[Antennas] Multiple dipole spacing

[Dave Shrader]

I have an air wound balun. You are correct, it is rated for 250 watts
[AM or CW].

One major advantage of the air wound balun is that it does NOT introduce
harmonics into the output due to core-saturation or non-linearity of the
B-H curve under high current or high VSWR conditions. The is because it
has NO magnetic material in the windings to increase the maximum flux
density!  It is air wound and linear.

Now, I also use an MFJ high power toroidal balun for 1KW and a balanced
centerfed antenna. Works fine on 40 and 30 but I have to limit my output
on 75/80 to about 500 watts. This is because above 500 watts I can
'hear' the balun vibrate. 

Wish I had a 1KW rated air wound balun!!

Deacon Dave, W1MCE
Manager, Textron Antenna Range, retired
Program Chief Engineer
____________________________________________

Les Severson wrote:
> 
> Hi Claus,
> Link coupling acts like a transformer with primary and secondary AIR wound coils
> in close proximity.   It very simply transforms the low impedance unbalanced coax
> output of most transmitters to high impedance balanced output to the ladder
> line,  like a balun transformer does, but very possibly more efficient.      I
> think Johnson and NyeViking are the only tuners on the used equipment market
> nowdays that use link coupling but many hams still use this method with their new
> rigs by home brewing their own balanced line tuners or by buying an older Johnson
> or Nye Viking  "Matchbox".
> Claus,  I'm not an RF. engineer.  hi   I just know is that it works great for a
> ladder line or
> twin lead feed to an all band single wire dipole.
> btw,  These old matchboxes generally work fine on the WARC bands by selecting an
> adjacent band on the bandswitch and adjusting the capacitance to match.
> I suppose the reason tuners are not made this way anymore is because it is much
> simpler
> and smaller in size to design a tuner with an unbalanced output and to include a
> 4:1 torroid balun for matching balanced lines.  (I wish some company would make a
> modern link coupled tuner)    Also, most hams want to use unbalanced coax
> to feed their antennas anyway... It's much easier to run into the shack.  hi
> The trouble
> with that is,  now they need a different antenna for each band because with
> unbalanced coax feed you need a resonant length antenna for reasonable swr. (
> unless they use lossy traps) (or some configuration of multiple wires)
> 
> I have seldom used baluns over the past 50 years but when I did,  I liked to use
> an air wound balun such as a Heathkit  B-1 broadband balun box.  (still available
> sometimes on Ebay auctions)   They seem to work fine but a limited to about 200
> watts.       I have to congratulate you though on building your own broadband
> baluns.  Sometimes they work good ... sometimes they don't.   I'm going to
> address this return letter to the antenna group also so you can get the feedback
> on my opinions from more knowledgeable antenna experts...    I'm sure you'll find
> some that disagree with me
> about efficiency and others who will say I'm too much from the "old school"   hi
> 73 & Good luck,   Les W�OJH
> 
> Claus Waldraff wrote:
> 
> > Les Severson schrieb:
> >
> > > line, tuner &
> > > balun for excellent all band results.   I personally  prefer a link coupled
> > > tuner such as
> > > a Johnson matchbox which eliminates the need for a balun.
> >
> > Can you point out that a bit more specific to me ?
> >
> > Why is there no need for a balun ?
> > Sounds appealing to me as I had some bad experience with broad band
> > baluns (home brewed)
> >
> > thanks in advance
> >
> > 73 de Claus
> 
> - - -
> 
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> Larry Wilson KE1HZ antennas-owner@mailman.qth.net
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