Hi;
Just wondering how high your noise level is before the mfj unit
and how much of a difference it makes? I have turned off the
things I suspect would be a problem and it makes no difference.
Without the preamp the noise is s 5 with the receive preamp on it
gets far worse. Its just not pleasant to listen to unless
someone is s 9. Thought a larger external speaker would help but
no success. richard
sent from my braille note
----- Original Message -----
From: eric oyen <[log in to unmask]
To: [log in to unmask]
Date sent: Sat, 1 Feb 2014 18:05:35 -0700
Subject: Re: Low Pass Filter
well,
the situation here is a bit close. I have 12.6 Kv lines directly
behind =
the hose. THe neighbors have outdoor florescent lights (and
there are =
even 2 bug zappers). I have checked and there are at least 14
wi-Fi =
access points within 400 feet of me. THe house itself has 2 AP
devices, =
about 300 feet of LAN cable, 2 switches and 6 computer systems
(the room =
mates have 3 desktop systems). I have 3 laptop machines, 2 of
which are =
turned off. Half the lights in here are of the tube variety
(those =
stupid cheap made "green lamps"). all of these make some noise.
As a =
result, I also have to have an MFJ 2500 series antenna noise =
cancellation unit in operation here just to remove all the
electrical =
noise. THe power lines are the worst of it.
Basically, I am using every trick I can find to reduce or
eliminate =
noise before it hits my radio.
-eric
On Feb 1, 2014, at 5:49 PM, John Miller wrote:
I actually never have lived in a place with a lot of noise.
It's =
funny,=20
when I first was a ham, I was living with my parents, in the
woods =
pretty=20
much with over a hundred feet between houses, well over 100 feet
and =
all=20
woods behind me. Next place, in a neighboring town I was in an
=
apartment in=20
the center of town, surrounded in a factory, houses, other
businesses, =
a=20
place that converts vans to wheel chair vans and works on them,
still =
never=20
had any noise for what ever reason and there you could about
reach out =
and=20
touch the neighbors. Now I'm in a trailer park and we're not
much =
further=20
away form each other I have a light off and on buzz here that my
noise=20=
blanker takes out and other than that, again very quiet. 2
meters I =
have=20
noise but I couldn't care less about that and even that is rare.
I =
don't=20
know why I'm that lucky. I spent 2 months with my in-laws at
one =
point,=20
there, I had a +40 noise level from 160 through 70 CM, I could
get on =
GMRS,=20
and 900 MHz from there, that was about it and no filtering
remotely =
helped=20
that but that was an area with all businesses and apartments
above =
them once=20
in a while.
----- Original Message -----=20
From: "eric oyen" <[log in to unmask]
To: <[log in to unmask]
Sent: Saturday, February 01, 2014 7:00 PM
Subject: Re: Low Pass Filter
=20
=20
the funny thing is that low pass filters operate
bi-directionally. If =
=3D
your radio produces harmonics that interfere above its normal =
operating =3D
range, then mix down products from sources above HF would also
cause =
=3D
interference on HF. THese mix down products are often caused by
=3D
interactions within the first stage of the IF in your radio.
SO, =
using a =3D
filter eliminates a lot of that from getting to your radio (thus
=3D
reducing or eliminating the problem).
=20
I have an FM radio station transmitter site less than 3 miles
from me =
=3D
producing several thousand watts. without the filter, I hear
what =
sounds =3D
like FM modulated signals in a couple of bands. I put the
filter in =3D=
place, and those signals disappeared. THere are other sources
(such =
as a =3D
wireless Access point, LAN switches and cable modems'DSL modems
that =
=3D
produce signals that can show up in HF directly. Filtering
these is a =
=3D
bit harder. I am having to use ferrite beads on the power leads
and =
also =3D
on the LAN cables to try and minimize some of these issues. I
have =
only =3D
been partially successful. I still get a lot of birdies in the
10 =
meter =3D
band (around 28.5). I am going to acquire a portable shortwave
=
receiver =3D
and try to track these signals to their source and see what I
can do =
to =3D
remove them.
=20
-eric
=20
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