wrapping ssb antenna on kevlar backstay
Dear all
May I pick-up on something mentioned in response to my earlier question. It was suggested that running a wire up a kevlar backstay is a simple soultion and avoids having to insulate a piece of conventional rigging. This sounds very sensible to me and plan to try it, it avoids having to mess with exposed connections to a wire backstay. However then Bruce in alaska said: Then just helical wrap the antenna wire around the Kevlar Backstay and have a really nice "Fully Loaded Antenna with alot of electrical length...... Could someone (Bruce perhaps?) explain this. Would I gain performance by simply wrapping the wire ? Is no of turns per length of backstay critical ? Is 'core' diameter critical ? Thanks Steve |
wrapping ssb antenna on kevlar backstay
"Steve (another one)" wrote in
: Dear all May I pick-up on something mentioned in response to my earlier question. It was suggested that running a wire up a kevlar backstay is a simple soultion and avoids having to insulate a piece of conventional rigging. This sounds very sensible to me and plan to try it, it avoids having to mess with exposed connections to a wire backstay. Isn't Kevlar made of CARBON fibers? Carbon, being a conductor and electrical dummy load, used in resistors for converting electrical energy (i.e. HF signals) into heat. Larry. |
wrapping ssb antenna on kevlar backstay
I looked up the Kevlar website at:
http://www.dupont.com/kevlar/whatiskevlar.html One interesting thing it says is: "Low Electrical Conductivity" What's interesting is what it DOESN'T say...NO electrical conductivity. Food cooking in my microwave oven has "low electrical conductivity", too, as it converts microwaves into heat. Most interesting topic. Dupont doesn't mention anything else as they try to sell the stuff. Larry |
wrapping ssb antenna on kevlar backstay
Actually, Kevlar and similar arimids have a dielectric constant range of
3.5 to 4.5 compared to plexiglass at 2.6 to 3.5. Larry W4CSC wrote: I looked up the Kevlar website at: http://www.dupont.com/kevlar/whatiskevlar.html One interesting thing it says is: "Low Electrical Conductivity" What's interesting is what it DOESN'T say...NO electrical conductivity. Food cooking in my microwave oven has "low electrical conductivity", too, as it converts microwaves into heat. Most interesting topic. Dupont doesn't mention anything else as they try to sell the stuff. Larry -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
wrapping ssb antenna on kevlar backstay
Steve (another one) wrote:
Dear all May I pick-up on something mentioned in response to my earlier question. It was suggested that running a wire up a kevlar backstay is a simple soultion and avoids having to insulate a piece of conventional rigging. This sounds very sensible to me and plan to try it, it avoids having to mess with exposed connections to a wire backstay. However then Bruce in alaska said: Then just helical wrap the antenna wire around the Kevlar Backstay and have a really nice "Fully Loaded Antenna with alot of electrical length...... Could someone (Bruce perhaps?) explain this. Would I gain performance by simply wrapping the wire ? Is no of turns per length of backstay critical ? Is 'core' diameter critical ? Thanks Steve Whilst Kevlar rope has high tensile strength and low weight, they fail to mention that it weakens rapidly under flexion, i.e. it should never be knotted or doubled back on itself, as when seizing around a snall-diameter thimble. I would think that poses several problem when using as a backstay, unless some kind of patent terminals are available. Our Kevlar main halyard parted quite suddenly and without warning at the thimble a few years ago, and I resolved to go back to wire-spliced pre-stretched polyester in future. Remove "nospam" from return address. |
wrapping ssb antenna on kevlar backstay
I am the one who posted re the kevlar backstay. I implemented it and used
the setup on a recent Mexico trip. I can only tell you that my rig was probably the best in the fleet of several boats. A lot of racing sailboats are switching their rod or wire backstays to Aramid at this time. The weight savings is dramatic, and the cost is roughly half of what a backstay with insulators would cost. It's interesting that with all the expertise on antennas in this group none sees fit to answer your original question, but rather they choose to critique a proven rigging advance. "Steve (another one)" wrote in message ... Dear all May I pick-up on something mentioned in response to my earlier question. It was suggested that running a wire up a kevlar backstay is a simple soultion and avoids having to insulate a piece of conventional rigging. This sounds very sensible to me and plan to try it, it avoids having to mess with exposed connections to a wire backstay. However then Bruce in alaska said: Then just helical wrap the antenna wire around the Kevlar Backstay and have a really nice "Fully Loaded Antenna with alot of electrical length...... Could someone (Bruce perhaps?) explain this. Would I gain performance by simply wrapping the wire ? Is no of turns per length of backstay critical ? Is 'core' diameter critical ? Thanks Steve |
