On 6/27/2014 10:15 AM, Ralph Mowery wrote:
I would like some opinions as if anyone could notice replacing 100 feet of
rg-213 with 7/8 inch or larger hardline would be noticiable.

One ham said when he did he could tell the differance. I just don't see
that going from about .4 db or less of loss to .15 db of loss on 80 meters
is going to be noticed. That is about like going from 100 watts of
transmitted power to maybe 105 watts or less.

In the past I have inserted some 1 and 3 db pads in line with a receiver to
see if I could tell the differance and have a hard time telling that even
the 3 db pad makes much differance in casual operation, especially below 20
MHz.
Maybe some have more sensitive ears than I have.



It was better, caused by the placebo effect.

It was better, caused by the extra dollars he spent.

It was better, because he thought it should be better.

Changing the coax made it 0.25db better, but he didn't hear it.



Mikek

"Ralph Mowery" wrote in message
m...


"Rob" wrote in message
...
One ham said when he did he could tell the differance. I just don't see
that going from about .4 db or less of loss to .15 db of loss on 80
meters
is going to be noticed.

But what when he was working on 70 centimeters instead of 80 meters?
Then it would be a large difference.

I should have made it clear that this is for 80 meters only, no higher band.
Also he did not say what kind of differance he noticed, just that he did.

Most of my work is 2 meters and higher and good transmission there is a
must. I just don't have the operating time on the low bands to know if that
extra .2 db would make any diffreance there. That is 2/10 of a db.
================================================== ========

Yes. It takes 6dB to make a 1 S-unit change. Almost all the time at 80m,
the atmospheric noise is much stronger than the receiver's thermal noise, so
the ability of the other guy to deliver enough signal power to you to be
louder than the atmospherics is the key. He controls that, not you.

On transmit, I suppose every dB counts, considering you're competing with
atmospherics for the other guy's ear. Sort of the inverse of the above.

"Sal"

El 01-07-14 4:41, amdx escribió:
On 6/27/2014 10:15 AM, Ralph Mowery wrote:
I would like some opinions as if anyone could notice replacing 100
feet of
rg-213 with 7/8 inch or larger hardline would be noticiable.

One ham said when he did he could tell the differance. I just don't see
that going from about .4 db or less of loss to .15 db of loss on 80
meters
is going to be noticed. That is about like going from 100 watts of
transmitted power to maybe 105 watts or less.

In the past I have inserted some 1 and 3 db pads in line with a
receiver to
see if I could tell the differance and have a hard time telling that
even
the 3 db pad makes much differance in casual operation, especially
below 20
MHz.
Maybe some have more sensitive ears than I have.



It was better, caused by the placebo effect.

It was better, caused by the extra dollars he spent.

It was better, because he thought it should be better.

Changing the coax made it 0.25db better, but he didn't hear it.



Mikek

Hello Mike,

You did read my mind!

--
Wim
PA3DJS
Please remove abc first in case of PM

On 6/30/2014 9:41 PM, amdx wrote:
On 6/27/2014 10:15 AM, Ralph Mowery wrote:
I would like some opinions as if anyone could notice replacing 100
feet of
rg-213 with 7/8 inch or larger hardline would be noticiable.

One ham said when he did he could tell the differance. I just don't see
that going from about .4 db or less of loss to .15 db of loss on 80
meters
is going to be noticed. That is about like going from 100 watts of
transmitted power to maybe 105 watts or less.

In the past I have inserted some 1 and 3 db pads in line with a
receiver to
see if I could tell the differance and have a hard time telling that even
the 3 db pad makes much differance in casual operation, especially
below 20
MHz.
Maybe some have more sensitive ears than I have.



It was better, caused by the placebo effect.

It was better, caused by the extra dollars he spent.

It was better, because he thought it should be better.

Changing the coax made it 0.25db better, but he didn't hear it.



Mikek

Very well said.

