Re: [Elecraft] Using your tower as a vertical - 160 or 80
Rich, Thanks for your reply; very helpful! Something similar to your shunt feeding method is what I have had in mind. Since my tower is a crankup (55 ft topped by about 22 ft of mast+antennas), I do have some misgivings about managing the wire running parallel to the tower, in the scenario where the tower sections are telescoping and releasing the tension on the wire. Maybe I should first try attaching the feed to the top of the bottom section rather than the top of the tower. The most interesting part of your installation is your grounding of most of the coax cables at the tower base, and also at the entry box. When I installed my tower in 1993 I had read a recommendation to let the cables form a gentle curve almost touching ground, which is what I did. The idea of grounding them at the tower base did not occur to me, and doesn't seem compatible with the gentle curve concept. At the house I did think about feedthrough panel that could be grounded, but I was in a hurry and didn't do the work. Some of my vhf/uhf cables are of the thick variety (much thicker than RG-213, and extra connectors cost significant money. Since then, it has been on my to-do list to go back, cut the cables, install connectors, and install a grounded plate or box. At the time when I wanted to try the tower as a 160 vertical, I didn't feel confident that doing that work would be as effective as choking off common mode currents with ferrites, and that did seem to work well as long as the cables fit in the device. After reading your post I get the impression that instead of obtaining choke(s) for the cable bundle as it is today, I should do the work of grounding the cables at the house entry and also at the tower base. For non-coax control cables I could apply my choke. You state that not all of your cables were grounded. For such a situation my first thought is that the result would depend on cable length and frequency, and if there is no problem in your situation then luck might have played a role. You did not mention trying your setup for 80. In my case, I have more need for 80m than 160, and I am still unsure if the whole metal tree might be on the big side for 80. That should be easy to determine with a model. Thanks for the details of your ground system. If I were to erect a separate vertical for 80, I would have to install a lot of radials, so doing the same around the tower is not a big deal. Like in your case, most of the radials would be on one side of the tower (directed away from the house). When I did feed the tower on 160 as an experiment years ago, I had (and still have) just two ground rods at the base, plus copper ribbon, which was meant to encircle the house, a project that was never finished, but has been on my to-do list ever since. I see a lot of similarity with your situation, but I need to put in some work to catch up! Now, supposing I get it all done, and it all works as expected, the next step is seeing the resulting 80m capability in the context of a 2-radio system. Obviously, only one radio can be on 80 at a given time, and it will use a bandpass filter but not a multiplexer. The 80m antenna (=tower) will be closer to the beam than my high-band vertical.The 80m rf will flow in very close proximity to the beam, the use of which by another radio is protected by both the multiplexer and the applicable bandpass filter. Will that be enough protection, given that the proximity situation is worse than with the high-band vertical? I am not totally sure, but it seems a reasonably good bet to me. 73, Erik K7TV --- Erik, I've been feeding K3 RF to my house bracketed, 75 ft Rohn 25 tower for years with great success on 160 Meters. The tower is topped with HF and VHF yagis which act as a capacitive top hat. The 50 Ohm coax feedline is connected to a tap on the coil of a parallel tuned circuit. The top of the LC circuit is connected to a #16 THHN wire which runs parallel to the tower, about 18" outside one of the legs and connects to a bolt around 10 ft down from the top of the tower. At the base of the tower I simply tune the capacitor and find the best spot on the coil to tap to obtain the lowest SWR. There are 16 quarter wave radials around the tower, most of them on the tower side of the house from south to north and a few wrapping around and under the back deck toward the northeast. There are around a dozen 8 ft ground rods connected to the tower with #6 wire and the tower also is connected to a perimeter ground system surrounding the house. The shields of most, but not all, of the coax cables leaving the tower are grounded at the tower base. Before all coax and control cables enter the shack they all are grounded at the steel entry box around 30 feet from the tower base. So how does a shunt fed 75 ft
Re: [Elecraft] Using your tower as a vertical - 160 or 80
