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Topic Title: Ham radio grounding,pme system
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Created On: 08 June 2018 01:31 PM
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 14 June 2018 12:04 PM
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mapj1

Posts: 10914
Joined: 22 July 2004

You have an inverted L, what is the coax inner and outer actually connected to at each end ?
and what is this antenna working against?
That is to say, when the signal comes down the wire that you want to receive, a current flows out of the end of the inverted L, though your receiver input stages, and then to where?
Normally you are expecting the current that comes in on the antenna to then continue out of the receiver via a connection to the ground under the antenna or a conducting surface or mesh on the ground to emulate that, or maybe a counterpoise element - in all cases you need current to flow through the receiver from somewhere to somewhere, and that current is what gets amplified and demodulated in the receiver to be the signal you hear. If you imagine the ground as a sheet of conductor, then to radio waves in the air it is a mirror, and your radio can be visualised as intercepting the current flowing between your antenna and its rather spotty mirror image in the ground.
If the return path is incomplete, then there will only be a weak signal, due to some current flow via capacitance between the radio chassis and ground, and perhaps via the PSU. Also if the return path to the ground beneath the antenna is not short and sweet, but incudes other generators of voltages the receiver will amplify and decode the resultant of your wanted signal and this interference voltage in series.

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regards Mike
 15 June 2018 10:14 AM
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MrPaul

Posts: 13
Joined: 08 June 2018

Hi mike,the antenna is connected to a matching transformer.it has a primary and secondary number of turns.then the other side of the transformer is connected to a couple of ground rods.(40 feet at the end of the garden)it also has three 66 foot counterpoises connected.the coax then comes down the garden and trough a small hole and connects to my receiver. I have looked at article on using the coax screen on the back of the pl259 to connect a ground wire to.is this ok to do with a pme system.
Regards
 15 June 2018 08:26 PM
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kellyselectric

Posts: 325
Joined: 22 July 2016

You cant just ground the coax on its own there must be a connection between the coax braid and the radio and ground as well. Ancient mariner the reason for the 100 Kilometre exclusion around charging cross is because there is some official use of that frequency in that area ive seen some VHF beams on official looking buildings so guess that the reason. Why oh why they have to say the distance in metric units? To state it in miles would be so much easier
IET » Wiring and the regulations » Ham radio grounding,pme system

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