Follow up on Transfer Impedance
 

After some correspondence with Charles Counselman, W1HIS, I have been
made aware of serious short comings in my testing procedure. Charles
pointed out that I could not make accurate enough to insure that what I
was
measuring was in fact TI and not common mode effect due to micro
imbalances
in my equipment.

Upon further thought and reflection, the fact that placing a number of
ferrite beads
along coax stops the "ingress" suggests that Charles is correct and
that it is
common mode effects I am measuring.

From some simple tests to check the balance of my BALUNs, I am
convinced that
I have errors of at least 15%. Even my trusty R390's balanced input is
far from a
"perfect" balance over the 5000KHz to 30MHz frequency range.

Charles Counselman's research into common mode effects and how to
reduce
it are a God send to my receiving pursuits.
http://www.yccc.org/Articles/W1HIS/C...S2006Apr06.pdf
I am grateful for his help in understanding where I went wrong. And I
am sorry
for any confussion I may have caused.

For a very inexpensive aid in RFI/EMI reduction, check out
http://www.hosfelt.com/,
scroll down to filters and take a look at the CURTIS, Mfg.# -
F1600CA03, 3A filters.
These have been a great help in stomping RFI before it gets started

Terry

Follow up on Transfer Impedance
 

wrote:
After some correspondence with Charles Counselman, W1HIS, I have been
made aware of serious short comings in my testing procedure. Charles
pointed out that I could not make accurate enough to insure that what I
was
measuring was in fact TI and not common mode effect due to micro
imbalances
in my equipment.

Upon further thought and reflection, the fact that placing a number of
ferrite beads
along coax stops the "ingress" suggests that Charles is correct and
that it is
common mode effects I am measuring.

From some simple tests to check the balance of my BALUNs, I am
convinced that
I have errors of at least 15%. Even my trusty R390's balanced input is
far from a
"perfect" balance over the 5000KHz to 30MHz frequency range.

Charles Counselman's research into common mode effects and how to
reduce
it are a God send to my receiving pursuits.
http://www.yccc.org/Articles/W1HIS/C...S2006Apr06.pdf
I am grateful for his help in understanding where I went wrong. And I
am sorry
for any confussion I may have caused.

For a very inexpensive aid in RFI/EMI reduction, check out
http://www.hosfelt.com/,
scroll down to filters and take a look at the CURTIS, Mfg.# -
F1600CA03, 3A filters.
These have been a great help in stomping RFI before it gets started

Terry

Terry -

Thanks, good info. The good news is the solution works for either
reason.... although Devoldere's/Bryants chokes remain a terrific tool
as well as the distributed beads.

Bob

Follow up on Transfer Impedance
 

Bob wrote:

Terry -

Thanks, good info. The good news is the solution works for either
reason.... although Devoldere's/Bryants chokes remain a terrific tool
as well as the distributed beads.

Bob

Don't forget to look at John Bryant's pdf showing another way to build
a
an effective common mode choke for receiving applications. Bryant's
torroid will over heat with as little as 10W on Tx!

http://www.dxing.info/equipment/coax_leadin_bryant.pdf

I have found that the most effective way to reduce your QTH noise level
is:
Step 1: Use a portable SW receiver, I use a DX398, with a simple loop
to check every circuit, and every device in your home and outbuildings.
Be certain to check everything. Doorbell, Smoke alarm, water heater,
PIR lights, coldcathode florescents lamps, telephone devices, TVs, VCRs
DVD/CD players, audio cassette decks(I had a pioneer that had a nasty
spur on ~5.1 @ S9), battery chargers, well you get the idea. Check
every
thing. A lot of the RF noise, in every case I have worked with, comes
from
within or very close to your home.
Step2:After finding and logging the noise, start fighting it. The
Curtis RFI
filters I mentioned are easily made into "things" to go between the AC
mains
and the device. They use PC style IEC power cord for inputs, so it will
be
useful to gather at least one per filter. For those devices with it
will take two
cords per filter, one for the AC in and another that you simply cut the
male
end off and solder to the filter's outputs. Other devices will need the
IEC input
cord and either have the device hard wired to the filter output, or the
use of a
suitable female connector.

