Thanks. I wasn't referring to a magnetic loop that uses the shield for
pickup. I was referring to the outer shield on the coax that runs from
any antenna to the shack. If you use an antenna that was chosen for its
specific directional and/or low-noise properties, and you don't isolate
There are two potential problems with this. As general rules:
1.) Grounding any antenna which is dependent on a ground system to be
resonant will maximize reradiation.
2.) Resonant elevated radials, even without an antenna connected, are
resonant and re-radiate.
3.) Things that are not
This is not encouraging news for those of us with towers already ground
and are either shunt fed or cage fed.
Shunt fed towers can be detuned, or taken out of the picture by phasing a
small sample of signals into the RX antenna.
I could try a motor driven inductor or capacitor (small) just
topic. Additionally, you seem to stress that using cheap RG-6 foil for
Beverage feedlines (apart from not being very durable over time) may be
not so wise if I am serious about common mode rejection.
RG-6 is a type of copper shield cable rarely seen, but same-size CATV and
MATV cables are
My rig (FT-dx5000) is located on a desk. Immediately under the desk is my
computer, and just above the rig is a shelf on which sits 2 flat-screen
monitors.
One of the points made in “Low-Band DXing” is the necessity of reducing
noise in the shack. The author states at page 7-75: “It is
White papers:
http://docs.commscope.com/Public/Coax101.pdf
Although the test frequency and method is not described, this shows the
difference between Quad shield and single foil and braid is 7 dB before
10,000 flexes and 13 dB after 10,000 flexes.
My measurements of F11 are at:
The subject was LMR-400 which, of course, is not flooded and uses a tinned
copper weave over aluminum foil.
Sorry. My mistake.
I thought the subject was receiving cables, related to Beverages, and common
mode noise, and that somehow a parallel was drawn to a stb measurement on
LMR400, which
Speaking of flooded coax...
I noticed something recently about at least one of my spools of flooded
quad-aluminum-shield RG-6. Since the flooding compound is only in the
outer shield (the braid right under the outer jacket), it seems possible
that under certain circumstances, water could
The inner foil usually has a plastic backing on the inside (the side
away from the braid). In the case of quad or tri-shield cable the outer
foil does not normally have a plastic coating. Remember that the outer
foil is between the braids in the case of quad-shield cable so there
needs to be
3- EMI/RFI has two components, electrical and magnetic field must be
blocked. My RX antennas has low gain and they work near RX noise floor
,that
requires a high gain preamp, my preamp has 40 db gain. Aluminum boxes
are
not enough to kill the magnetic field noise from the PC and from my 2
I was distracted for a week trying to recover a lost disk but I put the SSD
in place again yesterday. This time I wrapped the SSD in aluminium foil and
put 2 clamp on cores on the SATA cable. I fired up my system, and the extra
measures had no noticeable improvement on the birdie situation. The
I'm not disagreeing with anyone, but it is important to re-enforce how
things really behave and what actually causes problems.
Most RF noise escapes from equipment as current flowing on wiring,
either inside the box due to inadequate shielding and/or poor circuit
layout, and on external
A different company, Laird, sells three main mixes of ferrite
toroids/beads/snap-ons: LF, 28 and HF. Graphs in
http://www.lairdtech.com/WorkArea/linkit.aspx?LinkIdentifier=idItemID=3363
Laird mix 28 might be comparable to Fair-Rite 43, and Laird mix LF might
be good for 160M balun chokes.
Many years ago at 4U1ITU I found the Bird 43 grossly underestimated
the power output on 160, rather embarrassing at the temple of
regulation.
If that was the case, they had a bad slug. The rating of the Bird 43 and
standard slug is + or - 5% of full scale anywhere on the scale within the
ON4UN's book is minimally useful since his sources dont reveal the details
and appear to deliberately have misleading statements at times. Probably
to
protect their commercial endeavors.
It is not good fellowship, or good manners, to accuse someone as helpful as
ON4UN of intentionally lying
It's been there all along guys.
http://www.lairdtech.com/Products/EMI-Solutions/Ferrite-Products/Ferrite-Toroids/;
Hi Lee,
Laird does not have complete data on all of their cores. For example...
For higher power applications and to avoid heat, especially with unknown
load situations, we
For higher power applications and to avoid heat, especially with unknown
load situations, we want a core that has low loss tangent or high Q.
