[Elecraft] 4:1 balun

[Jim Dunstan]

At 03:03 PM 12/9/2011 -0800, you wrote:
>In the 1960's one very popular and cheap H.F. antenna was the folded dipole.
>Often they were made from the ubiquitous 300 ohm "twin lead" used on TV
>antennas and fed with the same twin lead since the impedance of a folded
>dipole is close to 300 ohms. The first time I saw 4:1 baluns being sold to
>Hams was to make it easy to connect the 300 ohm feeder to such a folded
>dipole to the output of a rig designed to feed 50 ohms.
>
>As Hams migrated away from rigs with tunable output networks to rigs with
>fixed tuned outputs, MFJ and others produced a line of antenna tuners
>specifically designed to correct feed line mismatches since that could no
>longer be done at the rig. They included the popular 4:1 balun for those who
>were feeding various open wire lines (typically 300 to 600 ohms but which
>may have significant SWR - so the impedance might vary much more).
>
>It seems that many Hams considered the 4:1 ratio some sort of magic number,
>when all it was intended to do was provide a good transfer between 300 ohms
>and 50 ohms.
>
>
>Ron AC7AC

Hi

Back in late 50's early 60's I bought my first balun from Heathkit ... made 
from special Bifiler wound
Airdux coils which could be connected in either 1:1 or 4:1 
configuration.  I still have that balun in its
5"x9"x9" aluminium case.  I used it with my first Xmiter which was 
homebrew, 300 watts, and
plate modulated AM.

I used a folded dipole made of 300 ohm twinlead fed by the same twinlead 
and the balun in a 4:1
configuration.  The dipole was strung between 70ft towers.  It was a 
wonderful setup at a wonderful
time (from a propagation point of view).  The ZL's and VK's were like 
locals!  es we used to chat
about the best way to grow tomatoes hihi

These days I still use a balanced feed system with either 300 or 450 ohm 
feed line ... but with
fixed impedance output xmiters and vy much lower power.  I no longer use 
fixed resonant
folded dipoles ... but a nonresonant dipole that is useable on multiple 
bands with a matching
unit at the shack.  The matching unit I use is a link coupled L network .. 
often referred to as
a "Z-match".

The system seems to be vy efficient as I have no problem working the world 
with 20 watts.  SSB
for local contacts and nets and CW/PSK for DX.  No problems with RFI 
!!  Back in the day .. my 300
watt AM xmiter was a TV killer .... but then no one in out neighborhood 
watched TV during the day
(week-ends excluded) and the (1 station) shut down at midnight.  I just had 
to stay up late and/or
skip school hi hi.

Jim, VE3CI






>-----Original Message-----
>
>I can attest to what Vic says. I have an 88-foot long doublet, hung about 45
>feet up, fed with 85 feet of 600-ohm ladder line. At the shack end I have a
>1:1 balun, and then about six feet of RG/8X running to the K3. The K3's
>tuner likes the combination. I tried replacing the 1:1 balun with a 4:1 from
>the same manufacturer. The K3 was quite unhappy with the change in
>components. The 4:1 went back on the shelf, the 1:1 went back inline. YMMV
>
>Jim / W6JHB