NATIONAL RADIO ASTRONOMY OBSERVATORY Green Bank, West Virginia Electronics Division Internal Report No. 88 MULTIFILTER RECEIVERS

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1 NATIONAL RADIO ASTRONOMY OBSERVATORY Green Bank, West Virginia Electronics Division Internal Report No. 88 MULTIFILTER RECEIVERS D. L. Thacker and Lewis Beale OCTOBER 1969 NUMBER OF COPIES: 100

2 MULTIFILTER RECEIVERS D. L. Thacker and Lewis Beale TABLE OF CONTENTS I. Abstract... (1) P...Mf II. General Description a woo eo *Go a 1 III. 40- Receivers 1 MHz and 5 MHz s IV. 50- Receivers 30 khz and 10 khz s... or I. ABSTRACT References: (1) Electronics Division Internal Report No. 70, "The NRAO 50- Spectral Line Receiver, " by Michael Balister. (2) Electronics Division Internal Report No. 79, "Synchronous Detector and Readout System, " by Kok Chen. (3) Electronics Division Internal Report No. 85 "The 40/50 Integrator/Multiplexer, " by Ray Hallman. (4) Computer Division Internal Report No. 7, "Multi- Receiver On-Line Programs, " by Bob Vance. This report contains the necessary block diagram and schematics for maintenance and interfacing with the new multifilter receiver plus a general, verbal description to acquaint the users with the filter bank. The above references must be consulted for a complete understanding of the system.

3 II. GENERAL DESCRIPTION A set of 5 multifilter banks has been built at NRAO for use on spectral line receivers or pulsar receivers. They are: khz (hereafter referred to as the old 50-channel) per channel using L. C. tuned amplifier for a contiguous filter bank. For a description of the receiver see EDIR No MHz per channel using passing L. C. filter (purchased from I-Tel), MHz per channel using passing L. C. filter (purchased from I-Tel) khz per channel using MHz crystal filter and separate LO' s for each channel khz per channel every MHz crystal filters and separate LO' s for each channel, Prototype parts have been ordered for two additional receivers, a 50-channel 100 khz per channel using MHz crystal filter and offset LO' s and a 50-channel (300 or 250) khz per channel using MHz L. C. filters and offset LO' s. In building the last four receivers listed above, the output levels, connectors, and input signal conversion that were used on the first 50-channel receiver were followed. (See Table 1.) This allows one to use the same software and interfacing with all systems. There are, of course, minor changes that have to be made when using the 40-channel receiver in place of the 50-channel because of the difference in number of channels. One simple expedient that has been used in the past has been to simulate channels by jumping selected channels of the receiver outputs to the channel input of the computer interface. For more information on the integration of the line receiver with the DDP-116 computer, see section 3 of EDIR No. 70. The following block diagram shows this chief difference between the 40-channel receiver and the new 50-channel receiver and it also sbould clarify crystal filter offset LO techniques. (See Figure 1 and Table 1.)

4 F P S FILTER INPUT p W L E1 -- R T T = AMP DC AMP II REPEATED 40 TIMES Immimums 8 WAY 5 WAY 40 CHANNEL IF INPUT PS OP W El R T IF MIXER ;1 0.7 MHz 10.7MHz AMP 'FILTER DC AMP DETECTO OUT OUT = CHANNEL SEPARATOR = I XTAL FILTER SAME FOR OTHER 48 CHANNELS 50 CHANNEL FIG, 1 OUT

5 3 TABLE 1 Multifilter Receiver of s IF Frequency Resolution ( Width) khz 100 khz (old) (1 db) MHz 1 MHz (3 db) MHz 5 MHz (3 de) khz 30 khz (6 db nom. ) khz 10 khz (6 db nom,. )

6 4 III. 40-CHANNEL RECEIVERS The two 40-channel receivers show a common IF driven box and therefore cannot be used simultaneously. Change over time from one bandwidth to another is approximately 1/2 hour. Note that the driver unit has a specially keyed DC power connector which prevents plugging in a standard DC power cord. Do not try to defeat its purpose. Table 2 lists the nominal center frequencies and bandwidths of the fixed, tuned 3-section L. C. filters that are used in the receivers. There is some distortion of the expected filter band shape and center frequency caused by the interaction of adjabent filters. This rarely causes a shift in center frequency of a channel larger than 30 percent of the channel bandwidth. The block diagram, schematics (Figs. 1-5), rear panel connector listings (Tables 3-5), and photographs are selfexplanatory. s on the 40-channel are left open-circuited.

