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Drake 2-B Receiver Dynamic Range & S/N Test Results




 
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Author Topic: Drake 2-B Receiver Dynamic Range & S/N Test Results  (Read 13105 times)
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W1VD
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« on: October 23, 2008, 11:39:35 AM »

Receiver: Drake 2-B

Band    MDSBlocking DR   Two-tone DR
  (20 kHz)  (20 kHz)
80 meters   -139 dBm        117 dB    83 dB
40 meters   -140 dBm        118 dB    84 dB
20 meters   -138 dBm        118 dB    87 dB

AM audio S/N: 35 dB

For comparison, measurements on other boat anchor receivers can be found at

http://www.w1vd.com/BAreceivertest.html

Guess it's not surprising that the 2-B tested on par with the 2-A + 2-AQ. The 2-Bs built in 500 Hz position and passband tuning is certainly a welcome improvement. Unfortunately, the widest bandwidth position is only 3.6 kHz as compared to 4.8 kHz for the 2-A. 

While measuring the AM audio S/N I happened to flip on the noise limiter. The limiter is not adjustable - it is simply on or off. This reduced the no modulation background noise about 14 dB and the 30% modulated signal about 1 dB improving the overall S/N to 48 dB...not that one would want to run the noise limiter to improve the S/N at the expense of increased distortion. I only mention this observation since there may be an easy way to improve the AM detector S/N...if someone had the time and interest.

           
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'Tnx Fer the Dope OM'.
N4DJ
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« Reply #1 on: January 17, 2010, 09:20:24 AM »

I just wanted to note that my Drake 2B (I got it new in December 1963) has a 4.8 kHz position. In June of 1969, Drake repaired and realigned my 2B.
Apparently I was too hard on the slide switches and switched the passband from .5 to 3.6 too many times in the first 5 years! They replaced the detector switch,"BFL switches" and the audio pot. They also said the Pass band tuner was defective (I think just the switch part). They replaced the complete pass band tuner with an R4B pass band. In those years I worked a lot of AM on 20 meters with a Viking Ranger II and my 2B.  The new passband was a major improvement on AM. It was also slightly better on CW with the .4 vs .5 position.
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