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Old March 25th 18, 04:09 AM posted to rec.radio.amateur.antenna
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Default Antennas That Don't Need Grounding For An Apt.

I am taking my ham test in two weeks and I just found out you have to ground your equipment. I live in a apt without copper, water pipes. I have heard a dipole antenna would work. Any comments.

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Old March 25th 18, 03:15 PM posted to rec.radio.amateur.antenna
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Default Antennas That Don't Need Grounding For An Apt.

In message , Catweazel
writes
On 25/03/2018 04:09, wrote:
I am taking my ham test in two weeks and I just found out you have to
ground your equipment. I live in a apt without copper, water pipes. I
have heard a dipole antenna would work. Any comments.

so would a loop antenna; no ground required.


I have a feeling that you might not be quite ready for your test -
unless the level required is (say) only for you to know where the on-off
switch is, and which socket is for the antenna and which is for the
microphone.

But to answer your post, it rather depends on what purpose the 'ground'
connection serves. If it's only for safety, it may serve no function for
carrying RF currents.

If the ground IS for RF purposes, maybe it helps if you think of feeding
RF into an antenna as being a bit like when you're sitting in a rowing
boat on a lake - but without any oars.

Assuming you don't resort to paddling with your hands (!), there are two
obvious ways you can make your boat (the RF) move:
1. Push against something that can't move (for example, the shore). In
this case, the shore doesn't move, and all the movement goes into your
boat.
2. Push against something that CAN move (for example, another, similar,
rowing boat). In this case BOTH boats will move - but half of the
movement goes into your boat, and half goes into the other boat.

[I'll leave it to you to work out which (rather crude) analogy applies
to an antenna that needs a ground, and which one doesn't.]

Of course, with some antennas the 'ground' might not be a physical
connection to ground (earth). The 'ground' (which doesn't radiate) might
be part of the antenna system that simply makes the 'hot' side of the
antenna (which does radiate) think that it DOES have a ground.

But as I said, before your test, you might need to do some very basic
study on some of various types of antenna, and how they work.
--
Ian
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Old March 25th 18, 08:10 PM posted to rec.radio.amateur.antenna
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Default Antennas That Don't Need Grounding For An Apt.

wrote:

I am taking my ham test in two weeks and I just found out you have to
ground your equipment. I live in a apt without copper, water pipes. I
have heard a dipole antenna would work. Any comments.


Others have dealt with RF grounding of the antenna. From the electrical
safety point of view whether you ground things and if so how depends in
part on what equipment you use and also what country you are in.

Don't worry about not fully understanding this point, many quite
experienced amateurs get this wrong.

--

Roger Hayter


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Old March 25th 18, 08:20 PM posted to rec.radio.amateur.antenna
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Default Antennas That Don't Need Grounding For An Apt.

On Sunday, March 25, 2018 at 12:10:36 PM UTC-7, Roger Hayter wrote:
wrote:

I am taking my ham test in two weeks and I just found out you have to
ground your equipment. I live in a apt without copper, water pipes. I
have heard a dipole antenna would work. Any comments.


Others have dealt with RF grounding of the antenna. From the electrical
safety point of view whether you ground things and if so how depends in
part on what equipment you use and also what country you are in.

Don't worry about not fully understanding this point, many quite
experienced amateurs get this wrong.

--

Roger Hayter


Thanks for your comments ppl. Happy hamming.
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Old March 27th 18, 07:46 PM posted to rec.radio.amateur.antenna
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Default Antennas That Don't Need Grounding For An Apt.

I am taking my ham test in two weeks and I just found out you have to ground your equipment. I live in a apt without copper, water pipes. I have heard a dipole antenna would work. Any
comments.


There are three issues here with respect to grounding.

One is "safety" grounding - grounding and static-discharge of outdoor
antennas, to deal with lighting and with dry-air static buildup. This
sort of grounding should be done outside the building structure, using
a proper lighting arrestor and heavy ground wire. It's more urgent in
some parts of the country than others, but it always a good idea.

A second is AC safety grounding - using proper three-prong AC outlets (with
building grounds) for any equipment that has a three-prong plug on its
power cord. Don't use "cheater" plugs which bypass the ground - it
could create a shock hazard. Proper grounding of the equipment
chassis also helps avoid RF burns, if any RF on the antenna "feeds
back" into the equipment chassis due to an antenna fault.

The third is using ground as part of the antenna system (as, for
example, HF monopoles do). This seems to be mostly what you were
asking about.

Yes, dipole antennas can operate without a connection to earth-ground,
as one half of the dipole provides a current path for the "ground"
side of the RF signal. In order to keep RF off of the outside of the
feedline (where it might travel back to the equipment chassis) it's a
good idea to install a balun of some sort at the connection between
the dipole antenna and the feedline. With a standard coax feedline
and a typical dipole you'd want a 1:1 balun; if you're using a folded
dipole you'd want a 4:1 balun; if you're using an off-center-fed
dipole you'd want something else (I think these usually use 4:1 baluns
as well).

