[Top] [All Lists]

Re: [TowerTalk] Balun Recommendation

Subject: Re: [TowerTalk] Balun Recommendation
From: Jim Brown <>
Date: Mon, 23 Apr 2012 08:59:45 -0700
List-post: <">>
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.

>   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.

> 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.

> ## 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 

> ##  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!

> 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.

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

TowerTalk mailing list
<Prev in Thread] Current Thread [Next in Thread>