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OT: balun rating exceeded

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Mike Markowski

OT: balun rating exceeded

The following happened to me a few years ago as a brand new ham in my
pre-Elecraft days and I wonder if anyone can explain to me the details. I
apparently had high swr and exceeded the rating on my balun. It suffered
accordingly but didn't completely fail. The result was when I transmitted cw on
40m an internal fuse would blow in the stereo which was on in the next room
room. It took two go rounds before I caught onto the cause and effect... A new
& better balun cured the problem.

At the time I had a Zepp (135') and 4:1 balun at the house entrance. I assume
the ruined balun was emitting all sorts of RF that the stereo amplifier picked
up, tried to amplify, and couldn't. But I don't understand exactly what would
make it draw that much current. Can someone enlighten me?

By the way, since then I put up a dipole, halfwave for 160m, about 200' behind
the house. That's what I should have begun with.

Thanks!
Mike ab3ap
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Brett gazdzinski-2

RE: OT: balun rating exceeded

What is the benefit of a balun?
I cant run them, as I run legal limit AM which
will toast any balun I ever heard of.

At 100 watts, or QRP, RF in the house cant be an issue,
I don't have problems with the AM and the G5RV right over the house.

I would think it would just add more loss.

I used to have resonant 80 and 40 meter dipoles, but took
them down and built a home made G5RV, #12 wire for the open wire
line, and only about 20 feet of RG214 coax into the tuner
or directly into the K2 with its built in atu.
I will have very high swr on both the open wire line
(does not matter as there is almost no loss),
and the RG214, but there is only 20 feet of that, so I would
guess the loss is slight.

Now I could fit a balun if I just used the K2, but what
would be the advantage?

I hear you should never run a balun with any swr, the losses
go way up. I think they now make tuners with the balun
before the tuner (rig, balun, tuner, antenna) that works
well....

Brett
N2DTS

>
> The following happened to me a few years ago as a brand new ham in my
> pre-Elecraft days and I wonder if anyone can explain to me
> the details. I
> apparently had high swr and exceeded the rating on my balun.
> It suffered
> accordingly but didn't completely fail. The result was when
> I transmitted cw on
> 40m an internal fuse would blow in the stereo which was on in
> the next room
> room. It took two go rounds before I caught onto the cause
> and effect... A new
> & better balun cured the problem.
>
> At the time I had a Zepp (135') and 4:1 balun at the house
> entrance. I assume
> the ruined balun was emitting all sorts of RF that the stereo
> amplifier picked
> up, tried to amplify, and couldn't. But I don't understand
> exactly what would
> make it draw that much current. Can someone enlighten me?
>
> By the way, since then I put up a dipole, halfwave for 160m,
> about 200' behind
> the house. That's what I should have begun with.
>
> Thanks!
> Mike ab3ap
> _______________________________________________
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Jozef Hand-Boniakowski

Re: OT: balun rating exceeded

A few years back I bought a Buxcom G5RV and running 600 watts into it,
the balun that it came with was toast. I replaced it with 10 turns of
coax wrapped around a Folger's coffee can. Reading what G5RV had
written about his antenna, he recommended that a balun not be used with
his antenna. See last link at
http://www.metaphoria.us/hamradio/ham_radio.htm

Jozef WB2MIC

Brett gazdzinski wrote:

>
>
> What is the benefit of a balun?
> I cant run them, as I run legal limit AM which
> will toast any balun I ever heard of.
>
> At 100 watts, or QRP, RF in the house cant be an issue,
> I don't have problems with the AM and the G5RV right over the house.
>
> I would think it would just add more loss.
>
> I used to have resonant 80 and 40 meter dipoles, but took
> them down and built a home made G5RV, #12 wire for the open wire
> line, and only about 20 feet of RG214 coax into the tuner
> or directly into the K2 with its built in atu.
> I will have very high swr on both the open wire line
> (does not matter as there is almost no loss),
> and the RG214, but there is only 20 feet of that, so I would
> guess the loss is slight.
>
> Now I could fit a balun if I just used the K2, but what
> would be the advantage?
>
> I hear you should never run a balun with any swr, the losses
> go way up. I think they now make tuners with the balun
> before the tuner (rig, balun, tuner, antenna) that works
> well....
>
>
> Brett
> N2DTS
>
>
>
>
>
>> The following happened to me a few years ago as a brand new ham in my
>> pre-Elecraft days and I wonder if anyone can explain to me
>> the details. I
>> apparently had high swr and exceeded the rating on my balun.
>> It suffered
>> accordingly but didn't completely fail. The result was when
>> I transmitted cw on
>> 40m an internal fuse would blow in the stereo which was on in
>> the next room
>> room. It took two go rounds before I caught onto the cause
>> and effect... A new
>> & better balun cured the problem.
>>
>> At the time I had a Zepp (135') and 4:1 balun at the house
>> entrance. I assume
>> the ruined balun was emitting all sorts of RF that the stereo
>> amplifier picked
>> up, tried to amplify, and couldn't. But I don't understand
>> exactly what would
>> make it draw that much current. Can someone enlighten me?
>>
>> By the way, since then I put up a dipole, halfwave for 160m,
>> about 200' behind
>> the house. That's what I should have begun with.
>>
>> Thanks!
>> Mike ab3ap
>> _______________________________________________
>> Elecraft mailing list
>> Post to: [hidden email]
>> You must be a subscriber to post to the list.
>> Subscriber Info (Addr. Change, sub, unsub etc.):
>> http://mailman.qth.net/mailman/listinfo/elecraft
>>
>> Help: http://mailman.qth.net/subscribers.htm
>> Elecraft web page: http://www.elecraft.com
>>
>>
>
> _______________________________________________
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>
>

