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Old 24-11-2020, 06:25   #1
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MF: 2 MHz marine frequencies and 160m amateur

I'm wondering:
- are the subject MF frequencies are used by cruisers?
- if so, for what purposes?
- are automatic antenna tuners are able to tune these with a backstay antenna?

- does anyone add manually switchable loading coil to improve tuning?


I've been experimenting enough with HF/MF to understand the theoretical utility of this band as well as the practical difficulties it poses. Under extremely poor propagation conditions when 80m is closed, 160m will usually still work. This occurs from time to time, in the winter, in early morning, during the sunspot low, especially in higher latitudes.


On land, MF has utility for NVIS where the high angle of incidence further reduces the usable frequency. (NVIS, Near Vertical Incidence Skywave, is a technique for short to medium range communications where terrain and distance make VHF unusable). It can also be used for groundwave communications, though for SSB a great deal of power is necessary. I don't see where groundwave is of much use on the water. NVIS might make sense in rivers or fjords.


The backstay is electrically too short for MF on anything smaller than superyachts, and I would expect that few automatic tuners would be able to find a match.
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Old 24-11-2020, 06:40   #2
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Re: MF: 2 MHz marine frequencies and 160m amateur

Quote:
Originally Posted by Jammer View Post
I
(snip)
The backstay is electrically too short for MF on anything smaller than superyachts, and I would expect that few automatic tuners would be able to find a match.
The icom at-140 tuner will tune down to 1.6 MHz with a minimum 23 ft antenna. 2182 is a distress frequency. I otherwise can't speak to the usefulness of the band. I don't have an at-140 and my tuner will not tune it.
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Old 25-11-2020, 00:24   #3
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Re: MF: 2 MHz marine frequencies and 160m amateur

Jammer,

Bottom line:
2mhz / MF not used by cruisers....and typically not needed.
Reasons:
--- 4mhz (and even 6mhz and 8mhz) usually work better for local / regional comms...it's damn rare that you'd find the critical freq below 4mhz and, at the same time the groundwave signal to be too weak....'cuz if you're close enough that a 70* to 90* angle signal isn't being reflected on 4mhz, you're close enough for groundwave on 4mhz (remember, we are over sea water, using vertical antennas....and that's a BIG advantage, can be as much as 30db - 40db better than a horz antenna on-land!! This is a situation where trying to use land-based 160m anecdotes can be problematic... )

--- lots of RFI as you move lower in freq (much caused by cheap, non-certified or fake-certified switch-mode power-supplies/chargers of consumer devices)

--- poor / inefficient antenna systems

--- poor antenna ground systems



Onto some specifics:

Good questions tonight...
But, I need to be brief....

BTW, reading between the lines of what you write, I think I see a bit too much reading of "ham" info from other hams? And, while in the past that was great, and one of the best ways to learn, but these days there is a lot of regurgitated crap out there that sounds official and learned, but is just some guy repeating what some other guys said or wrote....
The actual facts of 160m vs 80m propagation are not quite as you describe...it looks a bit like you generalized and over-emphasized a couple things....not a big deal, but...

But, like I said before, the actual facts of propagation have been known / understood for decades, and they're printed in lots of books....but few of these facts are found on-line....LOL

Further, one cool point....
Recent high-MF / 160m long-range skywave propagation research (done within the last 20 years) has shown an even higher requirement for vertical polarization and a high priority on the antenna ground system (for this vertical antenna).....these were originally thought to be of less importance by hams throughout the 1950's thru 2000....as their experiences on HF showed horizontal antennas (even mounted low in terms of wavelength), were far superior to verticals (except verticals over sea water), but in the past 20 years, real-world research has shown how mother nature throws a curve-ball on MF...

Bottom line:
Don't take everything you read as gospel....
Have a look at both the old Radio Engineering Handbook, The ARRL Handbook, The ARRL Antenna Book, ON4UN's Low-Band Dx'ing, RSGB radio handbook, etc. etc...and then have a look at W8JI's writings, and W2DU's...as well as those of W3LPL, and K3LR...

Steer clear of the "internet NVIS hype" guys, etc....
And, especially all those "internet guru's" that hype one specific antenna, etc....particularly anything that seems too good to be true, and/or seems like "if it were true everyone should know this"...'cuz usually most of that is BS... LOL


FYI, I personally have a good deal of experience in 160m operations, I will add some info below, if I have time....


