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Old 12-07-2014, 12:06   #1
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VHF Radio - Tricks

Considering the plight of cruisers whose main electronics become, for whatever reason, disabled, I thought I'd mention a few things I keep in my emergency bag o' tricks to make my handheld VHF more useful:

1) My handheld VHF is a glow in the dark waterproof unit with built-in GPS, and it can run on AAA batteries with the optional battery tray!
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2)I have an adapter so I can easily connect my handheld to the antenna cable of a useless fixed mount VHF and comm over my best/highest VHF antenna.

PL-259 Connectors, Adapters & Reducers | Amateur Radio Supplies

3)A ziplock bag full of AAA Batteries...lots of batteries, checked for expiration every year.


4) A 20' length of coax with PL259's on both ends.

5) A Metz whip. I can tie wrap it to a mast/shroud/backstay/pole/or just held up high if worst came to worst and I was transmitting from my liferaft.

Just unscrew the handheld's rubber duckie antenna, thread on the adapters, thread on the 20' co-ax and Metz. Hoist it up 20' and you are talking 5 watts long range with a bunch of back-up batteries. In tropical atmosphere the VHF 'skip' can add substantial distance over the horizon to your VHF.

All this stuff takes up practically no room, is easy and quick to set up, and it's a great little handheld for everyday use with it's regular rechargeable battery pack.
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Old 12-07-2014, 17:43   #2
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Re: VHF Radio - Tricks

Good tips, like the antenna adapter. What effect does the bigger antenna have on your handhelds range, give output is limited to 5watts rather than 25 watts?
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Old 12-07-2014, 18:01   #3
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Re: VHF Radio - Tricks

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Originally Posted by Snowpetrel View Post
Good tips, like the antenna adapter. What effect does the bigger antenna have on your handhelds range, give output is limited to 5watts rather than 25 watts?
Longbordz knows what he is doing. For VHF comms (line of sight at that frequency) antenna height is much more important than RF power. For example at 15 miles the handheld with its antenna at deck height won't be heard but using a mast antenna at 50' will be heard just as well as a fixed unit running those 25 watts.
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Old 12-07-2014, 20:59   #4
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Re: VHF Radio - Tricks

<<<For VHF comms (line of sight at that frequency) antenna height is much more important than RF power.>>>

More watts is better than less watts, especially in heavy radio traffic. A guy screaming "RADIO CHECK" at 25 watts will stomp all over a guy calling MAYDAY at 5 watts. But being persistent gets you heard and the USCG won't hesitate to declare a 'silence mayday' on 16 to work your case.

<<< For example at 15 miles the handheld with its antenna at deck height won't be heard but using a mast antenna at 50' will be heard just as well as a fixed unit running those 25 watts.>>>

Correct! 5 watts is a lot! A NASA guy pointed out that the stuff they send on trips to nowhere transmit back to earth with a fraction of a watt. With no competition on the frequency, that's all it takes.

In the middle of nowhere, 5 watts of MAYDAY on 16 with no frequency competition will be heard a long way and may break someones squelch, someone you cannot see. Provide your LAT/LON to them and close distance. It's amazing how Good Sams appear out of seemingly nowhere, like seagulls on the sandwich you put down for just a moment.

To that end, while sat-phones and cellphones are nice backups, the only people privy to your dilemma are you and the USCG Sector you called. I heard a VHF call to USCG about a guest having a heart attack on his boat midchannel between Catalina and DelRey. While the USCG was preparing to launch a helo, a good sam on a passing sailboat with a cardiologist on board responded in just a few minutes. Had the comms been on cell instead of VHF, that doctor would have just sailed right on by
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Old 12-07-2014, 21:21   #5
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Re: VHF Radio - Tricks

<i>What effect does the bigger antenna have on your handhelds range, give output is limited to 5watts rather than 25 watts?</i>

A higher gain antenna focuses your power a little better. But that's not the only benefit. Everything around an 8" antenna diminishes it's ability to radiate; your bimini, mast, even your hands and body. So a vertical higher gain antenna on a masthead or spreader has less signal interference, greater range and a bit more focus of your power. Every little bit helps; high antenna, straight up and down, higher gain, clean tight terminals.
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Old 12-07-2014, 21:34   #6
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Re: VHF Radio - Tricks

Thanks. Often had problems getting out with a handheld even at fairly close range with a good line of sight. Maybe sheilding from body and the low gain antenna. Another quick querry. Is the standard Vhf antenna tuned optimise range on ch 16? And if so does this reduce the range slightly when using other channels?
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Old 13-07-2014, 00:15   #7
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Re: VHF Radio - Tricks

<<< Is the standard Vhf antenna tuned optimise range on ch 16? And if so does this reduce the range slightly when using other channels?>>>

Good question. Short answer: I don't know.

After I do any work on a radio or antenna, I check the performance with a Shakespeare ART-3. I cannot discern any difference between 06/09/12/16/22/68/72.