I found it helpful to add a 0.1uF 1KV disk cap across the filter's
output. I
used liquid tape to unsulate the filters hot end, and in most cases I
used
large diameter heatshrink to protect the whole filter assembly. Regular
electrical tape would work, and the really industrious can build the
filters
into mini-boxes. For our HiFi/"Home Theatre" center I built my own
fitlered
power "strip" with 10 RFI filters in one metal box with 1 heavy AC
input
cord that I fan out to each filter input. I use some 1" square females
because
I had a chasies punch. I got fancy and added some relays to allow the
power
to be remoted. Most modern devices don'e have real power switches as
something
is always left alive, so by really turning everything off I reduce the
off state noise
and as important, reduce the chances of AC line spikes damaging
something.

For Wall Wart, I try to pick RF quite units to begin with, then add
ferrite on the
output, and in extreme cases I crack the case open and bypass the
diodes
with 1000pF/0.0001uF caps. As Telemon pointed out, it would be more
effective
to design and build a snubber for that specific circuit, but I have
found the 1000pF
to almost always work very well.

Be sure to check the phone line at the NID/demarcation box. A friend
had
nasty RFI coming down the phone line. With more DLS being added all the
time, I check mine once a week or anytime I hear a new constant RFI
source.
Ferrite will keep it out of your home.

Use a real RF ground and do not rely on the house hold electrical
ground.
Use good quality coax.
If you are using a "wire" antenna, be certain a matching transformer.
If you are using a non-dipole acitve antenna you will almost certainly
have
to use a lot more ferrite then you first would think. Active dipoles
are
much more imune, but still need some common mode filtering.

!!ALL of the active non-dipoles that I have played with require a very
good
ground at the base of the antenna.!! Good means at least a 4' ground
rod into moist soil. 8' is better, but awkward to move. I plan on using
a 4' until I find the quitest spot then switch to an 8' rod.


Sorry for the length of this, but I thought you mind find it useful.

Terry

Follow up on Transfer Impedance
 

wrote:

Don't forget to look at John Bryant's pdf showing another way to build
a
an effective common mode choke for receiving applications. Bryant's
torroid will over heat with as little as 10W on Tx!
__________________________________________________ ________________________
That's what I meant by Devoldere/Bryant, but I wasn't clear enough...
Devoldere's book (ARRL Low Band DXing) is where Bryant & Nelson got the
info from originally.
__________________________________________________ ________________________

http://www.dxing.info/equipment/coax_leadin_bryant.pdf

I have found that the most effective way to reduce your QTH noise level
is:
Step 1: Use a portable SW receiver, I use a DX398, with a simple loop
to check every circuit, and every device in your home and outbuildings.
Be certain to check everything. Doorbell, Smoke alarm, water heater,
PIR lights, coldcathode florescents lamps, telephone devices, TVs, VCRs
DVD/CD players, audio cassette decks(I had a pioneer that had a nasty
spur on ~5.1 @ S9), battery chargers, well you get the idea. Check
every
thing. A lot of the RF noise, in every case I have worked with, comes
from
within or very close to your home.
Step2:After finding and logging the noise, start fighting it. The
Curtis RFI
filters I mentioned are easily made into "things" to go between the AC
mains
and the device. They use PC style IEC power cord for inputs, so it will
be
useful to gather at least one per filter. For those devices with it
will take two
cords per filter, one for the AC in and another that you simply cut the
male
end off and solder to the filter's outputs. Other devices will need the
IEC input
cord and either have the device hard wired to the filter output, or the
use of a
suitable female connector.

I found it helpful to add a 0.1uF 1KV disk cap across the filter's
output. I
used liquid tape to unsulate the filters hot end, and in most cases I
used
large diameter heatshrink to protect the whole filter assembly. Regular
electrical tape would work, and the really industrious can build the
filters
into mini-boxes. For our HiFi/"Home Theatre" center I built my own
fitlered
power "strip" with 10 RFI filters in one metal box with 1 heavy AC
input
cord that I fan out to each filter input. I use some 1" square females
because
I had a chasies punch. I got fancy and added some relays to allow the
power
to be remoted. Most modern devices don'e have real power switches as
something
is always left alive, so by really turning everything off I reduce the
off state noise
and as important, reduce the chances of AC line spikes damaging
something.

