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Old 13-08-2019, 03:47   #46
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DIY HF whip

Dunno exactly where I am going mate.

Vanuatu and the South Pacific beckon. I’ve got all new standing rigging, courtesy of your mates in NZ, but I still feel it is prudent to have options if my sailing boat gets turned into an overweight motorboat by a bit of inclement weather or bad seamanship.

That’s pretty cool info on the APCs. I always assumed they were either:

a) worried about clearance
b) hiding.

As for an 85 foot antenna.... yeah... why not?
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Old 13-08-2019, 09:50   #47
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Re: DIY HF whip

Sorry to be late to the party. *grin*



Quote:
Originally Posted by Brian.D View Post
OK @GILow, the math is simplistic enough for results. Might not be the best results, but results none the less.

Simple but tedious. I built a spreadsheet that does the work for you for the band edges of all the marine and ham bands. Put the antenna length, including the GTO-15 from the tuner to the antenna (as noted, part of the antenna) in the box in the upper left and anything close to an integral multiple of a half-wavelength will turn red.



It's important to note that there isn't anything magic here. A hunk of wire is a hunk of wire. The issue with half-wavelengths is that the impendence at the feed point is really high and antenna tuners struggle to find a match. So 'red' doesn't mean it WON'T work, just that there is risk.


See http://auspiciousworks.com/AntennaLength.xlsx



Quote:
Originally Posted by Jammer View Post
Now if you are on a dismasted sailboat trying to get out on HF your choices are these:

1) You can use a very large, very expensive self-supporting commercial antenna such as the Shakespeare 5310-R, which is $500 plus freight (and still not really long enough)

2) You can use a horizontal antenna, such as the lifelines, and get good ERP but a bad takeoff angle. This will actually work well up to around 100 miles or so using NVIS techniques at around 4 MHz

3) You can use a kite, balloon, drone, etc. to pull a wire

4) You can use an inexpensive or homemade antenna that is, electrically, too short.

5) Carry a spool of wire (I carry 14AWG since it is a handy size) and use whatever you Jerry rig for sail to get it high.



Don't dismiss kites. Getting a lot of magnet wire in the air works really well.



Quote:
Originally Posted by Jammer View Post
... the fact that the tuner can match the impedance doesn't mean that the antenna will radiate efficiently or that it will radiate in a useful pattern.

This is important. For an expedient you an also move things around and try different configurations.


With regard to the discussion of the DSC receive antenna on 802 there are a couple of important points.


1. The DSC receive antenna and the dedicated receiver only applies to the reception of DSC from others. For a sailboat with limited range to assist the biggest problem is too much range. Our best ability to contribute is as a relay. If you receive an HF DSC from 2000 nm away just what are you going to do to help. In the far eastern Atlantic the alarm goes off a lot and keeps waking up the off-watch with no ability to be useful. I now use about 3 meters of bell wire in a PL-259 connector run horizontally about half a meter above the waterline.



2. DSC calls from you use the main antenna.
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Old 13-08-2019, 16:32   #48
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Re: DIY HF whip

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Originally Posted by Auspicious View Post
Sorry to be late to the party. *grin*
.

Better late than never.

I’m looking forward to trying that spreadsheet, it might jog a few memories from my license studies.

Also, I like your idea for the DSC receive antenna.
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Old 13-08-2019, 16:52   #49
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Re: DIY HF whip

IF you want a fun little antenna a metal slink with electrical streach out for your 23ft min antenna size.
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Old 13-08-2019, 16:59   #50
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Re: DIY HF whip

Andy if you want a fun antenna. Use a metal slinky. Its near 80ft of wire and streaches out to 25 ft or so.
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Old 13-08-2019, 18:24   #51
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Re: DIY HF whip

Matt,
I too, am sorry to be coming in late here....not the least of which is because many here are way over thinking this....(you can do this for just a few dollars, and make it effective, too!)

While dismastings are rare, it is good to know what things will cascade into issues that you'll need to deal with....and, yes preparing an emergency HF antenna is one of those things...