Quote:
Originally Posted by Jammer View Post
I'm wondering:
- are the subject MF frequencies are used by cruisers?
These days, No...

No cruisers I know have used the MF/2mhz simplex freqs in many decades...(although back in the 1960's and 70's, they were used....heck, in the Bahamas 2mhz Marine was the "CB Radio" of that era!....everyone used it everyday....I still remember "Children's Hour", etc....and the big 12vdc Dyno-Motor hi-voltage power supply that ran the old Raytheon vacuum-tube transmitter, gosh what a power hog!)
And, FYI, back then it was a 23' whip as antenna....and the tuner was built-in to the transmitter, and the GTO-15 ran right from the transmitter to the antenna....ah, the old days!

As for "2182khz SSB", nobody except for Bermuda Harbour Radio still monitors it....and, while it is still the sole Maritime MF GMDSS SSB Voice calling/safety frequency, and > 450 coast stations licensed worldwide, as well as 1000's of SOLAS merchant ships, are required to have 2182 SSB available for 2-way comms (after initial contact via 2187.5khz DSC), I'm not sure how many cruisers have ever used it....(I know I haven't used 2mhz / MF Marine in decades, I think the 1970's?)

BTW, Australia's AMSA never established a Sea Area A2, and therefore never used 2mhz/MF maritime band....

And, the USCG gave up on it over 7 years ago (citing poor comms reliability due to: high noise levels from consumer device RFI....and poor antenna efficiencies...)
https://www.govinfo.gov/content/pkg/...2013-16801.htm


Have a look here, for what the USCG currently uses...
https://www.navcen.uscg.gov/?pageName=cgcommsCall


- if so, for what purposes?
The only purpose would be to have two-way comms with a MF Coast Station, after initial contact via 2187.5khz DSC....(there are dozens and dozens...hundreds? in Europe)

Or the extremely rare instances where groundwave on 4mhz is unusable...and/or the "critical freq" (above which, no vertical ionosphere reflection takes place) falls below 4mhz, so NVIS comms are too weak on 4mhz...
Fyi, the "critical freq" is approx 1/3 of the ionospehere's current MUF, for the same location / comms path....

BTW, HF groundwave is of course weaker than MF groundwave signal strengths, assuming similar antenna system efficiencies....but, of course typically antenna efficiencies on 2mhz are very low, and hence 2mhz maritime comms are typically (almost always?) weaker and less reliable than 4mhz comms, at the same time and along the same comms path...

Also, please be aware that MF "groundwave" (and what little HF groundwave there is), over sea water, is significantly stronger (a LOT stronger!!!) than that over land!! And, since vertical polarization is required, most land-based antennas need large ground radial systems, and even then are generally inefficient (unless you have a big AM broadcast station tower...see below for details about that)

FYI, I do have experience in 3.6mhz NVIS vs. Groundwave comms....and it's strange when you hear the echo of the NVIS propagated signal after the groundwave signal....but...
But, in general, with horizontal antennas the NVIS signal is almost always the dominant one, and the groundwave is only ever heard when the critical freq falls below your operating freq! With vertical antennas, over ranges of > 30 - 50 miles, the groundwave signal can be heard, but again usually weaker than the NVIS signal....only on very short ranges of < 30 miles, and with vertical antennas, is the 3.6mhz - 4mhz groundwave signal usable above the NVIS signal...
At 1.8mhz - 1.9mhz, add 50% to 100% to these ranges, and this is what you have on 160m (and approx. the same on 2mhz maritime band)

Bottom line....if you're beyond VHF range, HF usually works fine....and no need for 2mhz..

And, to be honest, most cruisers find the "middle ranges" of the regional cruising nets, etc. to be most difficult...
25 - 250 miles, no problem
750 - 7500 miles no problem
250 - 750 miles is where some cruisers have issues (usually due to improper freq choice, combined with poor antenna systems...)

- are automatic antenna tuners are able to tune these with a backstay
antenna?
Yes, absolutely...
Whether you have a modern Icom AT-140, the older AT-130, or even the ancient AT-120....they all will tune (couple) the antenna to the transmitter just fine....as long as the antenna is at least 20' long (specs say 23')....
They will work from 1.6mhz thru 30mhz....

Although, like all remote auto-tuners, their efficiency is based on the impedence of the antenna....which means that their losses are high on 2mhz, if using a short antenna!!

