Offcum aerial

Discuss UK-based Radio outside the South East of England
e.g. Birmingham, Bristol, Leeds & Manchester
'Legal' radio topics often go here too.
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piraterx
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Offcum aerial

Post by piraterx » Thu Sep 13, 2018 2:36 pm

hi every1 am a newbie.

was watching documentary bout pirates



got a question.if you go to 5.02 mins in you see offcum dude holding a speccy analyser and a horizontal dipole says hes trying to find a pirate.but my question is most pirates use vertical dipoles.so assuming the signal hes trying to find is vertical would his horizontal dipole not cancel the signal out cos its the wrong polarisation?? or can you still directional find the vertical dipole with his horizontal dipole.

any1 explain it to me lol

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yellowbeard
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Re: Offcum aerial

Post by yellowbeard » Thu Sep 13, 2018 3:09 pm

Ifn he held it vertical it'd be omnidirectional and he wouldn't be able to get a bearing on the signal at all. Also they would know the rough area to get out of the van and start checking, so probably the signal is strong and having the antenna in the wrong polarity gives more range to the signal reading, especially if the RF gain on the receiver is already turned down. Howzat?

piraterx
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Re: Offcum aerial

Post by piraterx » Thu Sep 13, 2018 3:39 pm

Cheers for replyin yellowbeard

i just thot if he holds the aerial in wrong polarisation then it would cancel the signal out.

i know they say vertical dipole is omnidirectional but is it not like a figuer of 8 so if he held his dipole vertical and turned it around would he not get a null when facing the tx dipole?

offcum always going on about sophisticated df gear but what you see in the video is a bit unsophisticated lol

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Re: Offcum aerial

Post by Frequent Lee » Thu Sep 13, 2018 6:48 pm

Horizontal dipole becomes directional. Its not about if its unsophisticated, thats the laws of rf and physics, thats just how it works.

mixfm
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Re: Offcum aerial

Post by mixfm » Thu Sep 13, 2018 7:43 pm

they said 5 stations in the west mids... where, not now days 3 if your lucky;;;;

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Re: Offcum aerial

Post by cheese101 » Thu Sep 13, 2018 11:44 pm

....

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teckniqs
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Re: Offcum aerial

Post by teckniqs » Thu Sep 13, 2018 11:52 pm

At very close range it wouldn't cancel the very strong signal out and it's better to be able to tell if it's straight in front of you using an horizontal beam.

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nrgkits.nz
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Re: Offcum aerial

Post by nrgkits.nz » Fri Sep 14, 2018 10:40 pm

Holding a receive dipole up horizontal you can find the null by rotating it around 360deg - the null is where you lose reception or reception degrades the most. This gives you only two possible directions of the transmitter either in front or behind, then you repeat this from another point - its called triangulation. Usually you'd do it from high points where you're not going to get reflections off buildings etc...

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Re: Offcum aerial

Post by wazza » Mon Sep 17, 2018 8:45 pm

mixfm wrote:
Thu Sep 13, 2018 7:43 pm
they said 5 stations in the west mids... where, not now days 3 if your lucky;;;;
I count 5 in total now... Bcmr, hot 92, skyline, sting and kriss.

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