Programmable rate modem utilizing digital signal processing techniques

The engineering development study to follow was written to address the need for a Programmable Rate Digital Satellite Modem capable of supporting both burst and continuous transmission modes with either binary phase shift keying (BPSK) or quadrature phase shift keying (QPSK) modulation. The preferred implementation technique is an all digital one which utilizes as much digital signal processing (DSP) as possible. Here design tradeoffs in each portion of the modulator and demodulator subsystem are outlined, and viable circuit approaches which are easily repeatable, have low implementation losses and have low production costs are identified. The research involved for this study was divided into nine technical papers, each addressing a significant region of concern in a variable rate modem design. Trivial portions and basic support logic designs surrounding the nine major modem blocks were omitted. In brief, the nine topic areas were: (1) Transmit Data Filtering; (2) Transmit Clock Generation; (3) Carrier Synthesizer; (4) Receive AGC; (5) Receive Data Filtering; (6) RF Oscillator Phase Noise; (7) Receive Carrier Selectivity; (8) Carrier Recovery; and (9) Timing Recovery

A drawbar dynamometer and its use in soil tillage experiments

Publication authorized June 8, 1935.Digitized 2007 AES

A biologic study of macrosporium and related genera with an account of saltation

A cultural study has been made of three forms of Macrosporium Berk., three of Alternarla Nees., and one of Stemphylium Wallr . , all isolated by single spores from tomato fruits showing rots; also of a Macrosporium from decaying Echium vulgare. Named species have been cultured as controls; Pleospora herbarum, A.tenuis and S.ilicis.The cultural characters of these forms have been observed and compared on several media, under controlled environmental conditions.Strains of k'leospora herbarum (Pers.) Hbh. and A.tenuis to which the Macrosporium and Alternaria forms isolated from tomato belong, are distinguished by a consideration of macroscopic and microscopic cultural characters.The genera are to be distinguished by the shape and septation of the conidia, and as a rule by the conidiophores.The formation of conidia in chains is not a differentiating character between Alternaria and Macrosporium, since the forms of the latter genus studied have shown chain formation constantly.The type of conidiophore is generally an index to the genus but an exception is the Macrosporium from Echium vulgare, named M. Wilsoni n.sp., where instead of being club - shaped the conidiophores are characteristically long, dark, and wide throughout their length.The genera Alternaria and Stempnylium do not appear to have a perithecial stage; Macrosporium Wilsoni, n.sp., is exceptional in this genus in not having that stage.The time taken to form ripe ascospores in the perithecia of the genus Macrosporium varies between strains, and even between comparatble cultures of one strain. Generally five to seven weeks have been found necessary, but ascospores have peen found, capable of germination, eighteen days after growth was observed in a culture.Saltation has been observed in P.herbarum and in the three fords of M,eic6porium,which are considered strains of that species; also in A. tenuis and S.ilicis. In lvlacrosporium Wilsoni n.sp., a variant, probably a saltant, was observed but was not isolated pure.Saltant manifestations are found to be chiefly absence or loss of characters which are constant in the normal forms of a species or strain. Thus saltants have been thrown by forms having many perithecia and conidia and little mycelium while the saltant has few, sometimes late formed, perithecia and fewer , or no conidia. A physiological effect found in one saltant was an inconstant colouration of the medium and of the culture by a pink, and sometimes blue exudation. Other saltant characters are recorded.Saltation could not be induced artificially.Saltants may themselves saltate