the K3 or you would not have been able to get power out. Further elaboration off-line. 73, Guy K2AV Dave VW wrote: > > I apologize for the bandwidth, but I really trust the sources of info here > and it may help someone else starting out like me with specific K3 info > and > antenna theory. > > I've been playing around with my K3 in a portable capacity out in my yard. > Here is the setup: > > -K3 running @ 5W > -Antenna: 66' doublet made from 28g wire fed with open feedline made from > same, spaced apart with wood dowels 3" wide. It is placed up in a tree > about > 35' up with the ends coming down in an inverted v fashion. > -The antenna is fed to a BL2 with a 12" piece of coax to the K3. > > I used a similar setup last summer with my K2 and had what I thought was > pretty good success. In trying to evaluate this setup, I usually call CQ > as > opposed to answering one. This way I know that if I get a reply, the other > op heard me. During the exchange I will state my power info to which I > usually get positive comments about the K3 and/or the antenna setup - or > they quickly sign off (not sure why they do that if I got a 599 report). > > Yesterday, I was tuning around 40m when I heard a station calling CQ - QRP > on 7.059. He was a 479 here so I thought I would give him a call back. He > answered and gave me a report of 359. After the initial exchange, he > stated > he could not copy me - we tried a couple more times and then signed off. > He > was a definite solid copy on my end with the S-meter hitting S1-3 at times > with some QSB. It was like this the whole time. > > Now my questions: > 1 - with my antenna setup tuned with the KAT3, knowing that we were both > at > 5 watts, is it possible for the antenna to be more efficient at receiving > than transmitting? I guess I always thought that if an antenna "system" is > matched then the energy transfer is reciprocated for rcv and xmt. > > 2 - with all the great receiver reports I've read on the K3 - could it be > that I was simply hearing him better with my K3 than whatever he was using > (unfortunately I don't know what he used as we never got that far in the > QSO)? > > 3 - I did notice after the QSO that the balun was a little warm. If there > are transmission losses in the balun, would there not be reciprocated > losses > on the receive side? > > If you feel this is not list appropriate, please reply to me privately. > > Thanks for the bandwidth. > > 73, > Dave W8FGU > > > ___ > 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 > > -- View this message in context: http://www.nabble.com/OT%3A-K3-and-antenna-questions-tp18240875p18242928.html Sent from the Elecraft mailing list archive at Nabble.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.q
Re: [Elecraft] OT: K3 and antenna questions - variant
Dragging this slightly away from the topic - I've seen this said before, so would like some explanation please. I plan on using a doublet of non-determined resonance with my K3 portable. the arms are 18.3m and fedd with ~ 12m of 300 ohm ribbon (TV type), supported by a 10m telescopic carbon fibre pole. Arms in an inverted-V config. When I used this for the first time with the K3 via a BL2 the other week, untuned SWR was rather poor - > 20:1, but KAT3 tuned it ok. I'd be interested to know what people think/do with this when do using a balan - presumably you just connect one side to the center of a PL259 and the other to the shell? 73 de M0XDF, K3 #174 -- One glance at a book and you hear the voice of another person, perhaps someone dead for 1,000 years. To read is to voyage through time. -Carl Sagan, astronomer and writer (1934-1996) On 2 Jul 2008, at 18:01, Ron D'Eau Claire wrote: And a balun is completely unnecessary in most cases. ___ 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] OT: K3 and antenna questions
No apologies needed Dave. Based on the posts here over the past decade, your question is *very* list-appropriate. Don's comments are "right on" as always. Any warming of the balun is RF energy that was never radiated. At low powers, any noticeable heating is likely a big chunk of your power. And a balun is completely unnecessary in most cases. About the reciprocity issue, keep in mind that almost *any* receiver has plenty of gain to make up for poor antennas, where your transmit "gain" (rf power) is strictly limited. So almost any antenna will seem to "hear" much better than it transmits. That's why on-ground and even underground antennas often do very well for receiving but are abysmal transmitting antennas. The big issue with receiving is usually signal-to-noise ratio. Your transmitted signal is quite unaffected by local QRN, but your received signal is terribly affected by such noise. (Again, that's why some use on-ground or underground antennas for receiving. Local QRN is usually attenuated much more at ground level than the signals arriving from overhead, so such an antenna, while not providing as loud signals as a true "skywire" will often provide superior signal-to-noise ratios. The receiver makes up for the overall lower gain and so often you hear signals much better than with a skywire.) Ron AC7AC ___ 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] OT: K3 and antenna questions
