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need info on how to modify a sirio sy27-4 for 10m

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Old 11-05-2011, 08:28 AM
eacky's Avatar
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Thanks to all for the good info i will resize the elements and not bother with the spacing. I dont think the spacing will make to much of a difference, i'am new to ham radio and the internet. Got my ticket last month n' i've been a sw listener for about 15 years so i think i know a wee bit (not much) but its good to have the internet for info from people who know better thank guys. 73

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Old 11-06-2011, 11:42 AM
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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.

Best regards,

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 12:55 PM.

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Old 11-06-2011, 01:14 PM
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Thanks Robb much apprecitated man, now i know exactley what to do all the best, cheers.

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