Hi again. Today I could install my Sirio Vector 4000 on top of my house. It is about 12 feet above the house. House is 10 feet tall.
When adjusting on the back I did it on a 10 feet tall pipe with my MFJ Analizer. Here are the readings with 14 feet of RG-8x cable with a velocity factor of 82 according with specs. Using that info. and the formula to cut cables to a 1/2 wave, it gave me 14 feet.
Here are the numbers:
SWR ——- Frequency —R———-X
2.0 ———27,635 ———24 ———1
1.5 ———27,375 ———31 ———0
1.1 ———26,985 ———45 ———5
1.5 ———26,705 ———47 ———1
2.0 ———26,495 ———38 ———29
Bandwidth: 1,140 KHz
This bandwidth a little bit tighter than the 1,400KHz Sirio specs specifiy.
Here are the measurements:
L1= 36 5/8”. L2 = 25.0”. L3= My bad, I didn’t measure it, I had to make little adjustments from the factory recommendations, but I did measure the whole length of the radiating element , which is 25’, 8” .
Here comes the interesting part. When I took this antenna up to the roof ( flat concrete roof ), I took measurements again with the analizer, and bandwidth changed.
SWR——— Frequency———— R——-X
2.0————-28,335——————41——32
1.5————-27,850——————37——40
1.1————-26,583——————48——-0
1.5————-26,923——————31——-5
2.0————-26,460——————27——-12
Bandwidth: 1,875 KHz
By the way, I had to adjust L2 ( Gamma Match ) from what is recommended in the manual to 24.25” to drop the SWR to an acceptable 1.2. For some reason, when installing it above the house, things changed.
But, when measuring with the station SWR meter, readings are different, probably because it is measuring readings of the components between antenna and SWR meter, things like amplifier, antenna tuner and RCS-4 Ameritron Remote Antenna Switch . Bandwidth Goes up dramatically. Here are the readings with the station SWR meter.
SWR————Frequency
2.0—————-28,545
1.5—————-28,285
1.15—————26,975
1.5—————-26,195
2.0—————-25,775
Bandwidth = 2,770 KHz
Since I have a big difference in bandwidth, will this difference from the 1,400KHz affect the performance of the antenna?
