Radio Preppers

General Category => General Discussion => Topic started by: gil on May 09, 2017, 07:16:53 PM

Title: Praise For The 80m Band and NVIS.
Post by: gil on May 09, 2017, 07:16:53 PM
Hello,

Since I put up my 135ft Windom things have changed a bit, especially how I view local to regional communications... First with England. I am now able to reach several British locations on the VMARS net every Wednesday night on 3615 USB with my RT-320. The propagation isn't always good but I can usually make contact with at least one station, often three or four. The range seems to extend as far South as Italy from the North of France. I just had a QSO with Italy, another one with Germany near Lake Constance, nice chat, not just 5973. Then I hear ON7YU, still on 3560, only 90 miles from my location. He's running a K3 using 1W. For fun I lower my power to 500mW, then 100mW... My RST stays the same. He lowers his power to 100mW as well, same result. We continued a nice chat using 100mW CW on both ends. It's not line-of-sight, so QRPP NVIS (Very Low Power Near Vertical Incidence Skywave) :o for sure.

When I tested the W3EDP antenna, strung horizontally, using the PRC-320, I noticed very high reports on the Reverse Beacon Network, one at 36db over noise. NVIS rocks! Low power NVIS was a nice surprise. Ray had told me about it, but experiencing it is another story... There is a catch of course, the 135ft wire... That said, since it is horizontal, you don't need to put it very high. My Windom is only about 7m off the ground. Probably the reason why I can't get any DX out of it. My longest DX so far from here has been the U.S. using a 2.5m vertical whip!

My take on polarization now is to use verticals for 30m and above, horizontal for 40 and 80m. I'll use a vertical on 40m again when we climb up the solar cycle.

I will do more testing with 80m NVIS portable. It sure beats UHF which usually only works for 10-30 miles. With NVIS I basically rain RF on a 1000km radius. Right now it's still a bit cold out at night but it will be interesting to test 80m at night, clandestine portable style 8) I also plan on making the super gain 40m NVIS antenna I recently posted about:

http://radiopreppers.com/index.php/topic,1260.0.html (http://radiopreppers.com/index.php/topic,1260.0.html)

Even a tiny 80m QRP rig like the 1-Watter could be a viable bug-out bag radio. A thin 135ft wire and small end-fed tuner doesn't take much space and only needs eight AA cells for power. Those recent contacts certainly motivate me to box up my 80m 1-Watter, which works now and is waiting to be mounted in its Hammond case.

If I had the money right now I'd build a 40/80m K1, the ultimate NVIS machine! Long antennas are a pain but aren't impossible to use for portable operations. With decent band conditions, a wire only a few feet off the ground will work. Add reflectors and you even get some gain...

If you hesitate you give 80m a try because of antenna length, do it anyway. It's like having a regional telephone ;D

Gil.
Title: Re: Praise For The 80m Band and NVIS.
Post by: RadioRay on May 11, 2017, 10:54:21 AM
I do most of my radio play on 80 meters and occasionally 40 NVIS because conversations interest me.  Taking a page from Gil's Florida apartment station, I put up an EFHW, mine is for 80 meters.  Height is averaged at 20 feet on cheap fishing poles and posts.  The wire is not even straight, because I did not quite have enough room for that.  However, CW skeds on 80 meters work very well at QRP and even at milliWatt levels, like Gil reported. I have not tried SSB but I'd assume a similar low power requirement.  80 meters is IDEAL when camping to keep contact with friends back home, because a camp trip is rarely more than one-tank-of-gas distance from home. NOTE: During an emergency, what happens within that 'one-tank-of-gas' distance is usually the most important to you personally, not traffic conditions on the other side of the Earth.

Another factor is that conversations are far more common on the lower bands, rather than the inane '599 TU' manure increasingly common on the ham bands. Even 30 meters, which used to be a bastion for CW operators, now (in the USA) has the lower 15KHz or more covered in the one-call-wonders, letting a macro send their call "UP"  in response to a DX cluster spot , though they may have not have actually heard the 'DX themselves  ::) Every few seconds , the call pops out. ON 80 meters, you are likely to find FISTS, SKCC and other 'beginner friendly' groups who act as a spring board for new and returning CW users to practice.  I often go there and have a nice conversation, often with someone, for whom, this is 'the longest CW conversation I've ever had...".  That's a good thing.

Time for a cup of coffee and to tap some code before work.


73 de RadioRay  ..._  ._
Title: Re: Praise For The 80m Band and NVIS.
Post by: gil on May 11, 2017, 11:00:43 AM
Did you finish your Weber Survivor Ray?

Gil.
Title: Re: Praise For The 80m Band and NVIS.
Post by: gil on May 11, 2017, 01:14:09 PM
Boxing up my 80m 1-Watter tonight, another 80m transceiver, there will be more probably.

(http://radiopreppers.com/images/1Watter-case.jpg)

Gil.
Title: Re: Praise For The 80m Band and NVIS.
Post by: RadioRay on May 11, 2017, 02:39:24 PM
The Weber SURVIVOR is in the packed boxes ..... somewhere..... 'mostly built'.
Title: Re: Praise For The 80m Band and NVIS.
Post by: gil on May 31, 2017, 05:02:28 PM
Another great VMARS net tonight using NVIS! Testing a new RT-320. I got all around England, Near Brest France and Netherlands. 80m is really the regional telephone! You guys can listen to the net Wednesdays at 19:00Z on http://sdr.hu (http://sdr.hu) and of course on the air on 3615 USB.

Gil.
Title: Re: Praise For The 80m Band and NVIS.
Post by: N1KTJ on June 01, 2017, 01:26:32 PM
Thought NVIS was limited to 40m for the lowest frequency. That any NVIS below that would fail, like 80m?


