Near Vertical incidence Skywave Propagation NVIS Antennas - Ham Radio Q&A

Nice video. You can use any horizontal wire for NVIS. Like a random length wire or an end fed as long as it's horizontal and around 8 feet or so in height.

Thanks for the NVIS info and demonstration. Living in an HOA community I am using a stealth 53' EFLW at about 12' center and 9' each end thus giving me the NVIS effect. 90% of my contacts are within 350 miles. DX is very rare for me unless running FT-8. But, I am making contacts so I can't complain. 73!

How do you think the metal roof of your camper trailer may have influenced the propagation?

i got a 40 meter dipole i'm going to use mostly for WSPR, i'm interested on what i will receive via NVIS.I was very impressed with your QSO on Telephony (albeit on 50W - I can only 10W). your explanation and demo was very good. thank you !

Just passed my test(s) two days ago, technician and general, so I love watching these to learn. Just waiting for my call sign to post. This weekend is driving me crazy!

Very helpful. My brother-in-law and I live about 200 miles apart. So, we are skipping over the top of each other on HF. Thought we might try NVIS, and your video convinces me to give it a go. Thanks very much. BTW, still using the jpole at 35' for my vhf. Works great!

Great video!

so just any HF antenna mounted at a lower height? am i following correctly for NVIS ops?

Michael,
Can you give me details on the antenna that you used in this demo?
Thanks .73 George KB3WAQ

Great explanation, KN9VBR. THANKS!
de: KO4DJT

I used an NVIS on 80 and 75 M. I normally reached the Missouri Boot Heel - southeast corner part of Missouri.
Once I communicated with a ham in North Carolina, who gave me a phone patch and I was able to talk with my sister in the Huntsville, AL area.
I was using a Galaxy V at 300 W.
The antenna was a half wave dipole cut for 80 M. N0QFT

Thank you for the Video Michael, currently experimenting with these for local in-country Irish contesting and just for making other Irish contacts as I usually skip over them.
73s
EI5IMB

I am curious, for the NVIS to work, does the person replying have to have a NVIS set up as well? Sorry if this is a dumb question, so far the only other antenna I have used has be two J-Poles I have purchased from you.
Thanks again my friend, Keep up the great work.
PS, I am gearing up to some POTA stuff, learned about it from your channel as well.
Dale
KI5ARH

Awesome
Can you do this with an off center fed dipole...? Thank you sir

Using one for receiving on 40 and 80. My friend has a vertical for transmit, but in her neighborhood, the receive noise is S6. With a low dipole, the S meter is S1. Easy on the ears K2LNS

Good demo for NVIS. Explanation will surely help new HAMS understand NVIS more clearly.

Micheal, just a thought .... do you have a vid explaining how to properly set up/use a manual tuner? I want to share with local / newly licensed amateurs as needed or requested. Thanks.

Good job, going to build one. WY7RB

oh finally! i should have com here first

Hi, I'm almost complete studying for my Tech, and then will study for my General, and am trying to setup a system for emergency communications with people.
Do you recommend a minimal power output for this? I was hoping to be able to do this with a mobile unit.
Thanks very much for the great video.

i have been playing with nviz on 11.11M. over the last month(im pulling my hair out!) my mate has only cb.and lives 15 mile away over a mountain!He has an inverted "V" directed skyward and my horizontal 1/4wave dipole after trying to got through for a month, we had success yesterday......for 9 seconds(wall-wall) i want my mates to get there licence

Any recommendations on specific make and model for a portable NVIS antenna?

I never see someone testing an nvis to the same dipole at 50ft. I hear people talking about nvis,but not using it

I am guessing, and it's all theory anyway because we all know of hams using unconventional antenna deployments, but it seems you wouldn't make any contacts unless you could count on other hams to be configured similarly, whether on purpose or in compromised situations. A non-NVIS deployed antenna wouldn't emit a signal regionally, and a regionally-located ham wouldn't be able to respond or hear your signal with a non-NIVIS antenna, correct? Or maybe they could hear you, but perhaps couldn't respond? So NVIS-to-NVIS increases your chances of actually communicating (and here I think of the military's use of NVIS systems)?

In the army we used to pronounce these “nih-vis”. Cool video. What types of collapsible poles are those?

Thanks for the excellent tutorial ( and music)

Most of my operating is with NVIS... Even when I was in the military I used HF NVIS... W6PXL

"only about 50watts"
wow, how rich.

