Author Topic: Antennas/systems to maximize GroundWave propagation?  (Read 3609 times)

Offline stratigus

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Antennas/systems to maximize GroundWave propagation?
« on: March 29, 2016, 12:54:59 PM »
I've been looking into adding an NVIS antenna to my collection, goal being to fill in the "skip zones".
As I've been thinking about it, I see a few pretty good NVIS designs with high elevation, many more "DX" antennas with mid/low elevation, but I have yet to see any HF antenna designs that are intended to maximize the effects of groundwave propagation.
Has anyone come across an HF antenna system with maximizing groundwave being a design goal?
Something portable would be nice; I'd expect a good grip on the earth with a good grounding system would perhaps be much more important for taking advantage of groundwave, but I've found surprisingly little literature on it beyond "vertically polarized works best".
Any ideas? Anything that might be better than a well-grounded vertical?

Offline armymars

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Re: Antennas/systems to maximize GroundWave propagation?
« Reply #1 on: March 29, 2016, 04:00:15 PM »
  Ground wave antennas are most often verticals. The more radials the better. These are good for 0-25 miles. You can stretch this if you go to the bottom of 160 meters. For past 25 miles you need a NVIS antenna. The reason you can hear broadcast AM so far is the frequency. The point where adding more power means going farther with no skip ends at about 940 KHz. Some Mars types like the inverted L for that reason  mounted low. Some vertical, some NVIS. With a ratio of 1 part up 2 parts out. Plus lots of radials.

Offline Carl

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Re: Antennas/systems to maximize GroundWave propagation?
« Reply #2 on: March 29, 2016, 05:02:50 PM »
A vertically polarized loop will do for most any situation and proper use of frequency (80 / 75 meters) but there is really no one answer as many factors are not specified in your question as to station height above ground ,local to a water hazard for ground plane and while a vertical is good to transmit on,they often pick up too much noise to be of real value. also ,trust me on this...3 or 4 elevated ground radials ONE to 8 feet in the air will perform so close as to call it equal to 100 plus ground mounted radials.

USE VHF for local to 50 miles ,then HF 40-60-80 meters NVIS for the 25 to 200 mile zone, and finally a DX antenna ,if desired.

Offline Alan Georges

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Re: Antennas/systems to maximize GroundWave propagation?
« Reply #3 on: March 29, 2016, 05:39:55 PM »
  Ground wave antennas are most often verticals. The more radials the better. These are good for 0-25 miles.
~3-5x this if you happen to have a saltwater path.  Our communication needs do not always cooperate with this setup however.  It is astounding what AM stations can be picked up along the Gulf coast during the day: http://radio-locator.com/cgi-bin/patg?id=WWL-AM  One of these days I'm going to start playing with wires & weather balloons with 160m on the beach.  Just... not anytime around thunderstorms.
« Last Edit: March 29, 2016, 05:47:42 PM by Alan Georges »

Offline armymars

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Re: Antennas/systems to maximize GroundWave propagation?
« Reply #4 on: March 30, 2016, 08:50:51 AM »
I remember an artical in World Radio where a broadcast station had to replace it's 120 radials that were 1 foot off the ground. They found they could replace them with 6 radials 20 feet off the ground. On ham radio frequencies this works out to about 7 feet.

Offline stratigus

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Re: Antennas/systems to maximize GroundWave propagation?
« Reply #5 on: March 30, 2016, 10:11:24 AM »
Thanks for all of the information, folks!
It seems my understanding has mostly been confirmed regarding verticals being the best practical antennas. I suppose there's a reason why the broadcasters all use them, eh?
Interesting about the elevation of the radials having such an effect... I'll have to experiment some!

Now... who has a favorite setup for 40/80m verticals and loading coils?  :D

Offline Carl

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Re: Antennas/systems to maximize GroundWave propagation?
« Reply #6 on: March 30, 2016, 10:19:28 AM »
Thanks for all of the information, folks!
It seems my understanding has mostly been confirmed regarding verticals being the best practical antennas. I suppose there's a reason why the broadcasters all use them, eh?
Interesting about the elevation of the radials having such an effect... I'll have to experiment some!

Now... who has a favorite setup for 40/80m verticals and loading coils?  :D

With what little info you provided...I would use a 33 foot fiberglass pole (or a tree) to support a vertical wire (that is NOT 1/4 wave on either band) with a capacity hat and 4 or so elevated radials  cut to 17 feet 6 inches ,or as 1/4 wave on 40 and 4 also for 80 meters ...though you may find (as I had) that the 17 foot 6 inches for the radials works great for all bands  BUT 6 and 10/12 meters.

You can make a very effective antenna without over engineering it.