For good suppression, especially with unknown load situations, we want high
loss tangent and Q.
Should actually be:
For higher power applications and to
It's generally two inductors wound on a single core for common-mode
choking.
The result is that total common-mode inductance is 2*L while
differential-mode inductance cancels and equals zero.
Total common mode inductance is 1 times L, not two times L. This is because
the windings are
This MRFE6VP61K25H solid state device is catching on fast in amateur radio
circles. HF Amps next.
http://www.m2inc.com/pdf_manuals/2M-1K2.pdf
Here is the tough time with this, because I'm sure most people take device
manufacturer's data at surface value. All of this stuff, to this point of
Hi Bruce,
The new Harris Flexiva 10 KW FM band (not pulse) stereo transmitter is
not
having a heat problem with air cooling, in a reasonably small package . It
has individual modules that can be hot switched.
I'm sure Harris did a great job. The modules can be swapped while the TX is
on,
Yes, the broadcast 50 ohm load has a very low VSWR.
Harris claims that with the 75 % RF efficiency, and only 25 % heat
generation, it lets them to use air cooling.
Individual new power supply for each module.
Right. My point is people seem to be reading the data sheet for the device,
I've never experienced this before a year or so ago, when I had a Beverage
antenna melt in two from a nearby tree getting hit.
About a month ago I had about 300 feet of a Beverage just vanish from a hit
on a tree next to the wire.
Now it happened again this week, and long stretches of two
Hi Larry,
All of the links and data agree with what I found here in my measurements. I
think the real issue is some very creative marketing is being done, and the
factory data sheets can be a bit confusing. They certainly do not contain
linear data.
Here are the main points:
1.) The 1250
Are you sure you weren't the victim of ...copper nappers, possibly...?!
No, it was lightning.
Here are pictures from an earlier event:
http://www.w8ji.com/lightning_strikes.htm
Now the problem is making wires vanish for long lengths, hundreds of feet!!!
This problem seems to be getting
I can easily and quickly test any 8 foot length Mike.
I just added a scrap from my old Dish network system that blew off the roof
last week.
:-)
- Original Message -
From: Mike Waters mikew...@gmail.com
To: topband topband@contesting.com
Sent: Wednesday, July 11, 2012 5:07 PM
Subject:
Tom, I don't doubt that you performed the cable TI measurement correctly
but I have seen folks take data that is actually the TI of the test
fixture
and not the cables under test.
What TI impedance did you measure?
I can't actually measure it Dave. I have a spare port on my test fixture
Figure 5 of W1HIS's writeup. 15 pounds of ferrite beads.
http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf
Unfortunately that can lead to a waste of time and material, and even has
some bad advice.
Common mode chokes NEVER belong between transmitting device like a
Carl,
Regardless of what feelings people might have, beads and isolators really do
not belong on transmitter lines between amplifiers and radios, or between
filters and amplifiers.
There isn't any reasonable logical technical reason for using them there,
and there are many reasons not to use
Hi Carl,
Youre welcome to your opinion based upon your experience Tom.
It is much more than experience. Good science can be proven or illustrated
through experiments and measurements. Opinions are just opinions, and have
the same value as the effort that went into confirming them.
For
If ferrite isolators or beads have been determined to improve the shield
performance of a coaxial cable in your hamshack, something is
fundamentally wrong either with the cable (but most likely the connectors
at either end) or the shielded enclosure(s) its connected to.
I've seen
In my situation I have no control over RF grounding of the equipment since
the foundation is sitting in a hole blasted out of rock. Dirt all over the
property is only 1-2' on average.
Grounding of equipment on the desk has nothing to do with TVI or RFI, unless
you have terrible antenna common
I also use phono connectors on some older radios. I'd prefer to substitute
BNC connectors but I don't want to modify the equipment.
What I find helpful is to squeeze the shell of the plug so that it will
fit tightly on the female receptacle and cover the shell with heat
shrinkable tubing
One of the dumbest things I've seen recently from a very good company is
RF chokes in series with the shield connections on analog and RS232 I/O
boards for the Elecraft K3.
Shielding and grounding is probably the least known art, as are audio line
source and load impedances.