Hi Michael, very good presentation on the NVIS deployment of a dipole. You mentioned the ground wire under the antenna. I have the best results with the wire laid on the ground, directly under the elevated wire, with the ground wire being 5% shorter than the antenna wire. Give it a try next time you set up NVIS. For me, it gives a slight improvement. Enough to be worth doing.

This is good information. I live on the coast of Louisiana and am preparing my NVIS system for 40 and 80 meter comms in anticipation of another busy hurricane season! My longest experience without infrastructure was in '92 Hurricane Andrew. My area was in the direct path of the storm, no electricity, phone or water for 22 days. The local repeater on generator was my only ham radio option in those days! 73 de KI5IMV

I’d like to reach my kids who are around 35 miles away. Is that too close for NVIS?

What size wire do you use for this antenna ? Looking for the lightest 40m dipole wire that can handle 100w in the field.

Very good NVIS explanation and actual contact - W0BYU

Thank you Michael :-) 73

C00L

Where can you purchase this 40 meter dipole antenna?

How do you connect this to the painters pole and how do you attach the ends to a tree? Can you give details of such?

Thank you, Michael.
Doron, 4X4XM

How did he manage to connect to Charlie Brown's teacher via HF? 🤪🤪🤪 The camera really didn't pick up the audio from the radio well at all - unless that's what the radio actually sounds like (Yikes!).

NVIS works well, as long as you understand the associated problems. The closer your horizontal antenna is to ground, the higher the chances of ground loss. The lower the frequency, the more loss in the ground. Just like a ground mounted 1/4 wave vertical needs a good radial system to cut ground losses, an NVIS antenna can live or die by how much RF is lost in the ground. Laying a ground screen under the NVIS antenna will help, the more metal under the antenna, the better the efficiency of the antenna. You want the RF to reflect off the gound and go up, not warm the soil.

Another problem is the lower the NVIS antenna is to the ground, the lower the feedpoint impedance. If you look at charts of a dipole impedance versus height above ground, you will understand the issue. The lower the R value the higher the current, the more loss due to resistance in the antenna wire AND the feedline. Also the R value is directly correlated to the antenna efficiency, the lower the R value, the lower the radiation efficiency. If your feedpoint R is say, 25 ohms, the best efficiency you can expect if 50%, and that would be assuming a perfect ground with no loss.

In reality, a horizontal dipole very close (in terms of wavelenghts) to ground, performs more like a Beverge antenna, which uses the ground losses to improve thesignal to noise ratio.

The MUF plays a huge part of NVIS propagation as well. If the MUF is under 7 MHz, 40 meters will not support true NVIS propagation.

When the parameters are corerct an NVIS antenna is a great tool to have for those 100 to 300 or even 500 mile contacts. Several years ago, for ARRL Sweepstakes SSB, we used a 20 foot high 40 meter dipole with a 70 foot long wire laying on the ground parallel to the diploe. It was a fantastic antenna to make QSO's out to 500 miles or so. Further than 500 miles and the 40 meter dipole at 70 feet started to be the better antenna. Based on that performance, we tried a low dipole (25 feet above ground) for 80 meters with a 140 foot wire under it the next year. It made a quiet receiving antenna and that was about it. The following year, we tried the 80 meter NVIS game again and this time the dipole was at 40 feet and we placed five 140 foot long wires under the dipole, all parallel with the dipole, with about 8 feet between each wire. The results were noticeably better.

W9DP

No issues with a metal pole/mast in between the elements?

Thank you Michael, probably one of the best explanations and demonstrations that I have seen on NVIS. 73 de VE7WNO

Recently I added a 18” wide strip of galvanized chicken wire under both sides of my NVIS arrangement, and about 5% over length. I only run 40 meter band with this arrangement. SWR is less than 1:5-1. I’m in central KS, and have made contacts as far away as Alberta, Canada. Running a Yaesu FT710 on solar or battery power.

Does there need to be a standoff distance if the painters pole is aluminum?

There is a Maximum Usable Frequency for NVIS that depends on location and time of day, there are two online maps that show the current NVIS maximum usable frequency

Search for NVIS real time map

Usually for locations in North America the Maximum Usable Frequency for NVIS is between 4-8Mhz during the day and 2-4Mhz during night.

For instructions on how to build a good NVIS antenna look up

"A practical NVIS antenna for Emergency or Temporary communications" by DX engineerimg, its a free PDF file

I use an EFHW 4 feet off the ground QRP. Works good for SSB and data modes.

Have you used NVIS antennas? What are your experiences? I'd love to hear about it.