Aerial positioning

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Re: Aerial positioning

Postby alank950 » Mon Aug 21, 2017 10:03 am

From what i have gathered a simple run of wire from the tuner to a copper pipe on my central heating will be a good earth,worth a try to see whats what.Are you suggesting i earth the aerial if so how?.I intend acquiring the RX SPC ATU Receive SPC Antenna Tuning Unit. Made in Dorset, UK.This i am aquiring from an ebay seller who makes these so i will have some backup
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Re: Aerial positioning

Postby m0lsx » Mon Aug 21, 2017 10:48 am

alank950 wrote:From what i have gathered a simple run of wire from the tuner to a copper pipe on my central heating will be a good earth,


No..NEVER EVER do that. Not unless you know for an absolute fact that your home is not Protective Multiple Earthed.
If you did earth your radio to the heating system & your home is PME. Then an electrical fault not just within your home. But within any of the other buildings within your earthing system or the transformer it is fed off could leave your radio, your heating system & everything connected to them live.
Also connecting to a heating system is a good way of introducing unnecessary QRM. Whcich is man made interference. Into your radio system.
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Re: Aerial positioning

Postby m0lsx » Mon Aug 21, 2017 10:53 am

alank950 wrote:I intend acquiring the RX SPC ATU Receive SPC Antenna Tuning Unit. Made in Dorset, UK.This i am aquiring from an ebay seller who makes these so i will have some backup


There are a number of ways to earth your radio & the antenna system. BUT first you need to know if your house has PME.
With PME earthing a long wire at the feed point is fine providing you have no mains earthing beyond the normal one that comes as part of your homes wiring system.
What you do is use the second connection on the balun to feed against a earth stake rather than a counterpoise.
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Re: Aerial positioning

Postby alank950 » Mon Aug 21, 2017 12:15 pm

Thanks i will take your word for it..
I will try the radio without an earth and see how i get on
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Re: Aerial positioning

Postby m0lsx » Mon Aug 21, 2017 2:15 pm

There are various different meanings to the term earth.
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Re: Aerial positioning

Postby alank950 » Mon Aug 21, 2017 2:24 pm

This is the reply i got from the guy who builds the tuners

A single wire aerial and most vertical types are just the element and need to be tuned against ground. Some verticals rely on the support mast to provide the path to ground but often are better if elevated radials are fitted.
A long random wire is in effect a Marconi quarterwave with the element bent over, so it too need to be tuned against earth. By providing an earth connection on the ATU it ensures this is done otherwise the ATU has nothing to tune against.

Any length of wire will provide some sort of earth BUT as any wire will start to develop waves along it, it won't necessarily be low impedance at the frequency you wish to use. Indeed a ground wire only provides a low impedance if it is a small fraction of a wavelength or if it is a multiple of halfwave on the desired frequency. any wire connected from the ATU black terminal to ground will be better than no earth connection at all.

In older houses with copper central heating pipes they all had to be earthed via a decent size wire from near the central heating boiler to the earth connection of the mains supply. Check that this is so, and providing you haven't had any radiator pipes replaced by plastic ones you can be pretty sure then the nearest radiator would provide probably a better earth than an alternative wire to ground.

The RX SPC ATU is the best one for a long wire because it copes properly when the antenna is too long to be a multiple of 1/4 wave at a particular frequency and when the wire is too short to be an odd multiple of a 1/4 wave.
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Re: Aerial positioning

Postby m0lsx » Mon Aug 21, 2017 3:22 pm

Personally I have copper pipes & PME & I know of plenty of others in the same situation.

Take a read of..

http://rsgb.org/main/files/2012/11/EMC07-v3-Earthing-and-the-Radio-Amateur-Basic.pdf

It is heavy reading, but it is the only answer to what you have been told..And the above link is the BASIC leaflet. Earths are not to be messed with, unless you know what sort of earthing you have & I am really surprised anyone would tell you what you have been told, it's potentially dangerous.
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Re: Aerial positioning

Postby alank950 » Mon Aug 21, 2017 3:39 pm

Thanks i will read that link
............................................................................................................................................
What you do is use the second connection on the balun to feed against a earth stake rather than a counterpoise.
............................................................................................................................................


So is this the feed connection for the actuall long wire on the balun?
Are you suggesting i run a wire from this to a copper ground spike?
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Re: Aerial positioning

Postby alank950 » Wed Aug 30, 2017 10:29 am

I am measuring my yard for a longwire..
I read that a straight length is all thats needed...my question is as i have a yard that measures only approx 10 meters from top to bottom can i run the longwire around the yard in a U shape which will mean i can use up roughly 25 to 30 meters of wire outside, instead of running a straight piece at 10 meters?
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Re: Aerial positioning

Postby m0lsx » Wed Aug 30, 2017 10:42 am

alank950 wrote:I am measuring my yard for a longwire..
I read that a straight length is all thats needed...my question is as i have a yard that measures only approx 10 meters from top to bottom can i run the longwire around the yard in a U shape which will mean i can use up roughly 25 to 30 meters of wire outside, instead of running a straight piece at 10 meters?



There is no need for any wire antenna to be straight. Also 10 meters is not too bad a length for RX. It may not work great on TX especially on the longer wavelengths. But on RX, it's not such an issue.
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