US Navy RTTY Demodulators / FSK Converters

RTTY is also called RATT (Radio Teletype)

This page is for RTTY electronics - Go to Navy Teletype Page for actual TTY equipment

Early USN RTTY equipment - Click Here
           FRA, FRC, FRE, FRF, FRH receiving converters


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Dual Diversity system for use with RBP receivers
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general description from AN/FGC-1 manual (TM 11-356)

general description from AN/FGC-1A manual (Western Electric)

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KY-60/FRA-4 keyer
CM-26/FRA-24 comparator
PP-561/FRA-4 power supply

50 kc IF input triple diversity converter - for use with RBP or RCP rcvrs


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Manual NAVSHIPS 91496

another  spec sheet

AN/FRA-86 (AFSAV-133D)
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Twin-channel FSK & DFSK unit used by SECGRU - also by COMMSTAs?

Info - Description & Operation


more to post later

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AN/URA-6 diversity system comprises two CV-57/URR plus one CM-14/URR Comparator
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CV-57 - 455kc IF input converter with tuning scope

395-470kc IF input (photos thanks to Ken Schwieker)

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CM-14 comparator
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CM-14 controls

Photos thanks to W5JV
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ura6-w5jv-04.jpg (226153 bytes)

ura6-w5jv-01.jpg (161462 bytes)


AN/URA-7 diversity system comprises two CV-71/URR plus one CM-14/URR Comparator
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CV-71 50kc IF input converter with tuning scope

CM-14 - 
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47.5-52.5 kc IF input - otherwise appears identical to CV-57

cv71-urr-03.jpg (8933 bytes)


AN/URA-8 diversity system comprises two CV-60/URR plus one CM-14/URR Comparator
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CV-60 audio input converter with tuning scope

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CM-14 - 
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  • audio input unit - electrically same as CV-89A but externally same as CV-57

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  • Note: URA-8 is interchangeable with but not the same as URA-8A
  • manuf RCA
  • Spec Sheet
  • Manual NAVSHIPS 91339

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cv60-177.JPG (4123015 bytes) cv60-182.JPG (3973514 bytes) cv60-178.JPG (3852208 bytes) cv60-179.JPG (4117383 bytes)


AN/URA-8A diversity system comprises two CV-89/URA-8A plus one CM-22/URR Comparator in MT-719/URA-8A enclosure AN/URA-8B diversity system comprises two CV-89A/URA-8A plus one CM-22A/URR Comparator in MT-719/URA-8A enclosure Note: units and internal modules are interchangeable except URA-8B units have blowers on rear, URA-8A units do not.

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audio input converter with tuning scope

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CV-89A photo courtesy of Western Historic Radio Museum

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  • More CV-89 info here 
  • Manual NAVSHIPS 91278 (URA-8A) or 91490 (URA-8B)
  • USAF manual is T.O. 21R1-2URA8-11
  • manuf - 
    Hoffman &
    National (URA-8B)
ura8a_5350.JPG (2689736 bytes)
ura8a_5349.JPG (2822207 bytes) AN/URA-8B
ura8b-1307-01.jpg (545671 bytes)


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CV-89 rear - no fan connector
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CV-89 rear - no fan
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CV-89A rear - fan connector
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CV-89A fan
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  • See CQ Magazine June 1962, page 81, for hookup and operation info (see
  • See 73 Magazine,  June 1985, page 46 for hookup to RS-232

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cm22a-ura8-1312.jpg (127852 bytes)
cm22a-ura8-1311.jpg (53384 bytes)
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AN/URA-8B manual -
 download pdf

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(CV-89 schematic from manual T.O. 16-30URA8-6, thanks to a greenkeys list member)
  • audio input - pin A, pin B (AN3106-14S-7))
  • TTY - negative ground pin B, positive pin A (switched to ground) (AN3106-14S-9S)
  • power - 115vac pin C, pin A (AN3106-14S-7S)


AN/URA-12 diversity system comprises two CV-227/URR and one CM-42/URR comparator

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CV-227 - 200kc IF input converter 
190-210 kc input

