SSB / Wx antenna sharing

[tkeithlu]

OK, I confess. I've got eight antennas on my boat. But, the point is, a VHF 6dB wire antenna is dirt cheap, cheaper than a splitter, I think, and easy to install. Give it a try before spending a bunch of money on a complex solution to a simple problem.

Aside, a tuner only gets into this if you split between the transmitter and the tuner, and if you do that, god help your HF transceiver.

--K4TKL

[waterman46]

Connect your HF Wx receiver to one of your shroud chainplates ( but not one that has a direct connection to ground). The shroud has sufficient isolation from a backstay SSB antenna.

Some boats actually load up the whole rig as an SSB HF antenna. Shroud ought to give reasonably good HF signal capture for WFAX.

[jt11791]

Thanks for the insights. My fax receives on 4-12MHz. I can tune in the fax transmissions on my SSB, but I'd like to use the printer on the fax machine. Maybe more trouble than it's worth, but the equipment is there, so I'd like to at least try it out. As I said, the VHF style whip antenna that I have doesn't work, and I'd rather not add a new antenna, so the switch before the tuner sounds promising. I'll be sure not to transmit with the SSB without the antenna.

[jt11791]

Originally Posted by waterman46

Connect your HF Wx receiver to one of your shroud chainplates ( but not one that has a direct connection to ground). The shroud has sufficient isolation from a backstay SSB antenna.

Some boats actually load up the whole rig as an SSB HF antenna. Shroud ought to give reasonably good HF signal capture for WFAX.

My shrouds are all grounded and the backstay is the SSB antenna.

[S/V Illusion]

Originally Posted by Paul L

Greg
If the tuner is tuned to say 8mhz, does that do anything to improve the 8mhz reception?

This isn't the place to elaborate on the technical characteristics but, in answer to your question, yes.



Actually, it does but more important, it will attenuate signals not around the 8Mhz band.


Unfortunately, this site wont allow attaching a video or audio file or I could easily demonstrate how my manual tuner can significantly attenuate (or enhance) away from/closer to the frequency it is tuned to resonate.




This is one reason why auto-tuners can often work against you when you are listening to a wife range of frequencies (channels) unless it can be bypassed.

[jt11791]

Originally Posted by S/V Illusion

This is one reason why auto-tuners can often work against you when you are listening to a wife range of frequencies (channels) unless it can be bypassed.

Is that those high squealing sounds I hear sometimes?

[S/V Illusion]

Originally Posted by jt11791

Is that those high squealing sounds I hear sometimes?

My wife isn’t very wide but it appears my wide auto-correct feature doesn’t forgive my lack of proof-reading.

[continuouswave]

The device commonly called an "antenna tuner" does not actually adjust the tuning of the antenna. Most antenna tuners are connected into the transmission line between the antenna and transmitter (or receiver), and their function is to transform the feed point impedance of the antenna to be a match to the transmission line impedance.

The purpose of using an antenna tuner is to allow the most efficient transfer of power to the antenna from the transmitter. The actual resonant frequency or impedance of the antenna is not affected.

The antenna tuner contains some arrangement or network of components that produce the desired impedance transformation. These networks operate reciprocally, that is, they work the same in either direction. During transmission they improve the transfer of power to the antenna from the transmitter, and during reception they improve the transfer of power to the receiver from the antenna.

It is usually the case that if the antenna is non-resonant, the adjustment of the antenna tuner to produce the proper impedance transformation will be quite critical, or in radio terminology, have a High-Q. This means that if the frequency is changed slightly, the matching unit will need to be readjusted to produce the proper impedance transformation at the new frequency.

A better name for these devices is antenna matching unit, although antenna tuning unit is very commonly used. Generally the components in the matching unit are themselves frequency sensitive, and their arrangement often produces a frequency filtering action. Depending on the arrangement of components, the filter action can be high-pass, low-pass, notch, peak, or band pass. It is impossible to predict what action will occur with a particular antenna matching unit because there is no uniform or standard arrangement used.

As mentioned, if an antenna matching unit is adjusted for a particular frequency for producing a good transformation of the antenna impedance to the transmission line impedance at that frequency, there is no basis to assume that at some other frequency when not readjusted for the new frequency that the effect of the antenna tuning unit will be beneficial, unless the new frequency is very close to the original frequency that the matching unit was adjusted.