For Wall Wart, I try to pick RF quite units to begin with, then add
ferrite on the
output, and in extreme cases I crack the case open and bypass the
diodes
with 1000pF/0.0001uF caps. As Telemon pointed out, it would be more
effective
to design and build a snubber for that specific circuit, but I have
found the 1000pF
to almost always work very well.

Be sure to check the phone line at the NID/demarcation box. A friend
had
nasty RFI coming down the phone line. With more DLS being added all the
time, I check mine once a week or anytime I hear a new constant RFI
source.
Ferrite will keep it out of your home.

Use a real RF ground and do not rely on the house hold electrical
ground.
Use good quality coax.
If you are using a "wire" antenna, be certain a matching transformer.
If you are using a non-dipole acitve antenna you will almost certainly
have
to use a lot more ferrite then you first would think. Active dipoles
are
much more imune, but still need some common mode filtering.

!!ALL of the active non-dipoles that I have played with require a very
good
ground at the base of the antenna.!! Good means at least a 4' ground
rod into moist soil. 8' is better, but awkward to move. I plan on using
a 4' until I find the quitest spot then switch to an 8' rod.


Sorry for the length of this, but I thought you mind find it useful.

Terry

Not too long for the info given! I am working on these exact things
courtesy of information passed to me by your friend Will. You didn't
know you were helping somebody in Syracuse, NY, but you have been.
Will has been kind enough to send me a lot of details on how you showed
him your "noise audit" procedure and ways to kill the noise. I just
received 20 of the Curtis filters from Hosfelt.
You helped Will and a bunch has "trickeled down" to me. Thank you very
much.

Bob

Follow up on Transfer Impedance
 

Bob wrote:
Not too long for the info given! I am working on these exact things
courtesy of information passed to me by your friend Will. You didn't
know you were helping somebody in Syracuse, NY, but you have been.
Will has been kind enough to send me a lot of details on how you showed
him your "noise audit" procedure and ways to kill the noise. I just
received 20 of the Curtis filters from Hosfelt.
You helped Will and a bunch has "trickeled down" to me. Thank you very
much.

Bob

Glad to have helped. As people have helped me over the years,
I try to pass my bits of useful knowledge on to those who can
use them.

An often overlooked source of ferrite material is computer "stuff".

Keyboards, and mouses often have small ferrite beads inside.

VGA monitors often have big ferrite beads on the cable at the HD15
and right inside the monitor. They also often have other ferrite beads
inside and the better ones they have pretty good single stage RFI
filters on the power lead.

The switch mode power supplies have at least one, and often several,
ferrite toroids.

Even junk like VCRs and DVD players often have ferrite on the AC mains
and the PS unit often has ferrite cores.

Dead light dimmers are also good sources of ferrite torroids.

I have made it a point to scavenge every piece of ferrite I can lay my
hands on.

As W1HIS points out transmitting requires the selection of the correct
ferrite. But for receiving we want extra lossy ferrite. The lossier the
better.
Lossy ferrite wastes power by absorbing it and getting hot. And if your
receive ferrite gets hot you are too darn close to a MW power house!

Even iron dust cores do a suitable job of suppressing common mode
on coax, power lines and telephone lines.

And don't be saddened when you find the noise reduction process is
multi step. The first pass will get the big RFI sources, each succesive
pass will reduce the next level of RFI.

Another trick is to find some GE MOVs and disassemble them and add
a 1000pF cap across the hot to neutral and maybe hot to ground. And to
add a 1000pF across the light switches. This last step will stop, or
greatly
reduce the "pop" as lights are turned on or off. On unexpected
advantage
of adding MOVs across every circuit was the reduction of damage from
nearby lightning strikes.

You might find it usefull to make a sketch of your home showing every
outlet, switch and light fixture. Number them. Don't forget the smoke
alarm and door bell. Then number your circuit breakers and make a chart
showing which outlet is controlled by which breaker. Very handy when
non RFI troubles pop up.