I had problems
Hi Peter,
Hal said:
On Behalf Of Hal Kennedy
Common mode chokes DO NOT belong between boxes on your desk. As Tom and
others have said. The objective is to get them all at the same RF
potential, not isolate them from one another so they can seek their own
independent RF potential.
To
This thread has wandered away from the choke between amp and exciter or
whatever(never would do this but that has been beat to death )to what
choke impedances are and the measurement errors that can be encountered.
Which is probably beyond a general interest or benefit.
One thing that has
A monoband current forcing balun doesn't require as much coax as you might
think. The 1/4 wavelength of coax would probably be needed anyway, so the
only extra length is the 3/4 wavelength coax and thats only 35 feet of
RG-213 on 20 meters.
http://www.qsl.net/i0jx/balun.pdf
Very
Herb,
ADSL, which sounds like what you have, has carriers right up to mid
broadcast band or so. The upper frequency carriers that go up above 1 MHz
are the from the modem to your house, while stuff down low is from you back
to the DSLAM.
This makes modems very susceptible to 160 meter
I am replacing the coax in my Beverage system and have a dumb
question. When using flooded cable and compression F connectors, is
it necessary to clean the goo off the stripped cable prior to
installing the connector? If so, how?
You normally won't need to clean it, just cut to size, fold the
My Beverages run through forest. Falling trees caused many wire
breaks and high maintenance until I started using strain disconnects
at all ends. I use a fuse link of #18 soft copper wire between the
end insulator and the support pole/tree.
I use good end insulators, and bring the wire down
MEK), mostly to get a good visual on the strands. I apply
Noalox (contact grease) to restore water resistance.
Years and years ago, I headed enginering for a company that owned dozens of
cable and MATV systems. Because of FCC regulations and proximity of some
systems to airport flight paths,
Bingo. Any difference in the GE stuff and the silicon grease found in
auto
stores?
None that I can see. I use the stuff available from auto parts stores
without any issue. I use it on every outdoor electrical connection.
___
UR RST IS ... ...
However, single wire Beverages are out. The only way I can have
Beverages in more than a couple of directions (south, southwest, and
west) is to make them reversible. All feeds have to be on the end
that is on high ground so that leaves two-wire Beverages with a
reflection transformer at the
A time domain reflectometer (TDR) allows you to check all major components
(feedline, transformer antenna and termination) of your Beverage antenna
from the comfort of your hamshack.
73
Frank
W3LPL
I do that with my MFJ-259. :-)
Sweep a wide range and look at peaks and nulls, or use
I think that Harold Beverage also came up with one bi-directional design
that completely dispensed with a reflection transformer and instead used
one grounded wire and one floating wire. To make that work, isn't the
length of the Beverage tied to the desired frequency range?
That works after
Has anyone ever made any attempt to characterize the line at HF?
A simple process like that would eliminate all speculation about RF
performance, and make rational cost vs. performance decisions.
Surely someone somewhere has made some reasonable attempt at characterizing
the line.
73 Tom
Idea is each individual strand in the cable will act as one radial.
BUT I probable know the answer.
Unfortunately there is no magic. The objective of a radial is spread the
electric and magnetic fields out, so they are not as intense. The only real
solution is to fill a large physical area of
I think the characteristics of so-called WD-1 surplus phone line varies.
FWIW, the two short samples of WD-1 that I have here are as follows:
115 ohms impedance, calculated from the following: .033 diameter
(averaged), .0685 spacing. The dielectric constant of the insulation
(polyethylene) is
Gary, was your 140 ohm WD-1A made from .0393 (1mm) diameter wires, spaced
.118 center-to-center? My math says that should be a little over 140 ohms.
But the stuff I was talking about was a different diameter and spacing
(.033 diameter and .0685 center-to-center spacing.) The same math says
Hi Guy,
Good topic.
The losses as a reversible beverage would far exceed those used as a
balanced feedline, because of the balance partly cancelling fields in the
dielectric between them.
Slow wave structures are more common in microwave. Anything that increases
capacitance or inductance
From what I've read, the characteristics of WD-1x may vary quite a bit.
