Drake R-4A Communication Receiver - Early & Late Versions

Originally Posted by Donnie Garrett (WA9TGT)

I wish to express my thanks to everyone who responded to my R-4A Serial Number Survey request! The response was very good and was most appreciated! I now wish to share the R4A serial number survey and make a few comments concerning the R-4A receiver.

As many of you know Drake made 2 versions of the R-4A receiver. The early version was a 13-tube design, and the later version was an 11-tube design. Having both, I cannot 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. The later 11-tube version seems to be just a bit higher in tone. I have listed the tube line up (shown below) for both versions of the R-4A. The R-4A serial number survey is shown at the bottom of this article.

R4A (13 Tube) Early Version) 11/65

V1 – 12BZ6 – RF Amp
V2 – 6HS6 – 1st Mixer
V3 – 12BE6 – 2nd Mixer
V4 – 12BA6 – 50KC IF Amp
V5 – 12BA6 – 50KC IF Amp
V6 – 6GX6 – Prod Det/AF Amp
V7 – 6EH5 – AF Output
V8 – 6HS6 – Pre Mixer
V9 – 12BA6 – 50KC Amp/NB
V10 – 12AX7A – NB/Pulse Shaper Amp
V11 – OB2 Voltage Reg
V12 – 12BA6 – Xtal Cal
V13 – 12AV6 – AVC Amp/Rect

R-4A (11 Tube) Late Version 10/66

V1 – 12BZ6 – RF Amp
V2 – 6HS6 – 1st Mixer
V3 – 12BE6 – 2nd Mixer
V4 – 12BA6 – 50KC IF Amp
V5 – 12BA6 – 50KC IF Amp
V6 – Not Used
V7 – 6EH5 – AF Output
V8 – 6HS6 – Pre Mixer
V9 – 12BA6 – 50KC Amp/NB
V10 – 12AX7A – NB/Pulse Shaper Amp
V11 – OB2 – Voltage Reg
V12 – 12BA6 – Xtal Cal

In 2 areas, there are some significant differences in 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.

Also, you will find that in the earlier 13-tube version, Drake used a pair of 2N3858 transistors in the PTO circuit as the Oscillator and 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 R4B receiver. In an 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 biggest 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 R4A (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 favour of the R4B. My suggestion: Give the R4A a try. It’s a great receiver when working properly!

R-4A Serial Number Survey Results

Serial Number

Version

Manufacturing Date

2007
2019
2143
2250
2034
2387
2781
2847
2872
2912
2992
3234

13 Tube
13 Tube
13 Tube
13 Tube
13 Tube
13 Tube
13 Tube
13 Tube
13 Tube
13 Tube
13 Tube
13 Tube

Date (11/8/65 per schematic number code) Garey K4OAH
Date Unknown Joe / K9DMV early 1966
Date Unknown Tim / WB8OWX
Date Unknown Gary / W8PU
Date Unknown Jim / W8DRZ
Date Unknown Chuck / K1KW
Date circa 1965-66 Harold / NY7Y Original Owner
Date Unknown Don / WA9TGT
Date Unknown Tim / WB8OWX
Date Unknown Dean / KA6BGW
Date Unknown Al / W8UT
Date Unknown Mike / W3MC

3679B
4054
5036R
5057R
5140
5289R
5398B
5407B
5667G
5822R
6047G
6047G
6051G
6087G
6357R
6620B
6966B

11 Tube
11 Tube
11 Tube
11 Tube
11 Tube
11 Tube
11 Tube
11 Tube
11 Tube
11 Tube
11 Tube
11 Tube
11 Tube
11 Tube
11 Tube
11 Tube
11 Tube

Date Unknown Al / K0AL (I am awaiting reply on version conformation)
Date (8/25/66 per schematic number code) Garey K4OAH
Date Unknown Don / WA9TGT
Date Unknown Jim / W8DRZ
Date Unknown Dave
Date Unknown Jim / W8DRZ
Date Unknown Tom / DF2OO
Date 10-21-66 Don / WA9TGT (still has manufacture tag)
Date Unknown Don / WA9TGT
Date Unknown John / WA4OGD
Date Unknown Don / WA9TGT
Date Unknown Sindre / LA6OP
Date Unknown Don / WA9TGT
Date Unknown Gary / WB7FCQ
Date Unknown John
Date Unknown Sindre / LA6OP
Date Unknown Jack / WA9NQW

Last Updated : 27th August 2024

Drake R-4A Communication Receiver – Early & Late Versions