Terry

Follow up on Transfer Impedance
 

Follow up on Transfer Impedance
 

wrote:
Glad to have helped. As people have helped me over the years,
I try to pass my bits of useful knowledge on to those who can
use them.

Thanks again!

In your discussions with Charles Counselman, has he added anything yet
to his document? He had some blank sections that were to come later,
just wondering if he mentioned anything.

Bob

Follow up on Transfer Impedance
 

Bob wrote:
wrote:
Glad to have helped. As people have helped me over the years,
I try to pass my bits of useful knowledge on to those who can
use them.

Thanks again!

In your discussions with Charles Counselman, has he added anything yet
to his document? He had some blank sections that were to come later,
just wondering if he mentioned anything.

Bob

We covered many topics, but it would be hard to extract anything to
post here.
He does intend to post info on his search antenna. A simple 20 turn
loop wound
on a pill bottle will suffice to get you started.

Is your Email valid? I will ask Charles if it is OK to forward you his
B-field noise
sensing diagram.

Depending on how serious, or demented, you are, you might benifit from
rereading
my prior posts on RF hunts. The 20 turn loop is good for finding noisy
devices. A
smaller loop made from a salvaged 100uH axial ferrite inductor is great
for sniffing
around inside a device to find the exact noise source. I built mine in
a old
Sharpie dry marker case. While I added BNC females connectors to all my
probes
because I was in the process of trading for a spectrum anylzer and
wanted to
be able to use my probes with that test gear, a cheaper and more
effective option for
most people would be to use ~3' of RG174 terminated in the coorect
connector for
your noise sniffing receiver. I choose to use a DX398 because I have
one and becuase
it it reasonbly well shielded and does a good job as a sniffer.

Maybe 99% of devices radiate RFI over a very wide frequency range.
Digital noise
tends to be very broadband. Every so often you will find a device that
produces a
strong signal on a specific frequency and does not radiate general RFI.

One common frequency is 3.58MHz, US color refference burst. I had one
early Apex
DVD that I never could quiten down enough to live with. I suppose I
ought to dig through
my notes and list the more common "CPU' frequencies. As NTSC goes away,
and
TV horizontal moves away from 15.73426KHz, (from a grass valley "NTSC
Studio
Timing:") the harmonics that we are used to at ~15.73KHz increments
will vanish.
ATSC can be a can of snakes. (http://www.atsc.org/standards.html)
Butfrom what I
have seen so far ATSC will bigger VHF/UHF RFI issue.

Plasma big screens have their own nasty noise signature. LCDs are cold
cathode
florescent illumintated and the drive oscillators tend to be in the
35~50KHz range
and are fairly well shielded and (most) don't radiate too badly.Perhaps
the best thing
for modern SWLs is the move from over the air TV to cable and
satellite. Older tube
sets had very poor internal shielding and radiated sweep and color
burst back out
the antenna and that 300 ohm ribbon lead made a pretty effective
antenna.

Good hunting

Terry

Follow up on Transfer Impedance
 

Follow up on Transfer Impedance
 

Terry -

Have you found any specific wall warts that you would consider
reasonably electrically quiet?

Thanks again, Bob

Follow up on Transfer Impedance
 

Bob wrote:
Terry -

Have you found any specific wall warts that you would consider
reasonably electrically quiet?

Thanks again, Bob

Even with wall warts that appear to be identical, the RFI varies a
great deal.
I go to the local good will store once every couple of weeks with my
trusty
DX398 and check out their constantly changing stock for quite ones.
Stay away from switch mode wall warts. They are very light weight and
are RFI demons.

I try to keep a selection on hand of the more common voltages and try
to
limit my purchases to those that are fastened with screws.

At home I have modifed nearly everything in the radio room to run from
+12V so I
only have to worry about the one big supply. It also makes operation
during power
outages easier as I have several GellCells on constant float ready to
take over
when the grid goes down.

I will try to assemble/edit down a list of usefull links and email, or
get Will to
email, them to you. The r2000swl/swler accounts are dead. Too much hate

filled spam.