It's interesting to read the results of the comparison that Herb did
between some and open wire line back in 2008:
http://lists.contesting.com/_topband/2008-12/msg00016.html
From that link:
In theory two parallel 600
There is an excellent article in the July/August 2012 issue of QEX
describing how the author improved the performance of a Beverage by
breaking it into two in-line segments coupled by a pair of conventional
Beverage matching transformers. He also provides detailed construction
I have run about 400 ft of F6-type flooded coax from my shack to one end
of
my Beverage antenna. My question is: do I need to install a feedline
current choke about 20 feet from the end of the Beverage antenna (the
current choke would have its own separate ground.
While a dummy load test
Wayne is using a DX Engineering bi-directional system. Unless DXE changed
to ununs without telling anyone, he has little to worry about there. ;-)
Yes. Cable grounds are isolated from signal grounds. That unit uses
primary-secondary isolation transformers.
I do have an old page up about this:
http://www.w8ji.com/k9ay_flag_pennant_ewe.htm
___
UR RST IS ... ... ..9 QSB QSB - hw? BK
I need to construct a heavy-duty choke to be installed from the feed point
of my 160 meter vertical to ground, for static drain and for lightning
protection. How large does the wire, form, and inductance need to be?
Phil,
This is like any shunt or series choke problem. The choke needs to be
That is only 226 Ohms at 1.8MHz and at 1500W will be dissipating about 30W
in a 50 Ohm system but Phil didnt say how he is feeding his tower which is
resonant well below 160M.
That choke is probably too small and will change SWR, but thankfully
reactance in reactances does not dissipate
70 turns 2 diameter over 4 length would be 100 uH, and with an air core
and #16 magnet wire would have a Q of about 200 or so. That's 1000 ohms
impedance, a few hundred thousand ohms parallel resistance, and the
dissipation would be less than 1 watt at 1500.
Or 38 turns over 4 inches on a 4
30 watts is correct for 1500 watts in a 50 ohm system and a coil Q of 226.
The power loss is 0.1 dB and the coil temp rise is around 20 deg C.
No, it isn't.
1500 watts is 273 volts into 50 ohms.
If Q is 226, and reactance 226 ohms, Rp is 51,077 ohms. 273 volts is 1.46
watts heat.
To get 30
My Mistake:
To get 30 watts of heat with 226 ohms reactance, Q would have down near
unity. No one makes a coil that bad.
I misplaced a decimal. Q would have to be near ten in the coil with 226 ohms
reactance and 1500 watts to make 30W heat, not near 1.
The other numbers are correct. A Q of
Has anyone looked at, or looked for, cheap electric fence gaps??
My system copper pipes near tower legs work great for me on rigid towers, I
can bend them so they spring away from the tower and then slide an inner
pipe in or out to set gap distance. I'm thinking of gaps for wire antennas.
- Original Message -
From: Mike Waters mikew...@gmail.com
To: topband topband@contesting.com
Sent: Friday, July 27, 2012 11:33 AM
Subject: Re: Topband: Spark gaps
I don't think carbon balls are suitable for lightning protection.
I agree. The last thing we want is high surface
Man, I don't know, Dave. How long have they been selling those carbon
balls
for that purpose?
I've never seen a carbon ball in a lightning gap application. I'd have to
see a few after being in action a long time before trusting them.
Broadcast stations use hard metallic balls, as do
Static drain chokes and ground rods should be SOP. The chokes drain
static build up which usually prevents direct hits. The chokes are
available from various broadcast suppliers.
I have a picture of a very expensive broadcast suppressor on my web page. It
is nothing more than a long solenoid
I did a little more looking at the FCP system. I said this:
By the way, a check of voltages shows the voltage from radial center point
to ground is 226 volts RMS at 1500 watts when four radials are used. This
is
for infinite isolation. While this clearly shows we need a common mode
choke,
Elegant analysis, Tom. Thanks. I looked at Guy's very well done piece
in the National Contest Journal (the one timed for reading on the
airplane going to Dayton) and wondered why a serious common mode choke
would not work.
Thanks, not really so elegant though.
Any common common mode choke
Hi Guy,
The FCP is not resonant because it is designed specifically to
self-cancel fields, not to be resonant. Said another way, it's
DELIBERATELY not resonant.
A counterpoise that fully cancels its own fields, by definiton, cannot be a
counterpoise.
Following that logic, because it is
On Tue, Jul 31, 2012 at 5:23 PM, Rick Karlquist rich...@karlquist.com
wrote:
We already know that folding an antenna element has no advantage
over loading coils, why should radials be any different?