And, yes....the SEA 1600 series tuners, and the SGC 230's, will also tune 1.6mhz thru 30mhz, using a 23' antenna...
And, I believe so do all the Furuno, JRC, and Sailor/Thrane/Cohbam MF/HF GMDSS certified tuners...

{FYI, both my AT-140 and my back-up SG-235, tune my backstay just fine, from 1.6mhz thru 29mhz....(never tried it above 29mhz)}


- does anyone add manually switchable loading coil to improve tuning?
Not necessary at all....see details above...


But, FYI an odd irony here....
The Icom AT-131 and AT-141 tuners (the EU/UK and Aus certified tuners), and, I believe the new GMDSS certified Icom AT-140 tuner for the M-803, as well as the Furuno, JRC, and Sailor MF/HF GMDSS tuners, all have separate manual tuning coil and capacitor built-into them, that in the event of tuner failure, allows you to open up the tuner cabinet / chassis, and manually tune your antenna for 2mhz/MF use, therefore meeting the GMDSS requirements even in the event of tuner failure!


I've been experimenting enough with HF/MF to understand the theoretical utility of this band as well as the practical difficulties it poses. Under extremely poor propagation conditions when 80m is closed,
Except for geomagnetic storms / radio black-outs, I've never seen 80m "closed"???
Perhaps you meant, when the critical freq falls below 80m?
And, then, yes the 160m will work for NVIS comms, when 80m won't....just be aware that with the solar cycle now on the upswing, it's unlikely we'll see this condition much (if at all) in the coming half-dozen years...
160m will usually still work. This occurs from time to time, in the winter, in early morning, during the sunspot low, especially in higher latitudes.


On land, MF has utility for NVIS where the high angle of incidence further reduces the usable frequency. (NVIS, Near Vertical Incidence Skywave, is a technique for short to medium range communications where terrain and distance make VHF unusable). It can also be used for groundwave communications, though for SSB a great deal of power is necessary.

I don't see where groundwave is of much use on the water.
Well, for cruisers I agree....groundwave isn't a big plus...
But, in the real world, MF and lower HF groundwave over water is awesome!!
BTW, if you have a listen to US AM broadcast stations when heading to Bahamas or in a quiet anchorage there, you can hear a couple of the Miami, Ft. Lauderdale, West Palm, stations on groundwave during the day....and their signals are much stronger 100 - 150 miles to the east / offshore than they are 50 miles inland....

And, yes, MF vertical polarization skywave propagation over sea water is also great (just like it is for HF) and those same Miami stations, and thsoe from Jacksonville, FL (and one or two from New Orleans, etc.) that are NOT 50kw "clear channel" stations, but have much lower power at night, have great signals down-island at night....and they stand out like beacons on the band...

Not sure if it was WQAM, 560khz?? but, think so....
That has their antenna in the mangroves / salt marsh along Biscayne Bay....and wow, what a great signal...


NVIS might make sense in rivers or fjords.
NVIS is used darn near every day, by most cruisers!!!
It's just that they use it on 4mhz (or 6mhz, or 8mhz)....or 75m or 40m ham bands...

And, yes, vertical polarization is generally bad for NVIS...
But, good news is that those with backstays do have an advantage...
'Cuz, even a slight 15 degree slope (while not significantly presenting a null in the azimuth pattern), actually reduces the overhead null from 20+db to less than 6db....and on some freqs, the elevation pattern is very broad....

Hence, another reason 150 watt radios on sailboats with backstay antennas and decent ground systems (low-imp direct sea water connection) have as strong of signal as most 1500 watt ham stations on land!!
{FYI, a couple years ago, I was on 75m talking with my best friend....
---I was on-board my boat, at the dock, in S. Florida, floating on sea water....Icom M-802/AT-140, backstay antenna, wide copper strap to two big Dynaplates...
--- He was at home in N. Florida (about 200 miles from me), with a full-wave horz loop (i.e. "Loop Skywire") at 50' high, running about 1250 watts out...
We were chatting away....no issues...
Then a gentleman came on and asked me if I could move 2khz up, as they had a Net starting in a few minutes, 1khz away from where I was transmitting, and my signal was so strong he was concerned that we wouldn't just QRM each other, but that few of his Net stations would hear him...
It was no biggie for me and my buddy, so I wished him a good net, and we moved a few khz up and continued our conversation...
The hitch in this story??
The gentleman who came on saying my signal was "so strong" was in southern Argentina!! About 6000 miles away....
Now, of course this wasn't "groundwave", nor NVIS....rarther just good 'ole skywave....
Just showing this example that the same antenna can be useful for a WIDE variety of various propagation!!