7 4# I *8 c FILTER 71/1 (52.5/5) IMI /1 (62.5/5) 74/1 (67.5/5) 75/1 (72.5/5) DETECTOR & DC AMPLIFIER If CHANNEL * I, CON. c TO J2-FF OUT TO J5-8 J I & J 2 -TO COMPUTER J5 & J6 - TO ANALOG OUTPUT SYSTEM 4#2, COM. OUT + 3, COM. OUT #4, CON. OUT *5, CON. OUT li r TO J2-EE TO J5-A SWITCH SHOWN 100 K IN UP POSITION,613 _4 TO J2-JJ TO J5 -I) TO J2-HH TO J5 -C 100 K 100 K TOTAL POWER OUT 0 TOTAL POWER IN B.P. TOTAL 0-I> J6 -AA POWER SWITCH -I>Je-cc.001 #1 F. P. ALL UNITS ARE IDENTICAL TO ABOVE EXCEPT FOR FILTER CENTER FREQUENCY. (TOTAL OF EIGHT UNITS ) TOTAL OF 40 CKTS. IDENTICAL TO ABOVE, ONE FOR EACH CHANNEL TO J2 ee 10 BNC B.P. 10V cn FULL SCALE 2 V FULL SCALE low (227.5/5) 107/1 (232.5/5) DETECTOR & DC AMPLIFIER ti *36 37 TO J5-Z r... TO J2 c- TO J5-Y (3 461, i.LA METER 108/1 (237.5/5) 109/1 (242.5/5) 110/1 (247.5/5) 211 t1 # 38 # 39 # 40 CON. OUT TO J2-B TO J6 4, TO J2 TO J6 a, NOTE : NUMBERS IN ( ) REFER TO VALUES FOR 5 MHz /CHANNEL RECEIVER a,,41/4) BLOCK DIAGRAM OF 40 CHANNEL MULTIFILTER RECEIVERS FILTER BANK FIG.2

8 62.5/30 NOTES: 1. SAME DC AMP. AS FOR EACH CHANNEL EXCEPT USES EXTERNAL DETECTOR 2. ALL AMPLIFIERS APD-3 AVANTEK 7 3 / / FILTERS = 1-TEL FBT / 20 3 SECTION, 5O D, WITH BNC CONNECTORS EXCEPT WHERE NOTED 4. USE LOWER CHAIN FOR 1MHz FILTERS MHz 5 MHz H 7 8 /\ / / / 30 *a, / 6 IF INPUT -" FLT/ /50- -3A/3A FILTER I-TEL WAY POWER SPLI TTER r / / /30 LI HP ATTENUATOR ADP - 3B ISO - T TV C / 6 I / 30 Id FILTER I FBT/ 20-90/50 -- I 3/50-3A / 3A DETECTOR 103/ /30 ZERO 0 1 CHECK TOTAL POWER AMP. NOTE 1 W8/6 +28 V TOTAL BNC POWER B.P. OUT (DETECTOR OUT ) BLOCK DIAGRAM OF 40 CHANNEL MULTIFILTER RECEIVER DRIVER DRAWER FIG. 3.11a # 41.

9 7 I5V 20K +I5V 10M 200PF 390K 5.IK 20k BD-7 R I K at r 1100pF TRIM TRIM RESISTOR SUPPLIED WITH AMP. R SELECTED FOR BEST SQUARE LAW CHARACTERISTICS, TYPICAL VALUE ABOUT CKTS. SAME FOR 5 a 1 MHz RECEIVERS DETECTOR a DC AMPLIFICATION FOR 40 CHANNEL RECEIVERS FIG. 4

10 +28V (2) I.5K BNC ZERO CHECK 2.2K +15V 4.7K 22 I W 2N22I9 OR Ak 2NI V >TO AVANTEK MIN= OVOLTS =0 ( 7mA) -6 VOLTS OR OPEN CKT. = OPERATE ZERO CHECK CKT. for 40 CHANNEL DRIVER FIG. 5

11 9 TABLE 2 Center Frecitic)rwies 5 MHz Bandwidth 1 MHz Bandwidth

12 TABLE 3 Back Panel Connectors, Cable Connection, and Color Code for 40 and 50 J1 Pin Filter Bank Analog Buffer No. Color Code A Sig 3 16 Red B Black C Sig 4 17 White D Black Sig 5 18 Green F Black H Sig 6 19 Blue J Black K Sig 7 20 Brown L Black M Sig 8 21 Yellow N Black P Sig 9 22 Orange R Black S Sig Green T Red U Sig White V Red W Sig Blue X Red Y Sig Yellow Z Red a Sig Brown b Red C Sig Orange d Red Continued -- _

13 Table 5 (continued) Sig 15 Green Sig 16 Brown Green Sig 17 Orange Green Sig 18 Yellow Green Sig 19 Blue White Sig 20 Brown White Sig 21 White Sig 22 Yellow White Sig 23 Brown Blue Sig 24 Orange Blue Sig 25 1 Yellow Blue Hil tij KK LL MM NN Sig 26 Orange Brown Sig 27 Yellow Brown Sig 28 Red Violet