Rick N6RK
There is the problem. The folds in a single wire 5/16 wave folded
counterpoise
It's that thing about at the top that probably doesn't get past the
garden committee. Folks don't really understand reactionary until
you've crossed swords with the garden committee. Maybe something
that slides INSIDE a fiberglass flag pole.
The major problem with ANY 43 ft vertical is it
Good points regarding my statement about proven architecture - I should
have more properly stated as proven thus far by those in the field.
Hi Jack,
At this point proven is far too strong of a word, or the proven part is
not readily available.
Nothing I've read was proven, except a new
I think a more relevant question should be is there a better or simpler
elavated radial arrangement that can fit into the 66 foot linear space
that will radiate more effectively than the FCP design? I'd be willing to
extend that distance to 100 feet since many surburban lots can support a
Let me throw this out for comments.
I think I found a valid test for the theory the FCP does not radiate, and
thus does not have ground loss.
My countering statement was it cannot be a counterpoise, and cannot have
current, without E and H fields. Even if we null farfield radiation (which
is
Completely agree, but you didn't say how to get past the garden
committee. :) 73, Guy.
Thin wire or move.
___
UR RST IS ... ... ..9 QSB QSB - hw? BK
Hi Guy,
This is a non-issue, Tom.
I think it is a critical issue, because it demonstrates the difference
between EM radiation and induction fields that only store and return energy
to the system.
It stems from what I meant when I said cancel fields.
Apparently some considerable number,
Very interesting discussion. Can't we quantify our ground systems by placing
RF ammeters at the feed point?
No, we cannot obtain reliable useful information there. If we want to know
field strength change, we have to measure field strength change. :-)
It would seem to me that once the current
(1) 130 feet of 300 ohms twin lead with the far one end shorted and
pulled up over a coconut by a local climber $5 US max and connected to a
small nylon line for adjustment in an inverted or sloping fashion back
to my hotel room on the beach. (without the local climber bring along a
The claim was made in the last several editions of the Radio Handbook in
describing a TV twinlead folded Marconi for 160m.
I believe the idea was not in QST, because at that time QST had good
technical editing. There were very few gross technical gaffs in QST back
then.
As I recall, the idea
The so called T2FD's sold these days by the usual ham dealer suspects is
nowhere near the original design so its no stretch as to why its not a
great
performer.
Any antenna that increases bandwidth through a resistive termination will
always lose a substantial portion of power as heat on
So gently getting back to the topic of the original post which was:
Getting thoughts on relatively simple and relatively inexpensive
portable 160 m antenna, potentially deployable by one person, that
allows for flexibility and somewhat predictable tuning for use on modest
Dxpeds or rare location
So I modeled a half wave dipole in free space and sure enough the wire
segments on each side of the feed point carried equal current. I then placed
a resistive load at the center of one half-element (to simulate? a lossy
return) and now see that those segments no longer carry equal currents,
Hi Bill,
Tom, it's worth adding to this that trying to make current measurements in
the ground using 60hz is pretty useless for another reason: induced
currents from the ac power system (especially in north america). 60hz will
be present on just about anything -- you'll even see it on a
I had read in a Hand Book for the 1930's the 3 wire folded dipole and 2
wire folded dipole had a couple factor of 1. This would make this antenna
the preferred driven element for a long yagi.
Why? Unless we know what they meant by the use of the phrase coupling
factor, we can't possibly
You can not apply Kirchoff law from DC circuits to the current behavior
along the STANDING WAVE RF radiator.
Yes, we can.
Kirchhoff's law is Kirchhoff's law, and is not frequency dependent.
I can't imagine anyone thinking otherwise. Thinking Kirchhoff's law applied
only to dc circuits is
found that GE Silicone II Sealant, which is fine for outside, to work very
well for covering solder joints.
I've purchased it in many local hardware stores. It runs around $6 per
tube.
It cures in just a few hours, is rain resistant and does not affect the
solder
joint.
There were
You said 3.) Use the largest counterpoise possible, and use one that does
not
concentrate current, zig-zag current all around, or produce unnecessarily
high voltages. In 300 words or less please explain again Zig-zag current?
