GM Dave,
There are many elements to your problem, one of which may be your choice
of antennas. I'll begin with this. SWR IS NOT A MEASURE OF ANTENNA
PERFORMANCE! What matters are the EFFICIENCY of the antenna for
transmitting, the directional pattern in three dimensions, the ability
to HEAR other stations, and match between the rig and antenna so that it
accepts power. SWR, as measured in the shack, describes ONLY the last
of those factors. The company selling the antenna you have selected
says NOT A WORD about anything but SWR, and I saw nothing on their
website telling me anything about any matching network built into their
"black box." FWIW, $185 is a lot to spend on 130 ft of wire and a magic
box, which I would guess is most likely a transformer wound on some form
of ferrite or powdered iron core. $41 will get me 500 ft of wire, a
suitable core costs less than $10.
Second: Sadly, it is quite common for we hams to be surrounded by noise
sources, some of which are under our control and some of which are not.
Those noise sources in your living room ARE under your control, and you
should address them first. Study
http://k9yc.com/KillingReceiveNoise.pdf in text form, and
http://k9yc.com/KillingRXNoiseVisalia.pdf as slides for a talk at
Visalia a year or two ago.
Third, I strongly suggest that you STUDY and IMPLEMENT proper BONDING in
your home and station as described in my tutorial slide show on the
topic, and as described in N0AX's ARRL book on Grounding and Bonding.
Fourth, do you plan to operate (or listen seriously) on the new 630m
band or on the AM broadcast band? ONLY if the answer is Yes should you
choke noise sources in that frequency range. While many (most?) noise
sources are broadband (that is, extending from very low to very high
frequencies), we only need to choke them in the frequency range(s) where
we want to hear weak signals.
Fifth, the smartest hams who seriously want to operate or listen on
bands below 30m use some form of receiving loop antenna to minimize
noise. And this is AFTER they have put in serious effort to kill as many
noise sources as possible.
As to your question about multiple chokes -- Dave has given you the
right answer, but unless you want to seriously listen below 160M,
Fair-Rite #31 material is the only good choice.
I also suggest that you check the wiring of all the AC outlets in your
home, especially those to which anything is plugged in. Outlets are
wired by human beings, and we, as a species screw up now and then. There
are inexpensive outlet testers that will expose most wiring errors. A
decent AC voltmeter will also do the job, but takes longer. I found two
mis-wired outlets in the home I bought in W6 twelve years ago, and
MULTIPLE serious errors in grounding and bonding of the AC power system
that caused my house wiring to radiate noise coupled from the outside
power line!
The most serious issue was that the "ground" wire for the AC power,
telephone, and CATV went to a water hose faucet 40 ft from the power
entry, AND that faucet was fed by PVC pipe! The result was that the
only ground in my home was the rod driven for my ham station, which is
in the separate garage-apartment where my ham station is set up. In
addition to being illegal and unsafe, this wiring error caused noise
from outside power lines to go to ground through my ham station, which
made the ham bands VERY noisy!
73, Jim K9YC
On 9/30/2018 8:31 AM, Dave Van Wallaghen wrote:
First, thanks to all of you who replied on the list and privately. I
appreciate all the advise.
I just wanted to follow up on this as I tried a few things and I
sheepishly bring the solution to my buzzing noise problem on the low
end of the AM band and 600m in case anyone else runs into my situation.
I did run a separate AC ground back to the panel physically separating
my shack circuit from my problematic AV/TV circuit. This had no effect
what so ever. So while pondering why this noise is so prominent if my
antenna or rig is connected to the AC ground system, my inexperience
waned enough that I finally figured out what was going on. In my first
email, I failed to mention that the antenna I was using is a 80-10m
multi-band end fed from MyAntennas. This seemed like a logical choice
since it is resonant on all of the ham bands I wanted to test and does
fairly well on 160m and 600m as well.
So yes, the coax shield of the feedline of the antenna acts as the
counterpoise for this antenna, and in effect, everytime I connected
the AC ground to the rig or antenna ground, it was coupling the noise
directly to my antenna system and rig. Several turns of the feedline
through a #31 core at the rig end greatly reduces the buzzing. It
reduced the noise for S9+5 to a respectful S5-6 which is what I was
seeing when I floated the ground of the rig and antenna. I still have
a little noise between 380-480Khz that I will tweak and see if I can
eliminate all together.
This leads to my next question: I was thinking of using a #77 mix core
in series with the #31 to help here as the #77 has a higher impedance
in the lower frequencies. I may have missed it in Jim, K9YC's RFI pdf,
but does series mean the two cores together with the cable passing
through them simultaneously? Or two separately wound cores? I
apologize if this is a dumb question. I've learned a great deal
throughout this process and I might just be a little overloaded at the
moment ;-)
73,
Dave W8FGU
On September 13, 2018 14:23:44 Jim Brown <jim@audiosystemsgroup.com>
wrote:
On 9/13/2018 10:36 AM, Dave Van Wallaghen wrote:
So, my questions are: as the largest portion of this noise comes from
my TV plugged into the AV circuit, would running separate grounds for
my AV and shack circuits back to the panel help alleviate some of the
noise that I find on my shack circuit ground? Or do you think most of
it is being physically coupled? I would have tried this myself, but
while certainly doable, it will be a little work to make it happen.
Several thoughts on this.
First, RF noise from defective/poorly designed equipment OFTEN travels
on the green wire, so yes, separate green wires is a good thing.
Second, chokes to kill noise currents need to be tuned to the
frequency(ies) where you are bothered by the interference. While PROBING
for noise sources at lower frequencies can be effective, there's no need
to choke those frequencies unless you use your radio there.
Third, if the TV is a noise source, I would choke every cable connected
to it, starting with those that are likely to be the most effective
radiators, first the power cable and coax feeding it, then audio and
video cables if there are any.
I also read on the Polamar website about using #75 mix Clamp On cores
for use on frequency ranges down to 200 kHz. Is this something
applicable to my problem?
Only if you need to kill noise on the new 630M band, and only if you
wind a lot of turns. Simply clamping one or more of them onto cables is
unlikely to do much.
I'm surprised that you're hearing a lot of noise coming from an LCD TV.
The most likely source would be a poorly filtered switch-mode power
supply built into it. I would also look for other sources around the TV,
like switch-mode wall warts for various equipment, or built into other
equipment.
73, Jim K9YC
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