Thanks Wayne,

Its not a bad idea and I've considered horizontal loops but
if you knew what was in my ceiling I think you'd reconsider too!
In any event, I'm all studied up and planned on building a
magnetic loop which will meet all my needs.

Thanks for your consideration,

Irv VE6BP

On 1/22/2014 4:32 PM, Irv Finkleman wrote:
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!







Irv, I have a pdf file about ham antennas that is written in very nice
plain language and explains all the benefits and downfalls of different
types of antennas and grounds. If your email is correct I will send it
to you.

Michael

On Wednesday, January 22, 2014 4:32:31 PM UTC-6, Irv Finkleman wrote:
Q. Is there a relationship between the efficiency of an antenna and the

received signal strength?

Signal to noise ratio, very little. Received signal level vs
a more efficient antenna, can be quite a bit. But if the s/n
is appx the same, no biggie.. Lower level on the S meter, but
things should sound about the same when listening to it.





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?

It all depends what freq, type of operation, etc.. But for general
skywave HF, even a fairly inefficient antenna can be quite fine
for receiving in many cases. The level may drop with the inefficient
antenna, but assuming the same basic pattern, the s/n ratio should be
pretty much the same. If you have enough antenna to increase the
background noise when connecting the antenna to the radio, it should
be fine for general gov use.




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

to efficiency?

Quite a bit, but that's much more a transmitting concern than receive.




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

In general, adding more radials will decrease the bandwidth.



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.

You would be much better off ditching the vertical idea, and
try to figure out a way to string up a simple dipole for
one of the higher bands.

If you have room for radials, you should have enough room for
a simple dipole. And it doesn't have to be inline, or in any
particular orientation. For 20m, you could have a feed point
in one of the corners of a room, and have one 16 ft leg running
along one wall, and have the other leg running down the other
wall. The legs would be 90 degrees apart, but will still work
fine overall. The antenna will be efficient if fed with thin coax,
and likely beat the pants off most small vertical rigs.
But this sort of assumes there is not wiring or metal in the walls
to grossly detune the antenna.
In your case, receiving should be no problem. Even a length of
random wire will work for general HF. Your real issue is radiating
enough RF for people to hear you.

One thing about "short" verticals. A good ground/radial system is
more critical for those than it is for full length monopoles which
can often get by with no/few radials and still work well enough to use.
That's much harder to do with a very short loaded vertical.

If I were you, I'd be trying to find ways to run sneaky dipoles.
You could use real thin wire if needed to make it less visible.
If you stick to the higher bands, they won't be too long.
You can do 10m nicely if you can find a way to string up 16 ft of
wire total. Even a 32 ft 20 m dipole can be fit into many rooms.
Feed with thin coax, and no tuner, no tuner loss, and the efficiency
will be high. That's what you want with QRP.

Thanks Mark -- you answered my questions. I sort of knew the
answers but needed confirmation in my own mind.

If you read my post in the topic 'antenna theory made easy' you will
understand why dipoles are out of the question. Real Estate is my
limiting factor! A magloop will be built and should be running early
this summer -- earlier if weather permits!

Irv VE6BP

wrote in message
...

It all depends what freq, type of operation, etc.. But for general
skywave HF, even a fairly inefficient antenna can be quite fine
for receiving in many cases. The level may drop with the inefficient
antenna, but assuming the same basic pattern, the s/n ratio should be
pretty much the same. If you have enough antenna to increase the
background noise when connecting the antenna to the radio, it should
be fine for general gov use.


I always hear that, but it doesn't seem to be that way for me.

I have an off center fed antenna (about 125 feet long) mostly flat at 50
feet. Also a 3 element triband at 60 feet. Both fed by low loss rg8 type
coax. On some of the weaker signals on 20 meters I don't hear signals on
the OCF that are good copy on the beam. Also an 80 meter dipole at the 45
foot level at right angles to the 80 meter antenna will not hear what the
beam does in some cases. That is in a relative quiet location as far as
noise goes. The receive is an Icom 746pro.




---
This email is free from viruses and malware because avast! Antivirus protection is active.
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On Thursday, January 23, 2014 7:16:54 PM UTC-6, Ralph Mowery wrote:
wrote in message

...



It all depends what freq, type of operation, etc.. But for general

skywave HF, even a fairly inefficient antenna can be quite fine

for receiving in many cases. The level may drop with the inefficient

antenna, but assuming the same basic pattern, the s/n ratio should be

pretty much the same. If you have enough antenna to increase the

background noise when connecting the antenna to the radio, it should

be fine for general gov use.





I always hear that, but it doesn't seem to be that way for me.



I have an off center fed antenna (about 125 feet long) mostly flat at 50

feet. Also a 3 element triband at 60 feet. Both fed by low loss rg8 type

coax. On some of the weaker signals on 20 meters I don't hear signals on

the OCF that are good copy on the beam. Also an 80 meter dipole at the 45

foot level at right angles to the 80 meter antenna will not hear what the

beam does in some cases. That is in a relative quiet location as far as

noise goes. The receive is an Icom 746pro.


