11-06-2011, 12:42 PM
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Join Date: Dec 2008
Location: Silicon Valley CA, Storm Lake IA
Sent to me from Sirio/Italy:
Dear Mr. Xxxxxx:
SY 27-4 is not a tunable antenna and SIRIO ANTENNE doesn't effect
substitutions and doesn't guarantee the correct working of altered products.
However, if you really want to try to change the work freq. of the antenna,
I can give you a method.
To work at 27.555MHz you must to RESCALE all lengths using this formula:
Final_length = (27.2 / 27.555) x Initial_length = 0.9871 x Initial_length
REFLECTOR : New length = 0.9871 x 5740 = 5666 mm
DRIVEN: New length = 0.9871 x 5400 = 5330 mm
1 DIRECTOR: New length = 0.9871 x 5130 = 5064mm
2 DIRECTOR: New length = 0.9871 x 4890 = 4827 mm
Initially, I suggest to not rescale spacing between elements (only for
possible problems) and verify the correct electrical working.
After the rescale you must to tune the antenna moving the gamma-match and
using a ros-meter (I can't help you now; the new position is not prevedible)
If the antenna doesn't work well; then you can also try to rescale the spacing
between elements (using the same formula above)
Reflector-driven: New length = 0.9871 x 1570 = 1550 mm
Driven-1 director: New length = 0.9871 x 1020 = 1007 mm
Director 1 - director 2: New length = 0.9871 x 1410 = 1392 mm
Then re-tune the antenna by moving the gamma-match.
I remark that this is only a theoretical method and we don't guarantee the
correct working of antenna.
Ing. Mezzadrelli Lorenzo
BASE: Kenwood TS-2000, GAP Titan DX, Diamond X50A, Sirio SY27-4, and IMAX 2000.
MOBILE: Galaxy DX99V w/RF Limited CR-577 mic, Sirio Z-180. Yaesu FT-8800R & Diamond NR-770.
Last edited by Robb; 11-06-2011 at 01:55 PM.