Near Vertical incidence Skywave Propagation NVIS Antennas - Ham Radio Q&A
HTML-код
- Опубликовано: 31 май 2024
- Near Vertical Incidence Skywave Propagation is an effective form of HF communication for stations in a 100 - 300 mile range. Ideal for Emcomm, the emergency communicator should be familiar with the use of NVIS antennas and propagation.
Support Ham Radio Q&A by shopping at Amazon: amzn.to/2kO6LH7
Read my blog: www.jpole-antenna.com
Colophon:
Camera - Panasonic GH4: amzn.to/2GV2Og1
Lens - Panasonic 12-35 f2.8: amzn.to/2GWC5zU
Microphone: Azden Pro-XD wireless lav: amzn.to/2qt3vDc
Music by license: www.premiumbeats.com
#NVIS
#EMCOMM
#ARESRACES 
Наука
Have you used NVIS antennas? What are your experiences? I'd love to hear about it.
I have used it extensively. Regarding the wire on the ground parallel to the antenna I found this very useful when deployed in Afghanistan as the ground conditions there were very poor. Often the ground plane was several meters below the ground surface. A wire on the ground established a set ground plane so that I could avoid that the dipole was to high and thus loose its NVIS properties. I have used dipoles in Afghanistan where they lay on the ground and performed as if they were 10-15 meters above ground. Also the Harris RF-1943 H-antenna worked very good in Afghanistan and lousy back home because of this. It needs hight and in Afghanistan you got that free by laying it on the ground. Back home that never worked because of a solid ground plane just centimeters below the surface.
In my area the only drawback with NVIS is ionospheric condition. Especially when operating above the polar circle. Often the ionosphere does not play ball and the frequencies needed for NVIS is killed off in a strong D-layer or by other PCA-events. Then long-haul is necessary to get communication going.
Used NVIS antenna years before I knew what they were. I had a 10 meter mobile back in 88-93 with a whip antenna. I noticed that with the antenna unfurled I could talk to Russia, Hawaii, and Japan from California, but with the antenna clipped in a arc with the upper section mostly horizontal with the roofline of the car my 10 meter contacts were much closer to home. Being a new ham at the time I had no clue as to what was going on, just that the antenna clipped down didn't appear to work as well as upright in the breeze. Another thing I noticed is that with the antenna unfurled, if I went through some drive-throughs the antenna would "take-out" the flourescent light bulbs as I drove through the drive through...
Good PDF describing NVIS region6armymars.org/downloads/NVIS-Antenna-Theory-and-Design.pdf
I built a home-brew version of the AS-2259/GR antenna used by the US Military a few months ago. The mil-spec model used 25 and 38 foot elements for 5-10MHz, so I lengthened my wire elements to radiate more efficiently on 40 & 80M. So far, I have made contacts from my shack out to just under 500 Miles with my feed-point only 15ft up. I also found this antenna is excellent when working Winlink over Winmor. Two factors that definitely affect the feed-point impedance (and thus the SWR) are the HEIGHT of the feed-point above ground, and the ANGLE formed by the wire elements. I find my antenna performs best when the inverted-V forms an angle of AT LEAST 90 degrees, but the "best" HEIGHT for the feed-point varies with changes in ground conditions.
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
I use nothing but NVIS. 40 ft end fed at 10ft elev with tuner at feed point.My closest contact ws 2 miles and furthermost heard was over 6000 miles. Couldn't talk, only hear as I only use 10 watts. Normal distances for me are between 250 and 1200 miles. 80/40/30/20/17. I've heard stations on 15/12 but I was just spinning the dial. I used to complain about all the California kilowatts back in the 70's. Now days, it seems their all over the place now. That's why I operate only low pwr. It's a challenge.
NVIS - an old Indian term meaning "The smoke goes straight up." :)
I'm a big fan of this phenomenon. Thanks for an illustrative video.
You mean the FIRE goes straight up, smoke goes everywhere! Lol
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!
Thank you, Michael.
Doron, 4X4XM
Hello Mike, I know this is an older video of yours but I wanted to say you do an excellent job of making an easy to understand video. I have become interested in trying an NVIS antenna for near vertical wave communication. As normal for me, I tend to gorge myself with RUclips videos on a subject of interest. As I have found typical of your videos, you are very good at explaining things in a down to earth manner. Keep up the good work. WA4EOD - Tom
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
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!
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
Nice demo! I have used an end fed antenna (Ultimax-100, 24 feet long) inside a motel room at about 8 feet off the ground to make NVIS contacts on 80 meters!