[Brian.D]

I have found, and this was done with an HF transceiver / auto tuner / PC with sound card, that if I tune the radio and tuner to the 12MHz band to receive the WEFAX signal, I can also successfully receive in the 8MHz and 4MHz bands with little loss. However, if I tune in the 4MHz band, there is much signal degredation in the 8MHz and 12MHz bands.

Of course your results will very, but you may want to experiment with tuning the SSB in the 12MHz band and then try and receive the WEFAX in the 4MHz and 8MHz bands. Experiment and take notes.

[Topspin]

In case that you want to split your backstay antenna (with tuner) into your SSB and a second HF-WFax device for RX.....

I just found this solution: https://www.strictlyham.com.au/brows...es-mfj-1708sdr


I would instead use my main SSB transceiver and do the fax decode with my pactor modem.



-Richard (VK4WRS)


P.S.: I haven´t tried the VHF Sat reception, but isn´t that just plain SAT images with only limited information. Would be very difficult to receive with just a vertical masthead antenna.....

[ka4wja]

JT,

1) Well, first off a quick / direct answer....it is not "more trouble than it's worth"! To the contrary a dedicated WeFax receiver (whether a paper-based unit, like my Furuno FAX-408, or a computer-based unit) is still considered the gold-standard of offshore/hi-seas weather information! (as of 2012, the last year I have data for, still used by majority of professional ocean mariners)



And....and, until you've held a weather chart in your hand when planning a passage, or even better when in the middle of an ocean and you're looking for better wind, you won't grasp how nice it is!

And, since the solution to your issue is very easy! And cheap! (cost you about $20 retail...or, depending on exactly how your boat is set-up, maybe as much as $75...) And, will take you just a few minutes! (no longer than 30 minutes!)

Here are the details:

a) You can share your MF/HF-DSC Receive Antenna with your WeFax Receiver. A simple coaxial "tee" connector works well for this. Remember that HF (MF and HF) receiving is all about signal-to-noise ratio (S/N), and no decent quality modern HF receiver emits enough RF noise (nor harmful LO leakage) to adversely effect another receiver's performance. [of course in a professional comms network, there would be directional couplers / receiver-multi-couplers...but for our applications these are unnecessary]


b) In addition to doing this exact thing (using my MF/HF-DSC Receive antenna to feed both my Furuno FAX-408 and the Icom M-802's dedicated DSC receiver) on my current boat, since 2004, I have also done this on-shore for decades of HF ham receiver coupling, and did this decades ago with an old Alden MarineFAX and a shortwave receiver.







Now since MF/HF-DSC is part of the GMDSS, and have been with us now since 1992, and fully-implemented Jan 1999 (over 20 years ago!), let's not get all in huff if someone told you that a non-DSC maritime radio is "just fine"....
How many here still use the same cellphone / mobile device they used over 20 years ago? Who here is typing on the same computer they used over 20 years ago?
(Heck, there aren't many here that even use the same chartplotter for more than 10 years)
And, since Jan of 1999, there have been no HF-SSB Voice watchstanding by any merchant, coast guard, or naval vessels worldwide, rather using MF/HF-DSC as initial signaling/calling before passing two-way voice traffic via SSB-Voice....that means 1000's of SOLAS vessels worldwide are listening to the six int'l GMDSS/DSC freqs (not SSB Voice), and >80 HF-DSC Coast Stations worldwide, and > 450 MF-DSC Coast Stations worldwide....
And, except for the USCG, Australian AMSA and NZ Maritime Authority, there are no longer any Maritime SSB Voice radio watchstanding!
So...
So, when referring to "SSB" radio / "SSB" communications here online, for most of the past 15 - 20 years, we are talking about MF/HF-DSC-SSB Radiotelephones and MF/HF-DSC-SSB radio communications...
So...
So, everyone here with a modern boat that has "SSB" onboard probably has a MF/HF-DSC-SSB Radiotelephone (such as the Icom M-802, Furuno FS-1575/2575, or Sailor 6310/6320, or a JRC, or Skanti....MF/HF-DSC-SSB Radiotelephone)
So...
So, that's what we all assume here-abouts....


If you do not have such a radio....please read some of the stickies here, some of my other postings, and watch some of the videos linked to below....and you have more info about this than you could dream of...