El Ping and Jim Cate gave you great info....and there isn't too much more to add, but some clarifications might be good, yes?

1) There isn't one right answer here. What works for one boat / one situation, might not be as good on another....so, variations here are fine...



2) HF comms over sea water are fairly easy to accomplish, whether local/regional or long-range....but, each of these 2 scenarios usually require different antenna types for optimal performance....

{Hmmm, you're thinking...what is he rambling on about? I have a backstay antenna, and thought that was "best"? You're right....it's just that in an emergency (especially in heavy weather situations), after a dismasting, you may wish that you'd already determined where / how far, you need to communicate to and have an antenna already designed that can be easily erected, that best suits those communications paths...that is what I'm referring to...}

Fact one: Any vertical antenna operated against the sea water (or other counterpoise) will be good for longer range comms (typically on freqs of 7mhz/8mhz thru 14mhz/16mhz, or even as low as 3.6mhz/4mhz/6mhz, at nighttime), any vertical of 1/8-wave or longer would be of adequate efficiency to perform well, even without a ground system / counterpoise....and should also be easy to obtain a match with via your existing AT-130 tuner (or any decent tuner)....

Fact two: Any horizontal antenna (even one just a few feet off the deck) would be good for more local/regional comms (typically from 2mhz thru 7mhz/8mhz, or even as high as 12mhz at times...and can also be used for longer range comms on 12mhz thru 16mhz daytime and the lower freqs at nighttime), and here also, one of 1/8-wavelength or longer would be good, and would be of adequate efficiency to perform well, even without a ground system / counterpoise....and should also be easy to obtain a match with via your existing AT-130 tuner (or any decent tuner)....

[An important fyi here....most HF Maritime Comms occur on 8mhz, 12mhz, 4mhz, and 2mhz bands (in descending order)...with most long-range maritime comms on 12mhz and 8mhz, most local/regional maritime comms occurring on 8mhz and 4mhz (and some on 2mhz)....on the amateur radio bands (ham radio bands) it is less clear, but in general 14mhz being the most used / most popular for long-range comms, 7mhz followed closely in 2nd place, and 7mhz being #1 in regional amateur radio comms, with 3.8mhz band being 2nd place...]



3) Using these facts, and with all the above further info at hand....we can see that an antenna length of 30' to 35' is good for the lower bands and okay for the higher bands, but even antennas only 12' - 16' long can work well for the higher bands....BUT....

But, of course this does not have to be vertical, or more precisely it is better to have some of it vertical and some horizontal....or if that's not possible, just design one antenna that is 8' to 16' vertical....and one that is 12' - 40' long and horizontal....

Now, in full disclosure here, I have studied radiowave propagation and antenna system design since an adolescent in the early-mid 1970's...yes, that's >45 years ago....and I've taught seminars in both radiowave propagation and antenna system design on/off now for >40 years (and have designed/built many antennas in the real world over these years, both on shore and at sea)...so, please understand that you, my fellow sailors, do not need to know this stuff the way I do!! Nope, not necessary at all. Just want you all to know the "why's" and "how's" of what I recommend (and use myself)!!

So...
So, with all that in mind....in these situations, there is little need to have antenna more than 12' high vertically....and even one half that height could be adequate....and then run it horizontal at least as far as it is tall....and, it can be 2 or 3 (or 4) times as long horizontal as it is vertically....this is generically called an "inverted-L" antenna....and because of it's combination of both vertical and horizontal components (and depending on it's actual length vs. wavelength) can be a decently effective antenna for both long-range and local/regional comms...



4) So, what to do?
a) Well, having an antenna at the ready, that does not need lots of time to assemble / rig is the most important criteria in these situations! (a simple roll of wire is easiest....and something to support it....and some way to rig / support it in whatever arrangement is needed by the situation...)


It is also important (in my opinion, anyway) to have this emergency antenna stowed below decks....yes, some old-timers will say have a stern-rail-mounted antenna to use in case of dismasting...but...But, from what I have seen / read, dismastings will generally cause damage to a fair bit of other stuff (whether from the mast/rig going over itself, or from the proximate cause such as a 360* rollover), so I would rather keep my emergency antenna below-decks, and make sure it is easily/quickly rigged when needed....

