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Vintage Radio The Eddystone EC10 Mk2 All Transistor Shortwave Radio This all band set was UK-based Eddystone’s first release of an alltransistor receiver in 1973. It’s a good performer if noisy at full gain. It has a switchable AGC, a BFO, a bandpass filter and a fine-tuning knob. Its biggest weakness is non-linear tuning. By Ian Batty Y ou may recall that Sony began with a rice cooker and National/ Matsushita with a bicycle lamp. However, Stratton and Company (who would become Eddystone) began in 1860 making much more modest goods: steel pins and hairpins. Stratton expanded into gentlemen’s jewellery, ladies’ compacts, a variety of small metal products – including knitting needles, thimbles, hat pins and crochet hooks – and a whole range of do-it-yourself kits for making model ships and aeroplanes, pearl flowers, seagrass stools and timber bead mats. Changes in fashion saw the demand for hairpins slump in the early 1920s. Needing new products to survive, manager George Laughton’s son (a radio enthusiast) asked a simple question: “Why not make wireless components?” 88 Silicon Chip It was 1923 and the die was cast. Needing a trade name, what could be better to project an aura of reliability and prominence than that of the world’s first open ocean lighthouse, the Eddystone Light? First operational in 1699, it had given over 200 years of faithful, life-saving service by 1923. Listeners in 1927 must have been fascinated by Eddystone’s first shortwave receiver. They could see the parts moving and the valves light up through a glass panel. Eddystone expanded, becoming a world-famous leader in communications equipment. You’ll find their products, especially receivers, in collections around the world. I reckon that any collection lacking an Eddystone is ‘yet to be completed’. The year 1973 was Eddystone’s Australia's electronics magazine 50th anniversary, and valve-equipped receivers were being phased out. It was not due to a lack of demand but because obtaining many of the components was no longer possible. The EC10, Eddystone’s first all-­ transistor receiver, looks the goods. It has a large, easy-to-read dial, the famous flywheel-equipped tuning mechanism and a compact size. But don’t be fooled by that size – it competes well with its valve-equipped predecessors, but with the convenience of hundreds of hours of operation using internal batteries. Description The EC10 is a general-coverage, single-conversion superhet that operates from batteries or a plug-in mains supply that replaces the battery siliconchip.com.au The rear of the EC10 has the antenna socket on the left (three to allow for a wire antenna or telescopic rod) and both high and low impedance audio outputs on the right. compartment. It uses ten transistors: five alloy-diffused high-frequency types in the tuner/IF section and five alloyed-junction types in the audio section, all PNP. Its coverage is 550kHz to 30MHz and intermediate frequency (IF) is 465kHz: • Band 1 is 18MHz to 30MHz. • Band 2 is 8.5MHz to 18MHz. • Band 3 is 3.5MHz to 8.5MHz • Band 4 is 1.5MHz to 3.5MHz. • Band 5 is 550kHz to 1.5MHz. The Mark I uses three diodes, while the Mark II adds three, for a total of six. It features a signal strength meter, which is helpful when tuning. The Fine Tuning control, which operates a variable-capacitance diode (varicap) in the local oscillator (LO) section, is essential when tuning signals in the highest band. All models feature an RF gain control and a beat frequency oscillator (BFO) for use with CW or SSB signals. There is also a switchable audio filter centred on 1kHz to improve the clarity of CW signals. The audio output is quoted as 800mW into the internal speaker. An external speaker can be used, and there is a high-impedance audio output for connection to an external audio amplifier. The set can operate with various antennas: unbalanced, balanced or a short telescopic rod. Its input impedance is 75W on Bands 1 through 4 and 400W on Band 5. Sensitivity is quoted siliconchip.com.au as better than 5μV on Bands 2-5 and better than 15μV on Band 1. The EC10’s only limitation is the failure to use a straight-line frequency tuning capacitor, so the frequency divisions are compressed towards the top end of each band. Construction The set is well-built, with the traditional ‘flywheel’ on the tuning knob. This allows the highly-geared tuning system to spin rapidly from end to end across the selected band. The chassis and front panel withdraw easily from the case and the internal construction is sound. Most electronic components are mounted on two printed circuit boards: one for the tuner (RF) and the other for IF/ audio. The IF/audio board is mounted copper-side on top, so measurements are easily made. Unfortunately, two of the IF transformers use double slugs, and the service notes describe the relocation of