CV-227 controls
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spec sheet


prototype serial #1
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AN/URA-17 diversity system comprises two CV-483/URA-17

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audio input converter with tuning scope

Essentially a solid-state version of the CV-89A/URA-8A. 10 to 1000cps shift


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CV-483/URA-17 Schematic (thanks to Randy Guttery) 
click image above for 3300x750 or click here for 6500x1500

  • J6 TTY output - negative ground pin B, positive pin A  (switched to ground) (AN3106-14S-9S)

URA-17 Manual (thanks to Rice)

URA-17C Manual

URA-17D Manual (thanks to Hutch)


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cv483c-ura17-1207-01.jpg (35019 bytes)

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cv483c-ura17-1207-03.jpg (59920 bytes) AN/URA-17(XN-1) Prototype Concept
ura17-xn1-1.JPG (627985 bytes)

NOTE: AN/URA-17, AN/URA-17A, AN/URA-17B, AN/URA-17C, and AN/URA-17D are receive-only AFSK converters (see above)
NOTE: AN//URA-17E, AN/URA-17F, and AN/URA-17G are receive + transmit AFSK Terminal Units - see TU page


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dual diversity 455kc IF input converter

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Signal Corps procurement but used by USN as part of AN/FRR-38 dual diversity receiving system
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part of AN/FRR-24 receiver system

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50kc IF input converter - part of FRR-24 receiver - internal HV power supply only Please send me email if you have a CV-127 or any other FRR-24 parts for sale or trade-
  • Manuf - National Radio

(TMC model CFA-1)

cv763-01.jpg (46163 bytes)

audio input dual diversity converter 

Connections -
    audio input #1 - terminals 1,2
    audio input #2 - terminals 3,4
    ground - terminal 5
    loop supply pos - terminal 6
    loop supply neg - terminal 7
    TTY neg - terminal 8 (jumpered internally to terminal 7)
    TTY pos - terminal 9 (switched to terminal 6)


CV-2310()/G FSK and DFSK demodulator  - Perhaps the replacement for AN/FRA-86 (see above). Please send me e-mail if you have any info about this unit.

cv2310-01.jpg (552359 bytes)

cv2310-02.jpg (1374279 bytes) Colored cylinders are plug-in filters

cv2310-03.JPG (841349 bytes)

Please send me e-mail if you have any info about this unit.

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Hoffman Model 170 - prototype

Please send me e-mail if you have any info about this unit.

Dual Diversity RTTY converter

hoffman-fsk-01.jpg (1435951 bytes)

hoffman-fsk-02.jpg (2406438 bytes) --
Boehme 5-C Series B boehme5c-awa.jpg (24885 bytes) boehme5c-awa-02.jpg (61818 bytes) NAVSHIPS 92660


Keying converter

Converts on-off tone signals (not FSK) to loop current keying

Spec Sheet

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NAVSHIPS 91612 - pdf

Keying converter

Converts on-off tone signals (not FSK) to loop current keying Similar use as R-446/UC but also includes TTY sync pulse circuit NAVSHIPS 91907 - pdf

OSA Monitoring Scope
(Tuning Indicator)

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osa-01.jpg (82981 bytes) osa-02.jpg (72213 bytes) osa-03.jpg (132740 bytes)

designed to mount up high with a tilt-down swivel.

osa-100.jpg (84517 bytes) osa-101.jpg (120910 bytes) osa-102.jpg (78999 bytes) --
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IP-352/UR Monitoring Scope
(Tuning Indicator)
ratt-display-04.JPG (18928 bytes)

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Manuf by Hoffman and designed to mount up high with a tilt-down swivel.

Please send me e-mail if you have a NAVSHIPS 92705 manual

ratt-display-01.JPG (90796 bytes) ratt-display-02.JPG (107063 bytes) ratt-display-03.JPG (130799 bytes) --

Also see Navy RTTY Terminal Unit (converter + keyer) page

List of 61 military surplus RTTY units

Includes brief descriptions - See CQ magazine September 1972, page 83 (avail at

Northern Radio RTTY demods, FSK converters, etc.