{Fyi, in addition to the DSC-receive-only antenna usually being much shorter than optimal, the "commercially-sold HF-DSC-Receive whips" aren't designed for transmit power....and then when you add in the fact that this antenna could likely be damaged in a dismasting....these 3 things preclude using a stern-rail-mounted short DSC-Rec antenna as your "back-up" HF transmit antenna!!!

A few feet of wire, and a stick of wood, etc. and some rope....and you've got an effective emergency HF antenna....

See below, and above, for the details...}



b) A 20' to 25' length of GTO-15 is nice (but any wire will work!)....this allows you to rig / connect it to your existing GTO-15 wire coming up thru-deck (from your tuner) and have a decent length / efficient antenna...

And, a second piece the same length or a little shorter (15' - 20') that you can connect to the first piece and have one antenna that is 35' - 45' long....

A couple pieces (10' - 15' long) of 3/8" double-braided polyester line (like Sta-Set), that you can secure the ends of these pieces of wire, to some structure / pull-pit / pole / etc...



c) A simple fiberglass (GRP, for those non-USA sailors) fishing pole (mine are nice 7' long deep-sea poles with big reels), that fits easily into its pole holder on rear pushpit / stern rail, and/or into the flag-pole socket on transom, and/or easily rigged to whatever is left on deck....

Run the GTO-15 wire from tuner (or thru-deck gland) up along the fishing pole giving you an antenna that is about 12' vertical....and another 12' - 13' horizontal....

And, if you need/desire better comms on 2mhz thru 8mhz, you add the additional piece of wire...that's it....easy-peasy, and efficient....



This entire set-up takes less than 5 minutes....the lengths of GTO-15 wire, lengths of 3/8" double-braided line, a roll of electrical tape, a dozen or so cable ties, etc., are all stored in a canvas bag in a locker below-decks [I also have an older manually-adjusted antenna tuner, in this bag, along with a few lengths of RG-8x coax with connectors properly attached...allowing me to rig this antenna any where, even if my tuners (I have two) are destroyed or I cannot connect to them]....
My fishing poles (I have two) are usually in brackets along bulkhead below-decks (unless I'm actively fishing....which I'm unlikely to be doing in heavy weather...)

So, this is what I have designed (and have rigged it up and tested it) for emergency HF antennas...



5) You may notice that I haven't written any exact lengths?
Hmmm, you say..."everyone says it should be some xx length....or should not be some xx length....why is John not writing that?"

The answer is (forgive me everyone).....the answer is, because you do not need the damn thing to really be any precise length at all, and while it has become internet de rigueur to repeat the old adage of never trying to use end-fed antennas of 1/2-wave (and/or multiples of 1/2-waves), the facts are quite clear....for those using Icom remote tuners made in the past 25 years (AT-120, 130, 140, 131, 141...AH-2, AH-4) and/or using an SG-230 made years ago, etc...these tuners have no issue obtaining a match for your transmitter, even when feeding antennas of 1/2-wave long....(and in actual fact, your HF antenna system is substantially more efficient with an antenna of longer than 1/4-wave length (but still shorter than 0.64-wave), than one that is shorter than 1/4-wave....and this includes ones that are 1/2-wave long....

The only caveat for using an antenna of 1/2-wave long is if your tuner is kaput (that's an American technical term, meaning "broken")....then you'd want to trim the antenna to a length that is easier to match to your radio (or to whatever emergency tuner you have)....and that's gonna' be about 1/4-wavelength long overall...

I understand that this last section here (#5) that deals with not needing an antenna of a precise length nor avoiding some precise length, is contrary to others.....and I won't argue the point....just providing you all with the info....do with it as you desire...

FYI, I use my AT-140 with antenna of 1/2-wave....and have used it with rather short (~ 15' - 20') antenna...with no issues....and many years ago, I used an AH-2 with a 7' whip, worked okay...{the only exception here might be a very old, original AT-120 (from early 1980's), that was spec'd for use only between 2mhz and 22mhz....so it may not have as wide tuning capability??}



I do hope this helps.