the IF/audio board to allow access to the inside slugs for a complete alignment and other work. Circuit description I could not find a completely legible circuit diagram online, so I have redrawn Eddystone’s original for clarity and ease of description, including the power supply circuit from my EC10 MKII. I have moved some Australia's electronics magazine components from their original locations but retained Eddystone’s numbering – see Fig.1 overleaf. I have added DC circuit voltages to the diagram, with signal voltages in two tables at the right of the drawing. Note that the band change switch sections (S1a to S1j) are all shown with Band 2 selected and viewed from the rear. Band 1 is, thus, fully anti-­clockwise, while Band 5 is fully clockwise. Eddystone showed each section from its contact side. I found this confusing, as some sections have their contact sets on towards the front of the set and others to the rear. This demanded that one visualise some sections rotating clockwise and others anti-clockwise. The EC10 uses a grounded-base RF amplifier. We’re probably familiar with common-base’s low input impedance, typically in the low tens of ohms, and its current gain of just under unity. For these reasons, voltage amplifier designs adopted the common-emitter configuration, with its much higher input impedance and current gain. However, the common-base configuration has a very high output impedance, in the hundreds of kilohms at audio frequencies. As noted in the article on General Electric’s P-807 5-­ t ransistor set (November 2015 issue; siliconchip.au/Article/9405), common-­base’s power gain – due to its July 2025  89 high output impedance – can approach that of common-emitter. Common-base’s low feedback capacitance also makes it more suited to operation at higher frequencies than common emitter, even in wideband amplifiers such as video output stages in CRT-based televisions. Common-­ base’s low input impedance is easily matched in RF circuits by tapping the 90 Silicon Chip driving tuned circuit or matching coil. Common-base’s high output impedance minimises loading of the EC10’s selected RF transformer (L7~L11) primary, thus realising the maximum Q for each primary tuned circuit. Local oscillator TR3 also operates in grounded-base configuration. While the OC171 can, in theory, work easily to the top end of the HF band in Australia's electronics magazine common-­emitter, using common-base ensures more constant output as the set is tuned to 30MHz. Tuner section All trimmers are 6-25pF types, while all transistors in the tuner and IF sections are alloy-diffused OC171s in four-lead metal TO7 cases. Antenna selector S1a selects siliconchip.com.au Fig.1: my redrawn EC10 Mk2 circuit diagram. transformers L2 (Band 1) to L6 (Band 5). Bandstop filter L1/C2 is added in series on Band 5 to improve IF rejection. The input can be unbalanced (A1 to ground, input to A2), balanced (to A1 and A2), or a factory-supplied telescopic rod to A3. The RF stage is protected against damaging overload by D4/D5, back-toback silicon diodes that limit the signal siliconchip.com.au at the selected antenna coil primary to about 600mV peak-to-peak. The antenna transformer secondaries are tuned by the tuning gang’s antenna section, C15. Bands 5 and 4 use the full capacitance sweep of C15, while Bands 3, 2, and 1 are restricted by band spread capacitors (C8/C9/ C10). Band 1’s range (around 1:1.7) is further limited by 390pF padder C11. Australia's electronics magazine All transformers in the front end are slug-tuned for low-end alignment and trimmer-tuned for high-end alignment. S1b connects the selected antenna transformer secondary to the tuning gang’s antenna section, C15. A selector ring on S1b shorts the unused antenna transformers’ secondaries, eliminating the possibility of absorption and dead spots in tuning. July 2025  91 Shock hazards I have found English-manufactured equipment to generally have dangerous mains wiring. The EC10 has a plug-in power supply, with four-pole plug PL1 connecting the supply to the main chassis. Two wires carry the 9V DC supply, and the other two carry mains to the on/off switch in the RF gain control. The wiring is lightweight gauge, and its connections to the plug are not insulated. I can vouch for this, having found out by almost throwing the set off the bench in reaction to a nasty mains shock! Similarly, the connections to the back of the switch in the RF Gain control are not insulated. Two yellow paper dots should remind the user how to connect the plug if they have not fallen off. Although the plug is mechanically polarised, it may be possible to insert it backwards, reversing the -9V DC polarity and potentially destroying the set. Additionally, the power supply’s mains lead simply passed through a grommet with no cord anchor/clamp. I rectified the first hazard by disconnecting the leads to