Excellent demonstration Michael! 73
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!
Can you take the General and Technician both at the same time?
@@thegreatcornholio7255 Absolutely! I did the Technician, General, and Extra all same day, one after the other. I wouldn't recommend all three at one time. It fried my brain! Stopping at General would be my recommendation, then Extra at the next testing opportunity. -Stan AD7LX
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.
You are correct that at a low enough height‚ just about any wire antenna can be used in an NVIS configuration.
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
My focus right now is on portable emergency communications. I'm fairly new at HF and I'm wanting to understand NVIS more for SHTF scenarios. Thank you for this wonderful and clear explanation.
Glad to be of help. I gave a presentation on NVIS last fall at our state's ARES/RACES conference. You may find it of interest as it has a lot more expanded information than this video has. You can view a recording of it here: ruclips.net/video/VbxqrNjUkKE/видео.html
If you want to be really mobile, try a dual hamstick. It won't be as good as what you see here, but you can est it up in about 5 minutes, easy. Do a search for "dual hamstick nvis" and you'll find good info.
Excellent explanation and demonstration Micheal, I've been looking into NVIS antenna setups and this really helped me with understanding it, thank you & 73
Nice explaination and demonstration. Thanks for posting this.
Good demo for NVIS. Explanation will surely help new HAMS understand NVIS more clearly.
I have had very good results regularly with a longwise (22.6 meters long) and an earth steak. The antenna is usually about 10 to 15 foot above ground. Signal strength has been as high as 10 db over 9. Distances are between 100 to 600 kms using the 40 metre band. NVIS is very good!!
Ran one with a iCOM 7200 this week. Took calls from Peru to Canada. We were in Colorado.
Thank you Sir. Very well explained. Wife and I camp in remote locations where cell and repeaters are not an option, but this sounds like something we need to set up in the mountians for in state contacts.
finally a decent explanation of NVIS
I have not ever used one, I am very very new to this hobby, I have actually been pondering how well it would work in SE Oklahoma since there is a small mountain range there. Thanks for sharing the video sir, looks like you have a really cool camp there.
Thanks again for taking the time to make this video and I hope you have a blessed week.
Dale
KI5ARH
Love your videos. I'm another newby learning all you will share. Thanks
This was a great video showing what NVIS antenna is about, keep up the great informative videos, 73
Thanks, many hams have heard about the term, but have never seen NVIS in action. I'm glad you found the video informative.
Very informative. Thanks for sharing. Thumbs up.
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 !
Thanks for the excellent tutorial ( and music)
I have ran NVIS with my 40 meter half-wave dipole at 5' elevation and made routine contacts to New York State from my location here in SW Michigan on 5 watts with my Yaesu FT-817. Also, I was hiking at Isle Royale National Park in L. Superior and ran NVIS from there with the same antenna and radio and made a contact to SW Ohio on 5 watts.
Well done, Michael--thanks! :-)
I recently erected an EDZ cut for 3.5 MHz and fed by 600 ohm ladder line from an AH4 tuner. It matches perfectly on all bands 160 - 6 meters, and on the low bands works beautifully as an NVIS antenna at 15 - 25 feet. Great performance at 150 - 250 miles on 75/80m, and 200 - 500 miles on 40m. Running 100 watts max from IC7300. On 20m and higher, it performs as a standard dipole. The EDZ provides twice the gain of a standard dipole at the design frequency (3.5 MHz). Great combination for statewide communications. W0LEN
In the flat part of Texas I live in, this should work really well!!
I would think so. With HF and an NVIS antenna, you don't need a tall tower.
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
Great video Michael, have a bit better understanding of what coverage NVIS does now.
Most of my operating is with NVIS... Even when I was in the military I used HF NVIS... W6PXL
Just passed my general and extra class in one sitting and am building my first antenna (a dipole of course) to get on HF. My landlord recently cut down the last tall tree in the yard that died which would have been perfect to toss a line up into. Otherwise, now I have to look into a fiberglass super tall mast or going NVIS if I want to operate from home. New sub, and have been watching through your videos. Many thanks and 73
Congratulations on passing both the general and the extra! That's quite an accomplishment. I usually say: the best antenna is the one that gets you on the air. So if you have limited space, a short dipole or low NVIS style antenna may be your only choice. If you can't put up anything permanent, you may want to consider a portable vertical antenna like the Wolf River Coils Silver Bullet 1000 that I earlier reviewed: ruclips.net/video/6w-OaRrHpSY/видео.html
I have used NVIS many times on 40 meters. Here in W. Michigan I often reach out to Northern New York, Ottawa Canada and New Jersey - Often with just my little Yaesu FT-817 on 5 watts ! My 40 meter dipole is often at just four (4) feet height in the backyard. I have used my military AS-2259/GR NVIS antenna many times too but the simple 40 meter dipole seems to work just as good. 73.
