Yodar wrote:
By mounting one on a 8' ground rod in moise soil and adding enough ferrite
beads to choke off common mode noise this antenna does an aceptable, if
not respectable job.
Terry
Terry,
I am working off a vertical with active antenna properties.
Pray tell, where/how are the ferrite beads installed and their vendor and
part no?
yodar
See
http://www.yccc.org/Articles/W1HIS/C...S2006Apr06.pdf .
On page 6 he explains the different mixes.
As a ham, Chuck/W1HIS has to be concerned about the wrong ferrite
getting too hot and bad things, like a fire, happening. For us SWL
types, "bad" ferrite has more loss and can be a good thing. If you read
his pdf he explains the logic of how and why.
I have salvaged nearly 1000 various ferrite beads, or as Will calls
them, sleeves from
PCs, VGA monitors, on the power and video cable, printer cables. I had
access to a
metal salvage/recylcer and was allowed all of the cut off cables a man
could want.
If I wanted to do the job with store bought ferrite I would want to
cover the 100KHz through 30MHz range. I would most likely use mix 31.
In both of the commercial receiving set ups I built I used mix 31. The
trick is to use enough ferrite to give at least 1K Z at the lowest
frequency of interest. This can be accomplished with perhjaps 30 run of
the mill, unkown
sleeves, or 10 to 15 of the mixture 31.
To use them you simply remove the RF connector, slide on the sleeves or
torroids, and reinstall, a use a new, RF connector. You can also cheat
and use John Bryant's
method. See http://www.dxing.info/equipment/coax_leadin_bryant.pdf.
John's method make more sense becuase you can build the chokes and add
them to the
existing coax. If I were doing another commercial install I would in
all likelyhood go with
John's becuase it would be easy to build several chokes and add as many
as you needed.
But as W1HIS says, "hams are the cheapest people around", and I like to
waste my
money on other toys. From a practical point both methods will work
very well. I tend
to like distributing my ferrite beads/sleeves a long the length of the
cable to spread the
induction out. I have found this to be, maybe, more effective in
eleminating Transferr
Impedance. Coax isn't perfect and under the right, or more properly,
wrong condition,
TI can allow out side signals to intrude into the coax. Not all that
common and you
will only notice it after you have reduced all the other RFI to a low
level.
I hope this helps.
Terry