PL1, sliding heatshrink tubing over each lead, then reconnecting and shrinking the tubing to prevent any possibility of contact with the live terminals. I also fitted a cord anchor to securely retain the power supply’s mains lead. I strongly recommend that you examine any equipment – of any origin, but especially English – for safety and proper insulation of mains connections. Left: two of the tabs on PL1 carry mains and are not insulated from the factory. Below: the rest of the power supply section. The selected transformer secondary connects, via S1c, to the emitter of RF amplifier transistor TR1. This has AGC applied to its base, which is bypassed to RF ground. TR1’s collector connects to the primary of the selected RF transformer (L7~L11) via S1d. As with S1c, this includes a shorting ring. L7/L8 are also band spread via C20/C26. The selected transformer connects to the RF section of the tuning gang (C27) via S1e. Like Band 1 antenna transformer L2, Band 1’s RF transformer, L7, has a 390pF padding capacitor, C19. The selected RF transformer’s secondary is connected to the base of converter transistor TR2 via S1f. The local oscillator signal is supplied to TR2’s emitter from the selected LO transformer (L12~L16) via S1h. Capacitor C19 reduces the LO signal’s injection level on Band 1. The LO must track at 465kHz above the incoming signal, so it uses 92 Silicon Chip a combination of the usual padding and band spreading. Bands 5, 4 and 3 use the usual padding capacitors in series with the gang. Band 5’s padder capacitor C38 (500pF) seems about right for the broadcast band, but capacitor C37 for Band 4 is a non-standard value of 1.4nF. Band 3 uses another non-­ standard value of 7nf (C46). The increasing values of these padder capacitors means that they force progressively less padding effect as the LO’s frequency span rises from Band 5 (most effect) to Band 3 (least). For Band 2 (8.5~18MHz), a 465kHz offset between the LO and signal frequencies is negligible, so C45 (47nF) is not for padding. It’s simply there to block the LO’s DC collector voltage, which would otherwise be shorted to ground via the unselected LO primary/ tuned coils in the L12 to L16 coil set. Band 1 is spread by 400pF capacitor C44 to hold the LO to a restricted span Australia's electronics magazine (around 1:1.7), so it tracks with Band 1’s antenna and RF transformers. The LO frequency span is restricted by C44 (400pF), but without the IF offset we’re accustomed to in broadcast superhets. The MKII’s fine tuning is provided via varicap diode D6. This is most effective on the higher bands. The tuner section is fed from a stabilised -4.5V supply, derived from the main supply via zener diode D3 on the IF/ AF board. This reduces tuning drift due to mains variations or battery ageing. Drift figures are quoted at better than one part in 104 (<0.01%) per °C. Converter transistor TR2 feeds the IF signal via a shielded cable to the primary of first IF transformer IFT1 on the IF-AF board. IF section Both IF amplifier transistors (TR4/ TR5) are OC171s. These alloy-diffused types exhibit low feedback capacitances of around 2pF, so they operate without neutralisation. TR4 has AGC applied, while TR5 works with fixed bias. TR4’s supply is decoupled by 1.5kW resistor R24. The voltage drop across this resistor reverse-biases AGC extension diode D1. Its anode, connected to a tap on first IF transformer IFT1, is held close to the supply voltage via the converter’s 100W decoupling resistor R18. As the AGC begins to control TR4, its collector current falls, reducing the voltage drop across R24. Strong signals will bring D1 into conduction and dampen the signal at IFT1’s primary. This means the EC10 has three gain-controlled elements: the converter, the first IF amplifier and the extension diode, giving a near-­ constant output over a wide range of signal levels. IF transformers IFT1 and IFT2 both have tuned, tapped primaries and secondaries. Final transformer IFT3 uses a tuned, tapped primary, but an untuned secondary to feed the low impedance of demodulator diode D2. The demodulator feeds audio to the low-level audio output and, via the volume control, to the audio section. The DC voltage across the volume control also drives the 100µA Carrier Level meter via multiplier resistor R48a. The demodulator’s output supplies the AGC line via R28, with the audio signal filtered out by C63. AGC is useful when receiving amplitude-­ modulated signals but is siliconchip.com.au not effective when receiving CW/ MCW (‘Morse’) or single-sideband (SSB) signals. So the AGC can be deactivated by S2. This switch cuts off the AGC voltage and biases the AGC line to a fixed value via R22, while also reducing the sensitivity of the Carrier Level meter via R49a. The AGC line is also affected by RF Gain control RV1. This is in series with the bias divider for TR4 (R20/R21), allowing the lower