A very nice receiver that have received a lot of attention during the years, considered by some being one of the best receivers made.
My receiver is in the 24000-range, and a rather late version of the receiver. It has a number of modifications:
Among the standard options I have:
What I really miss is the NB-4 noise blanker. If you have one for sale, let me know!
From the Ham Radio Magazine February issue 1982. This is a version that allow one to use the original audio amplifier.
Change R5 from 1k5 to 470 ohms. (must say that I am not sure what this will do...)
From the 73 Magazine June issue 1979 "High-Performance Receiver Add-Ons". This mod involves a rerouting around the 6EJ7/EF184 tube. I have seen reports that this modification also creates problems with hum, white noise, etc. Not sure what is best here.
Fox-Tango Corporation sold a number of crystal filters (manufactured by Seiwa Corporation) for the first IF in the Drake R-4C. They were called GUF-1 and GUF-2, and was sold as:
For the noise blanker to work one need the 8 kHz bandwidth, otherwise it may misbehave. GUF-2/GUF-2E are switched in with a couple of relays in the CW-mode. The GUF-1L and GUF-2E are installed in my receiver.
This one comes from Sartori Associates. It cost $25.00 in August 1978. To get the lowest attenuation one also should use the TL442 product detector. The filter is tailored for SSB with a 2.2 kHz cut-off. The audio attenuation at 3 kHz is about 30 dB. So AM reception should sound a bit distorted, but in my experience it sound quite good.