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1930s Rack Transmitter

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The original PP 814 transmitter used for Field Day this year has been rebuilt into a 6ft wooden rack with new power supplies and some changes to the RF sections.  The amplifier’s HV supply now uses a recently acquired UTC S-48 transformer (refinished in gloss black with a wrinkled top plate) with taps for 1kV, 1.25kV, and 1.5kV.  These taps can be selected via banana jacks/plugs on a strip of bakelite between the transformer and the 866 mercury vapor rectifiers.

There are additional supplies for the filaments (6.3VAC and 10 VAC), the oscillator and doubler (75V and 225V regulated), buffer (600V using 816 mercury vapor rectifiers), amplifier screen (300V using 816s), and amplifier bias (-90V regulated with a 874), all of which, including the HV supply, populate the lower four decks.

The exciter was modified from it’s FD configuration, now using an 89 ECO oscillator choke coupled to a 42 Class A buffer (plate tuned to second harmonic of ECO grid) followed by an 802 buffer/driver.  Operation is much more stable than with the original two-stage circuit.

The amplifier now uses a pair of 814s in push-pull, providing more output power than the original PP 804s.

The antenna tuner is also being physically reconfigured, putting the RF current meter in the center of the panel and the tuning capacitors on either side, similar to many period tuners.  The circuit itself is unchanged.

The plan is to operate it Field Day style from the back porch in the PA QSO Party (SOLP CW only – Crawford Co.) and well as on 630M Sunday night (0000Z Monday), which is the first day of Amateur operations on the band for most stations.


Below are various images of the project (click any image to enlarge):

Sept 2017 Preliminary Sprint Results – NO3M wins

This was my first NA Sprint win!  Conditions and activity were down, but  slugged it out with decent first and third hour rates.  Always an honor to compete with the sharpest group of CW contest ops in the country.

Top Ten Scores
Call	Score	BndChgs	Qs Lost	00Z	01Z	02Z	03Z
NO3M	13,545	148	4	107	73	87	48
N9RV	13,288	132	1	108	62	72	60
K4RO	13,112	142	5	94	73	79	52
N5KO	12,728	94	4	99	70	66	61
N4AF	12,716	132	8	101	73	66	49
W9RE	12,470	118	5	96	69	78	47
N3BB	12,384	88	3	100	66	68	54
K0RF	12,364	76	7	81	71	74	55
AA3B	11,792	121	2	91	61	68	48
N6TV	11,726	72	0	101	69	63	53