Radio Netherlands Review Of The Lowe HF-225

Introduction

In the first half of 1987, a new shortwave communications receiver came onto the European market. The Lowe HF-125, as it was called, was then upgraded to the HF-225. A 19 inch rack version called the HF-325 was launched in 1990. This offers similar features, plus a few extras. Designed and built by Lowe Electronics of Derbyshire England, it is lightweight at 1.9 kg in its standard version, 2.6 kg if internal Ni-Cd batteries are installed. It measures 253 x 109 x 204 mm making it very compact. It is a double-conversion superhet design, with a high first intermediate frequency of 45 MHz. There is a "souped-up" version of the HF-225, called the HF-225 Europa. The Europa version has better specifications and better filters, but it is more expensive. The set reviewed here is the standard model!

The set comes with a 12 volt DC power adapter for use on 220 volts AC current in Europe. This external power supply gives no problems, providing the transformer box is kept well away from the receiver (i.e. do not put it next to the receiver, or AC mains fields tend to couple with the receiver's oscillator circuitry).

The beginner will have no problems connecting up an antenna, a pair of headphones or a tape-recorder. Lowe electronics have written a clear, logical instruction manual plus a booklet that explains what to listen out for when you start tuning around. Part of its attraction is the simplicity. There are just 9 controls on the front panel, which can be tilted up to face the operator.

Up to 30 frequencies can be stored in the radio's memory. Data is held in these memories using a lithium battery back-up. The memory channels can be quickly selected using the manual tuning knob. The tuning knob itself has a good feel to it, being large enough and offering a recess for the finger.

Tuning

A large clear green-coloured back-lit liquid crystal display shows the frequency being received with a resolution nearest 1 kilohertz. Frequency display shows the true carrier frequency, whatever the mode selected. The manual tuning knob offers FAST and SLOW tuning, depending on the speed with which the knob is rotated. The tuning increments vary with mode selected as follows:

Mode              Normal Speed           Fast Speed

LSB, USB, CW      	8 Hz                   250 Hz

AM                	50 Hz                  500 Hz

FM                	125 Hz                 500 Hz

AM sync           	8 Hz                   No fast mode available

The standard AM steps proved to be small enough for comfortable tuning without any annoying "chuffing" effects. If you select either upper/lower sideband or the CW mode as you would do for radio amateurs or telex stations, the slowest tuning step drops to 8 Hz. This is a considerable improvement over the older HF-125. Since the receiver is stable, the fine tuning steps allows you to accurately tune in a radio-teletype station with ease. The receiver also has a narrow-band FM option for monitoring citizen's band on 27 MHz for instance, but we didn't test this mode ourselves. The increment chosen for the AM sync mode is fine, but there is no provision for selecting either upper or lower sideband. We think this is a limitation. The keyboard comes as a separate option costing £39.50. It is a good idea to regard this option as essential, as tuning is made a lot easier. The keypad can be placed horizontally in front of the set, making it easy to punch in frequencies. The keyboard software is clever.

Stability and birdies

We put the receiver in a constant temperature environment (18 Centigrade) and tuned it to 12100 kHz. The set was then switched to the USB and LSB modes. After an hour, drift was less than 40 Hz in each instance. This is comparable with receivers in much higher price classes.

If you put a shortwave receiver inside a metal cage so that it's screened off from the outside world, you can then measure "ghost" signals on the dial generated by the set itself. They appear as a silent carrier if you're listening on AM or as a whistle if you're listening on single-sideband. Most sets of this price range suffer from these so-called "birdies", and you can't get rid of all of them without drastically increasing the price of the radio. The designer's aim is to make them as weak as possible and on frequencies that are outside major broadcast and amateur bands. We measured more than 25 low level birdies on the HF-225 (i.e. greater than 0.5 microVolt). Most of these disappear below the noise level when you connect an antenna, but we found 6 "birdies" which were above 1 microVolt, and therefore noticeable. If you try to tune in a station on these channels, you will get extra distortion or interference generated by the HF-225 itself. More expensive sets like the Yaesu FRG-8800 and ICOM ICR-71 have around the same number of birdies too. For a receiver of this price bracket, the number of birdies on the HF-225 is good, and better than the HF-150.

Sensitivity

In our tests we checked how much signal is needed at the 50 Ohm input to get a signal + noise/ noise ratio of 10 dB. Sensitivity often varies with frequency, and for that reason the HF-225 was measured at several points in the spectrum. We checked the AM mode (using 60% modulation) and SSB. The 4 kHz filter was selected for the measurements, being the filter than SW listeners are most likely to use for broadcast listening.

Sensitivity: In microVolts at 50 Ohms: 10 dB S+N/N, 60% mod AM, 100% SSB, 1 kHz tone.