Dave, W8FGU: Your questions are most appropriate, Elecraft and Amamteur Radio related. Dave wrote: Now my questions: 1 - with my antenna setup tuned with the KAT3, knowing that we were both at 5 watts, is it possible for the antenna to be more efficient at receiving than transmitting? I guess I always thought that if an antenna "system" is matched then the energy transfer is reciprocated for rcv and xmt. -Also might be one way propagation. 2 - with all the great receiver reports I've read on the K3 - could it be that I was simply hearing him better with my K3 than whatever he was using (unfortunately I don't know what he used as we never got that far in the QSO)? - that could be some of it. 3 - I did notice after the QSO that the balun was a little warm. If there are transmission losses in the balun, would there not be reciprocated losses on the receive side? - I doubt that 5 watts would heat it much, was it in the sun? That could heat it also. I have been getting interested in NVIS antennas and propagaton. This make me realize that low angles are not always the best for the desired communicatin. Yesterday (mid afternoon) I did some tests with a station 25 miles from me. We worked on 3523 KHz with weak signals, both running with 50 Watts. We tried 7023 KHz, nothing heard either way. Both our our antennas on those frequencies should have max raidation at 90°. >From the ARRL antenna book and other sources I made a chart of radiation angle >and distance covered. angle miles 80 50 72 100 63 150 56 200 49 250 42 350 29 500 Of course this also depends on the height of the refracting layer. You never said how far the other station was. I just made (noon here) a QSO from near Atlanta GA to a station near Miami FL. 600 miles. On 30 M, we gave each other 339 reports. It took several retrys for me to get his call. Such are the progagation conditions. 73, Ty, GA, W1TF, K3 #696 ___ 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] OT: K3 and antenna questions
Dave, Yes, the law of reciprocity applies on both TX and RX, but the K3 has a better receiver, so it is entirely possible for you to hear ones that you cannot work. His signal report to you indicates that is likely the case. Try your antenna without the balun - you should not notice heating at 5 watts unless there is considerable loss (maybe it was the sun shining on the balun :-) ). Usually in multi-band QRP field operations, a slightly unbalanced antenna radiation pattern is not a problem. If you end up with hot RF on the chassis, you can alter the feedline length to bring the impedance down and make the antenna easier to feed. Your current radiator plus feedline might have a high impedance at the rig end on 40 meters and up (the total feedline plus one leg of the antenna is near a half wave on 40m). 73, Don W3FPR Dave Van Wallaghen wrote: I apologize for the bandwidth, but I really trust the sources of info here and it may help someone else starting out like me with specific K3 info and antenna theory. I've been playing around with my K3 in a portable capacity out in my yard. Here is the setup: -K3 running @ 5W -Antenna: 66' doublet made from 28g wire fed with open feedline made from same, spaced apart with wood dowels 3" wide. It is placed up in a tree about 35' up with the ends coming down in an inverted v fashion. -The antenna is fed to a BL2 with a 12" piece of coax to the K3. I used a similar setup last summer with my K2 and had what I thought was pretty good success. In trying to evaluate this setup, I usually call CQ as opposed to answering one. This way I know that if I get a reply, the other op heard me. During the exchange I will state my power info to which I usually get positive comments about the K3 and/or the antenna setup - or they quickly sign off (not sure why they do that if I got a 599 report). Yesterday, I was tuning around 40m when I heard a station calling CQ - QRP on 7.059. He was a 479 here so I thought I would give him a call back. He answered and gave me a report of 359. After the initial exchange, he stated he could not copy me - we tried a couple more times and then signed off. He was a definite solid copy on my end with the S-meter hitting S1-3 at times with some QSB. It was like this the whole time. Now my questions: 1 - with my antenna setup tuned with the KAT3, knowing that we were both at 5 watts, is it possible for the antenna to be more efficient at receiving than transmitting? I guess I always thought that if an antenna "system" is matched then the energy transfer is reciprocated for rcv and xmt. 2 - with all the great receiver reports I've read on the K3 - could it be that I was simply hearing him better with my K3 than whatever he was using (unfortunately I don't know what he used as we never got that far in the QSO)? 3 - I did notice after the QSO that the balun was a little warm. If there are transmission losses in the balun, would there not be reciprocated losses on the receive side? If you feel this is not list appropriate, please reply to me privately. ___ 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
