Date: Mon, 23 Apr 2012 08:59:45 -0700
From: Jim Brown <firstname.lastname@example.org>
Subject: Re: [TowerTalk] Balun Recommendation
On 4/23/2012 3:03 AM, Jim Thomson wrote:
> ### There has not been a Pin 1 problem in pro audio gear in well over a
> Everything is referenced to the chassis.
You apparently still don't understand the Pin One Problem.
&&&&& Oh I fully understand the Pin 1 problem alright.
> Anybody making pro- audio gear with
> Pin 1 problems will be outa business in 15 mins flat.
I wish that were true. While things have gotten a lot better since Neil
Muncy first published his landmark paper in 1994, I still see products
with Pin One Problems as I tour the floor of a trade show.
&&& I have 2 x local friends who own 3 x large recording studios between them.
know several broadcast engineers. Even with the myriad of my own rack mount
audio gear, none
of us have any gear that has Pin 1 problems. We did have one case at work
with a one off audio
device that indeed had the pin 1 problem. The fix was easy, just ship it back
as.. unacceptable to
our engineering dept. I have yet to see any new gear with pin 1 problems
these days, but apparently you
are seeing it at trade shows. That new gear with pin 1 problems is a non
starter. Anybody who buys it will
ship it back after the fact. Word gets out asap and sales plummet. Or the
pin 1 problem is pointed out
in various equipment reviews.
> Nobody would buy it.
> These days its all servo balanced. Now if you really want to crank the CMRR
> specs through the roof, then add jensen transformers at each end.
Again, you apparently don't understand the Pin One Problem. The Pin One
Problem has NOTHING to do with a balanced interface. Nor do you
understand the balanced interface. Bill Whitlock got to the heart of it
in 1994 with his landmark AES paper on the subject. You can download and
study a tutorial on his Jensen Transformers website.
&&& Forget the pin 1 issue, cause it’s a non issue in 99.99% of all pro gear.
True servo balanced inputs, with no pin 1 problems usually have good CMMR
specs...as long as the balanced lines are short. Make em longer, and the CMRR
specs will drop off. In extreme cases, by using xfmrs on each end, the CMRR
will improve by a whole bunch. Equipment makers will try and avoid the use of
xfmrs like the plague. I can see why. At $75.00 a pop, you will have a
lot of $$
invested in xfmrs. I tried an experiment a few years ago..and
various pieces of audio gear with fiber optic cable. Now that solves every
problem you can think of. I think the icom 7800 has a fiber input on the rear
My gear will handle any of the various fiber standard commonly in use today.
My only problem with fiber is they will have both channels of a 2 x channel
of gear on one strand of fiber.
&& I also tried the other method, where digital is stuffed down balanced audio
This works great too. I use all the left channels for TX...and all the right
channels for RX.
By using digital, one can eliminate all the multiple A-D and D-A conversions
if analog is
used to interconnect. I’m talking about equipment that does all its processing
in the digital
> ## yaesu has pin 1 problems. Now that?s real easy to fix. The stock yaesu
> mic pre-amps are pure junk anyway, and noisy, plus have the Pin 1 problem.
> The easy fix is to just install a new RCA connector onto the rear chassis
> apron somewhere.
> Then use s 220 uf non polarized panasonic SU series coupling cap from the hot
> side of the newly installed rca female jack, directly to the balance
> modulator input.
> Then use a quality outboard audio pre-amp..with a balanced input, and use a
> balanced mic.
> Output of the pre-amp is also balanced..which in turn is fed to a jensen
> audio xfmr. Xfmr is
> wired balanced on the input side, and Un balanced on the output side. A real
> short length
> of small diam coax is run from xfmr output to newly installed rca input on
> ## problem solved, and you kill several birds with one stone.
The only part of this that matters is bonding the mic shield to the
&&& What about the original ....electronic ground. Is it to be chopped off, or
can it be bonded to the chassis as well.
