[Milsurplus] My Latest Project ART-13/B AM Transmitter

[Mack McCormick]

I'd like to thank those who responded to my ART-13 queries last week.

Here are two photos of my latest restoration project. This is a Collins
ART-13/B AM Transmitter. It came to me as a basket case last Monday
(purchased at Dayton) missing much of its paint and many parts. This unit,
the B model, features a rather rare crystal oscillator that allows up to 24
crystal controlled channels (20 HF and four LF) to be selected. I'm using
1,200 VDC on the plates, low B+ is 400 VDC and the filaments and tuning
motor uses 28 VDC at 10 amps.

*It is producing plenty of carrier and tunes nicely. It does seem to need
more audio modulation. I'm using an amplified D-104 which I've used
successfully with another ART-13. I tried another mic. The sidetone volume
is loud with this mic. The MCW tone is also way down on the carrier but not
on the sidetone jack. I'm wondering if I have a bad T202 transformer
between the speech amp and modulator tubes. Modulator tubes have 1,200 VDC
when keyed and zero volts when keyed with the emission switch in the CW
position (not a shorted relay). The plate current meter does swing on
talking but just about 40 ma. Look at the modulated carrier on a spectrum
analyzer does show modulation, just not a great deal (perhaps 20 %)
Suggestions?*

https://plus.google.com/photos/103063296550398702279/albums/5746961278027694465

You can read more about the radio here:
http://www.collinsclubs.com/carc/b-29/radio.html

You can see the auto tune in action at my QTH or via this YouTube video
produced by another ham.
http://www.youtube.com/watch?v=j1S6-FDRmlA

-- 
73,

Mack de W4AX
http://w4ax.com




-- 
73,

Mack de W4AX
http://w4ax.com




-- 
73,

Mack de W4AX
http://w4ax.com