wrapping ssb antenna on kevlar backstay
While I don't know much about the properties of kevlar, electrical or
physical, if it has good electrical properties at the RF frequencies involved then it should work ok. As far as wrapping the wire around it, I would use a very long wrap. Not many turns. While more turns will probably make an excellent antenna for the low frequencies, 2 and 4 mhz, it will hinder the higher frequencies. The coil will act as a choke at the higher frequencies and not allow them to pass. It will effectively make a rather short antenna at the higher frequencies. When the old 2 mhz marine antennas were made they had a wound coil in the fiberglass whip. It performed much better on 2 mhz than a straight whip with no coil. But it was next to useless on frequencies above 4 mhz as the coil effectively disconnected the upper part of the antenna on the higher frequencies. With the higher frequencies in common use now you will never see one of those loaded antennas in service anymore. Unless it is a dedicated 2 mhz antenna and there are other antennas for the other frequencies. That is the best of both worlds. Regards Gary On Sat, 12 Jun 2004 12:05:08 -0700, "Max Lynn" wrote: I am the one who posted re the kevlar backstay. I implemented it and used the setup on a recent Mexico trip. I can only tell you that my rig was probably the best in the fleet of several boats. A lot of racing sailboats are switching their rod or wire backstays to Aramid at this time. The weight savings is dramatic, and the cost is roughly half of what a backstay with insulators would cost. It's interesting that with all the expertise on antennas in this group none sees fit to answer your original question, but rather they choose to critique a proven rigging advance. "Steve (another one)" wrote in message ... Dear all May I pick-up on something mentioned in response to my earlier question. It was suggested that running a wire up a kevlar backstay is a simple soultion and avoids having to insulate a piece of conventional rigging. This sounds very sensible to me and plan to try it, it avoids having to mess with exposed connections to a wire backstay. However then Bruce in alaska said: Then just helical wrap the antenna wire around the Kevlar Backstay and have a really nice "Fully Loaded Antenna with alot of electrical length...... Could someone (Bruce perhaps?) explain this. Would I gain performance by simply wrapping the wire ? Is no of turns per length of backstay critical ? Is 'core' diameter critical ? Thanks Steve |
wrapping ssb antenna on kevlar backstay
In article ,
"Steve (another one)" wrote: Dear all May I pick-up on something mentioned in response to my earlier question. It was suggested that running a wire up a kevlar backstay is a simple soultion and avoids having to insulate a piece of conventional rigging. This sounds very sensible to me and plan to try it, it avoids having to mess with exposed connections to a wire backstay. However then Bruce in alaska said: Then just helical wrap the antenna wire around the Kevlar Backstay and have a really nice "Fully Loaded Antenna with alot of electrical length...... Could someone (Bruce perhaps?) explain this. Would I gain performance by simply wrapping the wire ? Is no of turns per length of backstay critical ? Is 'core' diameter critical ? Thanks Steve Gary has a valid point in that a tightly wound helical wire will tend to trap out the higher frequencies in the HF range. One thing to remeber however, is that if the band is open it doesn't take as efficent of antenna to communicate on these Higher Frequencies, and if the band is closed, no amount of antenna tuning or fooling around is going to allow communications. Where as on MF Frequencies, one needs all the length one can get for an efficent antenna, and the band is what it is, and really doesn't change much as far as open or closed, except for Day and Night. Better distances at night than during the day. A good compromise would seem to be a resonate 1/4 Wave at say 3200 Khz would allow for far efficency at 2182 Khz, by wrapping the helical windings tighter at the top of the antenna, give a reasonable length of wire on the lower part to resonate with the tuner at 12 Mhz, 16 Mhz, and 22 Mhz. Bruce in alaska -- add a 2 before @ |
wrapping ssb antenna on kevlar backstay
Oh boy..here we go...laughing.... see below....
