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Originally Posted By Jambalaya: I have a dumb question with regards to the ducting described in a few of the posts above. Is the theory that an atmospheric layer is acting like a wave guide (like a fiber optic cable, or stream of water conducts light) to conduct the RF signal from one place to another? Basically, yes. |
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Originally Posted By markl32: Has anyone done NVIS with a 40m or 75/80m ham stick dipole? If so how'd it work? At what height were the antennas? I've done several 40m POTA activations with a ham stick dipole on a 24 foot telescoping painter's pole off the back of my pickup or wherever. If they are out there, you will definitely get the closer contacts. Attached File |
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Originally Posted By Ersatz_Naugahyde: I've done several 40m POTA activations with a ham stick dipole on a 24 foot telescoping painter's pole off the back of my pickup or wherever. If they are out there, you will definitely get the closer contacts. https://www.ar15.com/media/mediaFiles/601210/NfndDerby_jpg-3371038.JPG That's what I'm talking about!! |
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Originally Posted By markl32: Has anyone done NVIS with a 40m or 75/80m ham stick dipole? If so how'd it work? At what height were the antennas? Anything will work a little bit. People work the world with 5W and tiny antennas, they just have to work at it longer and harder. Size = performance. A hamstick or Buddistick dipole will be down 10dB (1.5 S-units) from a regular half wave dipole on 40M, and down 18dB (3 S-units) on 80M. If you are OK with that then you will be happy. As the FAQ above says, 1/4 wavelength high is optimum, so if you can raise it up about 30ft that'll be great for 40M and very reasonable for 80M. |
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Originally Posted By aa777888-2: Anything will work a little bit. People work the world with 5W and tiny antennas, they just have to work at it longer and harder. Size = performance. A hamstick or Buddistick dipole will be down 10dB (1.5 S-units) from a regular half wave dipole on 40M, and down 18dB (3 S-units) on 80M. If you are OK with that then you will be happy. As the FAQ above says, 1/4 wavelength high is optimum, so if you can raise it up about 30ft that'll be great for 40M and very reasonable for 80M. I spent 10 days working in TN and NC on recovery. I was, at the time, a tech class and operating vhf. We had a lot of issues from terrain to local hams shutting down repeaters to stifle our efforts. HF / NVIS worked always. Always. The whole experience had a large impact on me. I studied on the plane on the way back home and passed to General the following day. Now I want to make sure I can do NVIS anywhere, any terrain, regardless of trees or structures. That's the genesis of my question. We used chameleon end fed antennas on 40 and 80 NVIS and they worked great. But wondering about operating in the desert or somewhere with no viable trees. Thanks for the all the input. |
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Originally Posted By markl32: I spent 10 days working in TN and NC on recovery. I was, at the time, a tech class and operating vhf. We had a lot of issues from terrain to local hams shutting down repeaters to stifle our efforts. HF / NVIS worked always. Always. The whole experience had a large impact on me. I studied on the plane on the way back home and passed to General the following day. Now I want to make sure I can do NVIS anywhere, any terrain, regardless of trees or structures. That's the genesis of my question. We used chameleon end fed antennas on 40 and 80 NVIS and they worked great. But wondering about operating in the desert or somewhere with no viable trees. Thanks for the all the input. Originally Posted By markl32: Originally Posted By aa777888-2: Anything will work a little bit. People work the world with 5W and tiny antennas, they just have to work at it longer and harder. Size = performance. A hamstick or Buddistick dipole will be down 10dB (1.5 S-units) from a regular half wave dipole on 40M, and down 18dB (3 S-units) on 80M. If you are OK with that then you will be happy. As the FAQ above says, 1/4 wavelength high is optimum, so if you can raise it up about 30ft that'll be great for 40M and very reasonable for 80M. I spent 10 days working in TN and NC on recovery. I was, at the time, a tech class and operating vhf. We had a lot of issues from terrain to local hams shutting down repeaters to stifle our efforts. HF / NVIS worked always. Always. The whole experience had a large impact on me. I studied on the plane on the way back home and passed to General the following day. Now I want to make sure I can do NVIS anywhere, any terrain, regardless of trees or structures. That's the genesis of my question. We used chameleon end fed antennas on 40 and 80 NVIS and they worked great. But wondering about operating in the desert or somewhere with no viable trees. Thanks for the all the input. |
Mach
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Nobody is coming to save us.
