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Topband: Pennant XFMR help

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Subject: Topband: Pennant XFMR help
From: (Luis Mansutti IV3PRK)
Date: Sat, 28 Sep 2002 23:42:20 +0200
Hi Earl and friends on the Reflector,

at last I could get some time to do some antenna works again and I began =
putting up the first couple of two groups of pennants switchable in a =
broadside configuration.
They are already working as expected: very quiet, with 15/20 dB of F/B =
ratio on 160 meters and much better on the BC band; sure their =
performance could improve after solving the transformer problem.
I bought some FT140-43 toroids from CWS (ex Amidon) and wound the =
transformers as indicated: Nr. 34 turns of #26 wire on the antenna side =
and nr. 8 turns for a 50 ohm feedline. They are housed in a PVC box =
containing 3 relays for switching both terminals of each group of four =
point-fed pennants. =20
For a bench test of the transformer I connected an 880 ohm resistor as a =
load and got these results on the CIA-HF Analyzer by AEA, (confirmed =
exactly on the RF-1 Analyst by Autek Research):
Fc. 1.830 Mhz    R =3D 65    X =3D 107    Z =3D 125    SWR =3D 5,44
I supposed the sense of the secondary winding could have been wrong and =
so I wound a second FT 140-43 with the same turns and just with a =
reversed winding; the results were still:
Fc 1.830 Mhz    R =3D 67    X =3D 110    Z =3D 128    SWR =3D 5.50
I played something with the number of turns but I have been unable to =
get close to the desired value, with the SWR never below the mark 4.

Then I tried the same kind of separate windings on other stuff I got =
here and suitable for such an application:

FT 114-77 - 22/5 turns - same load 880 ohm
Fc 1.830 MHz    R =3D 53    X =3D 28    Z =3D  60    SWR =3D 1,71

FT 50-43 -  28/7 turns - same load 880 ohm
Fc 1.830 MHz    R =3D 62    X =3D 30    Z =3D  69    SWR =3D 1,78
At this point I could get to the desired 50 ohm match with these =
toroids, but I should prefer the bigger ones, were the windings are well =
What's wrong ?=20
Could it have been a mistake with the material at CWS even if they =
labelled and invoiced "F-140-43 Ferrite toroidal core" at 3.75 unit =
price ?

Any help is welcome.
Best 73 to everyone, and hope conditions will improve this season!


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