2) Secondly, with a Hylas 54 (a modern vessel) you obviously do have a MF/HF-DSC-SSB radiotelephone (probably an Icom M-802), so your solution is quite easy-peasy.

http://www.icomamerica.com/en/products/marine/ssb/m802/

http://www.docksideradio.com/index.html

http://www.docksideradio.com/Icom%20SSB%20Radios.htm



a) Just connect a short coaxial jumper cable from your HF WeFax receiver to a coaxial "tee" connector, and another coaxial jumper cable from your M-802's DSC Receiver jack to this "tee" connector, and then the coax cable running to your MF/HF-DSC Receive antenna to the 3rd connection point of the coaxial "tee" connector....and you're all done.....but..



b) But, since we don't know what you're presently using for a MF/HF-DSC Receive antenna, we cannot know the effectiveness of your present antenna for HF WeFax reception.



c) Some will simply connect the center-conductor of a piece of coaxial cable to a chainplate or shroud tie-rod, etc., and thereby use the entire rig/mast as their MF/HF-DSC Receive and WeFax Receive antenna! (please understand that it doesn't matter if the chainplate/rigging is "grounded" or not, it will work the same)
Now, please know that this does work....and is easy-peasy....but...but, it can be problematic (it's almost impossible to know, as each boat / each set-up is different), as this can be a rather noisy antenna, meaning it can receive a good deal of radio noise / RFI (Radio Frequency Interference), and thereby not perform well....but, in some instances it can work very well! ?



d) The difficulty I have here in recommending that easy-peasy approach above (in "c"), is that while some might find it works well, since their primary use of this antenna is not voice comms and few sailors are experienced/trained radio operators and will usually not understand / notice the increase in received noise at some times / with some systems on-board running....so, I generally recommend using a separate antenna, even if it is just a random length of wire run up a halyard or even if run up along a shroud (yes, there will be some coupling to the rigging, but it's generally a much better approach than a direct connection to the standing rigging).... FYI, back in the late 70's I did just this, used a 30' length of wire (I used GTO-15, but didn't need to!), run thru a cable-clam deck fitting adjacent to a shroud and wound the wire spirally around the shroud (but could've just ran it straight up, I just wanted to reduce possible issues with sail contacting the shroud/wire)....this worked great with no issues for more than a decade, for HF-WeFax and Shortwave (and UK Longwave shipping forecasts), across the Atlantic, UK, the Med, and Caribbean....heck, I even remember the US Navy WeFax freqs, 8080khz and 10865khz, out of Norfolk, VA and Rota, Spain...and of course the 200khz / 190khz UK Longwave shipping forecasts...(fyi, I used a Palomar Engineering "VLF Converter" to allow reception of these Longwave signals)



e) Now, I'm a "radio nut", and have made my living in the communications industry....so, I do tend to go the extra mile....but, you can't fault me for making sure things work as best as they can...

For HF-WeFax and MF/HF-DSC reception, on my current boat since buying it in 2004, I've been using an insulated aft-lower shroud (~ 22' long)....it works very well!! (I get quite a few "all ships" HF-DSC calls just sitting at my dock....and get excellent HF-WeFax reception with my Furuno FAX-408, and prior to that my Alden MarineFAX)

This might be overkill for most....so, if you don't wish to go this far, please use my recommend above in "d".











And, an old pic...showing my old Alden MarineFAX (that I replaced a few years ago, when its auto-timer function quit)...




f) Now, some will want a commercial-made solution (why? I have no clue....but some just do)....So, some have used the Metz or GAM "WeFax / HF-DSC Antennas", which are 54" SS whip antennas with an easy-to-install base / coaxial connector.....and while these do work (I used one for a month), there are better ways to do this, such as my recommendations above in "d" and "e"....

http://www.fawcettboat.com/pc_product_detail.asp?key=7BFC582675674EE3A5162CF0 45A3160D

https://www.metzcommunication.com/radio-cb-emergency-transponders/

https://gamelectronicsinc.com/product/weatherfax-dsc/

https://www.defender.com/product.jsp?id=148079




3) You cannot easily share your backstay HF transmit/receive antenna with a second receiver....sure you can add an accessory (RF sensed T/R relay) to switch automatically, but in my opinion that is a big mistake, adding a failure point into a safety / communications system on-board is just not a good idea....