Jim,
While some forms of coiling, folding, and bending are better
Sooo, there is no current and voltage variation along the standing wave
resonant dipole?
S, Jasik et al, all those antenna books, modeling programs showing
RF CURRENT and/or RF VOLTAGE distribution along the (standing wave)
solid antenna wire are thinking otherwise?
Like parallel LC
to make a confirming measurement. When he did arrive at the chosen
measurement point he would find nearly but never all of the injected
current
had disappeared. This would not have been a surprise to him but maybe to
the rest of us. How could this have happened?
With an infinitely long
How much series C will it take to resonate a set of three guy wires 120
degrees apart that are 145 feet long each.
They are fed at the 60 foot level of a Rohn 25 tower, and slope down to 10
feet at the ends. They are guy wires that cannot be changed.
I want them to resonate on 1.830 khz.
I use 5 two wire Beverages for 10 directions and have good directivity down
to the 175 KHz LF BCB and they are only 500-700' long. Performance seems
to
exceed published info. On the US BCB its like aiming a long yagi on 2M,
multiple stations on the same frequency can be heard with ease during
If a radial runs along the ground and then up over a wall, what difference
would it make?
Good question.
The radial only goes up for 4 feet and back down for 4 feet.
That is exactly like adding a 4-foot shorted stub in series with the radial.
All that worry about induced current in a 4-foot
I'm not sure I'd go too far with the FCC map. At my QTH, which is shown
as average, actual ground/earth varies within a hundred feet from deep
old riverbottom loam to limestone with a thin covering of topsoil (or
sometimes none). While I don't know how this affects electrical ground
** That doesnt make sense since the books, etc claim virtually no
directivity at a 1/4 wave. At 175 KHz a 1/4 wave is 1406'.
I don't know what books, etc that comes from, but even over fairly good
soil a 600-foot Beverage models to have about 18 dB side null and a few dB
F/B at 175 kHz. It
Wayne,
Not enough information!!
Any preamplifiers? Any trace of additional modulation?
A mixing of BC signals will have at least a faint second modulation, **and**
a mixing of BC signals or a harmonic distortion spurious always falls on a
ten in the USA/Canada. It cannot fall on a five
I sometimes see spurious signals at the 5kHz points when using my K7JTR 8
circle
array. I tracked them down to powerful short wave station booming in when
propagation
is good. I think this is the curse of most broadband antenna sytems.
Roger,
Broadband systems do not need to be that bad. It
Don't take this the wrong way, but 160 meters is open all summer and all
winter long ***if*** people take time to operate. This is especially true in
the southern USA with our shorter summer daylight period.
It isn't unusual to work northern Europe or Japan even in mid-summer. There
really is
That's sad to hear at such a young age. UA9YAB was a regular on 80 and 160
meters. I'm sure Alex gave many people his zone and DXCC, but most important
he was a human and a fellow Ham.
I hope we all work harder to be respectful and mature, and not stereotype
people with ignorant comments.
73
ZR, Bruce and Bob, thanks for your info. There's the problem. I was
using the white ones and didn't know the black ones are UV resistant.
I'll check those out.
I learned a lesson a long time ago here, after I used big black tie-wraps on
all my cables on towers. I have white ties and
That doesn't work for me for some reason.
-Original Message-
From: topband-boun...@contesting.com
[mailto:topband-boun...@contesting.com]On Behalf Of Jerry Keller (K3BZ)
Sent: Friday, August 17, 2012 4:15 PM
To: (REFLECTOR) Topband
Subject: Topband: UA9YAB SK - PayPal Page
I
Good point, Dick.
So while this isn't a very efficient antenna system compared to one using
120 x 1/4-wave buried radials spaced every 3 degrees around the monopole,
it
does not show much directionality in the azimuth plane -- as might be
anticipated for the lopsided ground system it uses
Do you think that radials --either elevated or laying on the ground--
radiate? Or does all of the radiation come from the vertical monopole
under
the radial system?
There is no question radials radiate, and it is impossible to stop them from
radiating or coupling to things around them, at
It goes without saying that both halves of the antenna (radials and the
vertical) must be present in order for the bottom-fed vertical monopole to
radiate.
A vertical will radiate without any ground, and actually radiate pretty well
if the common mode feedline currents can be controlled and
1 - 100 of 818 matches
Mail list logo
