[Milsurplus] T-47/ART-13 into 50 ohm load

[Meir WF2U]

Joe,

These settings are pretty close to the settings Dennis indicated in a
previous posting. 

I tried his settings, and although the T-412/ART-13B put out 100W into the
dummy load, when I hooked it up to the MFJ automatic antenna tuner, which
has a frequency counter built in to indicate the transmitter frequency,
instead of the 3570 kHz OMRN CW net frequency it displayed 2872 kHz. This
could mean that the PA self-oscillates because of the output circuit. The
counter went back to indicate the correct frequency only when I put the 2000
pf shunt cap back, with 'C' back to 7. 
This is the same with both of my working ART-13's.
Of course, this could be a glitch in the frequency counter, but I'm still a
bit miffed. I'll listen to the signal with a general coverage receiver and
see whether there is indeed a spurious output, and if there is, what is its
relative strength to the desired output frequency.
To rehash, I use a fixed 2000pf cap between the CAP terminal and ground,
with control C on 7. This gives me a good match across the band with 92-100
watt output into 50 ohms (using the DY-17/ART-13 dynamotor), with the plate
current meter dip in the correct range,  with minimum tweaking of controls D
and E. D is between 10 and 30, and E between 120 and 130 throughout the
75/80 meter band.
Dennis is quoted here:  "using fixed shunt caps, 400pf for 75/80 meters, 200
for 40 and 100 for 20.  A 400pf variable would cover the whole range, of
course.  Range of adjustment inherent in the ART-13 tank circuit is very
wide, I can load into 50 ohms FB on 75M with only my 200pf  40M shunt
switched in for ex. and conversion articles I've seen over the years list
shunt cap. Values all over the lot."

I also prefer to use the RS-38 mike.

What day is your net and what frequency?

73, Meir WF2U

-----Original Message-----
From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Joe Munson
Sent: Tuesday, March 26, 2013 12:55 AM
To: milsurplus
Subject: [Milsurplus] T-47/ART-13 into 50 ohm load

I run my T-47/ART 13 powered by a DY 17 Dynamotour, and use a 560 Pf Large 
Variable Cap hooked to the shunt connector on the antenna out insulator.  On

3885, the cap is about 2/3 meshed, and D is at 15, C at 5 and E at 195. 
This give little over 100 watts out on a bird watt meter, and little over 2 
amps on RF amp meter.  The antenna is a 250 foot flattop, up about 25 feet, 
fed with ladder line.  I use a large home brew balanced tuner, using the 
Large 4 inch in Diameter B & W TV 1000 swinging link coils.  The tuner is 
fed via RG 213 coax from the transmitter.  With that cap, the set loads fine

business on 80, 40, and 20 meters.  I use a BC 348 from the dynamotour as 
the receiver and use it weekly on a local AM net.  I have found the RS 38C 
mic to produce  plenty of audio.  For anyone interested, the net as at 12 
noon EDT.   The area is Greater Cincinnati, Northern Kentucky, and S. E. 
Indiana.  Check in from Chicago, and other outlying areas are quite common.

Joe WA4VAG 


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