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Messages - Commsguy

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Either 2m ssb or 80m NVIS should work. For 75 miles I would go 2m ssb with a Yagi. This way you do not rely on the ionosphere at all.
Especially for that last factor, not relying on the ionosphere, 2m SSB would be the most reliable or best all-round solution. I'll keep it 'on board' as for being an option. What kind of power would do the trick at that distance? Obviously the number of elements and TX power can be changed somewhat to achieve the desired performance.

How many elements would you reckon to be suffice for that distance? A simple 3-element measuring tape yagi or an antenna with more elements?
How critical would it be to know someone's bearing? Does it have to be within a few degrees of accuracy?

What about something like a moxon antenna?

You've done your research - that's clear
I'm just trying to NOT reinvent the wheel here - by doing my part on the research I'm just making it much easier on myself later on. I just need someone with much more real-life experience to nudge me in the right directions and verify I'm having the right thoughts in regard to feasibility and such.


80m is my choice here for NVIS with regional friends, at almost 48 degrees north.  We have extreme reliability from 7 a.m. local often past noon and then from 15 Hours to a little after sunset, when the band goes long on 80m. Power levels run from .5 to 50 Watts.  As the thunder storms are becoming less frequent, lower power levels are easier.  This is why I prefer morning skeds - it's the lowest thunderstorm activity, so low noise, low absorption and less chance of receiving 'natural' electro-shock therapy from passing storm clouds.
I guess it'll need some testing to find the sweet spot in terms of the right time frame. Mornings would be great. Especially atmospheric noise is my biggest fear, since both parties would be running QRP power levels at 5W, at best.

Depends upon your latitude.  I'm rather far north, and our critical frequency for NVIS is rarely above 5MHz.


http://www.sws.bom.gov.au/Images/HF%20Systems/Global%20HF/Ionospheric%20Map/WorldIMap0.gif

Otherwise - yes! - I'd use 60m in a heart beat. Before the sun numbers tanked,  5371.5 USB was our community calling frequency very useful in this mountainous State.

I also think 60m is a bit too high around where I am at. Very few times have I seen the foF2 getting higher than 5Mhz in the 6 months I've been monitoring Dourbes.


Thanks everyone for their replies so far!

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I have started a new thread on this discussion to keep the Welcome Thread more on-topic for Welcoming new members.
Below I've re-stated some information from the other thread so everyone can easily read what it is I'm trying to achieve here. I've already had some great replies in the other thread for which I am thankful. I've quoted some replies below from the other thread to which have also written a reply - in this thread to keep the other one clean.

A close friend recently started prepping as well and I want to establish a (for HF) rather short-range method of communication. The ranges to think of are 15 or 20 to 75 miles. I'm having the hardest time with finding the right band & time that would provide the highest reliability for daily NVIS communication, all-year and preferably solar cycle round. In the Welcome Thread it was established that the 80m band is the most reliable in a low solar cycle during the day, like we are in now, with 80m being suitable for high solar cycles at midnight. 40 meter would be best during high solar cycles during the day. If I got any of this wrong - please correct me

Commsguy - VOACAP is correct - in winter months during lows in the solar cycle (like now) 80M generally becomes a DX band after dark.

I strongly advise you to regularly check live foF2 readings in your region - it's the magic critical frequency: http://www.digisonde.com/stationlist.html

If I could give one other piece of advice: in the time I've been licensed, I've learned there is no single magic band that's always reliable - so frequency agility is a must.

Whether it was sunspots, or Sporadic E's.... being able to switch bands made communications possible.
As for VOACAP, link probability drops like a brick just after sundown on 80 meters in the winter, only coming back a few hours later at 2300h for the short-distance link. Is that because of 80m opening for DX after sundown? What makes it come back for NVIS at 2300?
I'm well in the know about the critical frequency for NVIS, foF2, it's one of the first things I learned about when starting to looking into NVIS. That's also why I've been looking at the Dourbes Ionogram every day for the last 6 months or so.
I hardly have seen the critical frequency (foF2) above 60 meters, which caused my confusion with so many people and 'research papers' praising 40m for NVIS.

As stated above, opting for frequency agility would be the best solution to most problems, but it would also require more knowledge and equipment to achieve both 40 and 80 meter band capability.

For me personally the more required knowledge and hardware wouldn't be a problem since I am the commsguy in our small prepping group, and I have a nice multi-band rig myself already. I'm looking for a cheap solution to equip someone else, preferably for around 100-150 euros total so that two-way communication can take place. For one-way communications a shortwave receiver like the GP-5/SSB would be a great fit since it covers all bands and then some, but I'm mostly looking for two-way communications in that price range.

