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DDS VFO AD9850 + Arduino

Max Morris #19503 Hi all,? I have received the Bit X 40 for Christmas. What a wonderful TRX. Worked first up with great results. VFO is very unstable so I built another DDS VFO using an AD9850 and Arduino. I have built several of these to use in the MST40, MST80 and KNQ7 QRP radios. They all work a treat. However I cannot get one to work with the BIT X. I have the O/P freq at 5MHz at about 300mV. It does not work. When I connect an RF signal generator up, it doesn't start working till about 1.5V of RF is fed into the board. I have removed L4 from the circuit. Any ideas?? Max VK2XAM.
Darryl Harvey All Messages By This Member #19504 开云体育 I had to use a capacitor coupler to use my AD9850 DDS. ?I found different results with the different AD9850 outputs as well (one if filtered, one is not). I think you can also remove C91 from the Bitx40, that may reduce some load on the DDS, Darryl VK3DAZ. toggle quoted message Show quoted text On 29 Dec 2016, at 5:05 pm, Max Morris vk2xam@... [BITX20] <BITX20@...> wrote: Hi all,? I have received the Bit X 40 for Christmas. What a wonderful TRX. Worked first up with great results. VFO is very unstable so I built another DDS VFO using an AD9850 and Arduino. I have built several of these to use in the MST40, MST80 and KNQ7 QRP radios. They all work a treat. However I cannot get one to work with the BIT X. I have the O/P freq at 5MHz at about 300mV. It does not work. When I connect an RF signal generator up, it doesn't start working till about 1.5V of RF is fed into the board. I have removed L4 from the circuit. Any ideas?? Max VK2XAM.
Giuseppe Callipo All Messages By This Member #19505 Hi Max, I made successfull QSO with dds vfo. I add a 9850 based vfo plus a 2 x 2n2222 buffer amplifier to increase dds output signal. I connect the vfo to external input pin of bitx 40, before I removed L4 coil and C91 to avoid to send a lot of signal to ground. Now I have the same sensitivity that original VFO, but absolutely no drift. I Done 6 QSO with good reports. 73 ik8yfw.
ron van doremalen (PA3FAT) All Messages By This Member #19507 开云体育 Bfo/vco needs to be 12mhz-lsb offset 1500hz or what you think is best.? Sent from my iPhone On 29 Dec 2016, at 07:05, Max Morris vk2xam@... [BITX20] <BITX20@...> wrote: toggle quoted message Show quoted text ? Hi all,? I have received the Bit X 40 for Christmas. What a wonderful TRX. Worked first up with great results. VFO is very unstable so I built another DDS VFO using an AD9850 and Arduino. I have built several of these to use in the MST40, MST80 and KNQ7 QRP radios. They all work a treat. However I cannot get one to work with the BIT X. I have the O/P freq at 5MHz at about 300mV. It does not work. When I connect an RF signal generator up, it doesn't start working till about 1.5V of RF is fed into the board. I have removed L4 from the circuit. Any ideas?? Max VK2XAM.
Max Morris #19537 Thank you all for responses. I have set the offset on the VFO. (I used a function generator to calculate the correct frequency). I will try the cap and see what happens. I had thought of a small amp to increase O/P from VFO, but was curious as to why it needed such a high output to get the radio to work.... Non of my other QRP rigs need this. 200-300mV is fine. Not the 1.5V this one needs. toggle quoted message Show quoted text On Thu, Dec 29, 2016 at 7:23 PM, Darryl Harvey darryl@... [BITX20] <BITX20@...> wrote: ? I had to use a capacitor coupler to use my AD9850 DDS.? I found different results with the different AD9850 outputs as well (one if filtered, one is not). I think you can also remove C91 from the Bitx40, that may reduce some load on the DDS, Darryl VK3DAZ. On 29 Dec 2016, at 5:05 pm, Max Morris vk2xam@... [BITX20] <BITX20@...> wrote: Hi all,? I have received the Bit X 40 for Christmas. What a wonderful TRX. Worked first up with great results. VFO is very unstable so I built another DDS VFO using an AD9850 and Arduino. I have built several of these to use in the MST40, MST80 and KNQ7 QRP radios. They all work a treat. However I cannot get one to work with the BIT X. I have the O/P freq at 5MHz at about 300mV. It does not work. When I connect an RF signal generator up, it doesn't start working till about 1.5V of RF is fed into the board. I have removed L4 from the circuit. Any ideas?? Max VK2XAM.
Todd K7TFC All Messages By This Member #19538 On Dec 29, 2016 2:56 PM, "Max Morris vk2xam@... [BITX20]" wrote: >> was curious as to why it needed such a high output to get the radio to work.... Non of my other QRP rigs need this. 200-300mV is fine. Not the 1.5V this one needs.<< If your other rigs use mixers that provide some gain (such as the NE602) you can use lower VFO drive. Diode-ring mixers such as in the BitX need higher levels to turn on the diodes for the commutative mixing action to take place. 73, Todd K7TFC

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