HELP with tuning the ART-13

[K1CWS]

I have just finished restoring an ART-13 (aircraft version). Using the procedure in the manual I can find a slight plate current dip that is only about 40 ma. I am working on 3885 for now , but tried 7260, but found no dip anywhere. I am wondering if some sort of tuning network is needed on the output or am I doing something wrong.

[W7SOE]

Bruce,
    Have you added a loading cap to the output?  This makes it a Pi network.  I am looking at the "standard issue" 365 pF variable cap that I received 5 minutes ago for mine!!  What a coinkydink.

Cheers

Rich

[K1CWS]

OK Rich, NO I don't have one, but I did try a 300 pf silver mica from the "COND" terminal to GND. I couldn't find any dip at all that way.

[KB2WIG]

What kinda ant are you using?? The 'Maytag' was designed to work into various end fed configurations... Maybee throw a 20' piece of wire out the window, and load her up on 30m CW.....

FWIW, Electric Radio has a few nice pieces of info fer the '13... its in a dec 20?? issue.

I've got 2 of these things, but its a long, sad story that i'll not bore you with.

klc

[K1CWS]

Mostly testing with a dummy load. But I have loaded a 102' dipole fed w/ 600 ohm open wire fedder using a Dentron MT-3000A tuner. I get 110 watts out that way. I was just expecting a more pronounced dip. 10 ma variation doesn't seem normal. Doesn't act like my Valiant.

[WA4JK]

Well.. no it won't either. It's buiilt like a rock. Not a Turd. 110W sounds about right. Just load it within reason and peak the watts out and look for ma's out of the green and your in business...

[Steve - WB3HUZ]

A prounounced dip at what amount of loading? Any amp, when heavily loaded will have less of a dip. Or are you saying that even when you take it completely off resonance (turn the tuning control a large amount), the current only goes up 10 mA. If so, then you may have a soft 813. Off resonance, the plate current should soar.

Mostly testing with a dummy load. But I have loaded a 102' dipole fed w/ 600 ohm open wire fedder using a Dentron MT-3000A tuner. I get 110 watts out that way. I was just expecting a more pronounced dip. 10 ma variation doesn't seem normal. Doesn't act like my Valiant.

[KB2WIG]

 yeah, what he say


100w out is gud...


 There is an old '73'  artical about getting 250 watts out of this thing..... i've got it around here....  maybee i can find it and copy it fer u ....

klc

[W7SOE]

 There is an old '73'  artical about getting 250 watts out of this thing..... i've got it around here....  maybee i can find it and copy it fer u ....

klc

I would be interested in that as well if you can find it.

Rich

[k7yoo]

On 80 & 40 M an old multi-section variable out of an early HP audio gen is FB. I bent up a little box and hang it on the LH side of the rig and hook it the the "cond" post. This will make the rig put about 120 or so into a 50 ohm load. Hanging a 300 pf SM won't get the job done. A stock ART 13 was not designed for modern antennas and making a pi-net with the outboard cap gets you close, but not optimum. If you do the pi-net calculations for 80 & 40M the dial settings commonly used for those bands will not give you the L,C, or Q that the "book" says. I use the calculator in "Elsie" for my network design. I have taken the time to re-configure the entire tank on one ART-13 for optimum Q on each band but am not sure it was worth the effort. WITH A GOOD 813 they work fine as is. Load for max out and don't worry about the dip (just make sure you are not on a harmonic!!)
I have a small pamphlet that has original info NOT in any of the conversion manuals. It covers re-configuring the tank. I also have a chart with all of the calculations regarding load impedance, Q etc. If you are interested I will pass it to admin for posting in our tech section.
Skip

[K1CWS]

Yes, I am interested in the info you mentioned.

Can you say more about how to tell if you are tuning a harmonic?

[WA2TTP Steve]

Loading cap values.

On my ART 13 feeding a dummy load or my matched antenna I need about 1000 pf on 75 and about 300 on 40m.
I also looked at the output of the rig on my HP 8590L Spectrum Analyzer and noticed the second harmonic surpression was poor with light loading even if your getting near rated power output. A small increase in loading cap, say 10-15%, would result in a second harmonic decrease of another 20 or so DB over the 35 it started at. It also helped to surpress the sub harmonics of the VFO that appear in output.

I get about 135 watts output at 1150 volts B+.

Good Luck,
Steve
WA2TTP

[W2JBL]

 I use 1000 to 1300pf for loading caps on 75 and 160. 300-500 on 40. if you have the calibration book, use the tank circuit settings for "60 foot trailing wire" on 75. I use a big .001 mica in paralell with a dual 440 PF per section variable for the loading, built into the blank panel where the LF PTO goes. I switch out the .001 mica for the higher bands. at 1650-1700V on the plates you get a good 225-250 out. modified heisng around the mod transformer is required for this or your audio gets ratty above 150-175 out. use the built in RF ammeter for tuning, as in tune for max RF amps. be very careful where your plate tank switch is set, or you will end up on the second harmonic. the ART-13 is a superb and near bullet proof rig even at high power. I love mine...it's a 32V2 on steroids.

[WU2D]

Here is one high Power Article.

I run mine at low power and get 125W out. I use a three section variable as a loading control. Tune for max out. Never dipped anything.

Mike WU2D

[WU2D]

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[w1vtp]

Here's a short clip of an ART13 doing its auto thing.  I can't hear audio. 

http://homepage.fcgnetworks.net/w1vtp/art13/ART13.rm.ram

Al