As for a transceiver I've been looking at the QRP-Labs 5W CW transceiver kit. The reason that radio has the most interest from me is because of it's low price but much better quality than something like a Rockmite or Pixie. It is however monoband and would require some modding to be able to switch a band pass filter and low pass filter to get both 80 and 40 meter. A ready made multi-band QRP transceiver could also be the chinese X1M Pro QRP transceiver, which is around 250 euros. Such price increase doesn't currently fit the budget, also taking in to account that other accessories needs to be bought such as batteries and coax.

I can't find the context of the original quoted question:

"What would be the most reliable time of day to establish an communication on 80m? Early Morning, Noon, afternoon or at night/midnight?" but the answer depends on the location you are in the world, and the location of the other station! Is it 10,000km away or 10km or 100 or 1000? 80m generally speaking offers only local contacts up to a few hundred km during the day, but thousands of km (or more) depending on the antenna, at night. Near the equator there is a lot more static on 80m than at mid latitudes. Signals during the day are absorbed by the D layer, so don't reflect (refract) well hence short distances, again more so in summer than winter. You may look at 80m as being a band that favors darkness over light. BUT for short distances and NVIS at mid to high latitudes it is good. At mid to high latitudes at night though you especially need to make sure you have a horizontal dipole at a low height compared to 80m wavelength, as a vertical is more likely to give you sky wave reflection of F layer, not blocked by D layer, resulting in large dead "skip zone" before landing back to earth far away, for long distance "DX" contacts.

This plot of how a dipole radiates (low angles to the left and right are for long distance, you want the high straight up lobes for close-in contacts) at various heights, this is for 40m. It would be more helpful if I found one that gives height in relation to wavelength, but to make this valid exactly the same for 80m, simply double the heights given, e.g. the 10m high plot on this 40m graph would be 20m high on 80m, etc. Don't worry about the exact frequency, it will be much the same for 3.5 or 3.7 MHz in this case!



Look at the red line: this is what a dipole up 15m on 80m band would look like, so NVIS even at that height, and few can get an 80m dipole up that high! Look at the green line, if you can get it up 60m in the air, you will have BOTH low angle AND high angle but less intermediate angle radiation: good for local NVIS and long distance. But who can get it up 60m? But on 10m band you can get that green pattern at just 7.5m above normal ground. 10m of course is not much use at this part of the sunspot cycle, we have to wait many years, if ever, to get those good conditions again.

To reiterate, it's about 10 to 100kms that I'm trying to achieve here. From the amateur radio theory I have the understanding that the D-layer hardly absorbs 80m when the wave is perpendicular on the D-layer, so that would have much less impact on short-range NVIS operations.

I have some papers that go into detail about dipole heights and different bands, I'll have to gather all materials I've read so far on NVIS (which is a lot!) and find it again, but I'll upload the lot of it if there is any demand for it.





3
General Discussion / Re: PLEASE READ! Welcome to Radio Preppers.
« on: August 23, 2017, 01:45:34 PM »
Quote
What would be the most reliable time of day to establish an communication on 80m? Early Morning, Noon, afternoon or at night/midnight? And I also reckon seasonal change would have a large impact on this as well, so I'd love to have some more info on that

80m will work better after sunset and in winter.
So winter is in general better on 80m, and in both winter and summer it would work better after sunset.

Studying VOACAP all-year prediction gives a different result though, link probability gives higher reliability around noon during the winter, and probability drops to zero at sunset in the winter(around 1700h), opening later again at 2300h.
In the summer however VOACAP gives almost a round-the clock consistent link probability, almost not dropping below 90% for the entire day except between 2000h and 0500h

Quote
I'd need access to two buildings in order to cope with the rather flat terrain.

The trick here is to put your antenna on a mast or hung from a tree branch. 2m indeed will not work well with an antenna close to the ground, unlike NVIS on 80m.
I don't know what kind of height you were thinking of for 2m but I was planning on an 80m dipole at about 10 meters using a tree as a center support. It's easy to throw a small heavy object over a tree branch and get to that height.

Using a tree for a 2m SSB, it would be pretty hard to get above the general canopy/building roof height around here. A dipole is much easier to deploy the right way the first time.