Very informative . Now I know what NVis is Ty !🍺👍🤠🎙
Hi KB9VBR. This was a really great & informative video! You did a fantastic job of addressing and answering all of my questions regarding NVIS. de KM4JCV & 73!
I'm glad I'm able to get you going on the NVIS path.
Nice demo & explanation of NVIS !
73 N8AUM
Very instructive video.
I have a driveway that is over 100 feet long. I have set up NVIS on the driveway and while not scientifically examined I get good reports and I attribute the rebar in the concrete to give some added reflection to the signal.
That's an interesting observation. I could be possible that the rebar is helping reflect the signal upwards.
Very nice video I really like it
Thank you Michael :-) 73
Great video!
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.
Great video and demonstration. NVIS is viable and works great. I guess one small downside is the other station must also be working NVIS also and most station aren't setup for NVIS so this reduces the possibility of contact.
Yeah, for optimal performance everyone should be operating with NVIS propagation. Earlier in the day when I made the video I participated in our statewide ARES/RACES net on 75m. The signals would come in either full scale or S1, nothing in between. Listening in, it was easy to tell which stations had a greater skywave component to their signal than others.
I have been using the Chameleon EMCOMM II for a couple of years as 1 of my permanent antennas for 160, 80, and 40 meters. Works great! Just a reminder that the other stations do not need to be set up for NVIS to work. If you can hear them you can work them. Nice video.
In the army we used to pronounce these “nih-vis”. Cool video. What types of collapsible poles are those?
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
Very cool music for a nerd video!
Thank you for the great video, can you tell me who made your 40 meter dipole and what tuner did you use?
Antenna is a homebrew dipole. It's tuned for the lower end of the 40m band, but the SWR is only 1.5:1 in the phone segment. As for the tuner, it's an MFJ 945-C mobile tuner. It's compact so I keep it in my travel kit.
No issues with a metal pole/mast in between the elements?
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?
Thanks for the video. What mapping program did you use for line of sight distance?
de W2MSA
It was google maps. It has a tool for point to point measurements
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
Ha, I was typing this while I let he commercial play, you just answered my question with your current contact. Ha, thanks sir and have a blessed week.
Dale
I severely lack the education of how to know an antenna radiation pattern. I know that a UHF 3/4 wave antenna gives extremely high radiation patterns. Thus, use a quarter wave monopole, quarterwave ground plane, or a center fed vertical dipole or centered horizontal dipole. However this is just from memory. How does one calculate the radiation angle of an antenna?
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.
I haven't done that as a topic, so I'll add it to the list.
Awesome
Can you do this with an off center fed dipole...? Thank you sir
You should be about to. The key to NVIS is using a wire or horizontal antenna, so an OCF should work if it is mounted low enough.
What size wire do you use for this antenna ? Looking for the lightest 40m dipole wire that can handle 100w in the field.
22 gauge wire will handle 100 watts. Anything thinner than that and you have to be concerned about the structural integrity of the wire.
How do you think the metal roof of your camper trailer may have influenced the propagation?
I don't think it affected the propagation at all. The purpose of the antenna was for NVIS communication so even if the trailer made the signal travel upwards at a higher angle‚ it would've been better for my purposes.
I’d like to reach my kids who are around 35 miles away. Is that too close for NVIS?
Very good NVIS explanation and actual contact - W0BYU
What about polarization? I see you appear to be horizontal with your dipole. Does it help to radiate vertically at all (or hurt)? Any thoughts? I bought one of those fancy little auto-tune boxes ($220) a while back after a friend said he could tune right up using a 15 foot aluminum ladder - I laughed at him, but he had the last laugh as he tuned it right up (1.2 to 1) and proceeded to QSL 5/9 all over the state (I just stood there catching flies with my mouth open, starring at it) - Thanks & 73s , Richard - KA1BOU
A fifteen foot ladder!?!? I had to chuckle, but if it works, there’s nothing wrong with that. I’ve been an EE for 29 years and have spent most of my career designing RF equipment and antenna systems. I thought that I had heard of everything, until you said that he used an aluminum ladder. It’s actually a great idea, due to how easy it would be to adjust the length. (I’m assuming that it was an extension ladder.) For me, the best part of this hobby is experimentation. That’s why we have the vast selection of antennas, and other equipment, that we do. The next time you see your friend, please tell him that I said “Well done!”. Take care and 73’s.