MHz    0.2     2.2     8.0     12.1     16.0     26.0
AM     0.66    0.63    0.70     0.73     0.68     0.71
SSB    0.22    0.20    0.20     0.19     0.18     0.28

The receiver's built-in synthesiser generates a lot of noise between 30 and 70 kilohertz, way down in the very low frequency part of the spectrum. This masks most of the signals coming in. But from 100 kHz up to 30,000 kHz, covered continuously on this set with no breaks, the sensitivity is remarkably uniform. Sensitivity is also dependent on the chosen bandwidth filter. The following measurements were taken at 12.1 MHz.

Sensitivity in microVolts, measured at 50 Ohms: 10 dB S+N/N against bandwidth AM 60% at 12.1 MHz.

IF kHz          2.5     4.0     7.0     10.0
Sensitivity    0.49    0.71    0.70     0.78

The receiver offers an analogue signal strength meter which turns out to be very accurately calibrated, far more than just a tuning gimmick.

RF Attenuator/ Automatic Gain Control

A push-button attenuator is provided, offering around 17 dB attenuation when measured at 12 MHz. It consists of a resistance-network, which can be shorted out of circuit by a diode. After the initial attenuation is seen on the S-meter, there is no further indication that the attenuator is switched in.

The AGC is designed to keep the audio level at a fairly constant level, even though the signal may be fading. Using AM 60%, 1 kHz tone, at 12 MHz the audio level varies by 3 dB for antenna input between 0.7 microVolts and 120 milliVolts. The speed of the AGC is not selectable, and we found the time constant chosen to be adequate.

Static Selectivity

The HF-225 offers 4 different selectivity positions. There is a very wide 10 kHz setting, best suited when your listening to local medium wave stations, and then the low distortion audio (less than 3% at 100 mW) sounds very pleasant indeed to our European ears. The 7 kHz setting is best suited to shortwave when you've found a strong clear signal. The 4 kHz option is more useful when the signal you're listening to is suffering from strong stations operating on frequencies 5 kHz either side of the one you're trying to monitor. And finally, if you're trying to dig something out of the noise, or looking for utility stations, the 2.2 kHz filter is the best suited.

The first IF filter at 45 MHz has a fixed bandwidth of 15 kHz. In the second IF, use is made of switchable ceramic filters which are cascaded to improve the overall skirt selectivity, thus giving a 6:60 dB shape factor around 1:1.7. This is above average for the price range, even though Lowe has raised the price of the HF-225 by around £100 since it was first introduced.

Good Dynamic Range

Dynamic range is a measure of how large the difference in signal strength has to be between a weak and strong signal, before interference by the strong signal occurs. This is important if the receiver is to be used for DXing. Again using the standard CEPT measurements, the two signal generators are tuned to 10000 kHz and 10020 kHz respectively, i.e. 20 kHz apart. For the HF-225, the dynamic range turns out to be 88 dB.

No active antennas

The Lowe instruction book warns against connecting huge antennas. We found an active antenna such as the Datong AD-270 or Dressler ARA 30 was totally unsuitable with the HF-225 in Europe. With the 20 dB internal attenuator switched on, the active antennas were delivering signals than the radio could just about handle. The 10 metres of long wire or dipole recommended in the instruction book gave much better results. Lowe does market a special active antenna for use with this set, but we did not test this. In practice we found the medium wave performance to be good. In May 1989 we tested the HF-225 with a medium wave loop, and were able to log North American East Coast stations during good conditions.

Price

In its day, HF-225 cost £499 including Value Added Tax in Britain. For an extra £44.95 you can plug in a keyboard, and then enter frequencies directly into the set. The software here is friendly, simple and logical. For another £49.00, you can also have a FM board installed, plus a synchronous AM detector. This mode generally offers better audio fidelity on shortwave signals, especially during deep fades. Although the synchronous detection system does perform, it doesn't lock onto very weak signals, and when this mode is used, the audio sounds less pleasant. That comment is very subjective though. But unlike the cheaper SONY ICF-2001D or ICF-7600G, which also offers synchronous detection, you cannot select between upper and lower sideband. We would therefore rate the value of the synchronous detector as only FAIR.

More options

You can also have a rechargeable battery supply, which is an optional extra. For better fidelity (especially on medium-wave), Lowe introduced the XLS-1, this being a separate Wharfdale speaker measuring 190 x 203 x 240 mm. This costs £59.00 in the UK. A portable carrying case for the set, C-225 is also available.

Conclusions

The manufacturer's specifications check out perfectly, and Lowe electronics have achieved all the aims they have set themselves. The manual supplied with the radio was particularly clear and concise. The HF-225 will be of interest to the serious shortwave listener and beginning DXer looking for a no-frills receiver which sounds good, and can handle a wide range of signal modes. The cabinet is simple but durable and difficult to scratch. This is important if the receiver is to be used for portable work. The dynamic range is good for a receiver of this type, the 3rd order intercept point for interfering transmitters more than 20 kHz from the desired frequency being 13 dBm...a very acceptable figure.

Voted "Budget Receiver of the Year 1990" by the World Radio TV Handbook.

February 1997 Update

In January 1997 we were told that only a few units of the HF-225 and the HF-225 Europa remain in the Lowe warehouse. Availability of this receiver series is scarce.