I am afraid we are all guilty of that at times. I just bought a pixel
magnetic loop receiving antenna. At first blush I thought it was great.
Then I put together an A-B switch so that I can make a well thought out
review for e-ham. The loop has some advantages, especially during
electrical storm noise. However, it does not come close to equalling the
performance of a horizontal loop cut for the right frequency. I had
spent 500 dollars on this project, I wanted it to perform better and
then saw it better in my own mind. Careful measurements dispelled my
wild enthusiasm. I admit there are often times it is better at receiving
on 20, 15, and 10 than my 75 meter loop.

Michael

On Tuesday, July 1, 2014 1:51:23 PM UTC-5, FBMboomer wrote:

I am afraid we are all guilty of that at times. I just bought a pixel

magnetic loop receiving antenna. At first blush I thought it was great.

Then I put together an A-B switch so that I can make a well thought out

review for e-ham. The loop has some advantages, especially during

electrical storm noise. However, it does not come close to equalling the

performance of a horizontal loop cut for the right frequency.

What do you mean by performance? You will have trouble getting a decent
null using a horizontal loop. And the easily steerable nulls are 90% of the
reason to use a small loop.
But I only use small loops on low frequencies.. IE: LW to about 2.5 mhz or
so.. AM-BC more than anything, but I've used it on 160m at times.
A small loop can make an offensive ground or space wave signal disappear.
OK at night, but they are not near as effective nulling a sky wave signal
as a ground wave.

I think that some of the posts has gone off target on this one.

Simple math tells us that as long as the op is only wanting to compare power in vs power out and signal in vs signal out that he should be using Belden 9913 F7 or LMR 400 coax.

You wouldn't or couldn't use hardline for a dipole antenna, maybe for a beam antenna, if you were going to attach the hardline to the side of the tower or to a track. The Hardline would be too heavy to support with a rope.

RG 213 is not a very good coax from my perspective - especially if you want to get maximum performance out of a piece of coax.. At higher frequencies you are throwing away a proportional amount of signal in the coax and a proportional amount of power loss between the transmitter and the antenna.

If you were building a repeater, you would want hardline going up the tower to the antenna, regardless if it was 6 meters, 2 meters or 70 cm..

If you were trying to work rare DX on either of those bands, you would want to use the best possible coax with the lowest loss, and if you went to the expense to put up a tower and a stacked beam antenna array to work those bands, you would want hardline to feed those antenna's..

That is the purpose of hardline - not to feed a HF antenna!

On 7/1/2014 8:54 PM, wrote:
On Tuesday, July 1, 2014 1:51:23 PM UTC-5, FBMboomer wrote:

I am afraid we are all guilty of that at times. I just bought a pixel

magnetic loop receiving antenna. At first blush I thought it was great.

Then I put together an A-B switch so that I can make a well thought out

review for e-ham. The loop has some advantages, especially during

electrical storm noise. However, it does not come close to equalling the

performance of a horizontal loop cut for the right frequency.

What do you mean by performance? You will have trouble getting a decent
null using a horizontal loop. And the easily steerable nulls are 90% of the
reason to use a small loop.
But I only use small loops on low frequencies.. IE: LW to about 2.5 mhz or
so.. AM-BC more than anything, but I've used it on 160m at times.
A small loop can make an offensive ground or space wave signal disappear.
OK at night, but they are not near as effective nulling a sky wave signal
as a ground wave.


By performance, I mean the readability of a received signal. The signal
to noise ratio.

What I was trying to explain also was that my 75 meter horizontal full
wave loop does not receive as well on 20, 15, and 10. Generally!

When I operate on 20, 15, and 10, I use the pixel loop for receive. I
get a better signal to noise ration on these higher frequencies. I have
no idea why.

40 meters is kind of a crap shoot. The 75 meter loop might work better
for receive or the magnetic loop. That is one of the reason I made an AB
switch.

I do not know, but I can surmise that my receive on 75 would be better
on the magnetic loop if I was using a dipole for my antenna. I had a
dipole up at my lot a few years ago. The noise level in town was
horrendous. It was locking me out of using 75 meters. So I am now
comparing the pixel magnetic loop to a full size horizontal loop. This
may be kind of an unfair comparison. Most people probably would be
judging its improved performance over a dipole. I am currently unable to
make that kind of AB comparison. I took my dipole down in favour of the
full wave loop. The performance comparison between the dipole and loop
was profound. (meaning at least 10 db better S/N.

