[Amps] RF in the Audio

[Roger (sub1)]

On 9/25/2011 2:15 AM, Jeff Blaine wrote:
> Roger, you better keep your head down.  I'm not sure who it will be (the G5RV crowd or the "open wire is perfect" crowd), but the
> chances of you meeting a bad ending from this statement is high!  You are talking about the sacred cows here.  ha ha.

Yup, it's the way I've seen it work out time and again. As I said, 
sometimes it works fine and other times it doesn't.
Certainly it's low loss, but there's a reason we put a twist in window 
and twin lead and there's a reason we put it on stand offs to keep it 
away from metallic objects. <:-)) Also the wider the spacing the more 
sensitive it is to nearby objects.

73

Roger (K8RI)

> 73, Jeff ACØC
> www.ac0c.com
>
> -----Original Message-----
> From: Roger (sub1)
> Sent: Sunday, September 25, 2011 1:01 AM
> To: amps at contesting.com
> Subject: Re: [Amps] RF in the Audio
>
> On 9/25/2011 1:24 AM, Tom Thompson wrote:
>> On second thought, if all the impedances are equal, the currents are
>> equal but I doubt that can really occur in the real world.
> It's highly unlikely as open wire/ ladder line/ window line is highly
> sensitive to nearby objects.
> It could be a perfect balanced match at the antenna, and still end up
> unbalanced by the time it reaches the rig.
> Nearby metal objects, such as towers, roofing, antenna supports all
> effect the currents in each leg differently.  It may be small or large,
> but it does affect them.
>
> Then when you take into account the way balanced line or rather open
> wire line is used, it typically has highly unbalanced currents.  Even
> with center fed, horizontal dipoles it's difficult to get the currents
> matched perfectly.
>
> "I think" one answer *might* be a remote, coax fed,  balanced tuner with
> link coupling as close to the antenna as possible.  Even then the chokes
> "might" be a good idea.
>
> Every antenna installation is pretty much unique and particularly when
> antennas are fed with parallel line. You put them up, see what you get
> and then go from there. There are many out there that work great with no
> special attention and there are those that never seem to work right.
> Perhaps that is the point  to look into remote tuners, and chokes or
> even chokes at both ends of the open wire line. That I've never seen
> done.  What I don't like is the current and common practice of just
> feeding the parallel line with a 4:1 balun in the tuner.
>
> However when it comes to open wire line, after this many years I've made
> it a practice to *never* end up in the same tent with some one using it
> on Field Day!<:-))
>
> Although I didn't operate last year, I did visit the site and shoot
> photos.  I did notice the station using open wire line was by himself
> over in the far corner of the operations area.
>
> 73
>
> Roger (K8RI)
>> Tom   W0IVJ
>>
>> On 9/24/2011 11:13 PM, Tom Thompson wrote:
>>> On 9/24/2011 10:07 PM, Jim Brown wrote:
>>>> On 9/24/2011 5:20 PM, Peter Voelpel wrote:
>>>>> But the question concerned that perfectly! balanced open feeder which
>>>>> certainly carries no common mode current.
>>>        From Wikipedia:    In telecommunications
>>> <http://en.wikipedia.org/wiki/Telecommunication>    and professional audio
>>> <http://en.wikipedia.org/wiki/Professional_audio>, a *balanced line* or
>>> *balanced signal pair* is a transmission line
>>> <http://en.wikipedia.org/wiki/Transmission_line>    consisting of two
>>> conductors of the same type, each of which have equal impedances
>>> <http://en.wikipedia.org/wiki/Electrical_impedance>    along their lengths
>>> and equal impedances to ground
>>> <http://en.wikipedia.org/wiki/Ground_%28electricity%29>    and to other
>>> circuits.
>>>
>>> This does not imply that the currents in the wires are equal and
>>> opposite and if they are not, then a common mode current is present.
>>>
>>> Tom   W0IVJ
>>>
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