That would almost surely be more pattern related than efficiency.
And the beam has gain in the direction it's pointing.
If you took any one of those antennas on it's own and lowered
the efficiency by adding resistance at the feed, a more lossy
feed line, or added tuner loss, or even just used an attenuator,
the signal level will vary, but the s/n ratio should change very
little. Both the noise and desired signals are going to be reduced
equally. Only when you get to the point where hooking up the antenna
and not noticing a noise increase at all, are you starting to really
have a problem with reception due to lower system efficiency.

On 1/23/2014 7:18 PM, wrote:
On Wednesday, January 22, 2014 4:32:31 PM UTC-6, Irv Finkleman wrote:
Q. Is there a relationship between the efficiency of an antenna and the

received signal strength?

Signal to noise ratio, very little. Received signal level vs
a more efficient antenna, can be quite a bit. But if the s/n
is appx the same, no biggie.. Lower level on the S meter, but
things should sound about the same when listening to it.


You forgot the noise generated by the receiver. With a weaker signal,
the S/N ration will be lower.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

On Thursday, January 23, 2014 8:21:27 PM UTC-6, Jerry Stuckle wrote:
On 1/23/2014 7:18 PM, wrote:

On Wednesday, January 22, 2014 4:32:31 PM UTC-6, Irv Finkleman wrote:

Q. Is there a relationship between the efficiency of an antenna and the



received signal strength?



Signal to noise ratio, very little. Received signal level vs

a more efficient antenna, can be quite a bit. But if the s/n

is appx the same, no biggie.. Lower level on the S meter, but

things should sound about the same when listening to it.





You forgot the noise generated by the receiver. With a weaker signal,

the S/N ration will be lower.

That would be an issue on VHF/UHF. We are talking HF here.
On HF, external noise picked up by the antenna is almost surely
going to greatly swamp any internal receiver noise.
Assuming a decent receiver anyway, and the one he has should
be fairly good.
That's one reason why I say if the background noise increases when
connecting the antenna, it should be good enough. If it doesn't,
there could be a problem.
But it will take a really dead antenna system to be like that on HF.
Even just sticking a 5 feet piece of wire into the center pin of a
decent receiver will cause the noise level to increase, and thus be
a fairly viable antenna. Not that it's going to pick up everything,
but it should pick up quite a bit. Note the portable SW radios
with short whips, etc..

On 1/23/2014 9:42 PM, wrote:
On Thursday, January 23, 2014 8:21:27 PM UTC-6, Jerry Stuckle wrote:
On 1/23/2014 7:18 PM, wrote:

On Wednesday, January 22, 2014 4:32:31 PM UTC-6, Irv Finkleman wrote:

Q. Is there a relationship between the efficiency of an antenna and the



received signal strength?



Signal to noise ratio, very little. Received signal level vs

a more efficient antenna, can be quite a bit. But if the s/n

is appx the same, no biggie.. Lower level on the S meter, but

things should sound about the same when listening to it.





You forgot the noise generated by the receiver. With a weaker signal,

the S/N ration will be lower.

That would be an issue on VHF/UHF. We are talking HF here.
On HF, external noise picked up by the antenna is almost surely
going to greatly swamp any internal receiver noise.
Assuming a decent receiver anyway, and the one he has should
be fairly good.
That's one reason why I say if the background noise increases when
connecting the antenna, it should be good enough. If it doesn't,
there could be a problem.
But it will take a really dead antenna system to be like that on HF.
Even just sticking a 5 feet piece of wire into the center pin of a
decent receiver will cause the noise level to increase, and thus be
a fairly viable antenna. Not that it's going to pick up everything,
but it should pick up quite a bit. Note the portable SW radios
with short whips, etc..



It is also an issue on HF, especially with less expensive receivers.
You don't see it on the S-Meter because the meter is set such that the
typical receiver noise doesn't show up. But it is there. And it does
affect weak signal intelligibility.

--
==================
Remove the "x" from my email address
Jerry Stuckle

==================

On Thursday, January 23, 2014 9:45:31 PM UTC-6, Jerry Stuckle wrote:


It is also an issue on HF, especially with less expensive receivers.

You don't see it on the S-Meter because the meter is set such that the

typical receiver noise doesn't show up. But it is there. And it does

affect weak signal intelligibility.

I didn't say that internal receiver noise would show on the
S meter.
I suppose it's possible receiver noise could effect weak signal
reception on HF, but it's going to have to be a really low
level not to override the internal receiver noise on any modern
radio, unless it's some kind of abnormal birdy or whatever.
I just don't see it being a much of a problem on HF, particularly
20m.
If external noise or signals picked up by the antenna don't
override the internal receiver noise on 20m, something is broke
somewhere.
And if the system is that broke, might as well forget anyone hearing
him, particularly running QRP.
He should do OK with a small loop as long as it's built and working
right.