Vhf Radio

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Aja
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Vhf Radio

Postby Aja » Mon Mar 14, 2016 9:47 am

I know that some of you are pretty well clued up on this but noticed that Maplins were offering a SWR meter for £14.99 with free delivery.

http://www.maplin.co.uk/p/moonraker-swr-100-cb-swr-meter-a35gj

It's for a CB radio is it worthless for a marine VHF?

Donald

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cpedw
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Re: Vhf Radio

Postby cpedw » Mon Mar 14, 2016 7:18 pm

Aja wrote:It's for a CB radio is it worthless for a marine VHF?

Donald
I think so - it says "Frequency range 26-30 MHz" but Marine VHF is around 150MHz. Pity.

Derek

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sahona
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Re: Vhf Radio

Postby sahona » Tue Mar 15, 2016 12:09 am

I've been using a CB meter on boats for years. The thing to remember is that you are trying to measure/observe a RATIO so it doesn't really matter how efficiently matched the device is to the frequency,
In operation, you push the 'forward' switch and zero/calibrate the meter needle.
Then you shove the switch the other way and read the (reflected/backward) result.
It's self- adjusting due to the initial calibration.
Worth reiterating - we're only running 25 watts on our VHF sets, and they (nowadays) automatically turn down the transmit power if they perceive significant reflected energy, so they self-protect, but you lose power, =distance.
If you have an ammeter on the dashboard, you can expect to draw about 5 amps when you press transmit on a healthy set-up - significantly less current indicates shutdown and therefore a problem.
In my opinion, these meters are perfectly adequate to trouble-shoot the sort of antenna problems prevalent on boats. ie : mast-base connectors, water in the coax, and corrosion/seagull hits on the aerial itself .
Go for it Don!
http://trooncruisingclub.org/ 20' - 30' Berths available, Clyde.
Cruising, racing, maintenance facilities. Go take a look, you know you want to.

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mm5aho
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Re: Vhf Radio

Postby mm5aho » Tue Mar 15, 2016 8:31 pm

I agree with Sahona. Its too easy to be too purist in this area. An SWR meter will give you a good enough indication of the system being OK or duff. The actual output might not be accurate, but that doesn't matter.

But then don't expect to get a lot of use from it. I have several radio transmitters, marine, ham and some others, and can';t remember the last time I used that meter I have - maybe 10 years back?
Geoff.
"Contender" Rival 32: Roseneath this winter, Gourock in summer.

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sahona
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Re: Vhf Radio

Postby sahona » Thu Mar 17, 2016 11:26 am

I use mine quite a lot - on other peoples boats, especially this time of year.
http://trooncruisingclub.org/ 20' - 30' Berths available, Clyde.
Cruising, racing, maintenance facilities. Go take a look, you know you want to.

trev
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Re: Vhf Radio

Postby trev » Tue Mar 22, 2016 4:14 pm

mm5aho wrote:I agree with Sahona. Its too easy to be too purist in this area. An SWR meter will give you a good enough indication of the system being OK or duff. The actual output might not be accurate, but that doesn't matter.

But then don't expect to get a lot of use from it. I have several radio transmitters, marine, ham and some others, and can';t remember the last time I used that meter I have - maybe 10 years back?



I'll second that

G3WPS

trev
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Re: Vhf Radio

Postby trev » Wed Mar 30, 2016 5:07 pm

Perhaps worth giving a thought about what to do if the reading is too high, that is of course having decided how high is too high. If the wireless works - ie if you can talk to people on the thing - I would suggest the best thing to do would be nothing.

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Nick
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Re: Vhf Radio

Postby Nick » Wed Mar 30, 2016 10:57 pm

.
I have no idea what any of this means, but Donald says he gets an SQL error when replying to posts on his iPad, so I am replying to this post on my iPad.
- Nick 8)

Image

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Aja
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Re: Vhf Radio

Postby Aja » Thu Mar 31, 2016 9:36 am

To be honest, Nick - I'm not just saying I'm getting and SQL error - I also provided the error message:

"General Error
SQL ERROR [ mysqli ]

Incorrect string value: '\xF0\x9F\x99\x84.\x0A...' for column 'post_text' at row 1 [1366]

An SQL error occurred while fetching this page. Please contact the Board Administrator if this problem persists.
Please notify the board administrator or webmaster: nickb@webcraft.co.uk

Powered by phpBB® Forum Software © phpBB Group"

:? :? :?

Regards
Donald


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