The backstay is electrically too short for MF on anything smaller than superyachts, and I would expect that few automatic tuners would be able to find a match.
Most backstays are electrically short for even the lower HF freqs...
But, I've never found a marine tuner that wouldn't tune a backstay (or even a short 23' whip) on 2mhz / MF!!
Sorry for rambling on so much here....when the answer is 2mhz not used by cruisers, and not really needed, I probably shouldn't have wasted your time with all the rest...LOL


In addition to my decades old experiences on 2mhz / MF maritime....here is some first-hand 160m info....

--- In addition to using it casually for local work, for decades (before the NVIS-hype guys showed up online)....I have some other experiences...


---At a friend's house, where I operated from every week, for many years...I designed and built a 160m EDZ at 100' high...had a great NVIS signal all over Florida / Georgia, and even surprised others all over the eastern US with how great it worked...


--- Back in Jan 1990, I designed/coordinated a 160m contest effort with my friends in N. Florida...
I was the efforts designer and engineer...and out together a killer antenna system..
By happenstance I consulted on a job to inspect a defunct AM broadcast station in a marsh, near St. Augustine, FL....and, got permission from the property owner to use the property for our ham contest...

There was one tower totally collapsed, and a twisted mass of steel on the ground....and one tower that buckled in the middle, and looked like upside-down U....and one tower still standing, but leaning a little...
This one was usable....it was a 200' tall Rohn 25g, base insulated....with > 120 copper ground radials, and hundreds of sq feet of copper strapping/flashing at the tower base....
We parked an RV, next to the stripped-out transmitter building, used a Dentron Super-Tuner at the tower base, and my Drake TR-7 as our transceiver...
At that time my 1000watt amp (SB-221) didn't cover 160m, so I borrowed a 1500 watt amp from a friend...oppsss.
Well, his 1500 watt amp lasted all of about one hour, before it burnt...(piece of crap Ten Tec....I now own two Alpha's! but, this was 30 years ago!)
So, we ran the whole 160m contest barefoot, with just 150 watts out of my TR-7....

We came in second place in the whole SE US, and finished in the top 1/3 of all stations worldwide with only 150 watts, versus everyone else's 1500 watts!!

That 200' tall vertical, over dozens of radials (we could only find about 30 - 40 of the 120 radials to actually connect to), in a marsh, near St. Augustine, FL was a killer 160m long-range / DX antenna....but, we also worked everyone we could hear, even daytime groundwave all over Florida and Georgia!!

Btw, I also rigged a 600' long reversing-Beverage receive antenna, that also worked well....but, we were so far from any RFI, the only time we needed the Beverage to pull out some signals, was to pull 'em out of the QRM of others on-the-air....



Bottom line again:
Don't over-think this...
2mhz / MF not used by cruisers....and typically not needed.
I think this is situation where you're looking at a solution in search of a problem?

But, I do hope I helped?

Fair winds

John
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Old 25-11-2020, 03:00   #4
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Re: MF: 2 MHz marine frequencies and 160m amateur

Thanks, John. All makes perfect sense.


<<Steer clear of the "internet NVIS hype" guys, etc....>>


Yep. Don't know which is worse, the "NVIS hype" guys or the "NVIS doesn't exist" guys, I try to avoid them both.


Your comments on the differences resulting from seawater vs. soil are especially helpful.
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Old 25-11-2020, 14:25   #5
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Re: MF: 2 MHz marine frequencies and 160m amateur

Use a vertical, perhaps one of the MFJ collapsible verticals or just plain tubing...but of good height. Then feed it at the bottom thru a loading coil to resonate at those frequencies....You are never goiong to get a full sized antenna for those frequencies unless you have the queen Mary.


Of course be sure the vertical is not grounded. Find a ham in your area that has a antenna meter so you can check the resonant freq of the antenna
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Old 25-11-2020, 15:44   #6
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Re: MF: 2 MHz marine frequencies and 160m amateur

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Thanks for the 7Q7 qso on 15M CW on 5.11.20.
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