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Title: Finally, T-47/ART-13 ALIVE! Post by: SM6OID on March 16, 2019, 10:58:09 AM Hi!
Last evening my ART-13 came alive! Just had a QSO with LA2OLD with nice reports. However, the unit is not without problems, I suspect that there is a problem with the "B" switch, there is no grid drive on half of the bands, I see a pattern that leeds me to suspect one of the switch decks. Power output on 80 meters is approx 70 >W Carriers with a somewhat low "BATTERY" voltage, cranking up to closer to 28 rather than 25-ish Volts should do the trick? To begin with the modulation was weak usign the T-17 mic, since I knew that the mic is good I turned to the diagrams... The plan was to increase the mic bias, found the resistor I was looking for, 15 kOhms and fitted 3.9 kOhm, and all of a sudden, I have what appears to be around 90-100% modulation! Using the DY-12 dynamotor makes the schack.... not so quiet. Title: Re: Finally, T-47/ART-13 ALIVE! Post by: KL7OF on March 16, 2019, 01:09:22 PM Dynamotor...ART 13 ...auto tuning....too much fun! good luck Steve
Title: Re: Finally, T-47/ART-13 ALIVE! Post by: KE5YTV on March 16, 2019, 05:59:34 PM I'm jealous. I've yet to get my power supply built.
Title: Re: Finally, T-47/ART-13 ALIVE! Post by: W6TOM on March 16, 2019, 09:59:46 PM I have two ART-13's and also use a dynamotor. I'm using a D-104 microphone and had had issues of poor or no modulation with both ART-13's, replacing the electrolytic capacitors in the speech amp cured that problem.
Title: Re: Finally, T-47/ART-13 ALIVE! Post by: AJ1G on March 16, 2019, 10:41:03 PM You will have much more output with nominal 28 v on the dyno input. That’s what it would see in flight from the aircraft DC generator.
You can also add a 500pf variable across the output to the antenna to provide more loading capacity. Should get you over 100w into a 50-75 ohm non-reactive load. 73 de Chris AJ1G Stonington CT Title: Re: Finally, T-47/ART-13 ALIVE! Post by: SM6OID on March 17, 2019, 06:02:10 PM Hi!
Thanks for all the kind words and ideas! I will have to wait and see what kind of surprises the future may have, by experience I know that new faults may show up after some hours of usage... What about some additional fans to evacuate the heat from the glassware at the rear? The top lid get as expected quite warm. However, currently I do have 100 W+ with 26.3 V at the dynamotor on 80 meters, using a shunt capacitor at the output. Title: Re: Finally, T-47/ART-13 ALIVE! Post by: W6TOM on March 18, 2019, 01:59:25 PM Henry, WA7YBS, has some good info on the ART-13 including running it on a dynamotor and also the two home built power supplies he has built.
I'm using the same 28 volt, military PP-1104 power supply, that Henry is using, which I have strapped for 28 volts and am running off 220 volts AC. It spins the dynamotor OK. Title: Re: Finally, T-47/ART-13 ALIVE! Post by: W6TOM on March 18, 2019, 02:00:26 PM Link to Henry's (WA7YBS) site
https://www.radioblvd.com/art13.htm Title: Re: Finally, T-47/ART-13 ALIVE! Post by: W2PFY on March 21, 2019, 08:35:55 PM Quote Power output on 80 meters is approx 70 >W There are two dynamotors for the art-13. One has a 750 volt output and the other has 1200 vdc. The 1200 volt model has a barometric switch in it to reduce voltage at high altitude to 750 volts to prevent flashovers. I wonder what your plate voltage is? You are correct about raising the voltage to 28 volts to get more output voltage from the dynamotor. The float or fully charged voltage in lead acid batteries from WW2 would have been 2.55 volts per cell or full float voltage of 30.60 fully charged. Those old engine mounted generators in B-17 & B-29's most likely have been equipped with carbon pyle type voltage regulators. From what I can see on ebay, the aircraft carbon pyle regulars are set at 27.70 volts max output. When operating at 28 volts, there should be no fear of burning out the dynamotor. Title: Re: Finally, T-47/ART-13 ALIVE! Post by: SM6OID on April 08, 2019, 08:59:54 AM Hi!
Forgot to comment the plate voltage. I see a hair above 1150 V at no load. At 100 W+ out I see something like 100 V less. At max modulation it stays well above 1000 V. All reading were done with an AVO 8, checked against my calibrated Fluke 289. It will be interesting to see what happens when I get the “battery” voltage up to nominal. Title: Re: Finally, T-47/ART-13 ALIVE! Post by: W2PFY on April 09, 2019, 02:54:49 AM You will be 599 somewhere ;D ;D
Title: Re: Finally, T-47/ART-13 ALIVE! Post by: Opcom on April 09, 2019, 09:18:52 AM Oh yeah. The audio from those cuts right through. What it was made for! AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
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