What type receiver are you using?
What type antenna(s)....
What is your special interest...

It is hard to overestimate how much a good ground can improve every
situation.
"Good" is difficult to define, but in my mind it is much more then a
single
8' ground rod or a cold water pipe. A triad of three 8' ground rods
arranged in
a equalateral 12" triangle, interconnected by #8 solid copper wire is a
good
start. An alternative can be made with one 8' rod, and ~20' of soft
copper
tubing buried at lease a foot. The use of balanced antennas makes the
ground less critical. I am not a big fan of loops, but I have found
that active,
broadband dipoles, in the right places can reduce the need of a good
ground
nearly completly. And while I don't care much for loops, many first
class
DXers swear by them. Good, well balanced loops don't require much in
the
way of a ground.


Terry

Follow up on Transfer Impedance
 

Follow up on Transfer Impedance
 

Bob wrote:
wrote:
What type receiver are you using?
I have an Icom R75 and an Eton E1 and E5. Going to use the E5 for
"sniffing". I had a Drake R8 I used years ago when I was recovering
from hip replacement surgery, but I sold that one time when time & $
were scarce. If I get the noise under control, I may try to scheme up
a way to get an R8B, but don't know for sure. I liked the R8 a lot
except for carousel controls, crappy feet (broke one the first week I
had it, but epoxy repair lasted as long as I had it) and underwhelming
sync derector. Hence the R8B interest. So many toys, so little time
and $!

What type antenna(s)....
Am just starting on that. Have an indoor loop that is useless with
noise, so I'm not doing a lot of listening, just learning. We recently
moved into a "condo type" single level home with a homeowners
association and antenna restrictions. We are still unpacking the
basement and I have yet to find my soldering iron and some other stuff.
Just getting shelves set up so boxes can be unpacked. I figure active
antennas are the only real option, and again that's why I have to get
the noise out.

I have looked at RF Systems, LF Engineering, DX Engineering, Wellbrook,
Dressler....

I've narrowed it down some. Ordered a PA0RDT miniwhip, cause I can
hide it anywhere and if I choke the heck out of it maybe it will work
some. Will order ferrite toroids and LMR-100 (better shielded RG 174)
maybe this week. I've looked real hard at the AMRAD and at Dallas
Lankford's latest writings, but I'm no builder. yet, anyway :-). I
found a guy that builds the AMRAD unit. He has improved the design a
bit like clamping the heat sink to the Crystalonics unit. We have to
talk more, but I think I'll have him make me something. I've asked him
about Dallas' designs, but he has been travelling and it will be a week
or so to get it talked out I guess.

What is your special interest...

AM, tropical bands, and general shortwave.

It is hard to overestimate how much a good ground can improve every
situation.

I will hire someone to put a couple of 8 ft. ground rods near our deck,
and another one near our service entrance. The service panel is on one
side of the basement, and it connects to the incoming water line which
of course is at the opposite side of the basement. I thought I'd have
two rods at the deck connected by copper line similar to what Will did
and carry it (copper line) around the side to the ground rod near the
service entrance and a #2 or maybe 00 into the basement bonded to the
ground wire at the panel. That should improve the service ground too.
If we just do a slit like cable company does, I should get no heat from
the association, but the line probably won't be but a few inches deep.
I'm doing some work for the association, so hopefully have some good
will...

I am not a big fan of loops, but I have found
that active,
broadband dipoles, in the right places can reduce the need of a good
ground
nearly completly.

Noted.

And while I don't care much for loops, many first
class
DXers swear by them. Good, well balanced loops don't require much in
the
way of a ground.

I think active verticals or dipoles are more acceptable (mounted on or
near deck railing) than a loop visually. I doubt I could finese a loop
past the association. In a pinch, the AMRADs could mount 45 deg on
railing and be small flag poles.

