Squires-Sanders SS-1R

Just dial in the frequency
As you can see from the front panel of the SS-1R, there are a few new ideas employed in this receiver. Most obvious is the combination analog/digital dial. The frequency to 0.1 KHz is displayed on the linear analog dial. To the right of the tuning knob is a KHz odometer digital dial which reads kilocycles. I think it would have been nice if they had gone digital all the way with the odometer, just like the R-390. It would appear easier in some ways to go in that direction than build the complicated dial assembly used here.
If you look closely to the left of the tuning knob, you will see a small black rectangle. For all of its sophistication, this receiver shared crystals on some bands and the tuning was reversed. The low end of the band was at the right end of the scale. This meant that another digital dial had to be exposed which decremented when the tuning knob was turned clockwise. I have never understood the trade-offs involved when considering the mechanical complexity and the price of this receiver. Surely a couple of extra crystals in the high frequency oscillator couldn't cost that much.

Motorized tuning
The tuning rate of the main dial is 10 KHz per turn. To aid in getting from one end of the band to the other quickly, the two buttons below the tuning knob control a motor which drives the tuning knob upward or downward.

A completely new frontend
Aside from the tuning dial complication, the rest of the receiver holds a treasure-house of circuit innovation. First and foremost is the receiver frontend. If you remember receivers of the '60's, you remember little problems like frequency drift, images, marginal sensitivity, frontend overload and cross modulation. Unlike other receives of its time which almost universally used two tuned circuits and an RF amplifier stage in front of a first conversion mixer, the SS-1R used a single tuned circuit and no RF stage.

The incredible 7360 mixer tube
Taking advantage of a new type of vacuum tube, the 7360, the need for an RF stage was eliminated. Further, this tube was designed to be a balanced mixer and it took a lightning bolt to overload it. (Just kidding!) The 7360 was a very low noise, very linear mixer. Properly adjusted, there was little i.f. feedthrough and receiver sensitivity was at least a good as receiver employing "hot" r.f. stages. To take care of images, a 5 MHz i.f. was used. But, the high i.f. frequency was not enough to insure adequate image rejection since only a single tuned circuit precedes the 7360 mixer tube. What was done was to make the tuned circuit parallel resonant on the desired frequency and series resonant at the image frequency. That was a very neat trick. Best of all, it worked. It's unfortunate that this frontend design was not developed further.

The Specifications
Here is a quick rundown on the SS-1R specs:

Ham bands only
Selectivity - 5 KHz, 2.5 KHz, and .35 KHz The CW filter is only a two pole lattice filter. The 5 KHz filter is L-C's
Sensitivity: <0.5 uV except for 7 MHz where the sensitivity is 1 uV

Image ratio: 60 dB
Stability: <100 Hz
i.f.. rejection: 60 dB
Antenna impedance: 50 ohms. This was important. This receiver doesn't work with mismatched antennas.
Frequency accuracy: 1 KHz

These specifications don't reflect the receiver's main strength, it's ability to handle large signals. There were many receiver that could stand up to the SS-1R and many were better in the areas of sensitivity, readout accuracy, and selectivity but few of them could claim anywhere near the large single handling capability of the SS-1R.

The condition of this receiver is about an 7 or 8. The reflections from the flash camera make things look worse than they are. However, this receiver could use a complete overhaul as can most receivers of this vintage. I have done nothing to it except what was necessary to make it work. It deserves a proper restoration.