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Originally Posted By aa777888-2: Horizontal full-wave loop vs. dipole is pretty much a wash in terms of NVIS performance. Both want to be at 1/4 wavelength in height. Modelling says they are within a dB of each other for NVIS. Here's an interesting link: https://www.hamradio.me/antennas/nvis-gain-of-loop-and-dipole-vs-height.html If one had the supports, this would be an interesting twist (pardon the pun) on using a loop on two bands for NVIS. http://practicalantennas.com/designs/loops/bowtie/ |
This is...a clue - Pat_Rogers
I'm not adequately aluminumized for this thread. - gonzo_beyondo
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I'm not adequately aluminumized for this thread. - gonzo_beyondo
CO, MI, OR - Please lobby your legislators to end discrimination against non-resident CCW permit holders
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Originally Posted By markl32: I spent 10 days working in TN and NC on recovery. I was, at the time, a tech class and operating vhf. We had a lot of issues from terrain to local hams shutting down repeaters to stifle our efforts. HF / NVIS worked always. Always. The whole experience had a large impact on me. I studied on the plane on the way back home and passed to General the following day. Now I want to make sure I can do NVIS anywhere, any terrain, regardless of trees or structures. That's the genesis of my question. We used chameleon end fed antennas on 40 and 80 NVIS and they worked great. But wondering about operating in the desert or somewhere with no viable trees. Thanks for the all the input. Originally Posted By markl32: Originally Posted By aa777888-2: Anything will work a little bit. People work the world with 5W and tiny antennas, they just have to work at it longer and harder. Size = performance. A hamstick or Buddistick dipole will be down 10dB (1.5 S-units) from a regular half wave dipole on 40M, and down 18dB (3 S-units) on 80M. If you are OK with that then you will be happy. As the FAQ above says, 1/4 wavelength high is optimum, so if you can raise it up about 30ft that'll be great for 40M and very reasonable for 80M. I spent 10 days working in TN and NC on recovery. I was, at the time, a tech class and operating vhf. We had a lot of issues from terrain to local hams shutting down repeaters to stifle our efforts. HF / NVIS worked always. Always. The whole experience had a large impact on me. I studied on the plane on the way back home and passed to General the following day. Now I want to make sure I can do NVIS anywhere, any terrain, regardless of trees or structures. That's the genesis of my question. We used chameleon end fed antennas on 40 and 80 NVIS and they worked great. But wondering about operating in the desert or somewhere with no viable trees. Thanks for the all the input. I like my spider beams 10m telescoping mast for a wire antenna support. Very handy. Easy up/down…… can run all sorts of antennas. Only pic on this ipad is with a VHF antenna. Attached File I have been doing some testing with a couple mobile antennas, its been fun playing with various setups. Attached File |
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Originally Posted By markl32: We used chameleon end fed antennas on 40 and 80 NVIS and they worked great. But wondering about operating in the desert or somewhere with no viable trees. Did a portable operation recently using 16 feet of mil surplus camo poles for a center support, just pulled the dipole elements off in an X shape to function as the guys with rope at the ends of the wires. 20 feet of 1 1/2 or 2 inch PVC pipe would work the same. Could make the whole thing off the shelf of the farm store in an hour probably. 100 feet of wire gets you a 40/20 fan dipole, another 140 feet or so to add 80 meters. Of course 40/60/80 would work better up a little higher, but will work at ~20 feet, especially if you're just looking for shorter range contacts. |
This is...a clue - Pat_Rogers
I'm not adequately aluminumized for this thread. - gonzo_beyondo
CO, MI, OR - Please lobby your legislators to end discrimination against non-resident CCW permit holders
I'm not adequately aluminumized for this thread. - gonzo_beyondo
CO, MI, OR - Please lobby your legislators to end discrimination against non-resident CCW permit holders
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Originally Posted By RFB: What is the brand/model of the angle-adjustable base mount attached to your truck? Thank you. Attached File |
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Originally Posted By aa777888-2: Horizontal full-wave loop vs. dipole is pretty much a wash in terms of NVIS performance. Both want to be at 1/4 wavelength in height. Modelling says they are within a dB of each other for NVIS. Here's an interesting link: https://www.hamradio.me/antennas/nvis-gain-of-loop-and-dipole-vs-height.html In my experience, in a low to zero noise environment this is true. An 80m EFHW inverted V transmits about the same as an 80m horizontal delta loop. The wow factor comes in when dealing with man made noise, where the loop is typically 2-4 S units quieter noise floor and same or better signal strength RX. |
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Originally Posted By tyrex13: In my experience, in a low to zero noise environment this is true. An 80m EFHW inverted V transmits about the same as an 80m horizontal delta loop. The wow factor comes in when dealing with man made noise, where the loop is typically 2-4 S units quieter noise floor and same or better signal strength RX. Originally Posted By tyrex13: Originally Posted By aa777888-2: Horizontal full-wave loop vs. dipole is pretty much a wash in terms of NVIS performance. Both want to be at 1/4 wavelength in height. Modelling says they are within a dB of each other for NVIS. Here's an interesting link: https://www.hamradio.me/antennas/nvis-gain-of-loop-and-dipole-vs-height.html In my experience, in a low to zero noise environment this is true. An 80m EFHW inverted V transmits about the same as an 80m horizontal delta loop. The wow factor comes in when dealing with man made noise, where the loop is typically 2-4 S units quieter noise floor and same or better signal strength RX. So-called End Fed antennas are about the worst setup for local noise, since they are generally using the feedline as a counterpoise, which brings noise right to the antenna. A good common mode choke/coax balun will help a lot with noise on a dipole. Most of the perceived noise advantage of the loop is that they tend to reject common mode noise from the feedline better than a dipole when both are just connected directly to feedlines. Much local noise is picked up on feedlines and conducted out to the antenna if there aren't any chokes to stop it. |
This is...a clue - Pat_Rogers
I'm not adequately aluminumized for this thread. - gonzo_beyondo
CO, MI, OR - Please lobby your legislators to end discrimination against non-resident CCW permit holders
I'm not adequately aluminumized for this thread. - gonzo_beyondo
CO, MI, OR - Please lobby your legislators to end discrimination against non-resident CCW permit holders
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Originally Posted By Gamma762: So-called End Fed antennas are about the worst setup for local noise, since they are generally using the feedline as a counterpoise, which brings noise right to the antenna. A good common mode choke/coax balun will help a lot with noise on a dipole. Most of the perceived noise advantage of the loop is that they tend to reject common mode noise from the feedline better than a dipole when both are just connected directly to feedlines. Much local noise is picked up on feedlines and conducted out to the antenna if there aren't any chokes to stop it. I have not seen evidence of coax shielding picking up noise nor have I seen a good choke baluns reduce noise on an antenna system. End feds are dipoles and I have not seen a center fed dipole have different noise characteristics as an off center fed dipole or an end fed dipole installed in the same location. I’m working on a YouTube video series that will A/B antennas and hopefully dispel a lot of the conjecture. |