> ## beware of using a large number of coax wraps around cores. A buddy had all
> sorts of parasitic arcing
> between the last 2 turns, when using just 8-10 turns of Rg-162 teflon coax
> wound onto several 2.4 inch cores.
How much power was HE running? That symptom indicates an antenna that
is BADLY screwed up!
&&& I just checked my notes, and it was used on the INPUT side of a HB ant
tuner, a T type, using
vac caps and a rotary coil. it also had comp caps inside the tuner. This is
in the case of trying to use
a T tuner in conjunction with 450 ohm line to an ant. It arced with aprx 5
trying some more configs, we concluded that trying to use the T tuner with a
balun on the input
and open wire line on the output is not going to work. The T tuner in
balanced mode is not truly balanced.
W8JI was correct. You require like 50 k choke Z on the input of a T tuner to
make it work. Alpha unfortunately
is going to find this out the hard way on their new T type tuner. A better
tuner for open line is the balanced
L type, with 2 x rollers ganged together and one vac cap across their outputs.
Then the balun can be placed
on the input side. I think it was dean straws idea to 1st install the balun
on the input of a t type tuner. Great concept,
&& The fix for the above mess was to use a 1:4 balun in the back yard.
Coax back to output of T type tuner.
450 ohm line from 1:4 balun to ant. After destroying every balun on the
market, including palstar, amidon, Hb, etc,
array solutions supplied a 1:4 balun that would do the job. He cooked up a
5-10-20 kw version, to be used on the
outputs of T type tuners. It’s a high V version of your typ 1:4 balun.
> Jay at array solutions had warned us of that effect. Now that teflon coax
> also has a super HV type outer jacket.
> It had arced from the last turn to the next inner turn. It was wound solenoid
> fashion, very neatly. Now just think
> about it. You need a lot of voltage to puncture through TWO jackets. The
> answer was more cores, and less turns.
> 14 turns of RG-58 size coax is gonna result in problems when running high
> power under a lot of conditions.
Something does not compute here. RG58 is very lossy coax, and it doesn't
handle high power. Why in the world would anyone use it in a situation
that puts enough voltage across the choke for arcing to occur? The only
place I would use RG58 is on a receiving antenna, like a Beverage, where
power handling and loss don't matter, or in a car where I needed
something small to get through tiny spaces.
&&& whoa. I meant all the variants of the small teflon coax, which is aprx
the same OD as
RG-58u. Like 162U, 303U etc. Sri if I implied the use of RG-58. You
can only get like just
a few turns of the bigger RG-393 teflon coax through those small cores. The
idea of course was to
use teflon coax, in the small OD variety, so we could get more turns on the
small 2.4 inch OD cores.
My designs (and other advice) are based on legal ham power levels and
well designed antennas that are not "broken." If you want to cheat by
running more power than that, or use dumb antenna designs, you're on
your own. :)
73, Jim K9YC
&&& The FCC doesn’t set the power rules for the rest of the planet...only
I see that OM Power now makes a splitter-combiner in one box. You take the
of your xcvr, and run it into the splitter, where the 3 x outputs are used to
OM power amplifiers. The combiner merely sums the 3 outputs back together.
same arrangement can be used on other brands of amps. Remember those old Alpha
advertisements years ago, depicting OH2BH. He would use a splitter box to
drive 2 x
identical alpha amps. The output of each amp fed one yagi in a 2 yagi stack.
feed line was identical length. Now that’s one more way to do things.
That’s a grey area.
If the FCC rules say 1.5 kw from an amp, now what happens if you have an amp
ant in an array. What about 4 x yagis in a stack, each with its own
if one yagi in a 2 yagi stack, is pointed in the opposite direction...yet each
yagi has its own
&&& IMO, who really cares how one arrives at a given ERP. 1.5 kw into a 4
high stack of
20m monobanders is obviously more ERP than 5 kw into a dipole. Yet folks get
an uproar about some fellow with 2 kw into his 2 el quad at 50 feet.
later... Jim VE7RF
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