Erik, I've been feeding K3 RF to my house bracketed, 75 ft Rohn 25 tower for years with great success on 160 Meters. The tower is topped with HF and VHF yagis which act as a capacitive top hat. The 50 Ohm coax feedline is connected to a tap on the coil of a parallel tuned circuit. The top of the LC circuit is connected to a #16 THHN wire which runs parallel to the tower, about 18" outside one of the legs and connects to a bolt around 10 ft down from the top of the tower. At the base of the tower I simply tune the capacitor and find the best spot on the coil to tap to obtain the lowest SWR. There are 16 quarter wave radials around the tower, most of them on the tower side of the house from south to north and a few wrapping around and under the back deck toward the northeast. There are around a dozen 8 ft ground rods connected to the tower with #6 wire and the tower also is connected to a perimeter ground system surrounding the house. The shields of most, but not all, of the coax cables leaving the tower are grounded at the tower base. Before all coax and control cables enter the shack they all are grounded at the steel entry box around 30 feet from the tower base. So how does a shunt fed 75 ft tower work with a barefoot K3 feeding it? With 100 Watts I've confirmed 229 countries on the Topband and have worked 89 countries on all continents with QRP 5 Watts. You can check out the 160M QRP WAC cards at: http://www.qrz.com/db/K1HTV If you haven't tried shunt feeding your grounded tower, give it a try. You may be surprised at how well it can work on 160 Meters. 73, Rich - K1HTV = = = Erik, K7TV wrote: Years ago, after putting up a heavy-duty crank-up tower with several antennas on a tall mast at the top, I was interested in loading up the whole metal tree for 160 and/or 80. However, I didn't like the prospect of transmitted power getting back into the shack via the existing feedlines, causing all kinds of problems including losses. From a surplus vendor I obtained four square slabs of ferrite (no spec's) and taped them together to form a box-shaped common mode choke around the existing feedlines (and rotor control cable etc). I didn't have radials at the tower base, but a couple of long and wide copper strips buried and connected to ground rods to which the tower was grounded. I opened up the tower ground connection and I had a feed point. Finding resonance was not as easy as using my antenna analyzer. The signal from the analyzer was overwhelmed by picked-up broadcast signals, rendering the analyzer unuseable. I got by using a custom measurement setup. It turned out that the entire metal tree resonated in the broadcast band and was inductive at 160. I tuned it with a serial variable capacitor, and found the antenna worked very well on 160. However, I didn't continue using it, as I didn't feel safe not to have the tower grounded. I pondered schemes to add some kind of gamma-like matching device, but never got around to it. Also I never tried it on 80, but I suspect it would not been ideal for low angle radiation. Later I added more antennas to the mast, and with the added cables, the whole bundle would no longer fit in the makeshift ferrite choke. Out of curiosity I once again tried ungrounding the tower to check on its characteristics as a vertical antenna. I could no longer find the resonance I had seen and used before. Apparently, the ferrite choke had been a crucial part of the scheme. At this point I still don't have an antenna for 160 or 80. (I did try an inverted vee off the tower for 80, but it caused terrible de-tuning of the 40m part of my beam on the tower, so I gave up on that. Maybe I should try a sloper.) I am thinking of putting up a dedicated vertical, but on my small lot it would couple to the tower. Perhaps it would be better to give the tower another look as my low-band vertical? My source of ferrite slabs dried up years ago. I wonder if anyone else on the list has used a similar approach and found a good way to choke off RF on a bundle of feedlines? Individual chokes don't seem very attractive to me as I have many cables, but if one has to go that route then it would make sense to look very carefully at the choice of chokes. I would also be interested in knowing about others' experiences with feed systems that leave the tower grounded. Thanks in advance for any useful ideas! 73, Erik K7TV __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] Using your tower as a vertical - 160 or 80