On Sun, 13 Jun 2004 01:05:51 GMT, Bruce in Alaska wrote: In article , "Steve (another one)" wrote: Dear all May I pick-up on something mentioned in response to my earlier question. It was suggested that running a wire up a kevlar backstay is a simple soultion and avoids having to insulate a piece of conventional rigging. This sounds very sensible to me and plan to try it, it avoids having to mess with exposed connections to a wire backstay. However then Bruce in alaska said: Then just helical wrap the antenna wire around the Kevlar Backstay and have a really nice "Fully Loaded Antenna with alot of electrical length...... Could someone (Bruce perhaps?) explain this. Would I gain performance by simply wrapping the wire ? Is no of turns per length of backstay critical ? Is 'core' diameter critical ? Thanks Steve Gary has a valid point in that a tightly wound helical wire will tend to trap out the higher frequencies in the HF range. One thing to remeber however, is that if the band is open it doesn't take as efficent of antenna to communicate on these Higher Frequencies, and if the band is closed, no amount of antenna tuning or fooling around is going to allow communications. Where as on MF Frequencies, one needs all the length one can get for an efficent antenna, and the band is what it is, and really doesn't change much as far as open or closed, except for Day and Night. Better distances at night than during the day. A good compromise would seem to be a resonate 1/4 Wave at say 3200 Khz would allow for far efficency at 2182 Khz, by wrapping the helical windings tighter at the top of the antenna, give a reasonable length of wire on the lower part to resonate with the tuner at 12 Mhz, 16 Mhz, and 22 Mhz. Bruce in alaska Bruce has an excellent point re the windings...but I see a problem. Given a kelvar backstay length, how would one compute the pitch of the wrap? A turn every 6 inches for the first 2/3rds? Then every 2-3 inches for the remainder? Ouiji board? This topic is so interesting to me that short of buying a network analyzer, (I'll be honest, I can't afford one), I'm determined to figure out what simple test equipment I can use to evaluate various configurations, and then test them. Any ideas? Norm B |
wrapping ssb antenna on kevlar backstay
Glenn Ashmore wrote in
news:7jsyc.155$3W3.81@lakeread04: Actually, Kevlar and similar arimids have a dielectric constant range of 3.5 to 4.5 compared to plexiglass at 2.6 to 3.5. Then wrapping it should work just great..... |
wrapping ssb antenna on kevlar backstay
Bruce in Alaska wrote in
: day. A good compromise would seem to be a resonate 1/4 Wave at say 3200 Khz would allow for far efficency at 2182 Khz, by wrapping the helical windings tighter at the top of the antenna, give a reasonable length of wire on the lower part to resonate with the tuner at 12 Mhz, 16 Mhz, and 22 Mhz. Bruce in alaska I like the idea of the Kevlar as an insulator. But, instead of making it into some kind of untuned RF choke, why don't we make it into a TRAP SLOPER vertical by putting traps on the Kevlar, interconnected by straight conductors, for the upper bands, above the natural resonant length of the whole distance from feedpoint to mast, THEN use the tuner when the length of the backstay becomes too short. The coils in the traps will lower the natural resonant frequency below a straight backstay. The trap capacitors are too small to be significant at the low frequency bands. Below the natural resonance, the traps act like loading coils for the tuner, drawing more antenna CURRENT up the too-short radiator, which is never bad for good radiation. On any marine or ham band the traps are set up for, no tuner will be required and a resonant antenna is always a better radiator than this stupid old marine base-loaded clothes line or flagpole we're using, now. Larry Above 40 meters, you could leave the lossy tuner in THRU....(c; |
wrapping ssb antenna on kevlar backstay
In article ,
engsol wrote: Oh boy..here we go...laughing.... see below.... snipped for brevity Bruce has an excellent point re the windings...but I see a problem. Given a kelvar backstay length, how would one compute the pitch of the wrap? A turn every 6 inches for the first 2/3rds? Then every 2-3 inches for the remainder? Ouiji board? This topic is so interesting to me that short of buying a network analyzer, (I'll be honest, I can't afford one), I'm determined to figure out what simple test equipment I can use to evaluate various configurations, and then test them. Any ideas? Norm B Actually most of the work in this area was done by Ed Zanbergen, while he was Principal Partner and Chief Engineer of MORAD Electronics in Seattle, Wa. MORAD antennas are the defacto standard for commercial vessels in the North Pacific. They build some of the most rugged and effective antennas in the Marine Mobile Radio Service. Ed is long since gone to the Great Radioroom in the Sky, but his legacy is still around and being produced by MORAD today. When I was a beginner in this bizz, I worked for Northern Radio Co. which had a shop next door to Morad, and Ed and I became very good friends. I still have some custom antennas that he built for me, specifically for MF/HF Coast Station installations in alaska. I don't know if any of his notes were ever published, but he spent 40 years designing antennas in these Radio Services. One of the better designs that Ed built for me was a pair of matched Helically Loaded Whips that were resonate at 3300Khz. I mounted them at 60 Ft in a Dipole configuration, with PhosBronze feedwire, connected at the end of the 15 Ft Base tubes. Then feeding down to an Experimental SEA 1612B Autotuner that has twin tuning boards driven by a single CPU/ Sensor System, so that both dipole legs are effectivly tuned by the autotuner. This antenna can be heard, evey summer on the Marine Freqs as KWO-70/WDT-59 and operations on all Marine Bands from 2003Khz to 25 Mhz. Bruce in alaska -- add a 2 before @ |
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