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Re: #bitx40help BITX40 LSB Winlink #bitx40help

 

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¡°It¡¯s a competent enough device assuming the circuit around it is correct.¡±? Therein lies the rub.? The IRF510 requires more attentive circuitry around it to offset Miller capacitance effect than a nicely designed RF transistor like the RD15VHF1¡­ So some of that ¡°noise¡± may be backed up by theory.

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From: [email protected] [mailto:[email protected]] On Behalf Of ajparent1/KB1GMX
Sent: Friday, August 17, 2018 8:56 PM
To: [email protected]
Subject: Re: [BITX20] #bitx40help BITX40 LSB Winlink

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First the code (Arduino sketch)had to be changes to set the 5351 to the needed range for 20M.
That is both the LO and the BFO as needed.? You will need the 40M sketch to do that.

The 40M band pass filter gets changed to 20M, Look for the schematic of the older bitx20
series for values.

Then the 40M low pass filter needs to be changed.

Ignore any noise about changing the IRF510s.? I have run those to over 70mhz at?
high power (20W at 13.8V).? ?Its a competent enough device assuming the circuit
around it is correct.

>>The magic is in the ladder/BFO combination, which shears off the carrier and unwanted sideband, while passing the wanted sideband.??

Only half true.? The balanced modulator is to remove the carrier, the filter passes the desired
sideband (strips the other).

Allison


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