Emergency VHF antennae

laika

laika

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An emergency VHF antenna has been on my list of sensible equipment to acquire for a while. The two which seem to come up in searches are the glomex one and the vtronix one. I am not a radio geek so would appreciate recommendations from those in the know. I note the vtronix comes with 6m of RG174 (the glomex comes with 9m of unspecified coax). Possibly a stupid question but would there be issues connecting rg174 with the rg213 I have from the base of the mast to the chart table radio?

(I also need an antenna for a little experiment with a raspberry pi and AIS (no great coverage needed) but rather than muck about with youtube vdeos for making one I just thought I'd take the opportunity to fill a hole in my safety inventory)
 
I made one based on this diagram posted before on PBO by VicS

images
 
ProDave said:
Surely for an emergency aerial you forget any deck connections, and just plug the PL259 on the end of the emergency aerial directly into the back of the VHF radio?
Click to expand...
Correct, then stick the antenna on the end of the longest boathook or pole you've got to get it as high as possible.
 
I have the Glomex one. Used it a few times for testing sets at home and to identify if a fault was in the mast or not. Works is all I can say.
 
ProDave said:
Surely for an emergency aerial you forget any deck connections, and just plug the PL259 on the end of the emergency aerial directly into the back of the VHF radio?
Click to expand...

Getting to the back of the VHF requires some panel disassembly and reaching behind. If it was too wavey to open windows, running a cable from the vhf to the companionway and thence to somewhere I could secure a boathook would take a lot of that 6m. By contrast, dropping a cable through the swan neck and securing it to the existing connector would be easy and allow me to make use of whatever sticky-uppy thing (e.g. spinnaker pole) I was using in place of a mast, hence the question about connecting different sizes of coax, though clearly I'm not looking for flawless performance. I take the point however

Rogershaw said:
I made one based on this diagram posted before on PBO by VicS

images
Click to expand...

Do you have a link or do you mean the magazine?
 
You can get all sorts of coax connectors to fit most cable sizes, so connecting two different szied 50ohm cables is just a matter of having the right connectors or patch leads.
 
TernVI said:
You can get all sorts of coax connectors to fit most cable sizes, so connecting two different szied 50ohm cables is just a matter of having the right connectors or patch leads.
Click to expand...

It wasn't the connectors I was concerned about, more whether someone would say "You can't connect 6m of thin coax to 4m of thick Because Physics! But I suspect the whole "emergency" and "it's stuck precariously to a spinnaker pole" things probably negate niceties
 
What's the purpose of an emergency VHF antenna?
If you carry a hand held then you have comms if you are close enough to your intended recipient. If you have a mobile phone then again if you are close enough to land you have coms. I've had mobile data at 20nm believe it or not!

To my mind, and emergency VHF antenna is when time is critical and you can't reduce range. i.e offshore emergency which has taken out your primary antenna and you are time critical. So probably de-masted and taking on water.

If the mast is down, where did the cable break? if it did. Where is your closest connector? Has the mast ripped the cable at the deck gland or pulled it through and ripped at the under deck connector?

Time is critical or you would just reduce range, so let's have a simple solution. Connector at the back of the radio, long cable, lots of zip ties and a way of leading it outside.

Of course if time is that critical you should probably be activating your epirb!

For everything else HH radio will do.

I have a normal antenna with a long lead and a bag of zip ties but It's hard to think of a scenario where i would need it in an "emergency". It would replace my masthead if I needed to but going up the mast at sea isn't fun. Rather just wait till I'm closer and use the hand held.
 
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Mebbe it should be called ' handy VHF jury rigged aerial to temporarily replace the main one if it develops some fault that you can't fix til you get back to harbour' aerial? ?
 
capnsensible said:
Mebbe it should be called ' handy VHF jury rigged aerial to temporarily replace the main one if it develops some fault that you can't fix til you get back to harbour' aerial? ?
Click to expand...

Or perhaps "discretely small VHF antenna I can put amongst the tomato plants on the balcony without violating the terms of our rental agreement connected to the dAISy HAT I intend to acquire in order to test some issues someone is having with using my free software to send data to marinetraffic which I can later keep onboard and use as a backup to the two independent cables to two masthead VHF aerials , the primary of which is kept connected at the foot of the mast and the secondary disconnected". But that might be a bit of a mouthful.

Thanks for the link rogershaw but I there's no link in VicS's post where he mentions the PBO article (maybe removed?) and a "slim jim" is *definitely* too bulky for my needs.
 
HVJRATTRTMOIIDSFTYCFTYGBTH
pvb said:
That looks like the name of somewhere in Wales.
Click to expand...
It is. I remember going there on an A-Level Geography field trip to North Wales in 1967. Something about cwms and hanging valleys if I recall correctly. (They are probably not what you're thinking about right now!)
 
I have one, never used, unpacked once to check it, have a spare antenna on a pole on the stern, currently being used as masthead antenna fell off last summer and not gone aloft yet, blamed on cv19...!
 
On the same theme. I'm just changing the antenna on my AIS and needed to change the co-ax plug to a PL259.
The plug won't take solder and the cable braided screen is reluctant to accept it. I know the solder is ok, used the same roll many times before, flux cored. Anyone else had this problem. The plug (BNC) I cut off the co-ax to replace was crimped on and not soldered. Any ideas?
 
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