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AMATEUR RADIO By GARRY CHATT, VK2YBX Yaesu's new FRG 8800 • shortwave receiver Just when you thought that you owned the ultimate receiver, a new all singing, all dancing model arrives on the market. You ask yourself just how good is the receiver in my shack? That's what I did when the latest receiver from Yaesu, the FRG-8800, arrived for evaluation. The Yaesu Musen company of Japan has, for years, produced receivers for both shortwave listeners and amateurs alike. Among its offerings over the last 5 years have been the FRG-7 (or "Frog-7" as it was commonly known at the time), the FRG-7000 which like the FRG-7 used the Wadley Loop principle, the FRG-7700 (a PLL synthesised receiver), and now the FRG-8800 which is an even more advanced "semi-professional" receiver. Considering the expense of such receivers, I thought it would •be a worthwhile exercise to do a direct hands-on comparison between the FRG-8800 and its predecessor, the FRG-7700. Computer control Perhaps the most advertised feature of the FRG-8800 receiver is its ability to interface to a computer via an RS232 connection. This feature allows computer control of the frequency and mode of reception, and the selective scanning of any frequencies within the coverage of the receiver (150kHz to 29.999kHz). In addition, there is a facility to enable the "S" meter and squelch status to be recordes by the computer, thus virtually turning the unit into a programmable multimode HF scanner, complete with expanded memories (using the computer RAM or floppy disc). For example, as many shortwave broadcasters use several bands simultaneously for optimum coverage, a program can be written to turn the receiver on at predetermined intervals and test each frequency for signal strength, then select and change the receiving frequency, depending upon propagation conditions, for optimum reception. All this information can be stored in computer memory, providing a log of conditions, frequencies, dates, times and station callsigns. Of course, considerable effort must be expended to minimise the effects of computer generated noise on the receiver itself, but the FRG-8800 is certainly capable of all this, whilst the FGR-7700 is not. Improvements The Yaesu FRT-7700 antenna tuner is a worthwhile optional extra with the FRG-8800. Other optional extras include internal and external VHF converters, a lowpass filter and an active antenna. 66 SILICON CHIP Apart from the CAT (computer aided transceiver) features, it is pleasing to see that Yaesu has improved some of the shortcomings of the FRG-7700. These improvements include wiring the headphone socket so that either mono or stereo units can be used, an enhanced LCD display, a multi-mode squelch which really works and is not limited to FM reception only, a "Woodpecker" noise blanker, memory scanning, and a direct frequency entry keyboard. The direct entry keyboard allows The FRG-8800 can be linked to a computer, thus turning it into what is virtually a programmable multimode HF scanner. The keyboard allows direct entry of the desired frequency. the user to rapidly change from one frequency to another without endless rotation of the main tuning dial, which was an annoying necessity with the FRG-7700. One simply enters the desired frequency in either megahertz or kilohertz directly on the keyboard. Tuning is made easy by the provision of "fast" and "slow" modes, which result in tuning rates of either 125kHz or 6.25kHz per complete turn of the tuning knob. Another improvement in the FRG-8800 is the ability to connect a VHF converter (the FRV-8800) internally. This greatly simplifies antenna connection if using a dedicated VHF antenna and an antenna tuner with the receiver. This applies particularly if it is the genuine Yaesu (FRT-7700), as the wiring when using an external VHF converter (the only type available for the FRG-7700) can become quite a mess! In terms of RF performance, the specifications are little changed. Perusing the specifications for both receivers, it can be seen that the sensitivity and selectivity figures are identical, as are power consumption, size, weight, modes of reception and frequency range. About the only improved specification with any relevance to the actual reception of signals is the receiver stability which is considerably improved at less than 300Hz quoted drift during the first 30 minutes of operation from cold start. Even this parameter is not of extreme importance to shortwave reception. On-air tests On air testing revealed that there were some small differences in the performance of the two receivers when connected to a "long wire" antenna. Perhaps the most noticeable, in the presence of a weak signal, was the slight interference internally generated by the processor in the FRG-8800. This does slightly reduce its ability to recover intelligent speech. The FRG-7700 does not suffer the same problem. However, this inter- r- nally generated noise probably would not cause any significant difference when the receiver is connected to a suitable coaxially fed dipole or Yagi antenna. Eventually the considerations can be simplified to a tradeoff between additional purchase price and enhanced operator features. The FRG-8800 offers all the features that the amateur could want at an affordable price. However, if " no frills" shortwave listening is the ultimate goal it could be that your existing receiver fills the bill. The FRG-8800 is available from Dick Smith Electronics stores around Australia for $1295. The FRV-8800 VHF converter is available for $169. Both units come with a two year warranty. ~ ◄ -- l -~ ►1 \ "Length" In sulator Insulator COAX Cabl e Dipole Antenna A simple resonant dipole antenna will provide fair to good performance over a specific frequency hand. The dipole should be cut to resonate at the centre of the band according to the formula: length (metres) = 142.5/frequency (MHz). JA N UARY 1990 67