WJ DMS-105a-2 - Revision history

ThElectriCat at 20:49, 12 December 2018

2018-12-12T20:49:42Z

← Older revision		Revision as of 20:49, 12 December 2018
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	=General=		=General=
	The DMS-105a-2 receives the frequency range from '''1 to 1600 Kilocycles''' in 2 bands of '''1 to 600 Kilocycles''', and '''540 to 1600 Kilocycles'''. It is a heterodyne receiver, with a high IF of 2 Megacycles. Receive modes are AM, FM, CW, LSB, and USB. and it has bandwidths of 150 cycles through 16 Kilocycles in the dual sideband modes, and bandwidths of 2.5 through 8 Kilocycles in the single sideband modes.		The DMS-105a-2 receives the frequency range from '''1 to 1600 Kilocycles''' in 2 bands of '''1 to 600 Kilocycles''', and '''540 to 1600 Kilocycles'''. It is a heterodyne receiver, with a high IF of 2 Megacycles. Receive modes are AM, FM, CW, LSB, and USB. and it has bandwidths of 150 cycles through 16 Kilocycles in the dual sideband modes, and bandwidths of 2.5 through 8 Kilocycles in the single sideband modes.
		+	===History===
		+	The DMS-105a-2 was originally designed to demodulate subcarriers from frequency division multiplexed microwave systems. The presence of a single sideband bandwidth of 4 Kilocycles corroborates this, as that is the channel width of a single voice channel. The US department of defense and CIA were most likely the original customers this unit was built for, and the goverment cost in the early 70's was between $12000 and $16000.
	=Signal Path=		=Signal Path=
	====Front End====		====Front End====

ThElectriCat at 23:20, 19 April 2018

2018-04-19T23:20:01Z

← Older revision		Revision as of 23:20, 19 April 2018
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	Relay switched '''signal transformers''' precede the Front End Filter. They allow an input impedance of '''50 or 1000''' ohms in either band. The voltage sensitivity is subsequently decreased in the 1000 ohm setting, as no amplification precedes the filters.		Relay switched '''signal transformers''' precede the Front End Filter. They allow an input impedance of '''50 or 1000''' ohms in either band. The voltage sensitivity is subsequently decreased in the 1000 ohm setting, as no amplification precedes the filters.
	=====Dynamic range=====		=====Dynamic range=====
-	The receiver has a switchable attenuator which follows the filter network. The attenuator is variable in '''10 db steps''' from '''0 to 50 db'''. The dynamic range of the receiver is quite high even without the input attenuator, and will detect a minimum signal of about '''-130dbm''' (about '''2.2uV''' into 50 ohms or '''10uV''' into 1000 ohms) ~~even though the~~ sensitivity listed in the manual is 30uV.	+	The receiver has a switchable attenuator which follows the filter network. The attenuator is variable in '''10 db steps''' from '''0 to 50 db'''. The dynamic range of the receiver is quite high even without the input attenuator, and will detect a minimum signal of about '''-130dbm''' (about '''2.2uV''' into 50 ohms or '''10uV''' into 1000 ohms). The sensitivity listed in the manual is 30uV, However this represents the full scale value.
-	====downconversion and filtering====	+	=====downconversion and filtering=====
		+	The Mixer used in the WJ-DMS-105a is a custom WJ part, but it is a '''diode ring double balanced mixer'''. Its input is buffered by a '''push pull emitter follower''' to lower the noise figure and provide drive current and isolation. There are some filtering elements ahead of the buffer to block the '''Local Oscillator'''. The receivers '''AM,BFO,and FM modes share filters''', while the LSB and USB have their own. This is due to the asymmetrical nature of SSB filters. All bandwidths are '''crystal filters''',and each filter '''has its own buffer''' for input and output, which is powered only when that filter is selected. This means that if a filter stage fails, any other bandwidth can still be used. All of the symmetrical filters are centered on the 2 Megacycle IF, and the SSB filter band edges fall upon the IF.

ThElectriCat at 17:43, 4 April 2018

2018-04-04T17:43:43Z

← Older revision		Revision as of 17:43, 4 April 2018
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	Relay switched '''signal transformers''' precede the Front End Filter. They allow an input impedance of '''50 or 1000''' ohms in either band. The voltage sensitivity is subsequently decreased in the 1000 ohm setting, as no amplification precedes the filters.		Relay switched '''signal transformers''' precede the Front End Filter. They allow an input impedance of '''50 or 1000''' ohms in either band. The voltage sensitivity is subsequently decreased in the 1000 ohm setting, as no amplification precedes the filters.
	=====Dynamic range=====		=====Dynamic range=====
-	The receiver has a switchable attenuator which follows the filter network. The attenuator is variable in '''10 db steps''' from '''0 to 50 db'''.	+	The receiver has a switchable attenuator which follows the filter network. The attenuator is variable in '''10 db steps''' from '''0 to 50 db'''. The dynamic range of the receiver is quite high even without the input attenuator, and will detect a minimum signal of about '''-130dbm''' (about '''2.2uV''' into 50 ohms or '''10uV''' into 1000 ohms) even though the sensitivity listed in the manual is 30uV.
		+	====downconversion and filtering====