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Title: Re: Praise For The 80m Band and NVIS.
Post by: gil on June 01, 2017, 01:35:12 PM
Quote
Thought NVIS was limited to 40m for the lowest frequency. That any NVIS below that would fail, like 80m?

NVIS will work from approximately 3 to 10MHz.

Gil.
Title: Re: Praise For The 80m Band and NVIS.
Post by: Pensioner Prepper on August 03, 2017, 01:50:00 PM
Oftern think of Prepper communications as ripples on a pond. The most important stuff happens on your doorstep. In my case that is in my Village with my Group and Uhf covers that well. As the ripples go outwards I think of 2m FM, 80m Ground wave, 2m SSB, 80m NVIS and on up to 40 and 20m mainly for information gathering.

A Radio Prepper and a Radio Ameture are two different horses me thinks.
Title: Re: Praise For The 80m Band and NVIS.
Post by: RadioRay on August 03, 2017, 03:36:55 PM
For most of the northern hemisphere, 80m is your NVIS band - occasionally 60m.  The further north that you are, the LOWER the frequency required for NVIS.  Equatorial regions right now, might use NVIS as high as 10 MHz.  However, where I live, near 48 degrees north, the MUF for NVIS is rarely over 5 MHz, so we use 80 meters with only the noon time - with it's high absorption, being quite unreliable. 

Here is a map of the hourly NVIS maximum usable frequency.  Refresh it when you use it, because it's refreshed hourly.
http://www.sws.bom.gov.au/Images/HF%20Systems/Global%20HF/Ionospheric%20Map/WorldIMap0.gif (http://www.sws.bom.gov.au/Images/HF%20Systems/Global%20HF/Ionospheric%20Map/WorldIMap0.gif)

Now you know why I love 80 meters.

>RadioRay  ..._  ._


Title: Re: Praise For The 80m Band and NVIS.
Post by: Pensioner Prepper on August 03, 2017, 04:29:58 PM
Thanks for that Ray. Yes I agree 40m NVIS is a no no for us in the Uk.
Title: Re: Praise For The 80m Band and NVIS.
Post by: swxx on August 22, 2017, 10:13:35 PM
Great to be here and learn much from you all. Ray I recognise you :-) great to see you too. I also was reminded, looking elsewhere, thanks to you, about horizontal loop for 80m. Even low down, around the house, for those of us with small plots.

If not using a coax dipole but if you have a (manual) tuner with 1:1 balun, a doublet (double zepp) does not need to be as long as half wave length. One can get away with a lot shorter without too much loss of radiated power, e.g. 20% less length then isn't any problem. Also, or alternatively, as the radiation on dipoles is not off the ends of the antenna but the middle two thirds perhaps at half wavelength, bending the ends downward or in any direction is not a big problem, to make it fit. At the NVIS height that horizontal antennas pretty much probably have by default at 80m, direction of the wire is not a problem as it'd have little or no effect on azimuth pattern.

I made a small vertical for 80m, it is 4m long with about 96 turns base loading and on a squid pole up 4.5m at its base, with the very thin coax, even with one elevated radial, works fine, but less so for NVIS obviously, but for thousand km or more after dark is quite good.
Title: Re: Praise For The 80m Band and NVIS.
Post by: cockpitbob on August 23, 2017, 12:19:07 AM
SWXX, welcome to the board!
Title: Re: Praise For The 80m Band and NVIS.
Post by: swxx on August 23, 2017, 03:38:15 AM
SWXX, welcome to the board!
Thank you!
Title: Re: Praise For The 80m Band and NVIS.
Post by: gil on August 23, 2017, 05:10:38 AM
Quote
I made a small vertical for 80m, it is 4m long with about 96 turns base loading and on a squid pole up 4.5m at its base

What is the diameter of that loading coil? Wire?

Gil.
Title: Re: Praise For The 80m Band and NVIS.
Post by: cockpitbob on August 23, 2017, 10:04:14 AM
Here's a nice write-up on short 80M verticals.  Lots of good construction pictures and background info. 
https://www.nonstopsystems.com/radio/frank_radio_antenna_80m_vertical.htm (https://www.nonstopsystems.com/radio/frank_radio_antenna_80m_vertical.htm)

I have a home-brew 6M - 40M no-tuner vertical but need something for 80M with the sun going to sleep for the next 6 years.

Yeah, I should take pics and write-up my vertical.  It's pretty simple.  5' of aluminum tent poles(brass screws between sections), then a home brew coil on PVC pipe, then an MFJ 6' telescoping whip.  I cut grooves in the pipe so I can use a clip lead to adjust the number of turns.  To change bands I move the clip lead to the desired tap on the coil then adjust the length of the 2 radials I have on SOTAbeams wire winders.  I wind or unwind wire to set the radial length.  I have marks on the wires for typical lengths.  Having wire bunched up on the winder seems to be the same as not having it there at all.  It works quite nicely, though I should carry an antenna analyzer to make sure the tune is good.

For me, winding coils is a PITA.  So, here's a thought.  Use a $17 MFJ 30meter or 40meter hamstick as the base coil and attach whatever length of wire to the top to get it tuned for 75M or 80M.  If you can't get a string over a branch for pulling up the wire, a telescoping Jackite pole will work.  For mobile opps I use my 20M hamstick on 17M and 15M just by using shorter whips.  It will work the other direction by using a longer whip for lower bands.  MFJ makes 75M and 80M ham sticks, but they are too short (about 9' overall) to really work on such long wavelength bands.
Title: Re: Praise For The 80m Band and NVIS.
Post by: swxx on August 23, 2017, 11:00:47 AM
It would be good if you can get around to a write up and photos of your vertical. I should of course do the same for mine, but they are not made nicely and may not look great in photos.