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Author Topic: Vintage tube QRP rigs  (Read 876 times)

Offline ve3lyx

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Vintage tube QRP rigs
« on: May 19, 2015, 05:27:48 UTC »
At a local antique store I picked up a 1943 ARRL handbook. There is a breadboard transmitter in the transmitter chapter that looked interesting. I checked my junk box only to discover I had everything to build it except the breadboard. So I am underway. It is a crystal controlled 6v6or 6l6 rig Cw only. Low power tube rigs are for me a great source of fun. I am building it for 80M although the article has specs for 160M and 40M ops as well. 

Offline ve3lyx

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Re: Vintage tube QRP rigs
« Reply #1 on: May 23, 2015, 23:26:27 UTC »
It is up and running. Very stable with a nice note. I tried it both  with a 6v6 and a 6l6. Despite the lower voltage supply I have it on (246v key down) which should favour the 6v6 the 6l6 still performs noticeably better. Am testing on 3561KHZ (3561 crystal) when the band is open. CW only.
don

Offline ve3lyx

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Re: Vintage tube QRP rigs
« Reply #2 on: June 05, 2015, 11:33:55 UTC »
Making a matching receiver from the same 1943 ARRL handbook. Hope to operate this complete staion successfully soon.
don

Offline in3eqz

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Re: Vintage tube QRP rigs
« Reply #3 on: June 09, 2015, 12:23:57 UTC »
Well done, congrats !!! Renzo

Offline ve3lyx

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Re: Vintage tube QRP rigs
« Reply #4 on: July 09, 2015, 01:03:04 UTC »
Have used it successfully. Going to run it tonight too on 3561 khz approx.

don

Offline ve3lyx

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Re: Vintage tube QRP rigs
« Reply #5 on: July 21, 2015, 02:24:36 UTC »
Rig seems fairly effective. I am very happy with it. Was well worth the build and the build was easy. I now have it set up on a vintage table with nostalgia bulb lighting. This is fun.
don

Offline ON6KZ

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Re: Vintage tube QRP rigs
« Reply #6 on: July 21, 2015, 10:32:15 UTC »
Congratulations. Nice project. Wish I had the skills to build this.

Offline ve3lyx

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Re: Vintage tube QRP rigs
« Reply #7 on: July 21, 2015, 19:54:40 UTC »
They are really very easy. Do one connection each day and soon you are done.
BTW I just finished successful build of a TNT version of the same transmitter. TNT stands for Tuned Not Tuned and has a normal tuned plate tank circuit of very high Q (large diameter and good quality material usually air core). The grid coil is much smaller and uses no tuning capacitor but relys is on the inductance and normal inter-winding capacitance and the tubes natural capacitance to put it in the desired freq range. Because it has much lower Q is can be pulled on freq by the Plate tank and gives one a variable freq power oscillator (within a short range 50 to 75 khz). The grid coil keeps all in check allowing it to wander only so far. When all is well they work quite well and were popular till about 1935. Lately many vintage QRP folks have revived them for special contest nights such as the Bruce Kelly Memorial . They are limited to 5 watts  and are CW only. The tube must be pre 1929 to be valid in the contest. I wanted to see if a more modern tube from the mid thirties to 60s (6l6G) would function in the circuit as it has little difference to a Crystal controlled rig in basic design so I tried it. It works. Just got it going about an hour and a half ago. I have to optimize everything and make sure it is a clean signal then I will try it on air (7018khz) It was an interesting project and I am thrilled it worked. No good for the BK contest but will be fun on the air for QSOs.
don