DDS VFO this little useful nasty things has always intrigued me from the start. My tick-toe started when i first met dear friend VU2UPX he gave me a pcb & IC to populate to make dds vfo. I procued the at that time famours AD9851 CHINESE module from banglor priya sloka arya ji. He was a very good gentle-men. he gifted the arduino nano. At that time tried to make one DDS VFO BUT could not due to the software skill-set was not enough. My friend from the EU helped me in my medical as well DDS VFO. He made a shield for me. I tried to test but somehow could not make it. As at that time My computer was old and i did not know how to programe ARDUINO etc.
Time passed on. one fine day our beloved VU2DEV-SK also gave me a DDS VFO. even sasi bhusan of indian homebrewers forum gave a pcb but what i lacked was the ATMEGA328P a programmed IC but no one gave that to me that programmed. So, with time it went to dust.
Then few days back i saw on facebook one of my friend SHUDHINDRA of banglore providing the VFO based on si5351. i liked his short introductory vedio. I needed something which is not power guzzling. gurudevs VFO was boxed well but it required 12v 1Amp power source of its own and did not understand its functions. ordered teh VFO. i chatted with him on whats-up. oHH now i have two working fones. hee hee. Then deposited money & he sent me via INDIA POST. it arrived.
You can see its un-boxing vedio click here. I should appreciate his working skills are very good, nice packaging, boards are sweet may be specially custom made. I do not know from where this VFO+BFO is used. but anyway it is useful one.
After unboxing it i tested it for VFO sections. I had made a superhet receiver board with 10 Mhz IF. it utilized teh xtals. i could not get on air signals with it there is some loss or gain mismatch. hard to probe it. I used it for testing the transmitters signals. I connected that receiver and this new VFO section. i did not connect wire for 10 mhz OSC of si531. The vedio of test is here. I find the DDS VFO very stable and well marked. the display is good. hardware part nothing to tinker for we end user. he has done it carefully.
He has done everything. Software the arduino board has usb port so you can update if you have skills or simply replace it with y our own arduino. interesting. powered on and it started pumping the RF put to the diode mixer and it received my local Tx signal on 3686kc cw tx. interesting. single side reception is possible with superhet. It use the push button within rotary encoder for changing the resolution of 1 hz, 10 hz, 100 hz, 1k hz, 10 khz, 100 khz, 1 mhz in incremental step. With rotary you can increase or decrease the freq in step.
Everything was smooth but i am here to find the faults. lets find first fault. This push-button is with rotary encoder, so its very tiring to push and sometimes i miss it as i have not pressed hard. menu also opens up with this. So, this is software fault. One thing i noticed that push button increase the
freq STEP resolutions it does not decrease the resolution steps say from 10 khz you can
goto 100 khz step but can not goto 1 khz step. This is very annoying for rapidly
changing the frequency. this is software flow. i need to ask him is it intentional where this ckt is originally used may be that will be the case. up-down switch is highly recommend.
Second thing i find
very very annoying is that in this beautiful device there is no provision for
the BFO RIT. receiving side we need RIT. there must be a provision for changing BFO frequency, because our homebrew rigs xtals are not perfectly aligned and that is
detrimental to receiving and transmitting on same frequency. If one pot is fixed for this that will be a nice thing.
So, this are two flows and it related to the SOFTWARE. it can be changed and i also humbly suggested. May be he will come up with solutions to my questions one day. But over-all it is WORTH HAVING THIS DDS VFO.
i recommend to procure this DDS VFO
from him.
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