And, yes, you could install a manual antenna switch (at the Nav Station, into the coaxial cable going aft to the remote tuner), to switch between your WeFax receiver and your M-802 transceiver, but this can present two problems:

a) If you "powered on" the M-802 and pressed "TUNE", or transmitted with the radio....and then wanted to switch the backstay to the WeFax receiver, the remote tuner (AT-140 ?) will remain "tuned" to the M-802's last transmission frequency....which, if different than the WeFax freq, will reduce your WeFax signals....if you "tune" the remote tuner to the WeFax freq, this eliminates this problem, but does NOT improve reception versus simply allowing the remote tuner to operate in the "THRU" (bypass) mode (which is also done via the M-802's buttons)....

b) You have to remember to SWITCH the switch, when using the radio and/or the WeFax receiver....

c) If you use a decent antenna switch, one with adequate isolation (50db to 60db), such as a Daiwa CS-201, etc.....there will be no issues with damage to your WeFax receiver from transmit energy of the M-802....but.....But, if you use an inferior switch / one with unknown isolation, then you can risk damage to the wefax receiver.

SO...
So, as you see, there are some good reasons to not use a switch (or a relay, for that matter)....but, please note that the M-802 (like just about every modern solid-state transmitter) will fold-back its transmit power instantly if it sense a high VSWR, a shorted antenna connection, or no antenna connected at all....the M-802 (again, like just about every modern solid-state transmitter) will not "blow-up" if you transmit without the antenna connected! Although, good operating practice is to always listen before transmitting, and if you don't hear anything / hear no static, you'd quickly remember to switch the switch! (but, in times of emergency on-board, you're not going to be "listening first"!)





4) Please be sure to have a look at some of the "stickies" above, the Sailmail Primer, and of course the Youtube Playlists (that have videos sorted in a logical order for laypersons to follow along/learn about Offshore Weather receiving, HF-DSC Comms, HF-SSB Comms, etc.)

Please remember that these videos are done in the real-world (not simulations), on a real offshore cruising sailboat (not in a lab), with real LIVE operations (just like everyone experiences).....so they represent as close to your actual on-board situation/experience as possible without me actually being there teaching you personally! But, the downside to them is just that, they are real and live...and done by myself alone, no script, no director....just the radios, my fingers, and my narration (all done extemporaneously / off-the-top-of-my-head) live as-it-happens....

So, please read and watch, and enjoy! They're FREE....and nobody is selling you anything!!

Offshore Weather
https://www.youtube.com/playlist?list=PLnN6ygtZ3h2mPZAx2vWzdjTJjHlChruyY

(if you haven't the time to watch them all, please at least watch this first playlist....or at the very least the first couple videos in each playlist)

Offshore Weather
https://www.youtube.com/playlist?list=PLnN6ygtZ3h2mPZAx2vWzdjTJjHlChruyY


HF-DSC Comms
https://www.youtube.com/playlist?list=PLnN6ygtZ3h2n3z5nlv-ga2zYuPozhUXZX


Maritime HF Comms
https://www.youtube.com/playlist?list=PLnN6ygtZ3h2nPNdApNsZDo_Jk3NB_Bt1y


Icom M-802 Instruction Videos
https://www.youtube.com/playlist?list=PLnN6ygtZ3h2npivDjoFrC-8QKVyMb4tVr


Offshore Sailing
https://www.youtube.com/playlist?list=PLnN6ygtZ3h2nbwAGh5DKgTCj15iyl6qoY


Read these:

Marine SSB Stuff (how-to better use / proeprly-install SSB, & troubleshoot RFI, etc.)
http://www.cruisersforum.com/forums/f13/marine-ssb-stuff-how-to-better-use-proeprly-install-ssb-and-troubleshoot-rfi-etc-133496.html



HF-SSB Radio, Proper Installation Tips/Techniques, etc.
http://www.cruisersforum.com/forums/f13/hf-ssb-radio-proper-installation-tips-techniques-etc-198305.html

Sailmail Primer (lots of great HF comms / SSB install info)
https://sailmail.com/wp-content/uploads/2016/02/smprimer.htm





5) Btw, I'm hesitant to mention the misinformation here about direct reception of 137mhz NOAA Satellites, and I'm not going to write a treatise on it here....but feel it's needed to clear up confusion.

Unless something has changed in the past few months, there are NO WeFax charts / weather charts transmitted by the 137mhz signals from NOAA (and Russian) Low Earth Orbiting satellites....the 137mhz signal has the APT (Automatic Picture Transmission)...which is just what it seems, an automatic transmission of live earth images (visible in daylight, and Infared at night), as the satellite is flying over you!