Hi Erik, It is certainly possible to use a separate filter in the feedline to each antenna. For example, here's an article I wrote many years ago on how to homebrew your own: http://p1k.arrl.org/pubs_archive/89595 Those filters are only good for 100W or so, but there is no fundamental reason they couldn't be scaled up to 1500W. I haven't researched it, but I'm thinking there must be commercial equivalents as well. Alan N1AL On 02/28/2017 10:41 PM, Erik Basilier wrote: Alan, Thanks for your reply. Your approach would provide 40m capability to replace the 40m capability that my (Sommer) beam loses through detuning. However, I wonder how hard your tuner must work on 40? Enough to create substantial feedline losses when the tuner is in the shack? Anyway, I have another reason not to choose your approach: I am rebuilding my station to support SO2R, and it is tough to avoid interference between the two radios operating on different bands, especially 40 - 20 and with the antennas close together. I found to my surprise, before the QST review came out, that the Low Band Systems multiplexer and band pass filters (my setup includes 40m) eliminates the interference problem. However, this scheme requires that the antennas be on a shared feedline. With your approach the 40m antenna would no longer be on the same feedline as the higher bands. -Original Message- From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Alan Bloom Sent: Tuesday, February 28, 2017 11:09 PM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] Using your tower as a vertical - 160 or 80 I use two of the top guy wires as an inverted vee. There are insulators near the top of the guys and about 50 feet or so down. The vee is brought to resonance on 80 meters with a center-tapped loading coil, which also acts as a balun. The best match was with the coax tapped right about at the end of one side of the coil (and of course the coax shield to the grounded center tap). Works great on 80 meters without a tuner and on 40 meters with a tuner. Alan N1AL On 02/28/2017 09:42 PM, Erik Basilier wrote: Years ago, after putting up a heavy-duty crank-up tower with several antennas on a tall mast at the top, I was interested in loading up the whole metal tree for 160 and/or 80. However, I didn't like the prospect of transmitted power getting back into the shack via the existing feedlines, causing all kinds of problems including losses. From a surplus vendor I obtained four square slabs of ferrite (no spec's) and taped them together to form a box-shaped common mode choke around the existing feedlines (and rotor control cable etc). I didn't have radials at the tower base, but a couple of long and wide copper strips buried and connected to ground rods to which the tower was grounded. I opened up the tower ground connection and I had a feed point. Finding resonance was not as easy as using my antenna analyzer. The signal from the analyzer was overwhelmed by picked-up broadcast signals, rendering the analyzer unuseable. I got by using a custom measurement setup. It turned out that the entire metal tree resonated in the broadcast band and was inductive at 160. I tuned it with a serial variable capacitor, and found the antenna worked very well on 160. However, I didn't continue using it, as I didn't feel safe not to have the tower grounded. I pondered schemes to add some kind of gamma-like matching device, but never got around to it. Also I never tried it on 80, but I suspect it would not been ideal for low angle radiation. Later I added more antennas to the mast, and with the added cables, the whole bundle would no longer fit in the makeshift ferrite choke. Out of curiosity I once again tried ungrounding the tower to check on its characteristics as a vertical antenna. I could no longer find the resonance I had seen and used before. Apparently, the ferrite choke had been a crucial part of the scheme. At this point I still don't have an antenna for 160 or 80. (I did try an inverted vee off the tower for 80, but it caused terrible de-tuning of the 40m part of my beam on the tower, so I gave up on that. Maybe I should try a sloper.) I am thinking of putting up a dedicated vertical, but on my small lot it would couple to the tower. Perhaps it would be better to give the tower another look as my low-band vertical? My source of ferrite slabs dried up years ago. I wonder if anyone else on the list has used a similar approach and found a good way to choke off RF on a bundle of feedlines? Individual chokes don't seem very attractive to me as I have many cables, but if one has to go that route then it would make sense to look very carefully at the choice of chokes. I would also be interested in knowing about others' experiences with feed systems that leave the tower grounded. Thanks in advance for any useful ideas! 73, Erik K7TV __ Elecraft mailing
Re: [Elecraft] Using your tower as a vertical - 160 or 80
Alan, Thanks for your reply. Your approach would provide 40m capability to replace the 40m capability that my (Sommer) beam loses through detuning. However, I wonder how hard your tuner must work on 40? Enough to create substantial feedline losses when the tuner is in the shack? Anyway, I have another reason not to choose your approach: I am rebuilding my station to support SO2R, and it is tough to avoid interference between the two radios operating on different bands, especially 40 - 20 and with the antennas close together. I found to my surprise, before the QST review came out, that the Low Band Systems multiplexer and band pass filters (my setup includes 40m) eliminates the interference problem. However, this scheme requires that the antennas be on a shared feedline. With your approach the 