Alan Biocca

RE: OT: balun rating exceeded

In reply to this post by Brett gazdzinski-2

It does not take much RF in the shack/house to cause problems. Keep
the RF outside.

An effective balun goes a long way to avoid these problems.

Noise from the house couples to the antenna if there is not an
effective balun, raising the receiver noise level. Using an effective
balun can lower the receiver noise levels.

A good balun will have negligible loss (by design).

Operating Coax at high SWR (a la G5RV) can have significant loss.
Even a fairly short length. Run the feedline modelling software that
comes with the ARRL Antenna Books to quantify. Try to keep high SWR
coax lengths to several feet at most.

At least one company (DX Engineering) makes baluns that will handle
high power. Take one apart and inspect it, they are well made and
have a lot more ferrite than most.

Operating a balun with SWR is not a problem as long as the ratings
are not exceeded. The voltage and current are larger by as much as
the square root of the SWR, so a 10:1 swr will increase
voltage/current by as much as the square root of 10, or about 3. Use
a balun with adequate voltage/current ratings for the power and SWR.

A 4:1 balun current balun splits its ferrite in half for the two
internal 1:1 sections. So it has half the choking reactance of a
straight 1:1 for the same cost (ferrite quantity). Generally a 1:1
current balun is a better choice for high SWR use. Let the tuner do
the matching, allow the balun to do the balancing.

A voltage balun doesn't keep the RF out of the house, so is not of
much use here. Most 4:1 baluns are voltage type, so you have to shop carefully.

As to the original question about the balun failure, the ineffective
balun may have allowed considerable RF onto the ground system and
conducted into the stereo. The RF gets rectified and the stereo
attempts to amplify the resultant frequency components within its
passband (some possibly out of audio range). The high power
consumption pops the fuse.

Using balanced antennas and a quality effective balun keeps the RF
out of the house.

73,

-- Alan, wb6zqz

At 06:23 AM 5/15/2007, Brett gazdzinski wrote:

>
>
>What is the benefit of a balun?
>I cant run them, as I run legal limit AM which
>will toast any balun I ever heard of.
>
>At 100 watts, or QRP, RF in the house cant be an issue,
>I don't have problems with the AM and the G5RV right over the house.
>
>I would think it would just add more loss.
>
>I used to have resonant 80 and 40 meter dipoles, but took
>them down and built a home made G5RV, #12 wire for the open wire
>line, and only about 20 feet of RG214 coax into the tuner
>or directly into the K2 with its built in atu.
>I will have very high swr on both the open wire line
>(does not matter as there is almost no loss),
>and the RG214, but there is only 20 feet of that, so I would
>guess the loss is slight.
>
>Now I could fit a balun if I just used the K2, but what
>would be the advantage?
>
>I hear you should never run a balun with any swr, the losses
>go way up. I think they now make tuners with the balun
>before the tuner (rig, balun, tuner, antenna) that works
>well....
>
>
>Brett
>N2DTS
>
>
>
>
> >
> > The following happened to me a few years ago as a brand new ham in my
> > pre-Elecraft days and I wonder if anyone can explain to me
> > the details. I
> > apparently had high swr and exceeded the rating on my balun.
> > It suffered
> > accordingly but didn't completely fail. The result was when
> > I transmitted cw on
> > 40m an internal fuse would blow in the stereo which was on in
> > the next room
> > room. It took two go rounds before I caught onto the cause
> > and effect... A new
> > & better balun cured the problem.
> >
> > At the time I had a Zepp (135') and 4:1 balun at the house
> > entrance. I assume
> > the ruined balun was emitting all sorts of RF that the stereo
> > amplifier picked
> > up, tried to amplify, and couldn't. But I don't understand
> > exactly what would
> > make it draw that much current. Can someone enlighten me?
> >
> > By the way, since then I put up a dipole, halfwave for 160m,
> > about 200' behind
> > the house. That's what I should have begun with.
> >
> > Thanks!
> > Mike ab3ap

John Magliacane

Re: OT: balun rating exceeded

In reply to this post by Jozef Hand-Boniakowski

--- Jozef Hand-Boniakowski <[hidden email]> wrote:

> A few years back I bought a Buxcom G5RV and running 600 watts into it,
> the balun that it came with was toast. I replaced it with 10 turns of
> coax wrapped around a Folger's coffee can.

