8087RE: HFGCS on 11.175 kHz USB
- Feb 9, 2014
To truly ascertain the AM accuracy, and also an indicator of the BFO dependent oscillators in the DX-394, you would be better off using the likes of either a known frequency standard.
Examples of such would be the 10 MHz signal from a known good frequency counter -- where the accuracy is commonly to six to eight decimal points as in 10.00000 MHz, to to a secondary frequency standard such as Rb, where their 10 MHz oscillators are accurate to 12 decimal points as in 10.000000000000 MHz.
As Tom and others will tell you, you can check receiver PLL local (base) oscillator accuracy and sometimes (very rarely) make base PLL adjustment by beating the receiver PLL base against say WWV's 5 / 10 / 15 MHz signals (aka primary atomic standard accurate)...
... but you will have a very hard time hearing how close or far off a BFO oscillator is, more given to the sensitivity of the human ear, etc.
The BFO's in any receiver, PLL or not, drift as well, although such drift is fairly small, in some cases 15 to 30 Hz or more in a well designed BFO, but the human ear has an "excruciatingly" hard time hearing it. And adjusting what one might call the BFO "offset channel and frequencies" really should be done using a frequency counter, etc.
As a side note, if one has access to stable oscillators / counter or wants to try ones hand at checking or adjusting to WWV frequencies, do it after all concerned local hardware, including the DX-394, are warmed up for appropriate time periods.
Joe Rotello / Knoxville, TN / USA
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