And yes, BC band performance is better than my 75 meter loop.

On Thursday, July 3, 2014 4:20:56 PM UTC-5, FBMboomer wrote:


By performance, I mean the readability of a received signal. The signal

to noise ratio.



What I was trying to explain also was that my 75 meter horizontal full

wave loop does not receive as well on 20, 15, and 10. Generally!

It should be OK. But the pattern is going to change for each band,
and having modeled that antenna, most of the higher bands don't really
have a low angle pattern. But good enough for general use I guess.
But then you also have to consider if any decoupling problems, and
local shack noise being piped up and back down to the radio.
Only the operator can judge what any issues might be.




When I operate on 20, 15, and 10, I use the pixel loop for receive. I

get a better signal to noise ration on these higher frequencies. I have

no idea why.

Like I say, could be any number of reasons, from antenna pattern, to
excess shack noise due to decoupling issues. etc..



40 meters is kind of a crap shoot. The 75 meter loop might work better

for receive or the magnetic loop. That is one of the reason I made an AB

switch.

Handy to have.. I have several.. I usually keep one of those small ones
in my trunk for portable use.




I do not know, but I can surmise that my receive on 75 would be better

on the magnetic loop if I was using a dipole for my antenna.


I don't know what you mean by this. It's not going to change if you
change the full size antenna.

I had a

dipole up at my lot a few years ago. The noise level in town was

horrendous. It was locking me out of using 75 meters. So I am now

comparing the pixel magnetic loop to a full size horizontal loop. This

may be kind of an unfair comparison. Most people probably would be

judging its improved performance over a dipole. I am currently unable to

make that kind of AB comparison. I took my dipole down in favour of the

full wave loop. The performance comparison between the dipole and loop

was profound. (meaning at least 10 db better S/N.

Normally there shouldn't be much difference between the dipole
and horizontal loop. I've run both, and I never did see that much
difference. If you had less local noise, it was probably sort of a fluke
thing where the pattern of the loop just happened to be what you wanted for
that direction and angle to the noise source.
The sky wave patterns are pretty close overall. In fact, I found them
so close in performance, I quit using the loops because they take more
wire, and more of a hassle to string up and keep in the air.
Also the dipole will give me max current at the apex, which on mine is
always the highest point of the antenna.


And yes, BC band performance is better than my 75 meter loop.

That is what I mainly use mine for. I have a couple of them. One
is a round circle 16 inch dia loop. The other is a diamond that is
48 inches on each side. It's PVC, and stands on the floor in a
rotatable stand.

My loops cost me very little..
This is the basic design I use for the PVC loops.
http://home.comcast.net/~nm5k/loop5.jpg

I do not know, but I can surmise that my receive on 75 would be better

on the magnetic loop if I was using a dipole for my antenna.


I don't know what you mean by this. It's not going to change if you
change the full size antenna.


What I mean is that I once had a 120 foot dipole for 75 meters. It was
pretty damn noisy. I think that if I had it again to compare to the
pixel loop for receive, I am guessing that the pixel loop would have a
better S/N than the dipole. Just a guess.

On Thursday, July 3, 2014 6:30:35 PM UTC-5, FBMboomer wrote:

What I mean is that I once had a 120 foot dipole for 75 meters. It was

pretty damn noisy. I think that if I had it again to compare to the

pixel loop for receive, I am guessing that the pixel loop would have a

better S/N than the dipole. Just a guess.

Sounds normal to me, unless you were picking up shack noise.
Noise is RF the same as any other signal. It follows the same rules.
Properly functioning antennas should pick up a lot of noise if the
noise is there to be received. If they don't, they are not very good
antennas. Or at least as far as atmospheric noise.
If the noise is atmospheric, I suspect the s/n ratio of the small
loop would not be that much better than the dipole or loop. You can't
null general atmospheric noise, so the small loop has no real advantage
in that case.