Chitika: Dobbs-George

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Wow, that is one beautiful BITX. Nicely done Colin. But I must say that you are exhibiting an almost inhuman degree of patience! Who needs a case? Fire that thing up and make the traditional "still-on-the-workbench" initial contact.

Hi Guys,

I loved the last SolderSmoke, it was another great episode. It really does amaze me, that a few years ago, hams were saying that it was too difficult to build your own gear that would be anywhere near to the commercial stuff, but here we are with Arduinos etc bringing powerful functionality to the masses. I couldn't have imagined building an SSB rig with a pretty and functional LCD screen when I started in ham radio.

Bill, first regens, now SDRs? Amazing! I exchanged a few words with George Dobbs about your change of heart towards regenerative receivers, he seemed genuinely pleased. :)

Pete, your Si5351 work with the pretty displays is cool, I can see me getting pretty hooked! I have the Si5351 board, Paul M0XPD advised me to buy it. I'd love to build another SSB rig in a smaller box for regular SOTA activating. I must look into the pretty little displays and have a play with the Si5351. I notice that Hans Summers has now put out a cheap Si5351 based kit, handy for us guys in Eu. http://www.hanssummers.com/synth.html

I finished building my BITX board yesterday but wanted to have a sleep before applying power! Today I carefully checked the circuit for errors and found none, phew! I fired the rig up gently, watching the current carefully. I wound up the TX bias to 50mA as stated in the MKARS80 instructions, all went well. I plugged in the mic and spoke - BANG! - Everything went off. Oops - I had used a 500mA fuse for initial safety and forgot to swap it for the bigger one! I fitted a 1.6A fuse and hey presto, all was fine. I was absolutely amazed and to be honest, rather proud of myself. I think the TX is a little bit too hot, my meter is showing about 6W on voice peaks- eek! The rig seems to be perfectly behaved though, no wierd effects seem to be happening. I can just turn the bias down a bit, right?

Anyway, I was happy with my progress so I finished for the day. I still need to investigate and probably tweak the carrier suppression.

I spent a short while talking into a dummy load, using my FT817 to monitor the transmission. My 2yr old son was interested in my voice coming out of the 817'sspeaker!

Thanks for all the guidance and help along the way, I'm elated that I've built a voice rig that works! I've attached a pic of my finished board, I only just squeezed the circuit on, but isn't she pretty? :-)

Can't wait to get the rig built into it's case and score that first QSO.

73, Colin, M1BUU

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

George Dobbs, G3RJV

SolderSmoke Podcast #160:

http://soldersmoke.com/soldersmoke160.mp3

Bob Crane, W8SX, was out at the Four Days in May event and did an excellent series of interviews with the guys who made presentations:

Harold Smith, KE6TI
Many Ways To Homebrew

Chris Testa, KD2BMH
Battery Powered Software Radios:
Having your cake and eating it, too

George Dobbs, G3RJV
The Classic World of the Regenerative Receiver

Gary Breed, K9AY
Why Does My Rig Have a Receive Antenna Jack ?

Craig Behrens, NM4T
The Great Arduino, JT65 and Rebels Caper
High adventure with new radio paradigms

Dave Cripe, NM0S
PoW QRP

-------------------------------------

VIDEOS OF THE PRESENTATIONS ARE HERE:

http://www.ustream.tv/recorded/47599691

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

http://www.mds975.co.uk/Content/trfradios02.html

My feelings about regenerative receivers and their possible connections to the nether-world are well known. But the receiver described on this beautiful British web site is almost enough to make me change my mind. Thanks to Stephen, G7VFY, for alerting me to this (and to so many other great sites!) I also find myself forced to give regens another chance because George Dobbs, G3RJV, was the original source of this design. It comes from a book he wrote in 1972. I love the wooden bread-board construction. Thanks Stephen! Thanks George!

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

I am gathering parts and ideas for a BITX dual bander (20 and 40 meters). I know Farhan used a 10 MHz filter for his "Simple SSB Transceiver." But I was thinking of going a bit higher, to 11 MHz. This would allow me to run the VFO from 3.175 to 3.355 for 20 meters, and 3.695 to 3.875 for 40 meters. I'm hoping that I can do this with one single VFO (Farhan used two VFOs), perhaps with a reed relay switching in some additional capacitance for the other band. I'll also follow Farhan's lead and switch the Low-Pass and Band-Pass filters with DPDT relays.

I set up a simple spread sheet and looked at the VFO harmonics to see if any fell within the desired tuning ranges. That looks OK. I have not looked at mixing products between VFO and BFO. What do you folks think? Would the 11 MHz IF for these bands work? Or are there evil birdies lurking in my future?

I've gone ahead and bought another wood box for the new rig (I didn't even have to suffer through a second visit to the crafts store -- they are available on Amazon). I also got a roll of copper sheeting at Home Depot. This time I will prepare the box first, lining the inside with copper and preparing all the "socketry" (George Dobbs' word) before putting the PC board in.

It's ugly but it gets you there. I finally got the little 30 meter DSB/Direct Conversion transceiver that I built in Rome working on PSK-31 and JT-65. It features a VXO circuit from George Dobbs, an AF amplifier designed by Roger Hayward, and an RF amp chain designed by Peter Parker. It produces about 1 watt of RF. At first I was manually switching the rig from transmit to receive, but this got old real fast, so I built a little VOX circuit -- the AF from the sound card does the switching. Last night I fired it up on PSK-31 and stations were calling me (including one fellow in Cuba). Then I went to JT-65 and had a complete QSO with KT1B. Another this morning with K0ASK. It is kind of fun to combine the simple (this rig) with the complex (the computer and these digi modes). I find that I can work both JT65 and PSK 31 while keeping the VXO at 10.139 MHz.

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

Chitika

Colin Finishes His BITX

SolderSmoke Podcast 160: Special Four Days in May (FDIM) issue

The Ladybird TRF (Regen!) Receiver

11 MHz IF for new BITX 20/40 Dual Bander? Also: Cabinetry and Socketry

DSB Digital Success!

AHMED HASSAN MOHAMMED

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