SG-886A/UR Interference Generator

Background
Description
Photos
Related
Manuals
Links

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Background

This unit came from Steve Haney by means of the Army Radio Yahoo Group. 

Description

At first glance (Fig 1,2 & 3) it appears to be some type of jammer, like the HEXJAM or Motorola RF jammer, but after seeing the inside circuitry it's clearly an audio noise generator.  Tpub  TM-11-6940-210-24P (Fig 1 Sheet 1) which shows the U-228 type connector (Fig 3 below) as being part of the W1 and W2 accessory cables, not attached to the SG-886.  The other end of the W1 & W2 cables have U-77 10-pin mil plugs to be compatible with older equipment that used the H-33 handset.  The two cables attached to the SG-886 have U-229 type plugs.

The silver cap in the upper left of the panel is not a connector cover, but rather a battery cap.  The meter on the right has a red zone Replace Battery and a green zone Operational.  There isn't any other power source visible.  To get the meter to read in the green it takes between 8 and 23 VDC. 

The battery compartment is about 0.7" (18mm) ID and 2.3" (58mm) deep.  Looking at the Wiki List of Batteries shows the 4SR44 with dimensions of 13 dia x 25.2 long, 6.2 volts so two of these would come very close to fitting the battery compartment and putting the meter well in the green zone with a fresh voltage of 12.4.

The crypto backup or HUB battery BA-1372 (BA-5372) is about the right diameter and voltage (6.5) but is too long (1.3") so that two of them do not fit.
The PLGR HUB battery is about the right size for one to fit but is only 3.6 v.
A couple of PX28A enercell batteries (UPC 0 40293 02701 8) work, but they are too small in diameter to correctly fit. 
A 3x5 card folded in half lengthwise then wrapped around the two series batteries brings them nicely into the center of the battery cavity.
Uses the long obsolete BA-1363/U 12.15 Volt mercury battery (NSN: 135-00-577-8309, or commercial BT-70202.
This was made using a stack of nine each 625 button cells (9 * 1.35 = 12.15Volts).
So a modern replacement could be made in a similar way, but an end cap with a tit for the negative terminal would be required.

Controls & Indicators

Battery + Side Down
Audio Input - allow any audio source to be used for jamming.
Output pot - 0 no output, 20 max audio
The Mode & Type switches work together

	Noise	Tone
Mode 1	18 mV	900 Hz 22 mV
Mode 2	70 mV	780 Hz 60 mV

Meter - battery condition

Cables - the two white wires have the audio output.

What Goes Wrong

The wires going to the two audio cables have their insulation flaking off, its biodegraded.  This would make these units rejects because it tends to short out the audio or make it intermittent. See Fig 4 & Fig 5.

Photos

SG-886 Fig 1	SG-886 Fig 2 US Army Serial No....... Electronics Command x?ODE/Part No.     Mfr:  14058 ?0063-867168 SG-886A/UR Interference Generator Contract: DAA907-75-C-1938 NSN: 6940-00-474-9495 US	SG-886 Fig 3
SG-886 Fig 4	SG-886 Fig 5	SG-886 Fig 6

Related

HEXJAM & Motorola RF jammers
Noisecom 7110-FAC Programmable Noise Generator
NSLB Model NS-LB Noise Generator
RF Noise Source

Manuals

TM-11-6940-210-24P

Links to TPub.

SECTION I. INTRODUCTION - TM-11-6940-210-24P-20003
Special Information - TM-11-6940-210-24P-20004
Figure 1. Generator, Interference SG-886A-T/UR, Cover Assembly, Case A1, and Case Weldment Assembly A2 (Sheet 1 of 2).
Figure 1. Generator, Interference SG-886A-T/UR, Cover Assembly, Case A1, and Case Weldment Assembly A2 (Sheet 2 of 2).
GROUP OO GENERATOR, INTERFERENCE SG-886A-T/UR
Figure 2. Panel Assembly A3.
GROUP 03 PANEL ASSEMBLY A3
Figure 3. PCB Assembly A3A1.
GROUP 0301 PCA ASSEMBLY A301
Figure 4. Harness Assembly (Wired In) A3W1.
GROUP 0302 HARNESS ASSEMBLY (WIRED IN) A3W1
Figure 5. Harness Assembly (Wired In) A3W2.
GROUP 0303 HARNESS ASSEMBLY (WIRED IN) A3W2
Figure 6. Cable Assembly, Special Purpose W1.
GROUP 04: CABLE ASSEMBLY, SPECIAL PURPOSE W1
Figure 7. Cable assembly, Special Purpose W2.
GROUP 05: CABLE ASSEMBLY, SPECIAL PURPOSE W2
NATIONAL STOCK NUMBER AND PART NUMBER INDEX - TM-11-6940-210-24P-20020
LATEST NATIONAL STOCK NUMBER ASSIGNMENTS
Microform Test Target - TM-11-6940-210-24P-20031
TM-11-6940-210-24P-2 Generator Interference SG-886A-T/UR Manual

DA Pam-310 has a two page summary, but they mistakenly talk about VHF low band output.  That's a mistake since the output is only audio.

Links

PRC68, Alphanumeric Index of Web pages, Contact, Products for Sale
Web page created 12 Oct 2015