14 - 15a - TABLE 6 Back Panel Connectors, Cable Connection, and Color Code for 40 and 50 J6 Pin Filter Bank Color Code J6 Pin Filter Bank Color Code A B Sig 29 Red Black h j Sig 43 White Green C D Sig 30 White Black k 1 Sig 44 Brown Green E F Sig 31 Green Black m n Sig 45 Orange Green H Sig 32 Blue Black P r Sig 46 Yellow Green K L Sig Brown Black s t Sig 47 Blue White M N Sig 34 Yellow Black u v Sig 48 Brown White R Sig 35 Orange Black w x Sig 49 Orange White S T Sig 36 Green Red Y z Sig 50 Yellow White U V Sig 37 White Red AA BB Sig 51 Total power from BNC W X Sig 38 Blue Red CC DD Sig 52 Total power from BNC Y Z Sig 39 Yellow Red EE FF Sig 53 Spare a b Sig 40 Brown Red HH JJ Gnd 54 Gnd Spare c d Sig 41 Orange Red KK LL Gnd 55 Gnd Spare e I Sig 42 Blue Green MM NN Gnd Gnd Spare

15 Front Panel of 5 MHz Receiver Back Panel of 5 MHz Receiver

16 Iv. NEW 50-CHANNEL RECEIVER The 10 khz and 30 khz 50-channel receivers use the fixed filter, offset LO technique, that is shown in Figure 1. This permits the use of a standard filter to determine the bandpass characteristic of the channel, which results in greater repeatability from channel to channel plus greater economy. The center frequencies of the channels are determined by crystal oscillators, which gives better stability than L. C. filters plus the freedom to easily change center frequencies. The 10 and 30 khz receivers are similar in design with the only differences being the crystal filter and its matching resistors and the crystal frequency of the channel LO. Mechanically, the receivers are identical, which allows printed circuit cards to be interchanged or mixed. Output connectors and zero check levels are the same as on other receivers. Output level is nominally +1 volt DC. The following diagrams (Figs. 6-9), tables, and photographs are to assist in troubleshooting and repair and are essentially self-explanatory (Figs. 7-8). The cost for parts is approximately $100 per channel.

17 TOTAL POWER kv 1-25 CH. ZERO al CHECK 7./ INPUT 1-25 CH. BACK PANEL FILTER 30 Mc/3 6 db DIO DE H.:^4,1* TEN. SW. -10dB TOTAL PWR. DET. & AMP CH. INPUT CH. ( SAME AS ABOVE) TOTAL POWER k!!) CH. 100K K METER MONITOR F. P. 100K 100K 24K 0-2 V TOTAL POWER SW. BLOCK DIAGRAM OF 50 CHANNEL RECEIVER Figure 6 5 WAY POWER DIVIDER 5 C H. DETECTOR BOARDS I 2 OUTPUT TO 3 4 CONNECTORS 5 WNWHO

18 TO +I5V 100 p H p F K 200 pf XTAL 100 F 01 HI 150 RF INPUT NOTE: Rx VALUE DEPENDENT ON FILTER (EX: 30 KC /2K & 10KC/680A ) 1161 MIXER 12-8 pf C.F.NETWORKS XTAL FILTER A CKT.-# I CKT.# 2 CKT. # 3 CKT.4/.4 CKT.# 5 ALL CKTS. ( 5 )ARE IDENTICAL + 100/ CHANNEL FILTER DETECTOR BOARD Figure 7 390K.001 F 41, K ANALOG118 DEVICE 50K 20K 5.IK TRIM CARD CONNECTOR END OUT I OUT OUT OUTI OUT 1

19 N RF 11 IN 100 /1- N, RF -1 7.) OUT RF._1 01 1N IN 470 I00/.L1 RF OUT DIODE SWITCH I. 5K II V ZENER 1N4741 DIODE SWITCH DRIVER 50 CHANNEL MULTIFILTER 10-30KHz Figure 8

20 =IMO TOTAL POWER BACK PANEL SWAIM Aa B CKTS:-SAME FOR-30 a 10-KHz TOTAL POWER DETECTOR a DC AMPLIFICATION FOR 50 CHANNEL RECEIVERS Figure 9

21 TABLE 7 Crystal Frequency and Center Frequency for the 30 khz Multifilter Receiver Frequency LO (Crystal Oscillator Frequency) Frequency LO (Crystal Oscillator Frequency) L

22 TABLE 8 Crystal Frequency and Center Frequency for the 10 khz Multifilter Receiver Frequency LO (Crystal Oscillator Frequency) Frequency LO (Crystal Oscillator Frequency) , , i L I

23 - 24 -, Z 2-- Front Panel of khz Receiver Igy; 2.0V Back Panel of khz Receiver

- 25 - *NO. 1,1 Y 1,4 )1:7 AN ;YE "d ()(.

24 *NO. 1,1 Y 1,4 )1:7 AN ;YE "d ()(.= Top View of 30 khz and 10 khz Printed Circuit Board Botton View of 30 khz and 10 khz Printed Circuit Board

NATIONAL RADIO ASTRONOMY OBSERVATORY Green Bank, West Virginia Electronics Division Internal Report No. 88 MULTIFILTER RECEIVERS

NATIONAL RADIO ASTRONOMY OBSERVATORY Bank, West Virginia Electronics Division Internal Report No. 88 MULTIFILTER RECEIVERS D. L. Thacker and Lewis Beale OCTOBER 1969 NUMBER OF COPIES: 100 MULTIFILTER RECEIVERS