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.




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On 1/23/2014 3:30 PM, Channel Jumper wrote:

Jerry Stuckle;814478 Wrote:
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?
-

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.

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

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

I'm sorry Jerry, but you don't know what you are talking about.

Smith Charts do not have anything to do with antenna efficiency or
resonance.
The only thing that Smith Charts does is explain what is happening
inside of a piece of coax X inches long. Note I do not use feet -
since that is too vague.


Again, wrong. Smith Charts explain a LOT about antennas. But then I
can see you've never used one - but you have to try to correct someone
who knows more than you, anyway. But you only show your ignorance.

And BTW - I was using Smith Charts before you were born.

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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.

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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 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.

--
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==================

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.

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 1/24/2014 6:40 AM, wrote:
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.



Low antenna efficiency affects not only the received signal, but the
received noise.

And yes, many inexpensive "modern" receivers suffer from poor front
ends. And since transistors (especially bipolar) typically generate
more noise than tubes,
noise can be a worse problem now than in the 60's. You can get low
noise transistors, but these are more expensive.

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On 1/24/2014 2:38 AM, Jeff wrote:

I'm sorry Jerry, but you don't know what you are talking about.

Smith Charts do not have anything to do with antenna efficiency or
resonance.
The only thing that Smith Charts does is explain what is happening
inside of a piece of coax X inches long. Note I do not use feet -
since that is too vague.

Whilst I agree with your first point, Smiths Charts do not "explain what
is happening inside of a piece of coax X inches long". They are an easy
way to plot impedances, and show what happens if you *change* the length
of coax, but more importantly they give you an easy way of working out
how to match impedances (with or without any length of coax involved).
They can also display other valuable quantities such as Q.

jeff


They do if you know how to use them properly. For instance, they will
tell you when the reactive portion of the impedance is zero (neither
capacitive nor inductive), which indicates resonance. They will also
tell you the antenna's impedance at a specific frequency. Both can be
used to indirectly determine antenna efficiency.

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