View Single Post
Old 6-Jul-2016, 3:32 PM   #104
tripelo
Senior Member
 
Join Date: Jan 2010
Location: Dallas, TX
Posts: 127
Part 3 (continued from previous post)

Attached are Graphs depicting a summary of data analysis.

1. Average received power levels, (Image below):

An average 9 measurements of each channel (8 & 9) for each antenna (ClearStream 5 and Televes Yagi BIII).





2. Average Relative Gain per Channel (image below)

A nine-scan average of both antennas.





3. Average SWR 5 Antennas (image below)

SWR was derived from measured S11 (Return Loss). The curves represent the
smoothed scan averages for each antenna.





For mismatch Loss vs. SWR, see previous post*.

*Received Signal Strength and Data Analysis


No mismatch loss for SWR equal to 1, a SWR of 2 results in a mismatch loss of about 0.5 dB.


========== Comments ====================

The Antennas Direct ClearStream 5 (C5) and Televes Yagi BIII provided nearly the same average signal strength for Channel 8 and 9, with an approximately 0.1 dB advantage for the Televes antenna. Since 0.1 dB is near the measurement accuracy limits of the test configuration, the difference may not be very significant.

The per channel data shows that the Televes antenna provides a higher signal on channel 9 (by about 0.2 dB) relative to the Antennas Direct antenna. This could be a result normally expected of Yagi type antennas, that is the gain increasing with increasing frequencies, up to the design limit.

Test Location and Data Variability

Even though the test site is LOS to the DFW stations, some multipath has been observed at UHF with received signal on some channels. However, effects of multipath have not been explored at VHF frequencies, and there have been no symptoms to suggest it might be prevalent.

Several repeats of each measurement probably helped reduce any effects of brief transitory signal variability. The individual data sets were fairly consistent. Measurements using the Antennas Direct ClearStream 5 at both beginning-of-test and end-of-test somewhat verified data consistency. The Antennas Direct ClearStream 5 final-measurements averages were within a few hundredths of a dB of the signal strength of the beginning-measurements average.



(To be continued)

.
Attached Images
File Type: gif Compare C5 & Televes B-III.gif (5.0 KB, 4178 views)
File Type: gif C5 & BIII per Channel.gif (5.2 KB, 4499 views)
File Type: gif SWR - C5 & Televes BIII.gif (7.6 KB, 4607 views)
tripelo is offline   Reply With Quote