Offline Canadian Prepper

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Re: Antennas/systems to maximize GroundWave propagation?
« Reply #7 on: April 03, 2016, 09:17:12 PM »
I just took a peek at the forums after a couple of days away and thought that the following link would be of interest. Essentially there's been a group of hams in Southern Ontario that's been experimenting with daytime 80m groundwave nets using vertical antennas. If you peruse the various links they've got the findings of some experiments and some other suggestions based upon their experience. I'm sure that it would inspire lots of ideas and questions for anyone that's interested in this.

http://www.nparc.on.ca/gwen/

I haven't really played with this much as my MFJ 2886 "Big Stick" vertical is rated for 6 to 40m. Though I can get it to tune on 80m with my Kenwood auto tuner, with just a handful of counterpoise wires it's hardly optimal on that band to begin with, and my current setup isn't the best for laying down radials and counterpoises. I might add a 33 foot length of wire that I'd keep off ground to see if it would work as a hybrid vertical/NVIS setup, but that would probably be more suited for 40m and wouldn't truly be a groundwave setup.

Offline stratigus

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Re: Antennas/systems to maximize GroundWave propagation?
« Reply #8 on: April 05, 2016, 08:48:18 AM »
@Canadian Prepper
That is exactly the type of thing I was looking for!
The EmComm applications and implementations of Ground Wave that those guys are up to are very interesting!
With a hobby this large, I figured someone had to be utilizing the advantages of this propagation mode.
Thank you very much for finding and sharing this!

Offline Carl

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Re: Antennas/systems to maximize GroundWave propagation?
« Reply #9 on: April 05, 2016, 09:22:51 AM »
@Canadian Prepper
That is exactly the type of thing I was looking for!
The EmComm applications and implementations of Ground Wave that those guys are up to are very interesting!
With a hobby this large, I figured someone had to be utilizing the advantages of this propagation mode.
Thank you very much for finding and sharing this!

For 40/60/80 meters ...you should really look at NVIS and easy antennas to do NVIS...as it is more likely than ground wave .
I worked 40 meter NVIS with good consistency at about 150 miles. NVIS COMBINED with Ground wave will net you nearly complete area coverage and negate terrain variance or loss of signal.( a ridge or hill will block ground wave,but not NVIS


Offline stratigus

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Re: Antennas/systems to maximize GroundWave propagation?
« Reply #10 on: April 05, 2016, 09:48:02 AM »
NVIS is definitely something to use. It might not be "more likely" in a few cases, as NVIS it has it's own caveats such as inconsistency of coverage and instability of usable frequencies.
What the NPARC guys have shown is a consistent and reliable implementation of Groundwave, not as a replacement for NVIS, but as a way to have abilities that NVIS won't be able to reliably do.
Having the ability to do both is certainly a good idea, but it doesn't look like one is a direct replacement for the other. More options are certainly a good thing, however! If the goal is to fill in any "holes" in a station's coverage map, having the capability to do both is important.

Offline Canadian Prepper

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Re: Antennas/systems to maximize GroundWave propagation?
« Reply #11 on: April 05, 2016, 11:17:28 AM »
NVIS is definitely something to use. It might not be "more likely" in a few cases, as NVIS it has it's own caveats such as inconsistency of coverage and instability of usable frequencies.
What the NPARC guys have shown is a consistent and reliable implementation of Groundwave, not as a replacement for NVIS, but as a way to have abilities that NVIS won't be able to reliably do.
Having the ability to do both is certainly a good idea, but it doesn't look like one is a direct replacement for the other. More options are certainly a good thing, however! If the goal is to fill in any "holes" in a station's coverage map, having the capability to do both is important.

There's some good points on that website, but I think that the simplicity of an NVIS setup (to keep things simple, I'd suggest the W3EDP antenna discussed elsewhere) would with minimal outlay of funds or setup at least give you that initial capability for perhaps the price of a balun and some wire.

The vertical setups are interesting, but you'll probably be paying at least a few hundred dollars even for a used vertical and might find that you'll need to lay down lots of counterpoise or radial wire to get decent performance, which may take time, money and effort to perfect. And while the NPARC website is interesting, if you look at their listings of other hams using verticals for that network, I don't think that they've created a huge group of people to communicate with, given the peculiarities of their setup.

I'll probably try to setup a decent vertical antenna eventually when I get the time and a decent enough location to do so, if only to add the ability to transmit with a different radiation pattern over my other antennas or to try some higher frequency DX from time to time, but it's anyone's guess whether or not there will be a decent network of hams within my area to connect with on 80m groundwave by the time that happens. But I do know that there's quite a few people that I can communicate with already on 40 and 80m during the daytime with my W3EDP, which can be raised or lowered to effect different radiation patterns if the situation warrants it. I can also make up a second antenna to deploy portably with little outlay, while the vertical will essentially be a base station setup.

Offline Carl

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Re: Antennas/systems to maximize GroundWave propagation?
« Reply #12 on: April 05, 2016, 12:09:42 PM »
You are getting some mileage out of the W3EDP antenna,glad to see it is still in use. I have a friend with one strung IN HIS APARTMENT and having success with voice and PSK (who knew) he ignored the rules and still had good results. :) :popcorn: :popcorn: :popcorn: