Q. Is there a relationship between the efficiency of an antenna and the
received signal strength?

Just pondering on the matter. Because I have to operate with
restricted space antennas, usually with low efficiency, I wonder how
much of a relationship exists between Efficiency and Received Signal
Strength?

This leads to more questions such as how much do radials contribute
to efficiency?

IF that isn't enough, how much do radials contribute to the bandwidth?

And...

And...

I'm never to old to learn, but I am old enough that a lot of mathematical
mumbo jumbo and Smith Charts tend to confound me!

For starters, I will be operating using an MP-1 antenna and a Yaesu
FT-817ND. I also have an MFJ-931 Artificial Ground, but propose
attaching the radials to the feedpoint on the MP-1. I intend to cut four
radials for 20M and spread them around the base of the antenna in
my room, and once the weather warms up, I'll try the antenna out on
the balcony with the radials spread around whatever real estate it
provides.

Thanks for any input on the matter....

Irv VE6BP

RADIATE OR DIE TRYING!

On Wed, 22 Jan 2014 15:32:31 -0700, "Irv Finkleman"
wrote:

Q. Is there a relationship between the efficiency of an antenna and the
received signal strength?

Not really. Radiation efficiency is normally used with transmitting
antennas, not receiving. You're not radiating anything in receive.
http://en.wikipedia.org/wiki/Antenna_efficiency

Just pondering on the matter. Because I have to operate with
restricted space antennas, usually with low efficiency, I wonder how
much of a relationship exists between Efficiency and Received Signal
Strength?

Any loss of receive efficiency will show up in the antenna gain (or
lack of antenna gain). No need to deal with it separately.

This may help with conversions and computations:
http://www.tscm.com/fieldint.pdf

This leads to more questions such as how much do radials contribute
to efficiency?

I assume you mean ground radials, not antenna radials. The purpose of
the ground radials is to prevent the RF that's being radiated towards
the ground, from getting absorbed by the ground. With above ground
radials, they reflect the signal upwards, so that part of the signal
goes in hopefully some useful direction. (Note: This is not the
conventional wisdom).

IF that isn't enough, how much do radials contribute to the bandwidth?

That's what antenna models and simulations are for. Much depends on
the conductivity of the ground, the size and number of radials, type
of antenna, etc.

I'm never to old to learn, but I am old enough that a lot of mathematical
mumbo jumbo and Smith Charts tend to confound me!

See:
http://www.qsl.net/4nec2/
or
http://www.eznec.com
Both come with a large collection of ready to play antennas. Take
your location, your antenna, your ground, and your imagination, and
make a model. I've done that for my house. It started out fairly
simple, and has grown into a monster that takes hours to compute.
Still, it's quite worthwhile to see what changes, such as your ground
system, does to the pattern, gain, bandwidth, vswr, etc.

Incidentally, you can have:
Gain, bandwidth, or size. Pick any two.
What that means is that if you shrink the antenna, you're going to
lose either gain or bandwidth. No free lunch in antenna land.

For starters, I will be operating using an MP-1 antenna and a Yaesu
FT-817ND. I also have an MFJ-931 Artificial Ground, but propose
attaching the radials to the feedpoint on the MP-1. I intend to cut four
radials for 20M and spread them around the base of the antenna in
my room, and once the weather warms up, I'll try the antenna out on
the balcony with the radials spread around whatever real estate it
provides.

Sorry, no clue to what it will do. I convinced a friend to run his
2nd floor station with some welded fence wire under his carpet. It
worked fine until his wife made him remove the wire. Nothing would
roll over the carpet.

Thanks for any input on the matter....

Never thank anyone until it's done and working. Premature thanks is
bad luck.

Irv VE6BP
RADIATE OR DIE TRYING!

Calculations are worth more than the usual cut-n-try.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Wednesday, January 22, 2014 7:32:09 PM UTC-6, Jeff Liebermann wrote:
You're not radiating anything in receive.

Isn't part of the received signal re-radiated?
--
73, Cecil, w5dxp.com

On Fri, 24 Jan 2014 04:06:20 -0800 (PST), W5DXP
wrote:

On Wednesday, January 22, 2014 7:32:09 PM UTC-6, Jeff Liebermann wrote:
You're not radiating anything in receive.

Isn't part of the received signal re-radiated?

I have no idea. I guess it's possible for a received signal to
"bounce" off the wire and wander off elsewhere. With VSWR, the
reflected signal might be re-radiated if the source impedance is
mismatched. Dunno.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Jeff Liebermann" wrote in message
...
Isn't part of the received signal re-radiated?

I have no idea. I guess it's possible for a received signal to
"bounce" off the wire and wander off elsewhere. With VSWR, the
reflected signal might be re-radiated if the source impedance is
mismatched. Dunno.