NVIS antennas usually are horizontally polarized. The reason is that vertically polarized antennas on HF tend to have a low RF radiation take off angle, so more signal goes toward the horizon than straight up. I've done A-B switching between an NVIS dipole and the Silver Bullet 1000 vertical during our statewide ARES/RACES net on 75m and notice that the dipole will be 2-3 S units stronger for signals within the 200 mile radius.
As for loading up the ladder, if you have a big enough tuner, you can load up almost anything. During past Field Day events our club would have a 'strange antenna contest' as an educational activity. Ladders, lawn chairs, even wet t-shirts can be turned into a radiator.
Would you please share what auto tuner model do you or your friend have to load up the ladder? Thanks
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)?
Any recommendations on specific make and model for a portable NVIS antenna?
NVIS really isn't a style of antenna, but a form of operation. Almost any antenna can be NVIS if you mount it low enough. The Chameleon antennas, like the EMCOMM III and Tactical Delta Loop work well for NVIS. A simple dipole works great for NVIS. DXengineering makes an NVIS antenna based on the classic military NVIS style antenna: www.dxengineering.com/search/product-line/dx-engineering-8040-nvis-antennas/part-type/wire-antennas?fr=part-type&SortBy=BestKeywordMatch&SortOrder=Ascending&autoview=SKU&keyword=nvis
@@KB9VBRAntennas I bought the ECOMM III and was hoping to take it for a spin this weekend. Reading through the instructions, however, I realized the recommended NVIS configuration involves mounting it 25' high. They claim that lower could still work, but with degraded performance. I was hoping for a more mobile solution like you had with the painters pole. In fact i was hoping to get exactly what you had because I'm less interested in experimenting and more interested in getting something that's proven to work. Can you tell me exactly which antenna you use in the video?
so just any HF antenna mounted at a lower height? am i following correctly for NVIS ops?
In a very broad sense yes‚ but some antennas will perform better for NVIS than others. Shortened dipoles and end fed antennas can have better NVIS properties at lower heights. Vertical and loop antennas typically make poor NVIS antennas.
Nice vid as always Michael. Would love a camp tour of your set up thee, and that cool looking camper! 73 kc3cua
The little camper turns a lot of heads as we travel. A video on it is coming up. In the meantime, this is the guy that built it: www.tcteardrops.com/
I was also interested in that camper. My wife and I have owned three campers. (A pop-up, a 21’ trailer and a 32’ trailer.) We have had a terrible experiences with all of them. That camper looks well built and just the right size. It’s large enough for two people, but small enough to not take up a lot of room, when not using it. I have often said that I will never own another camper, but your camper might have just changed my mind. :-)
We've been tent campers for years so getting this trailer was a bit of a leap (as you see in the video, we still have to set up a tent for the kids). But we'll never go back. This is our first season with it and so far it's exceeded our expectations. It's lightweight, comfortable, and convenient. Our Subaru Forester can pull it. The guy that builds them uses marine grade plywood and 100% silicone sealer on all the seams. It's fully skinned with aluminum, no canvas or plastic to worry about. I should have the video tour of it up by Friday.
KB9VBR Antennas - Our last camper was 32’ and cost $26,000. Two years after we purchased it, it sprung a leak during the winter. When I went to our rec club in the spring to set it up, I discovered that the leak had rotted the floor out. Unfortunately, roof leaks aren’t covered under insurance. I was so aggravated, by this point, that I sold it to a friend for one dollar, so that I would never see it again. I often wondered why insurance companies wouldn’t insure campers against water damage until mine, and many of my friends, had it happen. We maintained the roof and it never moved from our campsite. I just can’t understand why camper companies can’t figure out how to make them waterproof.
I have been perusing the website that you provided in the above link. They look like some quality campers and aren’t really that expensive. They have a lot of great options, as well. I just have to decide if we’ll us it enough to make it worth it. I already have a building full of toys that I’m not using enough. Aww, heck.... what’s one more toy, right? :-)
Dipoles work better with receiving, I use a whip antenna for transmitting. I dont have the space for a dipole. will a whip antenna work for NVIS?