40m antenna would no longer be on the same feedline as the higher bands. -Original Message- From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Alan Bloom Sent: Tuesday, February 28, 2017 11:09 PM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] Using your tower as a vertical - 160 or 80 I use two of the top guy wires as an inverted vee. There are insulators near the top of the guys and about 50 feet or so down. The vee is brought to resonance on 80 meters with a center-tapped loading coil, which also acts as a balun. The best match was with the coax tapped right about at the end of one side of the coil (and of course the coax shield to the grounded center tap). Works great on 80 meters without a tuner and on 40 meters with a tuner. Alan N1AL On 02/28/2017 09:42 PM, Erik Basilier wrote: > Years ago, after putting up a heavy-duty crank-up tower with several > antennas on a tall mast at the top, I was interested in loading up the > whole metal tree for 160 and/or 80. However, I didn't like the > prospect of transmitted power getting back into the shack via the > existing feedlines, causing all kinds of problems including losses. > From a surplus vendor I obtained four square slabs of ferrite (no > spec's) and taped them together to form a box-shaped common mode choke > around the existing feedlines (and rotor control cable etc). I didn't > have radials at the tower base, but a couple of long and wide copper > strips buried and connected to ground rods to which the tower was > grounded. I opened up the tower ground connection and I had a feed > point. Finding resonance was not as easy as using my antenna analyzer. > The signal from the analyzer was overwhelmed by picked-up broadcast signals, rendering the analyzer unuseable. I got by using a custom measurement setup. > It turned out that the entire metal tree resonated in the broadcast > band and was inductive at 160. I tuned it with a serial variable > capacitor, and found the antenna worked very well on 160. However, I > didn't continue using it, as I didn't feel safe not to have the tower > grounded. I pondered schemes to add some kind of gamma-like matching > device, but never got around to it. Also I never tried it on 80, but I > suspect it would not been ideal for low angle radiation. > > > > Later I added more antennas to the mast, and with the added cables, > the whole bundle would no longer fit in the makeshift ferrite choke. > Out of curiosity I once again tried ungrounding the tower to check on > its characteristics as a vertical antenna. I could no longer find the > resonance I had seen and used before. Apparently, the ferrite choke > had been a crucial part of the scheme. > > > > At this point I still don't have an antenna for 160 or 80. (I did try > an inverted vee off the tower for 80, but it caused terrible de-tuning > of the 40m part of my beam on the tower, so I gave up on that. Maybe I > should try a > sloper.) I am thinking of putting up a dedicated vertical, but on my > small lot it would couple to the tower. Perhaps it would be better to > give the tower another look as my low-band vertical? My source of > ferrite slabs dried up years ago. I wonder if anyone else on the list > has used a similar approach and found a good way to choke off RF on a bundle of feedlines? > Individual chokes don't seem very attractive to me as I have many > cables, but if one has to go that route then it would make sense to > look very carefully at the choice of chokes. I would also be > interested in knowing about others' experiences with feed systems that leave the tower grounded. > > > > Thanks in advance for any useful ideas! > > > > 73, > > Erik K7TV > > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: ma
Re: [Elecraft] Using your tower as a vertical - 160 or 80
I use two of the top guy wires as an inverted vee. There are insulators near the top of the guys and about 50 feet or so down. The vee is brought to resonance on 80 meters with a center-tapped loading coil, which also acts as a balun. The best match was with the coax tapped right about at the end of one side of the coil (and of course the coax shield to the grounded center tap). Works great on 80 meters without a tuner and on 40 meters with a tuner. Alan N1AL On 02/28/2017 09:42 PM, Erik Basilier wrote: Years ago, after putting up a heavy-duty crank-up tower with several antennas on a tall mast at the top, I was interested in loading up the whole metal tree for 160 and/or 80. However, I didn't like the prospect of transmitted power getting back into the shack via the existing feedlines, causing all kinds of problems including losses. From a surplus vendor I obtained four square slabs of ferrite (no spec's) and taped them together to form a box-shaped common mode choke around the existing feedlines (and rotor control cable etc). I didn't have radials at the tower base, but a couple of long and wide copper strips buried and connected to ground rods to which the tower was grounded. I opened up the tower ground connection