Interisting thought. When the signal hits the receiver I am sure there is
some mismatch and part of it is reflected back to the antenna. Now what
hapens. All of it is radiated, part radiated and part reflected back, all
of it reflected back to the receiver ?



---
This email is free from viruses and malware because avast! Antivirus protection is active.
http://www.avast.com

It seems to me to be the same as a multipath TV signal causing
ghosting. The signal that is not on the direct path hits a building
and is reradiated and arrives at the TV at a different time.

....and how about the reflectors and directors on a Yagi antenna?

....where does the signal go when it hits something? It is either absorbed
or re-radiated -- some of course is lost in heating, but there is always
a little left over.

Food for thought!

Irv VE6BP

--
Political correctness is a doctrine, fostered by a delusional, illogical
minority, and rapidly promoted by an unscrupulous mainstream media, which
holds forth the proposition that it is entirely possible to pick up a piece
of **** by the clean end.

On Fri, 24 Jan 2014 04:06:20 -0800 (PST), W5DXP
wrote:

On Wednesday, January 22, 2014 7:32:09 PM UTC-6, Jeff Liebermann wrote:
You're not radiating anything in receive.

Isn't part of the received signal re-radiated?

I have no idea. I guess it's possible for a received signal to
"bounce" off the wire and wander off elsewhere. With VSWR, the
reflected signal might be re-radiated if the source impedance is
mismatched. Dunno.

My recollection is that in the best of cases (good match, no
dissipative losses), half of the RF energy which impinges on the
antenna goes into the feedline. The other half is re-radiated.

AIUI, the received EM field induces a current flow in the
antenna... and this current flow itself causes another EM field to be
generated and radiated away.

On Friday, January 24, 2014 1:22:02 PM UTC-6, David Platt wrote:
My recollection is that in the best of cases (good match, no
dissipative losses), half of the RF energy which impinges on the
antenna goes into the feedline. The other half is re-radiated.

That is my recollection also. 73, Cecil, w5dxp.com

Irv,
The very best advice we can give you is to advise you to find a good amateur radio club in your neighborhood and have you join.
Look for someone more knowledgeable then yourself - regardless of their age, and have them mentor you.
A decent Amateur Radio Club will have a hamshack - a place where it's members can operate.
There - you can take your radio and hook it up to their antenna's and operate.
The only other advice I can give you is to tell you to move!

Amateur radio isn't for everyone.
It does not allow us to bend or break the rules of Physic's.
There is a certain amount of effort that has to be done in order to get your signal up in the air and be able to broadcast it to the world.

The only option I have seen that was somewhat successful was a operator that bought Hamsticks and fabricated a mount, mounted the hamsticks on his porch railing, grounded the railing and used the hamsticks on 6 and 10 meters. 10 meters only requires a 9' long antenna - quarter wave, and a dipole on 6 is 9' long.

Your transceiver is marginal at best, not a real good performer to start with and handicapping it by using a non resonant antenna is only going to impede your amateur radio hobby much past listening to the bands.

On 1/22/2014 5:32 PM, Irv Finkleman wrote:
Q. Is there a relationship between the efficiency of an antenna and the
received signal strength?


Definitely. Antenna efficiency works both ways - a less efficient
antenna will affect both transmit and received signals.

Just pondering on the matter. Because I have to operate with
restricted space antennas, usually with low efficiency, I wonder how
much of a relationship exists between Efficiency and Received Signal
Strength?


Just as much as between efficiency and transmitted signal strength.

This leads to more questions such as how much do radials contribute
to efficiency?


That depends on a lot of factors such as number of radials, length,
height above ground and ground conductivity, for start. Each situation
is different. But generally, for antennas such as 1/4 wave verticals,
radials will help.

IF that isn't enough, how much do radials contribute to the bandwidth?


See above.

And...

And...

I'm never to old to learn, but I am old enough that a lot of mathematical
mumbo jumbo and Smith Charts tend to confound me!


Unfortunately, the only way to predict how an antenna is going to work
in a specific situation with any accuracy is with math and Smith Charts.
So you can use the "tried and true" method - put it up and see what
happens

For starters, I will be operating using an MP-1 antenna and a Yaesu
FT-817ND. I also have an MFJ-931 Artificial Ground, but propose
attaching the radials to the feedpoint on the MP-1. I intend to cut four
radials for 20M and spread them around the base of the antenna in
my room, and once the weather warms up, I'll try the antenna out on
the balcony with the radials spread around whatever real estate it
provides.


Not an ideal situation, but you do what you can.

Thanks for any input on the matter....

Irv VE6BP

RADIATE OR DIE TRYING!









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