In 1979, RadioShack / Tandy presented their DX-300, a compact desktop shortwave receiver based on the Wadley Loop circuit, in contrast to the earlier DX-200, a digital frequency display has been added.
The receiver is quite compact with 36 x 16,5 x 23,5 cm and a weight of 6 kg. It can be powered from 12 Volts DC from a car batterym from eight UM-1 batteries or from mains: the sets sold in Europa are wired for 220 Volts, the Amrican model 110 Volts AC.
In the middle of the front panel, You find the red LED frquency display. The outer ring of the main tuning knob lets You select the 1 MHz bands, the tuning knob itself tunes the Kilohertz in 1 kHz steps - it's not easy to recognize that the receiver is technically based on the Wadley Loop technology.
At the left, You find the signal strength meter, a tiny FINE TUNING knob just below detunes the receiver for 1,2 kHz without altering the frequency indication. The dial marks of the preselector dial at the left are easy to read, a red LED indicates the active preselector waveband.
In the left lower part of the frontpanel, just below the preselector tuning control, You find the preselector bandswitch. The preselector is inactive in the VLF range 10 - 150 kHz. Just at the right, You find three switches for the attenuator, the dial illumination and an audio filter. No joke: the bandwidths WIDE - NORMAL - NARROW are not I.F. bandwidths but the control does only affect the audio filter. This attempt of RadioShack / Tandy to make the impression, the receiver is equipped with three expensive I.F. bandwidth filters, was the reason of severe criticism to the set from the shortwave listeners community. RadioShack did correct this and the successor of the receiver, the DX-302 came with two proper I.F. bandwidth filters.
In the right lower corner, below the 12 cm diameter speaker,
You find the R.F. gain control, the volume control combined with the on/off switch and the modes switch - for single sideband reception, both sidebands can be selected independantly and in one AM position, a noise limiter is activated.
Operating the DX-300 is not all that easy because the receiver is based on the Wadley Loop technology: After having connected an antenna (not too long, to avoid overloading), turn on the set with the volume control until a slight hiss is audible from the speaker. The R.F. gain should be set to the most clockwise position, as usual in receivers with a R.F. gain control, the modes switch should be on AM.
Use the outer ring of the main tuning knob to select the desired 1 MHz band and the main tuning knob itself to tune the corresponding kHz digitas of the desired frequency. If the signal of ORF from Vienna is not yet audible on 6.1 5 5 MHz, set the preselector band switch to the 4,5-12 position and tweak the preselector to maximum signal in the speaker and maximum reading on the signal strength meter, a look at the coarse markings in the preselector dial might be helpful.
The radio's weak point is the poor selectivity: for strong signals from international shortwave broadcasters, the standard 6 kHz I.F. filter will do the job, for CW reception of Amateur radio signals, this filter is far too wide. The good sensitivity of the receiver and the fair to good dynamic range cannot overcome this weakness.
So, the RadioShack / Tandy DX-300 which is rarely found in Europe is in my eyes a nice example of a hybrid technology shortwave radio combining Wadley Loop circuitry with a digital frequency counter, it does not meet the DXers expectations. It might do the job only, if You intend just to monitor some of the major international shortwave broadcasters and there are much better and cheaper (even if found on the used market) receivers for this purpose.