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Test Results - 4248 vs. JBX21WB

Results Definition:

  • XX-XX = Measured signal strength level

  • 0-XX-XX = Signal locks on briefly but keeps dropping out

  • 0-50 = Signal was detected but not able to lock

  • N/A = No signal detected

Note: Signal level refers to the Dish 6000 indicator which measures the signal quality based on percentage of errors. As long as the indicator stays above 48-50%, the signal will lock. I assume that if you have over 50% errors, the Dish 6000 does not have enough good signal to decode properly. A reading of 100% would indicate no errors in signal. I have found that at 47% I will see pixelation in the picture and below 46% the picture will drop out completely.

Date: 05/13/01

I tested a Blake JBX21. It is a long yagi (100") with 21 director elements. The director and the pick up elements are bowtie shaped. Each leg of the 'Y' shape elements are 7.5". The reflectors are almost half the size as the CM-4248.

I did a several back to back tests with the 4248 and JBX21. The 4248 was the best antenna I tested up to now so I did not compare it to the 4221, 4228, 4251, 8800, or 9095. I tested the antenna with several tilt angles (-20,-10,0,+5,+8,+10,+20). I have already determined that the 4248 works best at +10 degrees so I did not test it again with multiple angles. With the JBX21 tilted to -10 and -20 degrees downward it had a hard time locking local channels. At -20 it could not lock any channels. The best position was between +5 to +10 degrees upward, I settled with +8 degree. The JBX21 comes with a special built in balun/element bracket. So I also tested it with a regular CM balun. The Blake balun provided a slightly stronger signal.


==================================================
ANTENNA= Channel Master 4248
AMP= CM-7775
VERTICAL ANGLE= +10 DEGREE
MT. WILSON, LOS ANGELES, DIST= 15.5 MILES
==================================================
KTLA 31...65-68
KNBC 36...59-61
KCAL 43...N/A
KABC 53...0-50
KCET 59...N/A
KCBS 60...0-42-62
KTTV 65...0-50
KCOP 66...0-50
MT. SOLEDAD, SAN DIEGO, DIST= 113 MILES
KGTV 25...0-40-78
KNSD 40...N/A
KFMB 55...0-49-69
MT. SAN MIGUEL, SAN DIEGO, DIST= 132 MILES
KSWB 19...0-45-62
KPBS 30...N/A
TIJUANA, DIST= 138 MILES
XETV 23...0-42-61


==================================================
ANTENNA= BLAKE JBX21WB
AMP= CM-7775
VERTICAL ANGLE= +8 DEGREE
MT. WILSON, LOS ANGELES, DIST= 15.5 MILES
==================================================
KTLA 31...58-60
KNBC 36...58-62
KCAL 43...N/A
KABC 53...0-50
KCET 59...0-50
KCBS 60...52-55
KTTV 65...54-57
KCOP 66...0-40-60
MT. SOLEDAD, SAN DIEGO, DIST= 113 MILES
KGTV 25...66-72
KNSD 40...0-50
KFMB 55...0-48-53
MT. SAN MIGUEL, SAN DIEGO, DIST= 132 MILES
KSWB 19...83-86
KPBS 30...N/A
TIJUANA, DIST= 138 MILES
XETV 23...65-72

Conclusion:

  • The JBX21 performed better than the CM-4248. It could pick up two more local channels and maintains a better signal lock on the San Diego channels.

 

  


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