MA5B background noise
 

I have finally got my Cushcraft MA5B up in the air. But I am very
disappointed with it.

Is it normal for this antenna to have a lot of background noise behind
strong signals 9+?

The reason I ask is that I also own a cobwebb antenna and the side by side
comparison between them, there is no background hiss on the same strong
signals on the cobwebb S4 - 9+ but there is on the same signal on the MA5B
and it is enough to make listening on the MA5B very unpleasant even at S9+.

Is this normal?

73 Andy

MA5B background noise
 

Andy,
This is pure speculation so take it that way. I've noticed that
any antenna with 'sharp points' associated with it has typically been
noisier than antennas without those sharp points (capacity hats in
this case). That's certainly not 'definitive' in any way, so...
speculation. Also, considering where those cap-hats are mounted,
using a very smooth huge ball instead of those 'sharp-points' is sort
of dumb. So they did the best they could, right?
- 'Doc


(Completely beside the point. Once used a very large metal ball as a
capacitive hat on a mobile antenna. Worked fine sitting still. Not
very broad banded, but certainly shorter than the usual whip.
Absolute catastrophe when trying to drive! Didn't last long at all.)

MA5B background noise
 

wrote:
This is pure speculation so take it that way. I've noticed that
any antenna with 'sharp points' associated with it has typically been
noisier than antennas without those sharp points ...

Not speculative at all. Corona loves sharp points.
--
73, Cecil http://www.w5dxp.com

MA5B background noise
 

On Jul 20, 5:23*am, "Andy" wrote:
I have finally got my Cushcraft MA5B up in the air. But I am very
disappointed with it.

Is it normal for this antenna to have a lot of background noise behind
strong signals 9+?

The reason I ask is that I also own a cobwebb antenna and the side by side
comparison between them, there is no background hiss on the same strong
signals on the cobwebb S4 - 9+ but there is on the same signal on the MA5B
and it is enough to make listening on the MA5B very unpleasant even at S9+.

Is this normal?

73 Andy

Dunno. Doesn't really make sense.. As far as receive, there should be
little difference between the two as far as s/n ratio.
I'm not sure if I'm buying that it's corona buildup. That would
depend on your climate, wx, etc..
Being as you seem to notice it most on the strongest signals,
I'd have to ask one thing first.
Is your noise blanker on?

MA5B background noise
 

No. The noise blanker is off.


Andy


wrote in message
...
On Jul 20, 5:23 am, "Andy" wrote:
I have finally got my Cushcraft MA5B up in the air. But I am very
disappointed with it.

Is it normal for this antenna to have a lot of background noise behind
strong signals 9+?

The reason I ask is that I also own a cobwebb antenna and the side by side
comparison between them, there is no background hiss on the same strong
signals on the cobwebb S4 - 9+ but there is on the same signal on the MA5B
and it is enough to make listening on the MA5B very unpleasant even at
S9+.

Is this normal?

73 Andy

Dunno. Doesn't really make sense.. As far as receive, there should be
little difference between the two as far as s/n ratio.
I'm not sure if I'm buying that it's corona buildup. That would
depend on your climate, wx, etc..
Being as you seem to notice it most on the strongest signals,
I'd have to ask one thing first.
Is your noise blanker on?

MA5B background noise
 

On Sun, 20 Jul 2008 11:23:02 +0100, "Andy"
wrote:

I have finally got my Cushcraft MA5B up in the air. But I am very
disappointed with it.

Is it normal for this antenna to have a lot of background noise behind
strong signals 9+?

The reason I ask is that I also own a cobwebb antenna and the side by side
comparison between them, there is no background hiss on the same strong
signals on the cobwebb S4 - 9+ but there is on the same signal on the MA5B
and it is enough to make listening on the MA5B very unpleasant even at S9+.

Is this normal?

73 Andy

I will place my bet on a bad connector. How hard is it to swap
feedlines?
John Ferrell W8CCW

MA5B background noise
 

I've swapped the feed line over and its still the same.

When I put the antenna together I made sure all connections where good and
the analyser gave a good match on the frequencies I want to use.

I did use some conductive grease for the first time on the antenna. Wonder
if the grease is the problem or maybe this antenna just picks up a lot of
background hiss.

Andy


"John Ferrell" wrote in message
...
On Sun, 20 Jul 2008 11:23:02 +0100, "Andy"
wrote:

I have finally got my Cushcraft MA5B up in the air. But I am very
disappointed with it.

Is it normal for this antenna to have a lot of background noise behind
strong signals 9+?

The reason I ask is that I also own a cobwebb antenna and the side by side
comparison between them, there is no background hiss on the same strong
signals on the cobwebb S4 - 9+ but there is on the same signal on the MA5B
and it is enough to make listening on the MA5B very unpleasant even at
S9+.

Is this normal?

