Linear permeability tuned VF0 with 1 kc dial divisions.

VF0 and crystal frequencies pre-mixed for all-band stability

Covers ham bands 80, 40, 20, 15 meters completely and 28.5 to 29.0 Mc of 10 meters with crystals furnished

Any ten 500 kc ranges between.1.5 and 30 Mc can be covered with accessory crystals for 180 meters, MARS, etc.(5.0-6.0 Mc not recommended)

Four bandwidths of selectivity, 0.4 kc, 3.2 kc, 2.4 kc and 4.8 kc

Pass-band tuning gives sideband selection without retuning

Noise blanker that works on CW, SSB, and AM is built-in

Notch filter and 25 Kc crystal calibrator are built-in

Product detector for SSB/CW, diode detector for AM

Crystal Lattice Filter gives superior cross modulation and overload characteristics

Solid State Permeability Tuned VFO

10 tubes, 10 transistors, 17 diodes and 2 integrated circuits

AVC for SSB or high-speed break-in CW

Excellent Overload and Cross Modulation characteristic

	FREQUENCY COVERAGE: 3 .5 -4 .0 MC , 7.0-7.5Mc, 14.0-14.5, 21.0-21.5, and 28.5-29.0 MC with crystals supplied.
	ACCESSORY COVERAGE: Ten accessory crystal sockets are provided for coverage of any 10 additional 500 KC ranges between 1.5 and 30 MC with the exception of 5.0 - 6.0 MC.
	SELECTIVITY: Drake tunable passband filter provides:  .4 KC at 6 DB down and 2.6 KC at 60 DB down 1.2 KC at 6 DB down and 4.8 KC at 60 DB down 2.4 KC at 6 DB down and 8.2 KC at 60 DB down 4.8 KC at 6 DB down and 20 KC at 60 DB down Selectivity switching is independent of detector and AVC switching.
	I.F. FREQUENCIES: First I. F. - 5645 KC crystal lattice filter; second I.F. 50 KC tunable L/C filter.
	STABILITY: Less than 100 cycles after warm up. Less than 100 cycles for 10% line voltage change.
	SENSITIVITY: Less than .5 uv for 10 DB signal plus noise to noise on all amateur bands.
	MODES OF OPERATION: SSB, CW, AM, RTTY
	DIAL CALIBRATION: Main dial calibrated 0 to 500 KC and 500 to 1000 KC in 5 KC divisions. Vernier dial calibrated 0 to 25 KC in 1 KC divisions.
	CALIBRATION ACCURACY: Better than 1 KC when calibrated at nearest 100 KC point.
	AVC: Amplified delayed AVC having  slow (. 75 sec .) or  fast (. 025 sec.) discharge; less than 100 microsecond charge.  AVC can also be switched off. 3 DB change in AF output with 60 DB change in RF input.
	AUDIO OUTPUT: 1.4 watts max. and .5 watts at AVC threshold.
	AUDIO OUTPUT IMPEDANCE: 4 ohms and hi impedance for anti-vox.
	ANTENNA INPUT: Nominal 52 ohms.
	SPURIOUS RESPONSES: Image rejection more than 60 DB. I. F. rejection more than 60 DB on ham ranges. Internal spurious responses in ham ranges less than the equivalent 1micro Volt signal on the antenna.
	POWER CONSUMPTION: 60 watts, 120/240 VAC, 50/60 cycles.
	DIMENSIONS: 5-1/2" high, 10-3/4" wide, cabinet depth 11-5/8"
	WEIGHT: 16 lbs

DIFFERENCE BETWEEN 13 tubes version and 11 Tubes version)
By WA9TGT / Donnie Garrett

	TUBE  13 tubes version	TUBE  11 tubes version	FUNCTION
V1	12BZ6	12BZ6	RF amp.
V2	6HS6	6HS6	1 st Mixer
V3	12BE6	12BE6	2 nd Mixer
V4	12BA6	12BA6	50 Kc IF Amp
V5	12BA6	12BA6	50 Kc IF Amp
V6	6GX6	NOT USED	Prod Det/AF Amp
V7	6EH5	6EH5	AF Output
V8	6HS6	6HS6	Pre Mixer
V9	12BA6	12BA6	50 KC Amp / NB
V10	12AX7A	12AX7A	NB / Pulse Shaper Amp
V11	OB2	OB2	Voltage Reg
V12	12BA6	12BA6	XTAL Cal
V13	12AV6	NOT USED	AVC Amp / Rect

Many of you may not know this but the R.L. Drake Company made 2 versions of the R4A receiver.  The early version was a 13-tube design and the later version was an 11-tube design.  Having both, I can not tell any noticeable difference in performance between the 2 versions. 
If I have noticed anything at all, it's just a slight difference in the sound of the audio coming out of the speaker.

There are some significant differences in 2 areas of the circuit design between the two versions.  Viewing both versions from the topside, you will find that everything appears to look the same except for the 2 extra tubes in the early version. 

Both of these tubes are located in front of T-10. The closest tube to T-10 is (V-13) a 12AV6 which serves as an AVC Amp / AVC Detector.  The second tube (V-6) a 6GX6 sits in front of the 12AV6.  V-6 functions as a Product Detector / Audio Amp.  Both these circuits were replaced with a combination of transistors and diodes in the later 11-tube version. 

The 11 Tube version used a pair of 2N3394's (Q7 & Q8) as the 1st AF/Amp, and it also used (2) 1N270 diodes in the product detector circuit.

You will also will find that in the earlier 13-tube version, Drake used a pair of 2N3858 transistors in the PTO circuit. One transistor serves as the Oscillator and the other serves as the Buffer amp.

The PTO was changed in the later 11-tube version to use a 2N706 Oscillator and a 2N3858 Buffer amp.  Both versions incorporate bipolar transistors. 
Drake switched to a FET as the PTO oscillator in the R-4B receiver in effort to obtain even better stability. 

I have experienced very few problems with the R4A PTO design. Most all R4A's seem to settle down after an initial warm up period.The most common problem I have found is that the mechanical parts of the PTO have become dirty. This can often lead to mechanical and electrical problems.

If you take 4 or 5 different R-4A receivers there will always be one or two that tend to be slightly better than the others as far as stability goes.  I also have had similar experience with the TR-4's.  Actually, Drake did a good job of temperature compensating their PTO's, some just turned out a little better than others.

All but one of my R-4A's that I have purchased had various problems.  These were problem's that quickly surfaced after just a few minutes of use. I once purchased a so-called good working R-4A (according to the seller) only to quickly realize how sick it was after I brought it home.  I don't think the person I purchased it from actually realized how bad it was.  I soon began to resolve each problem one at a time, slowly restoring it back to as near perfect operating condition as possible.

All in all a proper working R-4A receiver whether it be the early or late version is a superb receiver. 
The R4A's are quite often passed over in favor of the R-4B. 
Give the R-4A a try, it's a great receiver when working properly!

73, Donnie Garrett / WA9TGT - Thanks to Donnie