[Elecraft] open wire feeders

[ab2tc]

Hi,

Wow, gorgeously constructed tuner by WZ5Q. I wish I had one. But is the
center tap of the secondary really connected to the coax input ground as
indicated in the schematic?

AB2TC - Knut


Bill K9YEQ wrote
> 
> Ron,  
> 
> Thank you for the references.  I found the information very interesting to
> say the least.  Parts here would be an issue, but the construction and
> methods to check and adjust the tuner were most valuable.  Now just to
> have
> some drawer space!  As Don had mentioned in an earlier post, getting the
> balanced feed line to the shack can be quite a challenge, especially for
> those of us who have rebar enforce concrete with no simple method to feed
> through the wall.  I think even the double coax systems to be a difficulty
> especially when having to drill into the side of the house and miss all
> the
> surrounding materials, esp. the rebar.  This may not be my last shack so I
> have filed the project and will see what I can find for parts now before
> this stuff gets extinct.  That copper tubing is really becoming scarce and
> I
> am not even sure how much  copper really  is in the tubing and what impact
> it has on the coils if not of the same purity.
> 
> I did locate some surplus Comet vacuum capacitors in the $800+ range??!!! 
> 
> 73,
> Bill
> K9YEQ
> 
> 
> -----Original Message-----
> From: elecraft-bounces at .qth
> [mailto:elecraft-bounces at .qth] On Behalf Of Ron D'Eau Claire
> 
> 
> I have often had a voltage loop at the rig end of my open wire feed line
> and
> have never experienced a problem with stray RF, even though a neon bulb
> lying near the ATU blinked as I sent CW. 
> 
> HOWEVER - I do use a homebrew link-coupled ATU with open wire line. It
> lacks
> the dual-differential tuning capacitors that Johnson used to adjust
> virtual
> coil taps for the feed line in the Matchbox, but mine has a much wider
> matching range using actual taps on the coil. (The Johnson Matchbox is
> only
> rated to match balanced lines with impedances up to 1200 ohms).  
> 
> Link coupling has a number of advantages including a high order of
> suppression of stray signals since there is no direct electrical
> connection
> between the antenna and the rig. Everything coming in (or going out) has
> to
> pass magnetically across the link coupling and through the tuned circuit.
> That's especially handy if you live near a broadcast station. 
> 
> And of course, you can use the same tuner with unbalanced lines (e.g.
> coax).
> Just connect the shield to the center of the coil and tap the center
> conductor out to either side.
> 
> WZ5Q has a great example of a beautifully link coupled tuner at:
> 
> http://www.wz5q.net/index/shack_data/tuna.htm
> 
> It's bigger and neater than mine but the circuit is the same right down to
> the RF current sensors. 
> 
> Ron AC7AC
> <snip>
> 


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