73 Andy

I will place my bet on a bad connector. How hard is it to swap
feedlines?
John Ferrell W8CCW

MA5B background noise
 

On Jul 23, 3:34*am, "Andy" wrote:
I've swapped the feed line over and its still the same.

When I put the antenna together I made sure all connections where good and
the analyser gave a good match on the frequencies I want to use.

I did use some conductive grease for the first time on the antenna. Wonder
if the grease is the problem or maybe this antenna just picks up a lot of
background hiss.

Noise is RF the same as any other signal. The only exception would
be bad connections, etc that cause "locally generated" noise.
You need to find out if the source is received, or from a local
problem.
The SWR means little as far as receive. Any difference in level
due to SWR changes should be very small, and it would not effect
the s/n ratio if it did.
Does rotating the antenna vary the level of the noise? If so, the
noise is most likely received. You should be able to semi null
it out using the right direction if this was the case.
I doubt the element connections are the problem, or you would
see sudden spikes in the SWR when the connections flaked out.
What band is this on?
At this point just not enough info to tell what the deal is.
I could tell a lot more if I heard it. Can you record a sample
and post it somewhere?
Like I say, there should be little if any real difference in s/n
ratio if both antennas are pointed in the same direction.
Even if one had more gain in that direction, or was more
efficient overall, this would not effect the s/n ratio.
Noise and desired signals should increase in a linear
fashion.
IE: If antenna A receives the base noise level at S5, and the
desired signal is S8, and then you switch to antenna B
and the base noise is S7, and the desired signals are S9+,
they should still "sound" the same through the speaker.
The noise shouldn't seem any louder on antenna B, as
the desired signals and noise increase at an equal level.
This is why I say overall, it doesn't make much sense.
The reason I asked about the noise blanker is they
really degrade the dynamic range when strong signals
are present, and many overlook this while trying everything
else in the book. But.. A NB usually causes more of a
distorted audio sound, not static.
Do you get this same static when the band is "dead"?
That would tend to point to a pretty close noise source.
Either locally generated by bad connections, etc, or a
noise source nearby that is received normally.
But like I say, if you receive the noise, you should be
able to effect the level by turning the antenna.

MA5B background noise
 

Andy wrote:
I've swapped the feed line over and its still the same.

When I put the antenna together I made sure all connections where good and
the analyser gave a good match on the frequencies I want to use.

I did use some conductive grease for the first time on the antenna. Wonder
if the grease is the problem or maybe this antenna just picks up a lot of
background hiss.

Andy

The instruction manual for the antenna doesn't make it real obvious how
the feedline attaches, but it looks to me like the antenna doesn't have
a low DC resistance - like a loop would, for example. It's probably
reasonable to expect this type of antenna to be noisier than a loop. I
think Butternut attaches the feedline in a similar fashion on their
HF6V, but puts an air core choke (from memory, 15-20 turns, 14 awg,
approx 1" dia x 2.5" long) across the feedpoint. That may just be for
noise because the antenna seems to have the same performance with, or
without it. Perhaps you could try the same with the MA5V.

I think what the OP was getting at is the noise should be a lot louder
with just the center conductor attached to the radio, and then get
quieter when you thread the barrel on. If it doesn't do that, then
there may be a connectivity problem somewhere.

ac6xg

MA5B background noise
 

The noise stays the same when I turn the beam.

I will try to get a recording done this weekend if I can.

I just pulled out the PL259, so just the canter pin on the PL259 on the
canter fed dipole was connected
and the noise increased with the signal and then dropped when the PL259 was
screwed back in. I had the same on the Cobwebb.

When I did this on the MA5B the 10, 12, 15 and 17 meter bands did the same ,
on 20 meters it was different. When I pulled out the PL259 so just the
canter pin of the PL259 was connected the noise dropped and with the PL259
screwed in
fully the noise went up. The opposite to what I thought would happen after
trying this out on my other antennas.

Andy


"Jim Kelley" wrote in message
...
Andy wrote:
I've swapped the feed line over and its still the same.

When I put the antenna together I made sure all connections where good
and the analyser gave a good match on the frequencies I want to use.

I did use some conductive grease for the first time on the antenna.
Wonder if the grease is the problem or maybe this antenna just picks up a
lot of background hiss.

Andy

The instruction manual for the antenna doesn't make it real obvious how
the feedline attaches, but it looks to me like the antenna doesn't have a
low DC resistance - like a loop would, for example. It's probably
reasonable to expect this type of antenna to be noisier than a loop. I
think Butternut attaches the feedline in a similar fashion on their HF6V,
but puts an air core choke (from memory, 15-20 turns, 14 awg, approx 1"
dia x 2.5" long) across the feedpoint. That may just be for noise because
the antenna seems to have the same performance with, or without it.
Perhaps you could try the same with the MA5V.

I think what the OP was getting at is the noise should be a lot louder
with just the center conductor attached to the radio, and then get quieter
when you thread the barrel on. If it doesn't do that, then there may be a
connectivity problem somewhere.

ac6xg