ThElectriCat at 16:29, 4 April 2018

2018-04-04T16:29:07Z

← Older revision		Revision as of 16:29, 4 April 2018
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-	The '''Watkins Johnson DMS-105a-2''' is a VLF to MF receiver. While technically classified as a demodulator, It performs well as a standalone receiver when connected to a good antenna.	+	The '''Watkins Johnson DMS-105a-2''' is a '''VLF to MF receiver'''. While technically classified as a demodulator, It performs well as a standalone receiver when connected to a '''good''' antenna.
	(pictures are to come once they are formatted correctly)		(pictures are to come once they are formatted correctly)
	=General=		=General=

ThElectriCat at 16:15, 4 April 2018

2018-04-04T16:15:32Z

← Older revision		Revision as of 16:15, 4 April 2018
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	The '''Watkins Johnson DMS-105a-2''' is a VLF to MF receiver. While technically classified as a demodulator, It performs well as a standalone receiver when connected to a good antenna.		The '''Watkins Johnson DMS-105a-2''' is a VLF to MF receiver. While technically classified as a demodulator, It performs well as a standalone receiver when connected to a good antenna.
	(pictures are to come once they are formatted correctly)		(pictures are to come once they are formatted correctly)
		+	=General=
		+	The DMS-105a-2 receives the frequency range from '''1 to 1600 Kilocycles''' in 2 bands of '''1 to 600 Kilocycles''', and '''540 to 1600 Kilocycles'''. It is a heterodyne receiver, with a high IF of 2 Megacycles. Receive modes are AM, FM, CW, LSB, and USB. and it has bandwidths of 150 cycles through 16 Kilocycles in the dual sideband modes, and bandwidths of 2.5 through 8 Kilocycles in the single sideband modes.
		+	=Signal Path=
		+	====Front End====
		+	=====Filters=====
		+	The Front End of the WJ DMS-105a-2 is comprised of two '''impedance matching transformers''' and '''filters'''. the lower band uses a seven pole low pass filter, and the upper band uses a 14 pole bandpass filter. These preselectors are not tuneable, and pass the entire selected band.
		+	=====Impedance=====
		+	Relay switched '''signal transformers''' precede the Front End Filter. They allow an input impedance of '''50 or 1000''' ohms in either band. The voltage sensitivity is subsequently decreased in the 1000 ohm setting, as no amplification precedes the filters.
		+	=====Dynamic range=====
		+	The receiver has a switchable attenuator which follows the filter network. The attenuator is variable in '''10 db steps''' from '''0 to 50 db'''.

ThElectriCat at 15:39, 4 April 2018

2018-04-04T15:39:18Z

← Older revision		Revision as of 15:39, 4 April 2018
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-	The '''Watkins Johnson DMS-105a-2''' is a VLF to MF receiver. While technically classified as a demodulator, It performs well as a standalone receiver when connected to a good antenna.	+	The '''Watkins Johnson DMS-105a-2''' is a VLF to MF receiver. While technically classified as a demodulator, It performs well as a standalone receiver when connected to a good antenna.
		+	(pictures are to come once they are formatted correctly)

ThElectriCat at 04:05, 4 April 2018

2018-04-04T04:05:40Z

← Older revision		Revision as of 04:05, 4 April 2018
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-	The '''Watkins Johnson DMS-105a-2''' is a VLF to MF receiver. While technically classified as a demodulator, It performs well as a standalone receiver when connected to a good antenna.	+	The '''Watkins Johnson DMS-105a-2''' is a VLF to MF receiver. While technically classified as a demodulator, It performs well as a standalone receiver when connected to a good antenna.

ThElectriCat at 04:05, 4 April 2018

2018-04-04T04:05:00Z

← Older revision		Revision as of 04:05, 4 April 2018
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-	~~[[File:DMS-105a-2.jpg\|200px\|thumb\|left\|Watkins Johnson DMS-105a-2]]~~ The '''Watkins Johnson DMS-105a-2''' is a VLF to MF receiver. While technically classified as a demodulator, It performs well as a standalone receiver when connected to a good antenna.	+	The '''Watkins Johnson DMS-105a-2''' is a VLF to MF receiver. While technically classified as a demodulator, It performs well as a standalone receiver when connected to a good antenna.

ThElectriCat at 04:04, 4 April 2018

2018-04-04T04:04:26Z

← Older revision		Revision as of 04:04, 4 April 2018
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-	The '''Watkins Johnson DMS-105a-2''' is a VLF to MF receiver. While technically classified as a demodulator, It performs well as a standalone receiver when connected to a good antenna.	+	[[File:DMS-105a-2.jpg\|200px\|thumb\|left\|Watkins Johnson DMS-105a-2]] The '''Watkins Johnson DMS-105a-2''' is a VLF to MF receiver. While technically classified as a demodulator, It performs well as a standalone receiver when connected to a good antenna.

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2018-04-04T03:56:39Z

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The '''Watkins Johnson DMS-105a-2''' is a VLF to MF receiver. While technically classified as a demodulator, It performs well as a standalone receiver when connected to a good antenna.