This has gotten long, but thanks so much for your time.
Bob


For bang for the buck the North Country Active antenna works pretty
well.
According to Yodar from RHFs Yahoo antenna group they will assemble
it for you. It is small enough to hide and will work much better then
the
PA0RDT. In my opinnion, based on the tests that I have made, the
PA0RDT
simply doesn't have enough antenna to overcomm the internal noise in
the
active electronics. The North country would be my first choice if I
couldn't
get a Lankford, or it's near clone the AMRAD. The Real Deal LankFord is
significantly better then the AmRad. I have both. The North Country,
when
2 are connected for and active dipole similar to Dallas' summing is
almost
a great antenna. Biggest weakness comes from MW stations too close
bleeding
through. CBers close by can be a problem also.

The PA0RDT might work well enough for serious consideration with a
longer
antenna element.(and serious ferrite for common mode control and a very
good
ground) And for those who have used a PA0RDT and love it great. But I
base
my opinions on what I experience. The Wellbrook is highly praised and I
was
extremly unimpressed with it's performance. Right or Wrong I call it
like I see it.

One variation I am going to try and build of Dallas' active dipole is
to build it
like a VHF coaxial dipole. The lower element will be an outer sleeve
over a
center support member. It would be very easy to hide in plain sight,
and with
some care in routing the coax, you might get away with calling it a
bird feeder.
Hard to put into words, but I ought to be very doable.

The R8B is a SWEET receiver. I got in trade for some special advice
that saved
a former SWL a bundle of money on his custom designed home theater
system
where he was going to get ripped off for several K of wasted money for
a sloppy
design with inferrior equipement. 95% of the time anything I hear on
the R8B I
can hear on my R2000. But that other 5% of the time is heaven!

Terry

Follow up on Transfer Impedance
 

wrote:
For bang for the buck the North Country Active antenna works pretty
well.
According to Yodar from RHFs Yahoo antenna group they will assemble
it for you. It is small enough to hide and will work much better then
the
PA0RDT. In my opinnion, based on the tests that I have made, the
PA0RDT
simply doesn't have enough antenna to overcomm the internal noise in
the
active electronics. The North country would be my first choice if I
couldn't
get a Lankford, or it's near clone the AMRAD.

Thanks for reminding me of the North Country! I had seen Yodar's note
about them building him one, but had forgotten about it. I think I'd
prefer the AMRAD or Dallas' design if the builder can do, but it's
another option and only a little over $100 at that. While poking
around the North Country site after reading your message, I came across
this page in their tech section:

http://www.northcountryradio.com/Articles/actant3.htm

It is a clear, concise explanation of how and why to use a "Bryant type
choke" and a seperate ground rod on an active antenna to knock down
noise on the shield. The only critical comment I would have is they
never actually call the noise common mode noise. You could save some
typing by referring someone there :-)

One variation I am going to try and build of Dallas' active dipole is
to build it
like a VHF coaxial dipole. The lower element will be an outer sleeve
over a
center support member. It would be very easy to hide in plain sight,
and with
some care in routing the coax, you might get away with calling it a
bird feeder.
Hard to put into words, but I ought to be very doable.

My problem is that since the Homeowners Association does all lawn and
driveway maintenance, free standing things that require any extra
effort to mow or trim around are frowned upon. Bird feeders need to be
attached to home or deck.
As time goes on, and trees grow a bit, something in a tree with buried
coax may be possible.

The R8B is a SWEET receiver. 95% of the time anything I hear on
the R8B I
can hear on my R2000. But that other 5% of the time is heaven!

Yeah, right now it's on my "future budget list"...... How do you rate
its' synchronous detector vs what you have seen?

Bob

Follow up on Transfer Impedance
 

In article .com,
wrote:


Bob wrote:
Terry -

Have you found any specific wall warts that you would consider
reasonably electrically quiet?

Thanks again, Bob

Even with wall warts that appear to be identical, the RFI varies a
great deal. I go to the local good will store once every couple of
weeks with my trusty DX398 and check out their constantly changing
stock for quite ones. Stay away from switch mode wall warts. They are
very light weight and are RFI demons.

Very good observation. The supplies that are linear have transformers,
which have some weight to them are heaver than the more efficient
switching but RF noisy type.

--
Telamon
Ventura, California

Follow up on Transfer Impedance
 

Some of those cheap no good wall warts will mess up and blow out your
equipment.I have seen it happen before.
cuhulin