Sometimes one hears USCG unable to comm with a boat on 22 and switch them back to 16, but whether that's due to antenna specs or (?) I do not know.
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Old 13-07-2014, 00:33   #8
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Re: VHF Radio - Tricks

I use an antenna analyzer (MFJ 269, for what it is worth). While there is a difference across the marine VHF band, and a small difference between conventional VHF antennas and those nominally for AIS, there is not a difference that will be perceivable in normal operation.
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Old 13-07-2014, 02:06   #9
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Re: VHF Radio - Tricks

Quote:
Originally Posted by Snowpetrel View Post
Good tips, like the antenna adapter. What effect does the bigger antenna have on your handhelds range, give output is limited to 5watts rather than 25 watts?
The antenna is everything; output power very little indeed.

With my new antenna (Shakespeare Galaxy internal dipole) and good cabling, I once got a "weak but readable" signal report from 60 miles -- using one watt transmit power.

These are good tips. I also have an HX851 with the battery tray for my grab bag. The only refinement I would suggest for the OP's tips is that it's a good idea to vacuum seal the batteries so that they won't get doused with seawater in a hairy abandon ship scenario. I wouldn't trust a ziplock for that.

If God forbid I found myself in a liferaft, I would consider VHF comms to be absolutely key in waters with any traffic. I do keep a PLB on my person at all times, but I don't think that's any substitute for VHF comms if there is any traffic around -- you can't talk to anyone on the PLB or EPIRB, and it takes a lot of time to get a rescue organized. You will much prefer getting help from some nearby vessel if there is one.

Another tip which seems good to me is to keep an aircraft-band handy-talky in the grab bag.
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Old 13-07-2014, 05:28   #10
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Re: VHF Radio - Tricks

Quote:
Originally Posted by longbordz View Post
Considering the plight of cruisers whose main electronics become, for whatever reason, disabled, I thought I'd mention a few things I keep in my emergency bag o' tricks to make my handheld VHF more useful:

5) A Metz whip. I can tie wrap it to a mast/shroud/backstay/pole/or just held up high if worst came to worst and I was transmitting from my liferaft.

Just unscrew the handheld's rubber duckie antenna, thread on the adapters, thread on the 20' co-ax and Metz. Hoist it up 20' and you are talking 5 watts long range with a bunch of back-up batteries. In tropical atmosphere the VHF 'skip' can add substantial distance over the horizon to your VHF.

All this stuff takes up practically no room, is easy and quick to set up, and it's a great little handheld for everyday use with it's regular rechargeable battery pack.
Longbordz

I've been looking for a small antenna to mount as an emergency antenna on the boat's radar arch. All that I found were too long. Did not think about the Metz (which I have on the mast) glad you mentioned it.
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Old 13-07-2014, 07:13   #11
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Re: VHF Radio - Tricks

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The antenna is everything; output power very little indeed.

Actually, both are equally important but what is of paramount importance is effective radiated power, a combination of both output power and efficacy of the antenna.

As power is limited in any handheld, the only variable is in the antenna system ( antenna and feedline ). The ubiquitous "rubber duck" small antenna common to handhelds is a very, very poor radiator.

The best thing anyone can do to increase the effective range of their handheld is buy a decent extended antenna for the radio.
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Old 13-07-2014, 07:59   #12
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Re: VHF Radio - Tricks

<<<I've been looking for a small antenna to mount as an emergency antenna on the boat's radar arch. All that I found were too long. Did not think about the Metz (which I have on the mast) glad you mentioned it. >>>

Is that radar arch safely deck accessible?

My theory for the Metz and 20' coax cable is versatility and portability. I can get a lot of height jury-rigging it as needed, where needed. Height = range. It's such a light antenna that duck taping or tie-wrapping it up somewhere in an emergency is really simple.

As to zip locks versus vacpak storage; I use my batteries from the zip-lock stash, replacing them as I use them. I like bright flashlights. So no problem with corrosion. But vac packing some long expiration batteries for the ditch kit is a great idea.
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Old 13-07-2014, 08:39   #13
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Re: VHF Radio - Tricks

After arriving at the boat 1 time years ago and discovering the HH antenna AWOL.... I assembled a bag of connectors, adapters, and length of RG8 with conns... Less than $20, and wondered why it took me so long to have this backup in my arsenal...
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Old 13-07-2014, 19:00   #14
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Re: VHF Radio - Tricks

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Correct! 5 watts is a lot! A NASA guy pointed out that the stuff they send on trips to nowhere transmit back to earth with a fraction of a watt. With no competition on the frequency, that's all it takes.

Not sure your friend is right about the transmit power. Most deep space probes have large amounts of solar or nuclear power. Many (most?) use vacuum tubes for the transmitter. Also, NASA's deep space network (DSN) has receive antennas with huge gain factors. They have dishes that are 35 and 70 meters in diameter. They can gang them for even more gain.

The Mars rovers use an orbiting relay satellite to phone home. They can probably get by with a fraction of a watt. But the Voyager twins need a lot more power than that. They are about 20 watts as I recall. Still pretty tiny on a solar system scale.
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Old 14-07-2014, 02:28   #15
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Re: VHF Radio - Tricks

Anybody got the proper length to make your own vhf antenna. I saw instructions once in a vhf manual. Sounded like you peeled the coax away a set length to expose the core, and did some Thing with the cover? Cant quite remember what. But that would be a handy trick if it worked ok.
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