part of the divider to increase in resistance. This means that the ‘top’ end of R21, which connects directly to the AGC line, will become more negative as the gain control takes effect. The maximum gain reduction is about 30dB. RV1’s effect is augmented by the action of AGC extension diode D1. With no carrier, SSB signals cannot be resolved unless one is reinserted at demodulation. TR6, the beat frequency oscillator (BFO), generates a 465kHz signal that is fed back, via 1pF capacitor C67, to the collector of first IF transistor TR4. The BFO frequency is variable, via BFO Tune capacitor C70, to allow the exact adjustment needed to produce speech from an SSB transmission, rather than ‘duck talk’. Adjusting the BFO to produce a 1kHz tone is helpful when receiving weak CW signals and takes advantage of the 1kHz audio filter’s narrow passband when activated. The set can be muted using the Standby switch, which removes bias from the RF amp and the first IF amp by shorting the AGC line to ground. It’s a two-pole switch, with its second section available for custom wiring to control external equipment. allowing headphone-only operation. The output stage works with fixed bias, lacking the temperature compensation that was common in domestic receivers of the day. Power supply Power is supplied either from a plug-in battery pack containing six D cells, which were available virtually Audio section everywhere at the time, via 12V or In regular operation, the first audio 24V adaptors, or (for my set) a plug-in stage transistor TR7 (an OC81) acts as 110/240V mains supply. a simple preamplifier with load resisThe set connects to the power suptor R40. When the Audio Filter is acti- ply via a four-core cable carrying the vated, audio bandpass filter L18/C76 supply voltage and connections to the is put in series with R40. The filter, Operations switch S6, part of the RF tuned to 1kHz, gives a very narrow gain control, which selects between audio passband, greatly increasing a mains or battery power. 1kHz tone above the background noise. Be aware that the plug on the set side As noted earlier, setting the BFO is not insulated, leaving two exposed for a 1kHz tone allows the resolution metal connections at mains potential. of weak CW signals in the presence See the panel on shock hazards! of atmospheric noise or other interThe mains power supply uses a ference. transformer, selenium bridge rectifier TR7’s output goes to audio driver and pi filtering. The output voltage is transistor TR8. This feeds phase-­ held to -9V by shunt rectifier diode splitter transformer T1, which in turn D101. I found that this failed to regufeeds the two output transistors, TR9 late with low mains voltages, around and TR10, both OC83s. They form the 220V, as shown by the dial lights flickpush-pull Class-B output stage, deliv- ering on strong audio output. ering audio to the speaker via output The internal dial lights are switched transformer T2. by the momentary Dial Lights pushbutThe EC10 has a Phones socket that ton S5, allowing power conservation disconnects the internal speaker, during battery operation. The top view of the Eddystone EC10 radio with its cover removed. The resistor and capacitor added on this side of the board wire likely added at the factory as running changes. History and repairs I bought my EC10 at auction in Hawthorn back in the 1990s and it sat on the shelf for some years. In the early 2000s, I moved to Harcourt, near Castlemaine and finally popped it onto the test bench. On examination, it was pretty well dead in the RF section, although there was noise from the speaker. Examination showed that the antenna coil switch had suffered a broken wafer. I desoldered all the connections, applied superglue to each side, replaced it and rewired it. I was able to get signals, but the sensitivity was still very poor. I aligned and calibrated the RF stages, but the gain was still low. Loosening jammed slugs The IF showed a ‘double hump’, indicating severe misalignment. On correctly aligning the IF, the gain came up to the specified sensitivity of better than 5μV on Bands 5 to 2 and better than 15μV on Band 1. There are two sizes of coil slugs in the EC10: those in the RF section with hexagonal centre holes, and those in the IF transformers with continuous/ “through-hole” screwdriver slots. Be aware that these need a special long flat-bladed tool. Both types were either loose or jammed. I carefully freed all the jammed ones, but I wondered what to do so I could adjust them to position and not have them move. I long ago gave up on wax, liquid paper and nail polish, as I hope we all 1. Does the slug need alignment? You can save effort and time by using a ‘magic wand’, a piece of heatshrink tubing maybe 10cm long with a slim ferrite slug in one end and a brass slug in the other to find out before going any further. Slide the ferrite end into the coil can. If the signal improves, the coil needs more inductance for correct alignment. If that makes things worse, try sliding the brass end into the coil can. If the signal improves, the coil needs less inductance to align correctly. If both slugs make things worse, the coil is correctly aligned. 