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[TowerTalk] Balun Recommendation

To: <>
Subject: [TowerTalk] Balun Recommendation
From: "Jim Thomson" <>
Date: Tue, 24 Apr 2012 02:19:20 -0700
List-post: <">>
Date: Mon, 23 Apr 2012 08:59:45 -0700
From: Jim Brown <>
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 
> decade.
> 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. 
I also
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 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 
interconnected the 
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 
> xcvr.
> ## 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 
kw.    After 
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,
lousy implementation. 

&&  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 
the usa.  
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 
drive 3 
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 
for each
ant  in an array.   What about 4 x  yagis in a stack, each with its own 
amplifier.  What
if one yagi in a 2 yagi stack, is pointed in the opposite direction...yet each 
yagi has its own
dedicated amplifier. 

&&&  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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