[Elecraft] Toroid Balun Cores

Mon Oct 17 15:14:13 EDT 2011

I've never seen an HF Yagi with an air core balun at the feed point. Such
baluns for HF were typically a foot or more square! (The only ones I ever
messed with were mounted in the shack to connect a single-ended rig output
to a balanced feed line.)

By the 1980s ferrite baluns were very commonly used almost everywhere, so
I'd put money on your having a ferrite balun on that yagi. 

If the balun was abused, physically, with too much RF heating or by moisture
getting into the housing, it may be damaged. The same is true for traps.

73,

Ron AC7AC

-----Original Message-----
Someone mentioned the baluns on older yagis were air-core.  I have an 
older Hygain TH3mk4 with original balun (big black box connected to 
the hairpin stub and driven element.  The antenna is probably 20-30 
years old, so I wonder if anyone can tell me if it is likely air-core 
or ferrite?  Any advantage in replacing it?

I found that I had to use a tuner after installing it at 50-feet even 
with element lengths adjusted to min SWR per manual.  Now I wonder if 
this may be due to an aged balun?

The used antenna only cost me $75 so not a big investment.  But it 
does seem to "work" DX OK.  I worked T32 on 10m on Saturday with only 
8w SSB from my K3/10.  But eventually I will be running 300w so this 
may matter more.

Note that the tuner is required on all bands 20-15-10m.  10m was the 
hardest and would not tune very well in any position of the driven 
element.  Tuning was done with antenna pointed straight up when at 
ground level with reflector essentially at the ground.  I expected 
some shift in resonance once the tower was raised (all antennas 
installed before raising with a crane).

I suppose this may also point at bad traps (but for $75 it works).

73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ   500 KHz - 10-GHz   www.kl7uw.com
EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
DUBUS Magazine USA Rep dubususa at gmail.com
======================================

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html