Sirio SY-3 or SY27-3

[Alabama Buckeye]

Manuals (PDF file) for the SY-3 and SY27-3 are very similar but may lead to a measure of confusion. I've posted this as it may be of value. One or the other may be the "upgrade".

05.22.22 SY-3 Tuning Specifications

Freq. MHz	[A] Reflector		[B] Driven		[C] Director		L1	L2
27.0	806		535		474		952	518 +/-5
Difference	53/		48/		47/		38/
27.200	785[30.9"]7/8		516[20.3"]5/16		455[17.9"]7/8		937[36.9"]7/8	518 [20.39"]3/8
27.250	779.5		511		450		933
27.5	753		487		427		914	519 +/-5
Element Comparison
Source	Reflector		Driven		Director		Spacing
waoooo.com rfwireless-world.com mapleleaf.com Sirio SY-3 [1-3] AVG	18' 6" 17' 10.8" 18' 5.04" 19' 2.88" 18' 3.24"	.5 .9 .42 .24 .27	17' 5" 17' 1.44" 17' 4.68" 18' 4.32" 17' 3.72"	.42 .12 .39 .36 .31	16' 7" 15' 10.8" 16' 4.32" 18' 1.92" 16' 1.36"	.58 .9 .36 .16 .28	4' 5" 4' 6 1/4" 7' 1/2" 4.7/4.07

Reflector Tuning Section length of 806mm (31.73"), as indicated above for 27.000mHz, is longer than the actual measured length of 800mm (31.496"); which does not include the 72mm length of the Tuning section inserted into mid section S2; when combined the full length of the Tuning section is 34". Which can also be said for the 535mm and 474mm lengths within the table, also for 27.000mHz for Driven and Director elements. Hence, element lengths in table include the 72mm insertion portions, which were not included in the following measurements:
Sirio SY-3
Element Measurements
S3 108cm
S2 105cm
S1:
Reflector 80cm (31.496")
Driven 52.4cm (20.63") Questionable. Measure again.
Director 46.2cm (18.19")
Center Boom Connector 15cm width.
5700 or 18.7', maximum Reflector Element length.
5,148mm, 16.89', maximum Driven Element length . Questionable. Measure again.
5,024 maximum, 16.48', Director Element length.,
Therefore, derived Tuning section lengths for 27.200mHz elements in table above must include that 72mm portions, not included in measurements, otherwise.

Three online 3 Element Yagi Antenna Calculators used to arrive at [(1-3) AVG] element lengths. Sirio indicates all elements considerably longer, for 26.500mHz. There is similarity with element spacing, with mapleleaf.com, the exception. Sirio's specificity in element spacing is apparent in boom sections, with near 7" greater distance between reflector and driven elements.

Calculating element tuning section length begins with known tuning lengths for known frequencies, specifically 27.000 and 27.500mHz and establishing the target frequency 27.200mHz. The frequency difference of 50kHz is multiplied by 40% to obtain the desired target of 20kHz. Subsequent 40% and known values for each element tuning segments and the differences between the associated frequency lengths; indicated in the previous table in green, and 40% of the difference is subtracted from the larger value. The control is 27.250mHz, 50%.