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Date: Fri, 6 Dec 2013 15:00:44 -0500 (EST)
List-post: <">>
Hi All, there is one gotcha using the strap or wire and that is where you  
route it through a metallic panel/ chassis etc to get rf from one side of 
the  panel to the other.
The ground return doesn't want to penetrate the panel and can take a  
really circuitous route from one side to the other. The result is added  
inductance. Using a piece of coax eliminates that uncertainty.
Gerald K5GW
In a message dated 12/6/2013 11:40:04 A.M. Pacific Standard Time, writes:

I have  always thought that for lengths much less than a wavelength,
the impedance  looking into a transmission line is dominated by the
impedance of the load  connected to the end of the line. The
characteristic impedance of the  transmission line is pretty much
irrelevant until its length approaches a  fraction of a wavelength.
Thus, for short straps at HF frequencies, the  impedance of the strap,
length of coax, or whatever, doesn't really matter.  I believe this is
consistent with Carl's opinion.

I have heard  audiophiles worry that the "impedance mismatch" of their
50 ohm phono  cables with the 1Kohm input impedance of their preamps
introduces  distortion. As they say, a little knowledge is a  dangerous
Jim W8ZR
Sent from my iPhone

> On  Dec 6, 2013, at 11:54 AM, Jim Thomson <>  wrote:
> Date: Fri, 6 Dec 2013 10:21:59 -0500
> From:  "Carl" <>
> To: "Jim Thomson"  <>, <>
> Subject: Re:  [Amps] PARALLEL CAPS IN OUTPUT
>> ##  For  folks with a PI net, make sure you use a piece of 50 ohm coax
>>  between the load cap and the TR relay.
>> And with shield bonded to  chassis at BOTH ends.   If wire or cu strap is
>> used  instead...then u end up with a huge Z bump.
> **   The coax isnt long enough to act as a transmission line at  
> amps anyway.
> ####  OK, do it ur way.   Use a chunk of bare wire, strap etc..and watch 
> PI net load cap  values change asap.   Ditto with coax...and only 1 end 
of shield  bonded to
> chassis.
> ###  strap, wire, etc is NOT  50 ohms, not even close.  Try it  urself.
>> That alone will put the load cap  at something higher than a 50 ohm
>> point... increasing the peak  V.  On 10m band, the
>> stray L  of a piece of wire instead  of coax  will make the PI  now 
>> as a PI-L....  putting the load cap at a much
>> higher Z point.   same  deal peak V increases.     Now with a wide open 
>>  the ant, coax cable etc, the load cap
>> will weld  shut.
> **  All the coax does is act as a shielded cable  with some value of C.
> At 10M even 1/10 wave of cable is 1.6' so it is  invisible as coax.
> #####  I don’t believe it for a  second.  Of course, I have  tried it 
both ways.
> Replacing  the junk typ used from load cap to TR relay   will solve..and  
> solved all sorts of issues.
> Later.......  Jim   VE7RF
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