and I had a feed point. Finding resonance was not as easy as using my antenna analyzer. The signal from the analyzer was overwhelmed by picked-up broadcast signals, rendering the analyzer unuseable. I got by using a custom measurement setup. It turned out that the entire metal tree resonated in the broadcast band and was inductive at 160. I tuned it with a serial variable capacitor, and found the antenna worked very well on 160. However, I didn't continue using it, as I didn't feel safe not to have the tower grounded. I pondered schemes to add some kind of gamma-like matching device, but never got around to it. Also I never tried it on 80, but I suspect it would not been ideal for low angle radiation. Later I added more antennas to the mast, and with the added cables, the whole bundle would no longer fit in the makeshift ferrite choke. Out of curiosity I once again tried ungrounding the tower to check on its characteristics as a vertical antenna. I could no longer find the resonance I had seen and used before. Apparently, the ferrite choke had been a crucial part of the scheme. At this point I still don't have an antenna for 160 or 80. (I did try an inverted vee off the tower for 80, but it caused terrible de-tuning of the 40m part of my beam on the tower, so I gave up on that. Maybe I should try a sloper.) I am thinking of putting up a dedicated vertical, but on my small lot it would couple to the tower. Perhaps it would be better to give the tower another look as my low-band vertical? My source of ferrite slabs dried up years ago. I wonder if anyone else on the list has used a similar approach and found a good way to choke off RF on a bundle of feedlines? Individual chokes don't seem very attractive to me as I have many cables, but if one has to go that route then it would make sense to look very carefully at the choice of chokes. I would also be interested in knowing about others' experiences with feed systems that leave the tower grounded. Thanks in advance for any useful ideas! 73, Erik K7TV __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to n...@sonic.net __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
[Elecraft] Using your tower as a vertical - 160 or 80
Years ago, after putting up a heavy-duty crank-up tower with several antennas on a tall mast at the top, I was interested in loading up the whole metal tree for 160 and/or 80. However, I didn't like the prospect of transmitted power getting back into the shack via the existing feedlines, causing all kinds of problems including losses. From a surplus vendor I obtained four square slabs of ferrite (no spec's) and taped them together to form a box-shaped common mode choke around the existing feedlines (and rotor control cable etc). I didn't have radials at the tower base, but a couple of long and wide copper strips buried and connected to ground rods to which the tower was grounded. I opened up the tower ground connection and I had a feed point. Finding resonance was not as easy as using my antenna analyzer. The signal from the analyzer was overwhelmed by picked-up broadcast signals, rendering the analyzer unuseable. I got by using a custom measurement setup. It turned out that the entire metal tree resonated in the broadcast band and was inductive at 160. I tuned it with a serial variable capacitor, and found the antenna worked very well on 160. However, I didn't continue using it, as I didn't feel safe not to have the tower grounded. I pondered schemes to add some kind of gamma-like matching device, but never got around to it. Also I never tried it on 80, but I suspect it would not been ideal for low angle radiation. Later I added more antennas to the mast, and with the added cables, the whole bundle would no longer fit in the makeshift ferrite choke. Out of curiosity I once again tried ungrounding the tower to check on its characteristics as a vertical antenna. I could no longer find the resonance I had seen and used before. Apparently, the ferrite choke had been a crucial part of the scheme. At this point I still don't have an antenna for 160 or 80. (I did try an inverted vee off the tower for 80, but it caused terrible de-tuning of the 40m part of my beam on the tower, so I gave up on that. Maybe I should try a sloper.) I am thinking of putting up a dedicated vertical, but on my small lot it would couple to the tower. Perhaps it would be better to give the tower another look as my low-band vertical? My source of ferrite slabs dried up years ago. I wonder if anyone else on the list has used a similar approach and found a good way to choke off RF on a bundle of feedlines? Individual chokes don't seem very attractive to me as I have many cables, but if one has to go that route then it would make sense to look very carefully at the choice of chokes. I would also be interested in knowing about others' experiences with feed systems that leave the tower grounded. Thanks in advance for any useful ideas! 73, Erik K7TV __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