So, you replaced the balun you normally use with New Folger's Crystals. :-)

Seriously though, I've given this situation a lot of thought, and I'm not
thoroughly convinced an unshielded choke located in the nearfield of a
radiating structure would necessarily attenuate currents flowing on the outside
of the transmission line's shield.

I think even a perfectly functioning, perfectly shielded balun *at the antenna
feedpoint* might be somewhat moot unless the dipole is perfectly straight, and
the feedline is run exactly perpendicular to the dipole (to equalize coupling
to either side of the antenna).

By the same token, I've often wondered just how "balanced" a balanced feedline
really is under similar circumstances. Maybe twisting the line might help
improve transmission line balance. Maybe using a tuner that can compensate for
any voltage/current imbalance might be advantageous, as well.

There are many complicating factors when it comes to antenna installation and
operation. Fortunately, few, if any, turn out to be of much significance in
the grand scheme of things...

73, de John, KD2BD

Visit John on the Web at:

http://kd2bd.ham.org/
.
.
.
.

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Jozef Hand-Boniakowski

Re: OT: balun rating exceeded

Hello John:

Tnx much for the reply. The G5RV is as straight as gravity will allow
and the 450 ohm line is indeed perpendicular to the flattop. I use a
Palomar 1500CV with it and it works well. That said, I prefer my 33 ft
40 meter vertical with 37 radials and the 40 meter loop.

Jozef WB2MIC

John Magliacane wrote:

> --- Jozef Hand-Boniakowski <[hidden email]> wrote:
>
>
>> A few years back I bought a Buxcom G5RV and running 600 watts into it,
>> the balun that it came with was toast. I replaced it with 10 turns of
>> coax wrapped around a Folger's coffee can.
>>
>
> So, you replaced the balun you normally use with New Folger's Crystals. :-)
>
> Seriously though, I've given this situation a lot of thought, and I'm not
> thoroughly convinced an unshielded choke located in the nearfield of a
> radiating structure would necessarily attenuate currents flowing on the outside
> of the transmission line's shield.
>
> I think even a perfectly functioning, perfectly shielded balun *at the antenna
> feedpoint* might be somewhat moot unless the dipole is perfectly straight, and
> the feedline is run exactly perpendicular to the dipole (to equalize coupling
> to either side of the antenna).
>
> By the same token, I've often wondered just how "balanced" a balanced feedline
> really is under similar circumstances. Maybe twisting the line might help
> improve transmission line balance. Maybe using a tuner that can compensate for
> any voltage/current imbalance might be advantageous, as well.
>
> There are many complicating factors when it comes to antenna installation and
> operation. Fortunately, few, if any, turn out to be of much significance in
> the grand scheme of things...
>
>
> 73, de John, KD2BD
>
>
> Visit John on the Web at:
>
> http://kd2bd.ham.org/
> .
> .
> .
> .
>
>
>
> ____________________________________________________________________________________Get the Yahoo! toolbar and be alerted to new email wherever you're surfing.
> http://new.toolbar.yahoo.com/toolbar/features/mail/index.php
>
>

Ron D'Eau Claire-2

RE: OT: balun rating exceeded

In reply to this post by Mike Markowski

What usually happens under those conditions may not damage the balun but
does cause lots of RFI: the balun turns non-linear!

When the magnetic flux saturates the core it heats and its magnetic
properties change dramatically. That produces a non-linear transfer
function. Non-linearity is the hallmark of a good mixer! So your balun
starts making all sorts of unintentional RFI that wasn't at the output of
the transmitter.

Under such conditions the core is absorbing a lot of power too. Had you
touched it, you'd probably have found it noticeably warm, perhaps even hot,
possibly hot enough to blister your finger. At the extreme, the core will
heat and crack, ruining it and the balun.

But that doesn't always happen.

Another temporary failure mode is arcing. That may be more obvious since you
may hear it if the balun is nearby. Most baluns are not made to handle
really large RF voltages. There isn't enough spacing between leads and
terminals for that. The insulation on the wires isn't rated for high
voltages. So, when you have it at a voltage loop and crank up the power,
it's easy for an arc to occur across adjacent leads. If it's through the air
between metallic conductors usually no harm is done. Often it's through the
insulation of adjacent wires or across a PCB. In those cases a carbon trail
is formed that will have to be removed before the balun will work properly
again.

