Fw: Re: [Antennas] More Ladder Lines and Beams

[Don Havlicek]

Comments inserted:

Sandy and Kees Talen wrote:
> 
> Again, helpful info, Don. I had no idea that toroid balun losses were
> as low as 2%. Re your note........
> 
> >I still wonder why you would rather deal with all the problems of:
> >1. interaction with surrounding objects
> >2. impedance bumps/changes with variations in line and 'wind sway'
> >3. matching to the antenna
> >4. loss of antenna discrimination by having the feedline 'part of the
> >antenna'.
> 
> .......long run (250ft) to the antenna, can't afford or dig the trench
> for
> hardline, it's a little less power loss when running QRP, it's different
> from the coax most people use, readily lays the groundwork for more
> experimentation, more of a challenge, and I don't want to use a linear.
> Like my Radio Homepage says: "If I just wanted to talk, I'd use a cell
> phone".
Why do you feel you have to 'dig a trench' ?  I bury my coax with a
device that I built that I pull behind my garden tractor .. it has a
flat bed upon which I mount the coil of coax, and has a 'knife-blade'
[made of a triangular piece of 1/8" aluminum panel stock] under it which
cuts a swath in the turf .. it also has short lengths of aluminum tubing
[various diameters from 3/8" up to 1.5"} projecting underneath the 'bed'
which guide the coax, radial wire, etc... down into the 'slot'.  I can
'bury' 200' of coax in about ten minutes, just driving the tractor from
the shack to the antenna [or vice-versa].

> 
> >You COULD use a T-Match or Delta-Match, both of which would require you
> >to eliminate the open feed point at the boom, grounding the driven
> >element there.  The Delta-Match would pair up with your open-wire line
> >better than the T-Match.  Read the info in any antenna handbook about
> >those two matches.  [I use T-Matches, adjusted for about 200 ohms, and
> >matched to 50-ohm coax]
> 
> .......Worth looking into.
> 
> >That 'choke' is a BALUN [of sorts].
> 
> ....yep
> 
> >Depends on how you're feeding the driven element!  IF the connection is
> >directly to the driven element .. NO .. if through a balun, then the
> .GROUND [common] of the Balun is connected to the boom of the antenna
> >VERY close to the feedpoint. [some people do NOT do this, but simply run
> >the coax down to the shack - you'll have to ask them why!]
> 
> ....I agree with that.
> 
> >In my experience, the loss in the baluns I have built [some from Press -
> >the Wireman's - kits] runs in the neighborhood of 2% or LESS.
> 
> ......good information. I've never seen any real measured data, thanks.
> 
> >Why three cores?  The impedance transformation is NOT dependant
> >on the number of cores, but on the number[s] of TURNS in the BALUN!
> 
> ....yes, I realize normal impedance transformation is a result of turns
> and
> the number of cores has nothing to do with it. In fact, an UNbalanced
> to UNbalanced impedance transformer is easy on one core. However,
> draw up a 9:1 unbalanced to balanced bifilar/trifilar/whatever balun on
> one core. Required three cores to work for me

Let's see if I can type something which might be descriptive:

c---- A 
c  
c    winding #1
c
c---- B
c---- C
c
c    winding #2
c
c---- D
c---- E
c
c    winding #3
c
c---- F 

Connect B to C, D to E ... 50-ohm coax to F, shield/ground to D/E ..
450-ohm balanced line to A and F.
Voila!
Don - N8DE

> 
> >Any GOOD core material that will NOT saturate under use will do.
> 
> .....that's the key, never saturate the core.
> 
> 73s  Kees K5BCQ