"New front panel. Note that the power toggle switch replaces the BFO tuning knob and the two air variables for the front end are now stacked at the right -- necessary to give room for the coils. The bottom row of controls has been shuffled to reduce the length of the leads for the BFO tuning cap. The slide switches have been replaced with miniature toggle switches."

"HR-10 rear view. Lots of minor changes coming on the way to an HBR design, but the signal flow remains the same: front to rear along the left in this photo, across the rear through the xtal filter, forward up the IFs to right of center, then to the right through the detector and to the audio. Power supply is shown on the right."

"The tube added between the audio stage and the product detector is the BFO and bias rectifier. The calibrator and AGC detector is almost hidden behind the 3rd IFT, the one nearest the panel. Note that the 3rd IFT and the BFO coil have swapped places -- easy to do since the mountings are identical. This is necessary to shorten the BFO lead lengths and get this circuitry away from the IFs."

"The shield plate between antenna and mixer coils is essential and must be about this size to keep the RF stage from oscillating. Note the receptacle for the line cord. The BNC antenna connector will perfectly replace the small 'RCA' type connector of the HR-10. Above/between the meter terminals you can see the two diode strings I always put across unique meters before turning on the power. Three 1N4001 diodes in series each way will work just fine to protect the meter movement in case of a short."

"The bracket for the lower air variable was made by sawing off the old one. This cap is the calibration control. The coil at the rear is the oscillator coil; it occupies the old calibrator socket. The antenna coil (at the front) and mixer coil are in the space cleared by moving the calibration control to the right, under the antenna trimmer. The chassis arrangement actually turned out very well, with no problems with unwanted coupling between stages and reasonable lead lengths."