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Author Topic: "A Simple Two-Tube Transmitter" ARRL 1968 -- Build  (Read 201126 times)

VE3LYX

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RE: "A Simple Two-Tube Transmitter" ARRL 1968 -- Build
« Reply #195 on: December 01, 2014, 02:35:36 AM »

Just for fun this weekend I built a one tube Hartley Cw transmitter. I used a 01a tube however a 45 or a 2A3 could be subbed for more power. I used a clementine wooden crate for the chassis  fresh from the grocery store and recovered the bottom with Masonite also making a front panel. A few minutes with a brush and some flat black paint produced the 1920s look. While it was drying I looked in my junk box for suitable parts. Found a 1920s variable cap,  proper tube socket for the old 4 pin tubes, a heater control rheo from an old battery set. Some very old resistors which I paralleled to get around 12k for my grid leak and paired that with an ancient .003 paper cap for a gridleak assembly. Wound 14 turns of #16 wire on a three inch form with a centre tap. Found a RF choke of some description and a second .003 cap. Wired it all together Sat with a key jack in the cathode to coil centre tap lead . Fired it yesterday. Tunes both 80M and 40M . Keys well . Is fairly stable after a couple of minutes. Power input with a 01A tube was just over 4 watts. Will be trying it out this week. Out of pocket costs about $5. No schematic required because a Hartley osc should be committed to memory as it was part of our ham exam back in the day.  Quick review is  grid to grid leak assembly to top of the coil to centre tap which is connected to cathode(which with these old tubes is also one side of the filament) and bottom of the coil is grounded . Another cap capable of passing RF goes from grounded coil lead to plate. Plate power is fed from the power supply side of this connection through an RF choke to B+. If Rf choke is not available put enough scramble wound turns on a piece of small wooden dowel that if you were an electron you would be too tired to bother going through it. Wire up filament voltage (5 volts for 01A), supply B + and enjoy.
A second coil , (I used 1 turn ) is wound at the top of the main coil and provides ant and ground connection. Simple and works every time with no fussing. Parts values (fixed caps need to be able to pass RF and resistor can be anywhere from 5K to 1 meg and it will still function) are not critical. It is amazing what will work.
don

Please note, this is VFOed so you can roam free no crystals needed and is stable enough to use.
« Last Edit: December 01, 2014, 02:50:12 AM by VE3LYX »
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KC8FQD

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RE: "A Simple Two-Tube Transmitter" ARRL 1968 -- Build
« Reply #196 on: December 16, 2014, 07:24:58 AM »

Absolutely delightful. Nice pictures and great workmanship. Thank you for sharing!
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G3EDM

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RE: "A Simple Two-Tube Transmitter" ARRL 1968 -- Build
« Reply #197 on: January 12, 2015, 05:31:20 PM »

Absolutely delightful. Nice pictures and great workmanship. Thank you for sharing!

Thank you. I'm taking it to my local ham club for the annual "show and tell" later this week.

73 de Martin, KB1WSY
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KC8FQD

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RE: "A Simple Two-Tube Transmitter" ARRL 1968 -- Build
« Reply #198 on: January 12, 2015, 05:51:01 PM »

Thank you. I'm taking it to my local ham club for the annual "show and tell" later this week.

73 de Martin, KB1WSY

Those lucky dogs!
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GW3OQK

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RE: "A Simple Two-Tube Transmitter" ARRL 1968 -- Build
« Reply #199 on: January 13, 2015, 01:48:04 AM »

I might as well add my 12w 80 metre CW TX.  6BW6 Colpitts osc and 5B254M PA. It uses switched HC49U crystals with 100pf variable in series to give a 1 kHz VXO range. I mention the "QRP" crystals because some folks have advised they cant stand the voltage, which the obviously can.
73
Andrew





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K8AXW

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RE: "A Simple Two-Tube Transmitter" ARRL 1968 -- Build
« Reply #200 on: January 13, 2015, 09:49:46 AM »

Quote
Absolutely delightful. Nice pictures and great workmanship.

"Pictures"  I can find no pictures.  Where did I miss them?
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N2EY

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RE: "A Simple Two-Tube Transmitter" ARRL 1968 -- Build
« Reply #201 on: January 13, 2015, 02:26:48 PM »

Rather than post them all again, I'll just post a link. Hope that's OK:


http://forums.qrz.com/showthread.php?453281-A-Few-Pictures-of-the-Southgate-Type-7

73 de Jim, N2EY
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G3EDM

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RE: "A Simple Two-Tube Transmitter" ARRL 1968 -- Build
« Reply #202 on: January 13, 2015, 05:57:52 PM »

Quote
Absolutely delightful. Nice pictures and great workmanship.

"Pictures"  I can find no pictures.  Where did I miss them?

Not sure whose pics you're referring to, Al. I know you've already seen mine but in case anyone else hasn't: http://www.eham.net/ehamforum/smf/index.php/topic,97719.msg773505.html#msg773505. (These are the same picture links that were posted months ago in this thread.)

Jim/N2EY's description of his rig (referenced in his post, above) shows what can be achieved by someone with way more homebrew (and rig design) experience than I have!

Unfortunately, in my shack, Ham radio has been obliterated by Life in the past few months. Not sure when I'll get back to it, but It Will Happen.

Happy New Year everyone.

73 de Martin, KB1WSY
« Last Edit: January 13, 2015, 06:00:23 PM by KB1WSY »
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K8AXW

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RE: "A Simple Two-Tube Transmitter" ARRL 1968 -- Build
« Reply #203 on: January 14, 2015, 10:11:48 AM »

Thank you for the link Jim.  I thought I read all of your posts but seem to have missed the pictures. 

Martin, I have seen the photos of your fantastic build. 

I wish you all a very happy and prosperous New Year as well.

Martin.....can understand your "obliterated by Life" statement.  Life has been a disaster her for over 4 months and I can no longer walk through the shack without feeling like I'm in Herman Munster's mansion!
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