The bottom line is that modern baluns are NOT designed to be used in systems
with a wide range of impedances. You can get away with using a balun in a
multiband doublet, Windom fed with parallel lines, G5RV, etc., only when
those antennas happen to provide a reasonable impedance at the balun:
neither too low (which would produce high RF currents) or too high (which
would produce high RF voltages).

Many years ago many of us did use baluns in such systems quite successfully.
They used air core coils. Air does not saturate magnetically. They had large
enough spacing to avoid arcing at high RF voltages. Such baluns commonly
measured a foot square, or larger, by nearly a foot deep. They were
generally mounted on the wall well away from anything that might draw an
unintentional arc from the coils - such as the operator!

There are times when size does matter!

Ron AC7AC

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Mike Markowski
Sent: Tuesday, May 15, 2007 6:08 AM
To: Elecraft
Subject: [Elecraft] OT: balun rating exceeded

The following happened to me a few years ago as a brand new ham in my
pre-Elecraft days and I wonder if anyone can explain to me the details. I
apparently had high swr and exceeded the rating on my balun. It suffered
accordingly but didn't completely fail. The result was when I transmitted
cw on 40m an internal fuse would blow in the stereo which was on in the next
room room. It took two go rounds before I caught onto the cause and
effect... A new & better balun cured the problem.

At the time I had a Zepp (135') and 4:1 balun at the house entrance. I
assume the ruined balun was emitting all sorts of RF that the stereo
amplifier picked up, tried to amplify, and couldn't. But I don't understand
exactly what would make it draw that much current. Can someone enlighten
me?

By the way, since then I put up a dipole, halfwave for 160m, about 200'
behind the house. That's what I should have begun with.

Thanks!
Mike ab3ap
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Jim Brown-10

RE: OT: balun rating exceeded

On Tue, 15 May 2007 09:35:03 -0700, Ron D'Eau Claire wrote:

>The bottom line is that modern baluns are NOT designed to be used in systems
>with a wide range of impedances.

I suggest that those interested in this thread study my tutorial on RFI
and ferrites. It includes a long section on choke baluns.

http://audiosystemsgroup.com/RFI-Ham.pdf

I am currently working on updating the "cookbook" section with improved
specific recommendations about how coaxial choke baluns must be wound
to minimize stray capacitance. I've done enough work on this to have a
good handle on what works and what doesn't, but had to interrupt it for
a biz trip to Europe. Until I've finished that and posted it, I'll
simply say that the coax should be closely spaced ONLY where it goes
through the toroids, and VERY WIDELY SPACED everywhere else. The
difference between a coaxial choke with close spaced turns and one with
wide spaced turns is HUGE.

For example, five CLOSE-spaced turns of RG8 through five #31 toroids
will cause a resonance (and peak performance) in the 2-3 MHz range,
while WIDE-spaced turns will yield excellent performance all the way up
to 10 meters.

73,

Jim Brown K9YC

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Stuart Rohre

Re: OT: balun rating exceeded

In reply to this post by Brett gazdzinski-2

Brett,
There ARE kilowatt baluns, but the balun probably will not help a G5RV due
to the fact it is resonant on 20 as a gain antenna, and somewhat of a
mismatch on any other band. In fact, you would be better off running open
wire line all the way to a Tee tuner, then using a ferrite bead 1:1 balun
after the tuner and before the balanced line, ONLY if you have any RF on the
tuner or rig chassis. From what you say, in your case, location has worked
to mitigate imbalance and you do not need a balun if you do not see stray RF
effects.

Look to suppliers such as <thewireman.com> for high power balun kits if ever
you need one.

A balun is not very lossy to your signal, UNLESS it gets saturated. A bead
balun on coax should only be handling minimal power from stray pickup to
outer of the coax shield, and thus will not be saturating, to the extent
other baluns might.

However, G5RV and others analyzing his antenna have remarked that the balun
at junction of parallel line and any coax to shack may show no benefit from
a balun. Originally, the G5RV was done without a balun. It theoretically
"looks" like it would be necessary, but even the venerable balanced line end
fed Zepp only shows 10 per cent imbalance when end fed, per L. B. Cebik's
analysis. (see www.cebik.com for extensive antenna info.)

If the balun materials are big enough, they are not lossy to a significant
degree, when appropriately applied to specific impedance transformation as
well as balancing.

Loss in a balun can be noted by seeing if it heats up.
No heating from ambient to full power says there is no loss at the balun.
In some applications, critical lengths of line can place the balun in a
point of too high SWR, but proper design puts the balun at an appropriate
point.

Stuart
K5KVH

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