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RF Amplifiers

From QRP to QRO
Scientific Radio Systems SR-204 Front Panel & Chassis Frame
(EQP) SR-204
Scientific Radio Systems SR-204 Front Panel & Chassis Frame. This was the beginning of the assembly process for building a 100 watt, 1.6 to 30 MHz, 6 channel crystal controlled transceiver. Their beginning is your avenue to high power from your home brew or kit QRP rig to a professional looking rig. All the hard part of homebrewing is done. Just mount your board(s) in the frame and make interconnections to the front panel controls and rear panel connectors. Matching set of knobs included.

Included on the front panel are the controls, switches, jacks and a lighted 0 - 1 mA meter marked in "S" units and watts. An ancillary board for setting individual transmit audio levels for each channel is mounted and includes six 10k ohm trimpots and miscellaneous parts.

The complete receive audio board that takes output from the detector and boosts it to up to 6 watts out into the 4 ohm speaker is also mounted on the front panel and is included. No more headphones only listening. Also on this board are the transmit tone oscillator for tune up of an SSB transmitter, 2 matching line inputs from 600 ohm balanced feeds, one for transmit audio, the other for receive audio and the T/R relay driver.

Also in this frame is the majority of the high power RF deck. This deck was designed to use two 6LQ6 sweep tubes (not included) driven by an MJE340. The MJE340 was driven by a 2N1613 from another board (not included) which is a general purpose 1/2 to 3 watt transitor All parts for the RF deck are included except: two 6LQ6 tubes, 4PDT, 12 vdc, T/R relay and the tank circuit (coil and variable capacitors). It also includes a calibrated RF sampler used to drive the front panel meter through existing wiring on the chassis.

The front panel channel switch extends though the RF compartment and could be used to select pre-tuned tank circuit taps and capacitors. The switch is a 7 pole, 12 position switch with 3 poles in the RF compartment and 4 in the front panel compartment. An alternative is to remove the channel switch for a single band radio and mount the frequency tuning control in its place.

In the original design, this radio included the power supply in the frame to provide all required voltages from either 115 / 230 vac or 12 vdc. If you want to use the 6LQ6 finals, buy the optional power supply of your choice below. Or, gut the RF deck and install you own solid state PA - no power supply needed. A 3-5/8" externally mounted square fan is required for high power operation. A suitable unit is listed on our MUFFIN FANS page.

Ventilated bottom cover included. No top covers available.

A full manual for the SR-204 is included with each unit.

Select from the SR-204 which has a gray silk screened front panel with handles or the SR-204D (below) which is olive drab with no handles. Internally they are the same.

• External dimensions: 13-3/8" wide x 15" deep x 4-1/4"H
• Internal dimensions:
Power Supply section: 6-1/4" x 6-1/4"
Receiver Section: 4" x 6-1/4"
PA Compartment: 6-1/4" x 6"
Exciter Section: 4" x 5"
$50 each

From QRP to QRO
Scientific Radio Systems SR-204 Front Panel & Chassis Frame
(EQP) SR-204D
Scientific Radio Systems SR-204 Front Panel & Chassis Frame same as above except olive drab color. No covers available.
$50 each

SR-204 AC Power Supply

(EQP) SR-AR250-4
Scientific Radio Systems SR-204 AC power supply. Connects to SR-204 frame with 3 plugs and connections to fuseholder. Uses HP style power cord. Requires 3 amp or 1-1/2 amp fuses. SRS P/N: 204400.

• Input: 115 / 230 vac, switch selectable
• Output: 12 vdc reg. 18 vdc, -40 -60 vdc bias, -60 vdc, +84 vdc, +157 vdc and
+550 vdc
 

SR-204 DC Power Supply

(SRS) SR-AR260-4
Scientific Radio Systems SR-204 DC power supply. Requires 25 amp fuse. Use Cinch-Jones P-2404-SB female on power cord to connect to power supply. SRS P/N: 204450.

• Input: 12 vdc
• Output: 12 vdc reg. 18 vdc, -40 -60 vdc bias, -60 vdc, +84 vdc, +157 vdc and
+550 vdc
$95 each
 
$95 each

Solid State HF Broadband
RF Amplifier

(EQP) SR-370AMP
Scientific Radio Systems SR-370 solid state PA board and heatsink. A matched pair of SD1285 transistors in push-pull drive, 2 pair or MRF458 transistors in push-pull to conservatively produce 140 watts output from as little as 1/2 watt drive. Unit is broadbanded and covers from 1.69 to 30 MHz. External bandpass filters are highly recommended. Requires 13.6 vdc at 25 amps for full output.

On board thermal sensors on the output transistors provide input to an external bias control circuit to reduce output power due to high temp and control an external fan on the heatsink (not included).

Heatsink is 9-1/8" x 4" x 1-5/16" - PC board adds 7/8" to thickness. Manual included. Includes filter. Transistors alone are over $200.
 

Band Pass Filter Board for
RF Amplifier

Scientific Radio Systems band pass filter board for RF amplifier (left). This circuit board contains 6 bandpass filters to reduce harmonic output. Each filter is relay switched by grounding the appropriate line.

