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R-390A/URR Communications Receiver
This radio is in use at WB6FZH's Northern California QTH
R-390A/URR Technical Information
- Production Years: 1954-1984 (Atleast 67,000 produced)
- Manufacturers: Collins, Motorola, Stewart Warner, EAC, Teledyne Systems, Imperial, Communications Systems, Dittmore-Freimuth Corp, & Fowler Industries.
- Weight: 95 lbs.
- The R-390A/URR is a redesigned R-390 (1949) w/mechanical filters
- CV-591/URR SSB- A SSB product detector & Audio Unit- Rack Mounted
- CV-116/URR FSK- Radio Teletype converter (Diversity Reception 2- RX)
- Collins Radio Company Design- 19" Rack- Mainframe with 6 sub-chassis
- 500 khz to 32 mhz in 32 Bands- Mechanical-Digital readout to 100cps
- Triple Conversion below 8 mhz, Dual conversion above.
- Crystal Controlled first and second conversion oscillators
- Collins PTO type variable frequency control with separate unit
- All tuning is linear with mechanical control of coil slugs,etc.
- Antenna input: 125 ohms balanced("C"connector), and 50 ohm unbalanced
- Neon bulb across input to reduce static
- 6DC6 low noise first RF amplifier
- Mixers all AGC controlled, with 6C4 triodes
- PTO Sealed and "ovenized" (Collins Design) Silica Gel unit on top
- Second Oscillator 6AK5W- Oven controlled crystal oscillator
- Audio Filters used in wide/narrow selectivity (800 cps min)
- 4th IF Amplifier transformer coupled to 5814 Plate Detector
- AGC speeds: .015, .30, and 5 seconds
- BFO is a "Mini PTO" sealed in a shielded enclosure
- Dual audio channels, 5814 pre-amps to 6AK6 audio outputs (600 ohm Line & Local Headphones)
- VU Meter @ 600 ohm line great for calibrating and remote audio feed
- AC Power Supply: 220/110 AC 60 cycle (26Z5 rectifiers produce 240 VDC)
- OA2- regulates the 150 volt line to oscillators
- Filiaments of VFO & BFO are fed through a ballast tube RT-510/3TF7
- Mechanical Marvel to operate and service
- Performance Data
- Harmonic Distortion: 6.2% @ 4khz, 1,000 RF input 30% modulation at 600 ohm line
- BFO distortion 9.6%
- Noise floor: .14uv (-127dbm) @ 2khz bandwidth, .013uv @ 100cps bw
- 10 db S/N Ratio, .44 uv @ 2 khz bandwith
- AM Sensitivity: 1 uv
- Power Supply Ripple: .012%
- Blocking Dynamic Range: 72.1db(2kc bw w/200kc freq. separation)
- 2-tone, 3rd order dynamic range: 52.7 db @ 10kc signal separation
- Stability: 1hr-+210 cps(20min), +140(1hr) from cold start
- Crystal Oscillator Stability: 1st & 2nd Xtal Osc- 2 cps
- PTO Stability: after 1 hour-=260cps, 3hr= +75cps, 1 cps in 3 days!
- Radiation from original Meters: 50mr per hour at face, 6"=.13mr per hour at 6"
- Common Modifications
- The Audio can be improved for tone and distortion.
- Some remove RF Gain Control in Front end Cathode(V201)
- Solid State ballast for PTO/BFO.
- Solid State conversion of AC PS rectifiers
More Technical Information about this receiver will be posted soon.
Suggestions
- Be sure to obtain the Manual for Maintenance TM-11-5820-358-35 (Army)
- Use Line to Voice transformer between LINE output to a 4-8 ohm speaker.
- Keep the area around the Receiver clean.
- Use fan to keep dust away and add to air circulation.
- Look for a parts unit right a way just incase.
- Keep spare tubes, especially: 6DC6, 3TF7 ballast and 26Z5 rectifiers.
- Enjoy one of my favorite receivers- 73 DE WB6FZH- Greg Greenwood
MORE INFORMATION POSTED SOON!
Last Updated: September 5, 1998