2. Do not use spray lubricants. Most of these include organic oils that can actually jam a slug in its thread. 3. If the slug has a screwdriver slot and the slot is damaged, trying to screw the slug out of the coil towards you is the worst of all worlds. You are trying to drive the slug back against the force of the screwdriver, and there may be slug debris in the threads! If the coil has two slugs, try screwing the opposite slug right out of the coil. Now that you have a (hopefully) untouched slot available on the inside of the jammed slug, use that good slot to carefully screw the jammed slug into the centre and out the end you are driving from. You can improve your chances by cleaning the coil former’s available screw threads as thoroughly as you can before trying this. Some threads in coil formers conform to Whitworth/SAE standards. 4. If you cannot get to the good end of the slug, try the ‘fridge move’. Put the set in the fridge and leave it for a few hours. Differential contraction between the slug and the former may loosen it once it all warms up. I have also successfully used a variable-temperature hot air gun to cause differential expansion. Set it to around 70ºC. Warm the coil, occasionally withdrawing the gun to feel how hot the coil or its can is. If you can leave a finger on the can for a second or two, that’s good. Anything hotter risks melting or distorting plastic parts. This method will likely soften any wax, grease or vanish, easing the job. I used this method to recover an Emerson hybrid’s IF trannie that I had unwisely used WD-40 on. 5. If the slug has a hexagonal hole (TV IF strips, Eddystone EC10 type) or a slim slot (‘Neosid’ type) going all the way through, it may be cracked into two or more parts along its length. This is the worst of all possibilities, and you may need to replace the entire coil. Destroying the slug and shaking the bits out may be possible, but you can do a lot of damage to the coil l former. In the worst case, where you cannot get an exact replacement for the windings, you may be able to find a similar, good coil l former and can, warm the coils, draw them off from the jammed former, and replace them onto the good spare. 6. If you get the slug out, thoroughly clean out the former’s threads with a tiny bottle brush or compressed air (gently!). Do not use solvents, especially acetone, as they will dissolve many plastics. Test with a good slug or a suitable thread tap. Once the thread is clear, you’ll find that slugs/taps are often a little loose in a clean former. 7. When you replace the slug(s), use thin ‘plumber’s tape’ to stop the slugs from moving – it will hold them in place but will not gum up or jam. have. My ‘magic ingredient’ is Teflon plumber’s tape, which I also use in my plumbing and irrigation work. With the RF coils’ large threads, I found I needed to fold a length of tape over itself a few times to make the slugs fit snugly. I used a single wrap of tape for the finer-thread IF coils. I used the set for a while, and two subsequent faults appeared. First, the BFO (needed for CW & SSB reception) stopped working. The oscillator used an OC171. This transistor had presumably succumbed to the dreaded ‘whiskers’, where minute dendrites grow between the transistor element and the grounded metal case within the device and eventually stop it from working. Since the BFO operated at around 465kHz, the OC171 was considerably under-rated. I had no spares, but an OC400 (with a lower cutoff frequency) worked just fine. I did need to adjust the circuit capacitance to bring the BFO back to the correct frequency, but it calibrated up correctly. The second fault appeared with massive amounts of breakthrough of the local FM band stations into the broadcast band. I lived less than 10km from Mount Alexander, which hosts most of the FM radio and TV transmitters for the Central Highlands and Goldfields. On examination, a wire connecting to the broadcast (Band 5) antenna coil had come adrift, open-circuiting the tuning for this stage. Given the amount of signal flooding in on the FM band, it appears that the front end was rectifying the FM signals and allowing them to cross-modulate into the IF. The audio filter worked, but was centred on about 800Hz and would not adjust sufficiently. I replaced the 100nF tuning capacitor C76 with a 56nF type, and got the filter to its 1kHz design frequency. A curious thing The alignment guide states that injecting a signal at the input to the IF strip needs only about 4μV to give 50mW audio output if the alignment is correct. That implies the entire RF section