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4 hours ago
Thursday, November 8, 2012
8 Transistors = 40M DSB XCVR (on an Australian Beach)
Another brilliant rig from DSB guru Peter Parker, VK3YE. I really liked this one.
I loved his drawing of the circuit diagram -- right there on the beach! Lots to be learned from this video. Thanks Peter!
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One omission: Rx path: Ant -> LPF -> Relay -> ?? - > Bal.Mod ...
ReplyDelete73 de ZL2DEX
Yeah, he did leave that out. Presumably if you're using a PTT Mic, the PTT switch keys a Relay (DPDT). One side of the relay switches 12V RX/TX - 12vTX to MIC, TX Amp, TX PA, and 12vRX to RX AMP. Unkeyed is 'RX'. Other relay side switches ANT. OSC/Buffer is powered always.
ReplyDeleteThis is a fascinating video. I think I've found an experimenting project. Hours of good soldersmoke.
Mike Yancey, KM5Z
Dallas, Texas
I think Peter has come up with a DSB Pixie here!
ReplyDeleteI would love to see a PCB for it. I am not too confident with ugly construction, so a PCB would be really handy.
Stephen Walters
G7VFY
I'm just searching 'round and I can't find a 7.200 Mhz resonator.
ReplyDeleteMike Y
KM5Z
Great video/channel from down under. Pete's a real enthusiast.
ReplyDelete73,
David, KE0AZ
(FoSS - Fan of SolderSmoke)
This comment has been removed by the author.
ReplyDeletePeter is an absolute trooper. Did you see how he soldiered on when he needed to swat a fly at 26:38. Hardly missed a beat. What dedication! I also liked the "2N2-triple-two transista". ;-).
ReplyDeletePeter explained the connection of the receive side of the antenna relay during the circuit re-hash at 23:57. The RF portion of the T/R relay switches the LPF from the TX output transistor to the secondary of the diode ring matching transformer through a 0.1 uF cap.. The input to the TX low-level amp. (2N2222) is not switched.
Great stuff, Peter, keep it coming.
73.......Steve Smith WB6TNL
"Snort Rosin"
This comment has been removed by the author.
ReplyDeleteHello Stephen,
ReplyDeleteYou should give it a go. I believe that Bill would agree, building over a copper ground plane reduces noise, increases stability and allows for easy modifications and repairs.
Peter's design could be built on a single, double-sided sheet of copper-clad board with the VXO, balanced modulator, mic. amp. and receive audio amp. on one side and the transmitter amplifier chain on the other making it quite compact.
I'm certain there are plenty of hams out there who prefer phone operation and would like to construct a simple QRP rig. IMO, this is that radio.
73.......Steve Smith WB6TNL
"Snort Rosin"
could someone please help me.
ReplyDeletepeter refers to the modulator coil as a 4t 10t bifilar toroid but does that mean the two wires are twisted but only enough in the cnter to give the 4t and the rest either side on a round toriod, or 2 wires twisted for each of the 4t and 10t coils, ive tried a few different ways but cant get any audio with the carrier. thanks in advance
Simon: I don't think that is a bifilar transformer. It is simply 4 turns in the primary and 10 turns in the secondary. Just wind the ten turns first, then wind the 4 turns on top of that. 73 Bill N2CQR
ReplyDeleteIm kf4jqr and my name is keith. Sorry for the anonymous comment. I'm not sure about the type of bn series cores that is used. I had some bn43-2402 and it works but the received audio is very low even through a 2n3904 preamp stage and a radioshack amplified speaker. I'm not sure if the bn43-2402 is too small or what. They have about 1uh per turn. It kind of acts like the rf signal is weak getting back to the mixer. I'm not sure though if someone could help me with this problem it would be very much appreciated.
ReplyDeleteKF4JQR: I have asked Peter Parker, designer of the Beach 40, to answer your questions. Keep an eye on the comments section of this post. Bill
ReplyDeleteThe ferrite used for the balanced modulator came from TV baluns which were commonly used to convert 300 ohm to 75 ohm. Example: http://www.jaycar.com.au/productView.asp?ID=LF1220
ReplyDeleteThanks for the reply Peter. I really like building my own Radios. I was just wondering if the same rf cores was used in the pa circuit?
DeleteKF4JQR....
hi peter. could you possibly confirm bills comment regarding the coil windings? is it 4 turns on the diode side and 10 turns on the output side as i cannot impress any audio. many thanks in advance and keep up the good work. Simon M6EKL
ReplyDeleteSimon: This schematic show 4turns on the diode side, 10Turns on the output side.
ReplyDeletehttp://4.bp.blogspot.com/-feVxGR31GBU/UKeKlfEE4OI/AAAAAAAAS3c/t8E_JydAeg4/s1600/VK3YE+DSB.png
And, of course, lots of good advice here from the master:
ReplyDeletehttp://home.alphalink.com.au/~parkerp/projects/projbeach40.htm
Hi I was just wondering if someone could figure out this problem I'm having. I built a beach 40 and it receives well and puts out about 2.5 watts into a dummy load. I can listen to the audio on another homebrew regen receiver that I built and the audio sounds good as far as I can tell. The problem I'm having is I'm using a halfwave end fed antenna up about 30 feet with insulators on the ends. I'm using a end fed half wave tuner that I made using a t50-2 toroid and a polyvaracon tuning capacitor with the coax ground and the counterpoise ground connection isolated through the transformer. I tried all different lengths of counterpoise and its getting rf in the power cables and on the chassis and its getting in the audio when I use it on the antenna. Any help would be greatly appericated. Keith KF4JQR...
ReplyDeleteKeith: Welcome to my world! Amplifiers that want to be oscillators. We very often see what you are experiencing: everything fine into the dummy load, but all hell breaks loose when the antenna is connected. It could be that your amplifier doesn't like the load presented by your tuner/antenna (Could you try a simple dipole?) It could be that the audio (mic) amplifier needs shielding and bypass to prevent RF from getting into the rig through the mic connector. Make sure your leads are all short. Try to figure out what the feedback path is, then break it. Hang in there. We all suffer with this. Send me an e-mail address so we can get Pete Juliano and Peter Parker on the case. 73 Bill
DeleteOk Bill my email address is keith332009@Yahoo.com. thanks for the help I can also send you a picture of my radio. I will try an inverted v or center fed halfwave dipole. I know endfed halfwave antennas can have all kinds of problems with rf getting into the audio and also getting rf on the chassis and in the power supply.
Delete