SolderSmoke Podcast #241 is available
Audio (podcast): http://soldersmoke.com/soldersmoke241.mp3
Video (YouTube): (215) SolderSmoke Podcast #241 October 28, 2022 - YouTube
Introduction:
Back on Mars. Opposition
approaching. I have a Mars filter. And (like T.O.M.) a Mars
globe.
N2CQR DXCC done
SolderSmoke in the WayBack
Machine
Sticker news
PARTS CANDY -- Don't Scrimp with a Crimp!
Bill's Bench
School DC RX projects -- in
Hyderabad and Northern Virginia.
Direct Conversion Receivers --
Keeping it Simple, Learning a Lot. A step beyond the Michigan Mighty Mite.
Do we really need 100db? Do we really need to shield VFOs? Farhan's
super-simple and stable Colpitts PTO. Audio amps, 1000-8 transformers and
rolling your own LM386
PTOs and Glue Stick PTOs.
Paul Clark WA1MAC. Brass vs. Steel bolts. #20 thread vs. #28
thread. Backlash Blues. The best Glue Sticks.
2 meters and the VWS.
Bill has a Baofeng.
SHAMELESS COMMERCE:
MOSTLY DIY RF
Pete's Bench
20th Anniversary of the
BITX20 Pete's early BITX rigs.
Computer Woes
The Multus Proficio SDR rig
Simple SSB in China
BA7LNN
Things of beauty: Tempo
One, NCX-3 and a SBE-33
MAILBAG
-- NS7V is listening.
-- Graham G3MFJ
sent SPRAT on a stick.
-- Nick
M0NTV FB Glue Stick and 17 Shelf videos.
-- Dino KL0S
HP8640 Junior
-- Mark AA7TA Read the SolderSmoke Book
-- Steve EI5DD Connaught
(Ireland) Regional News
-- Dave
K8WPE Planting the seeds of ham radio
interest
-- Peter VK3YE
Ruler idea on PTO frequency readout
-- Michael AG5VG Glue
Stick PTO
-- Tobias A polymath with UK and Italy
connections. And cool tattoos.
-- Alain
F4EIT French DC receiver
-- Michael
S. was in USMC, working on PCM/TDM gear
-- Alan Yates
writes up Amazon transformer problem
-- Todd VE7BPO, Dale W4OP, Wes W7ZOI
-- Farhan VU2ESE
sent me an sBITX
-- Todd K7TFC The Revenge of Analog
-- Jim Olds Building QRP HB gear
Posts
Every cellphone has several direct conversion receivers built in. LTE/5G, WIFi and Bluetooth all use Direct conversion transmitters and receivers, so they're all over the place.
ReplyDeleteAgreed. Thanks for commenting DaveB. Respectfully, some listeners might infer that the direct conversion receiver is a 'downgrade'
ReplyDeletefrom superhet architecture --- I think it actually might be the opposite in the modern era.
I prefer the term direction conversion architecture as DC radio = more than 1 thing or concept --- you may build a simple receiver that lacks any image-reject topologies --- however, once you decide to generate and then process the output in-phase (I) and quadrature-phase (Q) signals, then the world becomes your oyster. You might process them using audio techniques including phasing and the Weaver method. However, you might also run the signals into an ADC and then process them digitally with software. All this and more are part of the direct conversion toolkit.
We may employ these techniques in both transmitters and receivers to up- and down-convert the RF carrier frequency and base band signals in quadrature -- or not.
My complex, high grade phasing DC receivers sound incredible as I process the base band audio with low noise, low distortion,"HiFi" AF stages with filters, tone controls and a well-designed PA stage. With home brew mixers, that about $15.00 in parts. In my astronomy receivers, I employ DC with image-reject topologies and avoid the birdies and problems associated with superhets which contain 2 or more additional oscillators depending on the receive frequency.
Modern cell phones employ digital I/Q modulation and demodulation ( now the whole transceiver is on 1 chip ) When transmitting voice or data from the smartphone to a carrier, the RF up-converts the modem’s base band signal to a high GHz cellular frequencies to send data up and down the network whether cellular ore WiFi or…...
When receiving, signals get down-converted by beating with the RF to base band frequencies for modem processing. Chips like the Exynos RF 5500 in my current Smart phone have 14 receiver paths for download, and supports 4×4 MIMO (Multiple-Input, Multiple-Output) and higher-order 256 QAM (Quadrature Amplitude Modulation) scheme to maximize the data transfer rates over the networks including 5G.
A challenge for all --- please consider building a DC architecture phasing receiver and compare it to your superhet! You may enjoy the experience.
Best to all!
Thanks to David and Vasily (!) for the comments. But I have a question: With HF radios we see a trend AWAY from the use of dual Direct Conversion radios (I and Q) and TOWARD the use of Direct Sampling (a fast ADC at the front end). This is what happens in an Icom 7300, for example. Won't we see a similar trend in cell phones? 73 Bill
ReplyDeleteHello Bill - I enjoyed the latest Solder Smoke podcast/video, and in particular, was interested in your efforts toward a 'discrete LM386'. I have an 8-transistor design that is just about as simple as can be to provide anything like the performance to an LM386 IC. As you know there is a lot of advantage of having so many components on one IC die, and the 386 is a decent chip for what it does and its intended use. Of course, now we have so many good Class-D audio amp IC's around to play with as well that are very efficient and do not even require a heat sink in many cases. Unfortunately, I do not currently have a home lab to build my design as I am 'between digs' as they say, but I would be glad to share the design (done in LTSPICE) if someone would like to build one up and test it. Please let me know and I can send the spice file or a screen cap of the schematic, along with some design notes.
ReplyDeleteThanks Tee -- Yes, please sent the LTSpice files and screen captures of the schematic to soldersmoke@yahoo.com 73 Bill
Delete