Topband: pennant, flag receiving antennas for 160m. and 80m: input transformer data.

Doug Waller
Thu, 10 Oct 2002 17:58:51 -0400

> FT114-F core:
> enameled wire diameter 0.80 (millimeters, metrical)
> primary number of turns: 5
> secondary n. of turns:   20
> at  1.830 MHz     R=51 Ohm      Ros= 1,3
> at  3.800 MHz     R=51 Ohm      Ros= 1,8
> at  7.000 MHz     R=62 Ohm      Ros= 2,9
> I believe it is a reasonably good result to cover both 80 and 160 meters.
> Best 73.                                                  Sergio, IK4AUY

OK, I am convinced to try replacing my FT140-43 core with some of the
smaller and higher permeability cores, as a test.  Ordered some FT114-77.
But the following still needs to be taken into consideration.

Higher permeability cores saturate quicker with presence of strong local
signals.  ( local 1.710 AM BC station is 80 dB over).

These cores are more prone to being permanently damaged by magnetic spikes.
( this is the lightning strike capitol of the world).

SWR's somewhat higher than normally tolerated for transmitting systems, are
of little concern where antenna gains begin at -30 dBi, and preamps are a

However, it makes sense to remove all losses possible, and the requirement
of less turns of wire is good for antenna function, as well the winder.

Will smaller diameter cores increase capacitance between the two windings &
therefore increase the common mode intrusion?  The answer is probably
irrelevant if one is using the ON4UN "Python Choke".  I call it that because
at a claimed 3Kohm of choking impedance @ 1.8mHz, very little gets into my
coax.  It is this FT150A-F / 7-T. mini coax choke that brought my Flag to

My thanks also to all contributing information.

73, Doug / NX4D, nr Orlando, Fla