If the whip antenna is in the horizontal position, it will exhibit some NVIS qualities. It's common for HF mobile operators using a 102 inch whip to bend it into a horizontal position for NVIS. So the same procedure should work for you. It won't be an ideal situation, but it is certainly better than nothing.
Ok i will give it a try. Thank you. I have an end feed antenna and so far it is not working well, When the whip antenna comes i will compare the two.
I never see someone testing an nvis to the same dipole at 50ft. I hear people talking about nvis,but not using it
Don't you get most of the effects of NVIS if your dipole is below 1/4 wavelength for the frequency? My understanding is that at 1/4 wave or higher is good for DX, but below 1/4 wave you have a "cloud burner", good for NVIS contacts.
You are correct. Broadly speaking, as you lower your antenna below 1/4 wave in height, it will exhibit more and more of a vertical RF radiation pattern. In experimentation, it seems that the 'sweet spot' is about 15 feet for the 40 meter band, and a little higher for the 75 meter band.
Good job, going to build one. WY7RB
Where can you purchase this 40 meter dipole antenna?
Most people build their own. Here's a video that shows you how: ruclips.net/video/zvtKlqQ6DSo/видео.html
Optimum height for NVIS antennas is 0.12 wavelengths. About 15ft for 40m, and 31ft for 80m.
It's not an exact science.
@@OH8STN correct! tactical HF operator for state entity here. In Tn the best NVIS height is 10-20 ft. They read stats in a book. We do this state wide every week on 100 - 20 watts
Will an internal turner tune this antenna?
The antenna I was using was a 40m dipole, so no tuner was necessary on the 40m band. I had to use an external tuner on the 80m band as the match was about 5:1 without the tuner. Most internal tuners will only match 3:1 or better.
Michael,
Can you give me details on the antenna that you used in this demo?
Thanks .73 George KB3WAQ
The antenna is a simple 1/2 wave dipole antenna cut for 40 meters.
@@KB9VBRAntennas Michael Thanks 73
oh finally! i should have com here first
hi there im making an inverted "V" on 11.11m, im trying to get through to my mate, he is15miles away but over a mountain (scotish highlands) can i bounce 27Mhz of the ionosphere with NVIS? He has got 10W and he is limited to legal CB.he also has 155mhz-450mhz aprox. boafeng, is that a better option?
NVIS is most useful with frequencies below 10Mhz. I think that with 27 Mhz, the wavelength is going to be so small that the signal still may skip over the other station. I did a longer presentation on NVIS that you may find interesting: ruclips.net/video/VbxqrNjUkKE/видео.html
My friend is good beautiful and very very best 73,s and good dx for you. 😉🆗👍
I want to see a video of an NVIS antenna and a dipole setup at a proper height and observe the difference.
well he showed you a map how close he was able to pick up the other guy. A higher antenna would give him dx further away and not able to hear the close in stuff. No need for video.
Great explanation, KN9VBR. THANKS!
de: KO4DJT
An 88 foot doublet (2x44 ft legs) will tune 80-10.
An 88 foot doublet may be a viable option. It is relatively short. The only downside is that it's fed with ladder line and you will need a capable tuner for the lower bands.
KB9VBR Antennas I found a decent autotuner fed by a 1:1 Balun would tune no issues. Only thing to consider is length of ladderline as this can affect tuning
That type of setup would work well. Thanks for sharing.
Roger Roger.... lol
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!).
C00L
modelled this ..please can you help me understand the SWR mess ? or have you made electrical changes somewhere - see screenshot of model here -
drive.google.com/open?id=1XVtozv_3CsVoyRdeo4AJfsSxnHEY3hFx
"only about 50watts"
wow, how rich.
NVIS is simply the notion that "ground wave" doesn't exist on 80 and 40m. Test it yourself - try ANY contacts at ANY distance around you on a closed 40m band, even direct line-of-sight, and you will see that "ground wave" is not a happening thing, even with severe amounts of horsepower - TRY it and you will see. ALL PROPAGATION after 10km is ALL NVIS, ie, "off the ionosphere".
"NVIS antennas" is fantasy that you can build a radiator that will increase one angle of radiation and restrict the other - not going to happen, except in some manufacturers catalog - and they would have to be brave or stupid to try sell that.
You won't get much, or any, groundwave from a horizontal dipole. You must radiate a vertically polarised signal. Here in the UK for emercomms we plan on 12 km on 80m and 20km on 160m, but frequently exceed these ranges in practice. From G4FSN.