This board also includes RF output voltage and current sensing to detect SWR variations. As the output SWR diverges from 50 ohms, it is evidenced by output voltage and / or current changes. As a result, the bias on the final transistors is adjusted to reduce power output. Similarly, the output transistor case temperature monitored on the PA board is also used to control an external cooling fan and adjust the bias as needed. Supply voltage changes are also an input to this bias control circuit to reduce power output as supply voltage drops so that the output stage remains linear.

There are also 5v and 8v regulators on this board for various uses in the original radio. Manual included. Circuit board measures 12" x 7" x 1-3/4".
$495 each

2 Tube 811A Amplifier Starter Kit
Military Tank Style!!


Click here to enlarge image
Constant Frequency Control
(EQP) C1155/MRN
Litton 60 Hz frequency control was designed many decades ago to maintain constant 60 Hz on 115 vac equipment. Vacuum tube technology at its best. I doubt anyone will purchase one of these tanks for it's intended use but what a plethora of dandy amplifier parts. New in the box too. 27" wide x 22" deep x 10-1/2" high. Some of the parts included are:

• TUBES: (2) 3B28, (2) 811A, (2) 5763, (1) 6X4, (1) 0A3, (1) 12AT7, (1) 5814

• Frequency Meter 60 Hz Reed Type

• Oil Capacitors (2) 1500v, 4 µF

• Plate Transformer: Freed 30994, 115v, 45-60 Hz primary // 2540 vct 400 madc secondary.
Measures 6" x 7" x 7" high. Hermetically sealed.

• Filament Transformer: Freed 30993, 115v, 45-60 Hz primary // 2.5v @ 10 amps secondary. 1050v high pot. Measures 2-3/4" x 3" x 4" high. Hermetically sealed.

• Modulation Transformer: Freed 31001, 18k ohm center tapped primary // 165 ohm secondary. Drives plates of (2) 811A's. 80 watts. Hermetically sealed.

• Plate Choke: Freed 30997, 4 Hy @ 400 madc, 35 ohms DCR, 1350v high pot.
Measures 3-1/2" x 4" x 6" high. Hermetically sealed.

• Swinging Choke: Freed 30996, 6-12 Hy @ 400 - 100 ma, 40 ohms DCR, 1964v high pot.
Measures 4" x 4" x 5-1/2" high. Hermetically sealed.

• Filament Transformer: Freed 30999, 115v, 45-65 Hz primary // 6.3 vct @ 8 amps and 6v @ 1.5 amps secondaries. Measures 3" x 3-3/4" x 5-1/2" high. Hermetically sealed.

• Impedance Transformer: Freed 31002, 8 kct @ 50ma to 2500 ohm ct @ 50ma.
Measures 3" x 3-1/4" x 5" high. Hermetically sealed.
NEW LOW PRICE!!! - ONLY $795

Mackay Linear Amplifier
2 kw HF Amplifier Deck
1.6 to 25.1 MHz *

(EQP) MR105-40A
This Mackay Marine linear amplifier seems to be in very good condition. 19" rack width, 24" deep, 21" high. Missing top and bottom covers, 2 knobs and 4CX250 driver. Long wire output. Sold as-is. No power supply.

* 1.6-25.1 MHz in 9 bands including these frequencies:

• 1.6 - 4.5 MHz, 6 - 7 MHz, 8 - 9 MHz, 12 - 13 MHz, 16 - 17 MHz and 22 - 25.1 MHz
• 4CX1500B PA Tube included
• 4 panel meters to monitor RF amps, grid and plate RF volts and a multimeter
• 2 air variables
• 2 nice, large radio switches
• 3 nice, silver edge wound coils that are tapped
• Input tuning
$1,495

Kilowatt HF "RF Deck"
1.6 - 30 MHz

   

Features from left to right:

• Motorized Inductor
• Motorized Bandswitch
• B&W 802 Plate Choke
• 3-500Z sockets
Side view of SR-110   Front view of SR-110 Bottom view of SR-110
(EQP) SR-110D
Scientific Radio Systems RF decks for the SR-110 Kilowatt Amplifier line. These complete decks were ready for insertion into the 3' standard rack. Will produce legal limit with a pair of 3-500Z's (not included). Just add the power supply and go. 10 channels completely preset and auto-tuned as operator makes selection. Each channel can be set for separate ham band, with bandwidth to boot. This is a premium quality commercial / military product and not a cheap imitation. 19" wide (rack mount), 21" deep, 17" high. Brand new!! Optional power supply below.

