Removing DDS generated noise noise from a QRP transceiver
Вставка
- Опубліковано 2 жов 2024
- Adding a DDS VFO to a QRP transceiver can improve frequency stability and provide digital frequency readout. However it can also generate noise that affects reception. Video demonstrates how noise in a Bitx transceiver was found and cured with three added parts.
PS: If you liked this video please consider supporting Amateur Radio VK3YE by:
* Subscribing on UA-cam
* Checking my books page at books.vk3ye.com
* Shopping on Amazon via: amzn.to/3iiDQXv, or
* Shopping on eBay via: ebay.us/i9DuWP
(then if you buy something I'll get a small commission at no cost to you)
a low dropout regulator would be smaller and more effective. holtek parts like HT7533 may work. A C multiplier may help too
Good A/B test proves the DC filter's effect. Might be worth experimenting with a 1mH RFC in place of the resistor.
Thanks Paul - I did try a lower value ferrite but it had no effect. Besides resistors are cheaper and I had the box of them close at hand!
I know this goes back to the before times, but I was wondering if you had considered the customary 0.1uF ceramic caps in parallel with the electros to compensate for the higher frequency stuff
Wow this is a conversation in slomo. I would definitely parallel a 100nF. Not sure why it may have been left off. You cant have too many 100nF caps!@@MidlifeRenaissanceMan
I bought a cheap Chinese DDS VFO and man it has a nasty output. The DDS VFO inputs into and also shares a power supply with a DC receiver. This little filter circuit removed most of the noise. I still hear some hum, but I think that once I've got the receiver in a metal enclosure, most of that will go away. Thanks!
A PI filter in a power supply goes to show There is no school like old school ; )
Excellent video and explanations thanks Peter.
Vk5fkov
Thanks Peter. I was having the noise problem with my CDV. You filter worked great.
Good video 73
you prolly dont give a shit but if you guys are stoned like me during the covid times you can stream all of the new movies on InstaFlixxer. Been watching with my girlfriend lately :)
@Alessandro Wyatt yup, have been watching on instaflixxer for months myself :D
Nice job - the end result is impressive! I love it when you find a simple and effective cure for noise.
Great information for tracking down noise! I added this to my bitx40 and got rid of noise coming in from my switching power supply as well as from the DDS. I did hear the DDS noise coming in over the actual DDS line (not power line) but that was easily remedied with an inline filter capacitor (I used 220uF)
Excellent demonstration of a good engineering practice!
fantastic information!
Good job !
WA8QFE