"Owen Duffy" wrote in message
...
"David" wrote in
news
If you own or have used the Cushcraft MA5B in the past could you let
me know what the noise floor reading is/was and the rough height of
your antenna?

I know that the noise floor will be different location to location but
it will give me some idea of what I should be looking at.

I have had mine up for a couple of years now and although the signals
increase 3-5 S points better than my Cobwebb and Dipole on receive the
noise floor has always been S7-8 on 14MHz. It is 0-1 S point on my
other two antennas. So any signal received on the MA5B less than
S9+10db has a lot of noise in there audio.
SWR is good on all 5 bands.

If the noise is received equally from all directions, then the amount of
noise power received is proportional to the average gain of the antenna
system, which is essentially, the inverse of the efficiency of the
system.

Some noise sources are not very directional, eg galactic noise. Manmade
noise could me non-directional, it just depends on the physical
distribution of those noise sources at a particular instant of time at
your location.

You can of course determine if noise is non-directional, rotate the
antenna and observe the noise level. If you want to measure ambient
noise, have a look at http://www.vk1od.net/calc/anc.htm .

I calculated the expected ambient noise due to the sources discussed in
ITU P.372-8 and documented it at
http://www.vk1od.net/measurement/noi...bientNoise.htm , you may find
it interesting. Broady, if you have a receive noise level way below that
expectation, it may be sign of an inefficient antenna system.

Owen

The noise level does not change when I turn the beam 360 deg.

I have used the Cobwebb and the Cushcraft R5 in the same location and I do
not get the same noise. The noise is also present in the audio on stronger
signals.
Its the same noise you get on a weak station, where its combined in with the
audio except I get the same noise mixed with the stronger stations audio. I
do not get this on any other antenna's apart from the Cushcraft MA5B.

Does any one have any ideas to what could be the cause of this?

73 Dave