Since the topic of discussion of this thread is HF-WeFax reception (and the synoptic weather charts drawn by experience maritime meteorologists), further discussion here about 137mhz APT reception is rather moot....but...

But, just in case some wish to know....here some brief facts: The APT signals are rather easy to receive with simple equipment (yes, I've done this, as well as the 1691mhz signals from the GOES sats), and since costs are low, the best approach is with a dedicated receiver (designed specifically for these wideband transmissions), with either a quadrifilar or turnsytle antenna, and rather easy-to-use software on your laptop connected to the receiver. (some have tried with a police scanner and/or a modified 2m ham radio, and have gotten them to work, but results are poor....others have used an SDR USB dongle to good results....but better results come from a dedicated receiver designed just for this purpose....and since it costs just a couple hundred dollars, all-in....if you find yourself in need of these weather images, it makes sense to go with the best approach to reception)

I doubt many here have any need for further info here, as those sailing the areas of the world where 137mhz APT images are needed will already know most of this....but for the curious (fyi, there are many < $50 solutions found on-line...please note that I'd not recommend them for use offshore where you NEED this weather info, they're more for the hobbyist / experimenter, but if you do wish to play with this, start with the rtl-sdr.com solutions):

https://www.wraase.de/shop/

https://amsat-uk.org/faq/receiving-weather-sats/

http://www.ka7oei.com/wxsat.html

Now, if you're sailing the Southern Ocean (where weather systems move fast and there is little other weather info), the Indian Ocean (where, except for those from Aus and SA, there are few sources of live offshore weather info), and/or other very high latitude sailing / NW Passage / etc. (where HF reception can be effected by high geomagnetic activity (northern/southern lights) and outside of the coverage of US, Japan, Russian, or German weather bureaus), in these areas live 137mhz APT images can be of great help! Of course, you the sailor will need to understand maritime weather systems and make some of your own forecasts, but if you're sailing those areas, you are almost assuredly experienced enough with all of this.






My Holiday Wishes and fair winds to everyone!


BTW, sorry I haven't been around here in a while, I've been dealing with elderly family medical issue and other serious family matters, but it looks as though we've had somewhat of a Christmas Miracle...so, I have some time this week to check things out here-abouts.

Although it seems well-meaning, I've seen some fairly inaccurate and misleading info here in some of these posts. And, instead of detailing falsehoods and starting arguments, I thought I'd just add some helpful (?) and factual info! Hope this helped?

John

[hzcruiser]

Originally Posted by continuouswave

The device commonly called an "antenna tuner" does not actually adjust the tuning of the antenna. Most antenna tuners are connected into the transmission line between the antenna and transmitter (or receiver), and their function is to transform the feed point impedance of the antenna to be a match to the transmission line impedance.

[...]

Your post is a superb summary of antenna and tuner principles, I have to say!


Unfortunately, IMHO it is impossible to convey such a complex matter in a dozen paragraphs, hence people that don't already know a whole lot of antenna theory might not benefit from it as much as they could.

[continuouswave]

Originally Posted by hzcruiser

Your post is a superb summary of antenna and tuner principles, I have to say!


Unfortunately, IMHO it is impossible to convey such a complex matter in a dozen paragraphs, hence people that don't already know a whole lot of antenna theory might not benefit from it as much as they could.

We are in a postlapsarian world, so I just do my best.

Thanks for your kind comments about my brief remarks on the function of antenna matching units.

[slug]

Originally Posted by jt11791

I have a weather fax receiver/printer that needs an antenna. I tried using my VHF antenna but performance was really poor, I guess because it is designed for different frequencies. I also have an SSB that uses an antenna tuner hooked to the backstay for its antenna. Can the tuner/backstay setup somehow be shared with the weather fax?

Use your ssb to receive the fax transmission then translate the data with a laptop

Much better than some kind antenna switch

[SuzieWong]

Hi John,

First of all thank you for sharing all the information.
Stuck between countries which still adhere to strict Covid rules I will try to escape here before tropical storm season starts.
Anyway, long story short: Of what I can read as information I should be able to share the SSB DSC antenna with weather fax, and I assume this also should apply to Navtex (518kHz).
Dedicated DSC antenna is an active HF-100Rx. Can I use a simple T coax connector also on the Rx part (not antenna part) of the out on the amplifier unit to share the antenna with DSC, weather fax and Navtex?

Many thanks for your help,
Hanno