I think it'd best if this discussion was set forth in a new thread, this thread being a welcome thread and all

4
General Discussion / Re: PLEASE READ! Welcome to Radio Preppers.
« on: August 23, 2017, 12:35:54 PM »

The most reliable band for NVIS is 80m.
What would be the most reliable time of day to establish an communication on 80m? Early Morning, Noon, afternoon or at night/midnight? And I also reckon seasonal change would have a large impact on this as well, so I'd love to have some more info on that

Don't ditch the 2m band... Using USB on 2m can greatly increase its range. 2m USB can cover the near-regional range and 80m the far-regional range.
2m would be a great band too, but unless you're within omni-directional range(saw your video on it) you'd also need to know someones bearing to use SSB with an Yagi antenna, plus there are a few more factors, like me suspecting I'd need access to two buildings in order to cope with the rather flat terrain.


In any case the most prominent limiting factor for the set-up in mind is the cost of a second, third or fourth rig that can operate the desired band and mode. Since I am the commsguy in my prepping group, I have a nice QRP do-all rig, but now I am looking to create a set-up for the other people in our group with a means to communicate "when SHTF". I've been looking at the recently announced QRP-Labs single band CW transceiver, which looks promising even for people who don't know morse code since it has a built-in decoder and message keyer.
https://www.qrp-labs.com/qcx.html

That way some very basic communication can happen, which would have effect on further SHTF-plan execution and decision-making for both parties communicating, or scheduling a rendez-vous point and time for instance. I'm not aiming for long rag-chews but short, easy & "robust" pre-selected messages that can deliver a situational report to other members

I've gained a lot of "inspiration" for what I'm trying to achieve from Guerrillacomm NVIS experiments, which I'm sort of trying to copy https://www.youtube.com/watch?v=N_F_2BcfqC0

5
General Discussion / Re: PLEASE READ! Welcome to Radio Preppers.
« on: August 16, 2017, 07:29:58 AM »
Hello everyone,

I'm a prepper located in Western Europe and I stumbled upon this forum in the links section of the webpage of OH8STN - awesome to find an entire forum dedicated to ham radio & preparedness, without too much focus on only either of those topics, but the best intersection where both topics meet.

As a prepper I got in to ham radio & comms-gear a few years ago when I picked up a scanner and later a few chinese HT's and I extensively started testing ranges to get a good understanding of communication capabilities. A huge pet-peeve within the prepper communities are people buy a few Baofengs and basically make grotesque assumptions on their capabilities or usefulness, nor not even practice using & operating their radios. Not to mention how little time people spend on finding & evaluating the right or up-to-date frequencies to get news or information from.

I've come to the conclusion that 2m & 70cm is pretty much only useful for short-range, tactical communications for those people in your prepper group that are very near or with whom you are directly working together. For instance the neighborhood watch, on patrol or in vehicle convoys or vehicle to dismounted. Unless Party A and Party B both have Diamond VHF/UHF antennas on their roof, I've kept VHF & UHF prepper communications within 5 Miles tactical range (that is with external DIY antenna's but not in any optimum situation. Better to be conservative with range rather than overestimate). For obvious reasons I do not wish to rely on amateur repeaters.

That brings me to my next and latest research, where I've spent the last year looking into: NVIS. I've already ready a few threads on this forum and I've spend so much time reading all available articles and research into, ranging from the USMC antenna books to the latest research on NVIS from 2015 (http://www.vederfonds.veron.nl/PhD%20Thesis%20B.A.Witvliet%202015.pdf)

A few problems I can't get around are so many articles praising NVIS on 40 meters. Most of the amateur radio articles on NVIS are from the United States, and I have some problems with that:
  • The Unites States is huge compared to Europe, if one makes an international contact 320 kilometers out (200 miles) that would be in the States only the next state over
  • After keeping an eye on ionograms (http://digisonde.oma.be/latestFrames.htm) daily for a year, I've never seen the foF2 frequency above 60 meters, and I hardly ever hear amateurs from my country on 40 meters, and the times I did I suspect it was the groundwave playing a factor.
     I know the solar cycle is currently at a minimum, and foF2 could easily go to 40 meters in a maximum
  • professional or commercial articles on NVIS only give very broad and shallow information in regard to frequency choice which are no help at all

A close friend recently started prepping as well and I want to establish a (for HF very) short-range method of communication. The ranges to think of are 15 to 75 miles. I'm having the hardest time with finding the right frequency band that would provide the highest reliability for daily communication, all-year and preferably solar cycle round.

PS: Saw the CB sub-board, maybe that should/could be expanded to general license-free comms (to include PMR446 for instance) and add an NVIS subboard.

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