A full-wavelength horizontal loop is another sort of balanced antenna
that doesn't require a ground connection.

A third choice is a "small" or "magnetic" loop antenna. These have
the advantage of small size (relatively speaking) and they can usually
be tuned to cover several of the amateur HF bands. They have
disadvantages - relatively low electrical efficiency (high losses), a
narrow operating bandwidth (they must be re-tuned every time you
change frequencies more than slightly), and high RF voltages and
currents that can present a shock or RF-exposure hazard. The good
ones aren't cheap, as they need an adjustable capacitor which can
handle those high RF voltages without arcing and the high RF currents
without burning up due to electrical losses. One of these might be
your only good choice if you're working HF from an apartment and don't
have the ability to install a big outdoor antenna.

As for operation on VHF (2 meters and so forth) - the issues are a lot
simpler in practice. There are numerous 2-meter antennas which don't
require a ground connection to work - they're either dipoles, or "end
fed" antennas, or they have their own radials which serve as a ground
plane.

You can make a very simple and effective "ground plane" 2-meter
antenna yourself, from little more than an SO-239 socket and five
pieces of stiff copper wire. This is electrically quite similar to a
simple vertical dipole - its radiation pattern and electrical
efficiency are almost the same as a center-fed vertical dipole - and
it's quite apartment-and-balcony friendly.

http://www.hamuniverse.com/2metergp.html







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Old March 28th 18, 12:08 AM posted to rec.radio.amateur.antenna
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Default Antennas That Don't Need Grounding For An Apt.

On Tuesday, March 27, 2018 at 11:46:25 AM UTC-7, Dave Platt wrote:
I am taking my ham test in two weeks and I just found out you have to ground your equipment. I live in a apt without copper, water pipes. I have heard a dipole antenna would work. Any
comments.


There are three issues here with respect to grounding.

One is "safety" grounding - grounding and static-discharge of outdoor
antennas, to deal with lighting and with dry-air static buildup. This
sort of grounding should be done outside the building structure, using
a proper lighting arrestor and heavy ground wire. It's more urgent in
some parts of the country than others, but it always a good idea.

A second is AC safety grounding - using proper three-prong AC outlets (with
building grounds) for any equipment that has a three-prong plug on its
power cord. Don't use "cheater" plugs which bypass the ground - it
could create a shock hazard. Proper grounding of the equipment
chassis also helps avoid RF burns, if any RF on the antenna "feeds
back" into the equipment chassis due to an antenna fault.

The third is using ground as part of the antenna system (as, for
example, HF monopoles do). This seems to be mostly what you were
asking about.

Yes, dipole antennas can operate without a connection to earth-ground,
as one half of the dipole provides a current path for the "ground"
side of the RF signal. In order to keep RF off of the outside of the
feedline (where it might travel back to the equipment chassis) it's a
good idea to install a balun of some sort at the connection between
the dipole antenna and the feedline. With a standard coax feedline
and a typical dipole you'd want a 1:1 balun; if you're using a folded
dipole you'd want a 4:1 balun; if you're using an off-center-fed
dipole you'd want something else (I think these usually use 4:1 baluns
as well).

A full-wavelength horizontal loop is another sort of balanced antenna
that doesn't require a ground connection.

A third choice is a "small" or "magnetic" loop antenna. These have
the advantage of small size (relatively speaking) and they can usually
be tuned to cover several of the amateur HF bands. They have
disadvantages - relatively low electrical efficiency (high losses), a
narrow operating bandwidth (they must be re-tuned every time you
change frequencies more than slightly), and high RF voltages and
currents that can present a shock or RF-exposure hazard. The good
ones aren't cheap, as they need an adjustable capacitor which can
handle those high RF voltages without arcing and the high RF currents
without burning up due to electrical losses. One of these might be
your only good choice if you're working HF from an apartment and don't
have the ability to install a big outdoor antenna.

As for operation on VHF (2 meters and so forth) - the issues are a lot
simpler in practice. There are numerous 2-meter antennas which don't
require a ground connection to work - they're either dipoles, or "end
fed" antennas, or they have their own radials which serve as a ground
plane.

You can make a very simple and effective "ground plane" 2-meter
antenna yourself, from little more than an SO-239 socket and five
pieces of stiff copper wire. This is electrically quite similar to a
simple vertical dipole - its radiation pattern and electrical
efficiency are almost the same as a center-fed vertical dipole - and
it's quite apartment-and-balcony friendly.

http://www.hamuniverse.com/2metergp.html


Thanks.


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