(1) Radio Switch 4P12T Model 88 high voltage / current band switch
(2) Johnson 122-275 ceramic sockets
(16) Various doorknob transmitting capacitors
(1) Fan for tubes w/ airflow switch
(1) B&W Model 802 Plate Choke1) Complete manual compliment for finished equipment "SR-110" in English, French or Spanish!
$795

High Altitude
SR-110H

Added features:
• Chimneys
• Large Tarzan fan on front
• Muffin fan internally or right
• 3-500Z tubes optional
Top inside view of SR-110H   Front view of SR-110H
 
(EQP) SR-110H
Beefed up version of the SR-110, this amplifier outfitted with high capacity blower, chimneys, extra internal ducting and an extra internal fan. Side and top panels included.
$1,145 each
(EQP) SR-110HT
Everything you see above plus a pair of factory installed / tested Eimac 3-500Z triodes.
$1,595 each

200 Watt HF "RF Deck" Amplifier Project
1.6 / 30 MHz

   
 
• (3) 6146W's in Parallel
• 12BY7A Driver
• 12DZ6 Driver		 • 750 vdc @ 1/2 amp
• 240 vdc @ 1/2 amp
• 120 vdc @ 50ma
• 12 vdc @ 1 amp
• Filaments for Tubes
SR-200 Series - 3 Tube Deck      
(EQP) SR-200AMP
Scientific Radio Systems RF decks for the SR-210 / SR-240 Series of Transmitter. All final tested and ready for insertion into chassis. They plug together. Just add input and output tuning and you're ready to go! Ten card edge sockets at top of picture show SRS input boards. Available separately for $45 each. Power supply weighs 18 pounds. 6-1/2" x 8" x 5" high. RF deck is 8" x 8" x 6-1/2" high. Brand new!

• Brand New General Electric 6146W's
• Great building block for QRP Linear Amplifier. Milliwatts drive to full output.
• Full manual and schematic documentation included with purchase.
$239 / Pair - Deck & Power Supply
 

SR-200 Amplifier Channel Strip
Input Boards

Shown: (EQP) SR-200393-2
Required to tune the tube stages of the amplifier. Low-level stages are broad-band, no tuning required. Use up to "10" input boards. Some boards not complete but parts are included.
 
 
Part Number
Mfg. P/N
Frequency
Price
(EQP) SR-200393-2 200393-2 2.25 - 2.5 MHz
45.00
(EQP) SR-200393-3 200393-3 2.5 - 3.0 MHz
45.00
(EQP) SR-200393-5 200393-5 3.5 - 4.0 MHz
45.00
(EQP) SR-200393-6 200393-6 4.0 - 5.0 MHz
45.00
(EQP) SR-200393-13 200393-13 14.0 - 16.0 MHz
45.00
(EQP) SR-200393-14 200393-14 16.0 - 18.0 MHz
45.00
(EQP) SR-200393-15 200393-15 18.0 - 20.0 MHz
45.00
(EQP) SR-200393-16 200393-16 20.0 - 22.0 MHz
45.00

42 MHz VHF Amplifier
6 or 10 Meters?
Control panel view (back?) of amplifier. Verniers control air variable capacitors. Also shown are blower, in/out N connectors, voltage input terminal block.
Inside view of 42 MHz KW    
(RF) AMP42
These amplifier decks are removed in A-1 working condition from medical imaging equipment. Will produce legal limit with 4PR-1000A (included). Just add power supply and go. Add capacity / inductance to get down to 10 meters or decrease capacity / coils to get up to 6 meters. Uses highest quality components. 19" wide (rack mount), 10-1/2" deep, 16" high. Made in Germany.
(1) 4PR-1000A Eimac tube, chimney
(2) 20-110 pF 4kv air variables
(1) 500pF 13kv Draloric PD70*
(1) 50pF 14kv Draloric PD70*1) 1200pF 13kv Draloric PD100
(1) EBM G2E160AD01-01 High Volume Blower, 220v, 1.15 amps
* Draloric PD70 ceramic capacitors rated at 16 amps RMS. PD100 rated at 25 amps.
$1,495

X Band - Radar
Transmitter / Receiver

  
 
(EQP) MI-555601A
New, unused RCA Marine Transmitter Receivers. 1960-70 technology. Yes, that means vacuum tubes. Manufactured in May, 1963. Includes HV power supply. 10-1/2" x 12-1/2" x 25-1/2" long. Some tubes were removed by previous owner, thus units not operational. Sold as-is. No nomenclature.Vacuum tubes include (but not limited to):
• Mullard JP9-2.5 Magnetron with WR-90 output.
• Six 6EW6
• 6EA8
• Four 0A2
• 115NO180 Time Delay Relay
$495 each

SR-110
Complete Amplifiers
SR-110's Side by Side
(EQP) SR-110
Scientific Radio Systems SR-110 Kilowatt Amplifier's shown in stand-by and main mode, side by side. This 48" cabinet has empty area as pictured for exciter, originally to be an SR-380. RF deck and power supply final tested with Eimac 3-500Z's at factory and ready to go. Sold in 1996 for $11,000 each. Brand new!
 

Power Supply
2500v - 3000v

SR-110 Power Supply
(EQP) AR-150A
Scientific Radio Systems power supply for the SR-110 Kilowatt Amplifier. Supplies 1 amp continuous. 19" wide (rack mount), very heavy. Get a load of the huge BASLER hypersil transformer. Oil capacitor not included. Sold separately or with RF decks above. Multi-tapped transformer matches any input. Brand new!
$4,900 each
 
$795 each