has near-unity gain. This mirrors the advice for an Eddystone VHF/ UHF set, the 770U, which I’d previously worked on. It appears that Eddystone regards the RF section as a ‘preselector’, siliconchip.com.au An underside view of the set. The EC10 uses 10 transistors and 18 inductors which you can see tightly packed into the central section of the board. Note the speaker, which has a relatively rare rated impedance of 3W. siliconchip.com.au Australia's electronics magazine July 2025  95 relying on the IF/AF sections to provide the majority of the gain. Performance For a first outing, it’s pretty good. I was surprised that Eddystone did not use a gang with straight-line frequency plates. The result is that frequency calibration is compressed towards the top end of each band, as happened with pocket transistor radios of the day. Roger Lapthorne (G3XBM) noted that the entire 10m band (28MHz to 29.7MHz) is only about 10mm wide on the scale. Pye Australia’s contemporary PHA 520, developed for the Colombo Plan, did use a straight-line frequency cut, making tuning much easier, especially towards the top end of its 14.5~30MHz band. The Fine Tuning control’s authority varies, giving a range of some ±30kHz at 29MHz, but only around ±2.5kHz at 1400kHz. The EC10 specification requires 50mW output, with a signal-plus-noise to noise (S+N:N) ratio of 15dB from a signal under 6µV on all bands. Table 1 shows my actual measurements. Superhet receivers are prone to image response interference, where a signal that is twice the IF frequency above (or below) the desired signal will also be received. This is rarely a problem with broadcast radios, where the antenna tuned circuit can attenuate the image by 60dB or more. A tuned RF amplifier – by virtue of its tuned interstage circuit – will improve this figure. At higher frequencies, image rejection is compromised as the bandwidth of front-end tuned circuits widens. The EC10 displayed such behaviour – see Table 2. At 600kHz, the -3dB bandwidth is ±2.2kHz, while at -60dB, it’s ±12.7kHz. The audio bandwidth from the volume control to the speaker is 80Hz to 11kHz (-3dB). While that is impressive, the response from the antenna to the speaker is only 60~1750Hz due to the IF strip’s narrow bandwidth. The audio filter, useful with CW/ MCW reception, has a -3dB bandwidth of around ±50Hz at 1kHz. Audio output was around 400mW at clipping, with 10% total harmonic distortion (THD). At 50mW, THD was a low 1.8%, rising to 3% at 10mW, evidence of crossover distortion at low levels. Figs.2 & 3: the signal strength meter indication vs input signal level with AGC on (left) and off (right). Frequency Input signal level Using three control stages, the AGC gave a 12dB rise for a signal range of 90dB. Wow. In use For the first-generation unit that it is, the EC10 works well. It is noisy at full gain, with S+N:N ratios as low as 3dB. This implies that the equivalent front-end noise is equal to the actual signal level. As noted with the Sony TR-712, it’s possible to get a lot of gain with a good amplifier design. Still, such an approach is compromised by device noise, for which germanium transistors are especially bad. Additionally, the background noise across the broadcast/HF bands, even in areas well away from the ‘fog’ created by switchmode power supplies, is commonly “some tens” of microvolts per metre. Such a noise floor means that the EC10’s useful performance will, in practice, rival that of valveequipped competitors of the day. At my location, on Victoria’s Mornington Peninsula, the broadcast band’s residual noise level well exceeds 50μV/m! This set, a Mark II, has a signal strength meter, which measures the demodulator’s DC output. With the AGC on, it effectively measures the AGC voltage, giving an essentially logarithmic response. Due to the AGC action, it provides a compressed indication on signals of any strength, showing a very broad tuning peak. With the AGC off, the meter’s indication loosely tracks the input signal’s strength, reaching the ‘8’ mark at about 35μV. Above that, the set overloads and the signal becomes distorted, so either the RF gain must be reduced or the AGC switched in. For SSB reception, you would commonly have the AGC off and use the RF gain control to adjust the set’s gain. Fig.2 shows that the signal strength meter response is logarithmic with AGC on, while Fig.3 demonstrates it’s linear, with AGC off, up to the point SC of overload. S+N:N 15dB input signal level 600kHz 2.0μV 6dB 6μV 1400kHz 0.3μV ♦ 3dB 2.5μV 1.6MHz 1.2μV 3dB 4.5μV 3.5MHz 1.5μV ♦ 3dB 5μV 3.8MHz 1.0μV 3dB 4μV Frequency Image rejection 8.0MHz 1.0μV 3dB 5μV 600kHz 64dB 9.0MHz 1.2μV 5dB 3.5μV 1.6MHz 53dB 17.5MHz 1.0μV 7dB 3μV 3.8MHz 58dB 18.5MHz 2.0μV 7dB 4μV 9.0MHz 36dB 29MHz 1.0μV 3dB 5μV 18.5MHz 16dB Table 1 – sensitivity vs frequency ♦ gain was reduced to get a useful reading Table 2 – freq vs image rejection