Fair winds and 73,

John
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Old 14-08-2019, 01:48   #52
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Re: DIY HF whip

Hi John!
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Old 14-08-2019, 06:28   #53
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Re: DIY HF whip

Quote:
Originally Posted by ka4wja View Post
Matt,
I too, am sorry to be coming in late here....


.....

I do hope this helps.

Fair winds and 73,

John
John,

Great post, and as always, you've put lots in. I will certainly try that L shaped configuration you've suggested, probably with a "permanent" vertical whip made from aluminium tube.

Looking forward to some of these HF experiments, and having the time to perform them.

Matt
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Old 19-08-2019, 13:49   #54
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Re: DIY HF whip

I would add an inexpensive manual tuner to that kit, in case the fancy one craps out.

Working radio from my boat is one of the things I am most looking forward to.
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Old 19-08-2019, 14:17   #55
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Re: DIY HF whip

stimpsonjcat,
Although I did mention this above, I suspect that it might've gotten lost in all the other info...
So, thank you for this.
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Originally Posted by stimpsonjcat View Post
I would add an inexpensive manual tuner to that kit, in case the fancy one craps out.

Working radio from my boat is one of the things I am most looking forward to.
FYI, except for a direct lightning strike, I've never had an Icom remote tuner fail...(oh, and the insides of the tuner struck by lightning looked "charred" all over, with chunks of coils looking like bits of charcoal...LOL)

In years past (1980s and 90's) SGC tuners were also damned reliable....but over the past dozen years I've personally seen new sgc tuners not work correctly, right-out-of-the-box....and seen some more SGC tuners fail within a year or two of installation (no lightning)...heck, a few years ago, I had an SGC tuner fail under warranty, go back to SGC for repair, and then fail again in another few months (it now sits on a self in a closet on-shore, can't sell that POS to anyone, can't bring myself to throw it away!)

Having said all of this, in addition to my AT-140, I do carry a manual tuner (as associated cables, meters, etc.) to use in case of tuner failure....[but, I also have a second M-802 on-board as well! so, that's just me...]
Quote:
Originally Posted by ka4wja View Post
.... [I also have an older manually-adjusted antenna tuner, in this bag, along with a few lengths of RG-8x coax with connectors properly attached...allowing me to rig this antenna any where, even if my tuners (I have two) are destroyed or I cannot connect to them]....

<snip>

The only caveat for using an antenna of 1/2-wave long is if your tuner is kaput (that's an American technical term, meaning "broken")....then you'd want to trim the antenna to a length that is easier to match to your radio (or to whatever emergency tuner you have)....and that's gonna' be about 1/4-wavelength long overall...



Fair winds.

John
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Old 19-08-2019, 16:18   #56
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Re: DIY HF whip

Screwdriver antenna from Tarheel Ant or an Outback ant. Easy and can’t be better. Marc N5PSL 😎
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Old 19-08-2019, 16:36   #57
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Re: DIY HF whip

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Screwdriver antenna from Tarheel Ant or an Outback ant. Easy and can’t be better. Marc N5PSL 😎
If you had written that 4 pages ago, it would have saved a lot of needless rhetoric. To the OP- do what this says.
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Old 19-08-2019, 16:52   #58
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Re: DIY HF whip

https://www.defender.com/product3.js...29060&id=70975
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Old 19-08-2019, 17:04   #59
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Re: DIY HF whip

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If you had written that 4 pages ago, it would have saved a lot of needless rhetoric. To the OP- do what this says.
If that had been written 4 pages ago it would still be no help:

A) Price - see remark in initial post about budget.
B) Location - I am in Australia.

If I wanted to buy/could afford a commercial antenna I would get the locally made Moonraker.
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Old 19-08-2019, 17:05   #60
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Re: DIY HF whip

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You just linked a 25 watt VHF antenna.

I have a 150 watt HF radio.

Somehow, I don't think that will end well.
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