Living with the Eton E1 - Chapter 2 - the Tech review

The Eton E1 as a medium wave receiver

The Eton E1has been hailed as a successor to the Sony ICF2010, and although it is larger and heavier than the 2010, it still is reasonably portable. It is a very capable receiver, and indeed has a few features that invite comparison with communications receivers as well as with the venerable 2010. In this review, it will be compared with a relatively late model stock ICF2010, and occasionally with a Drake R8. A better table-top receiver comparison might have been the very respectable ICOM R75, as its price is closer to the E1’s, and it is still available new.

What are the E1 features that would make a serious DXer consider this receiver? Unlike the 2010, the E1’s manual actually gives some hard specifications of interest to DXers, similar to the way communications receivers are characterized. Sensitivity, signal handling, IF filter skirts, and image rejection specifications are very respectable for a portable. The following details should be noted, especially as the first two are not available on the ICF2010, and the following three offer more features than the 2010 did:

• switchable fast/slow AGC

• passband tuning (PBT)

• 3 filter bandwidths (2.3, 4.0, 7.0 kHz) • AM / AM synchronous detection (LSB, USB, DSB) as well as LSB / USB

• Digital signal strength meter, calibrated in S-units

• Choice of internal whip antenna or 50/75 ohm impedance external antenna

• “DX” mode for greater sensitivity from either antenna (this switches in a preamplifier rather than switching out an attenuator) • line out for external recording

Sensitivity

{mosimage}Generally speaking, the E1 and the 2010 seemed to have similar sensitivity when using their respective internal antennas. The 2010 was a bit better on the low MW band; the E1 was slightly more sensitive on the higher band. I tried to use similar modes and IF bandwidth on both radios for tests, though the E1 has the advantage of a 2.3 kHz IF filter that often helped improve signal to noise ratio on received signal. The E1’s internal MW/LW antenna is the same whip that is used for shortwave and FM, so does not allow nulling interfering signals the way that the 2010’s internal loop antenna does. The whip must be extended fully for maximum sensitivity, which limits portability a little further.

Some examples of “barefoot” DX heard during quite good conditions early April 2007, in Victoria, BC:

• beacon “SQM” 529 from Level Island, Alaska was heard in LSB on 2010 but was not there at all on the E1 until an external antenna was applied

• RVC-530 from Turks and Caicos, could be heard on both radios, but was marginally more readable on the 2010 • JOUB-774’s signal from Japan was comparable (meaning only occasionally strong enough to be audible) on both radios, but when fading, disappeared first on the E1, and returned slightly later than on the 2010.

• HLAZ-1566 from South Korea was also comparable, but there were moments of clarity of audio on the E1 when the 2010 wasn't really delivering. Both the radios used AM SYNC for this reception.

• In the daytime, KXL-750, over 300 km away, was slightly better on the 2010, but KPBC-1640, at a similar distance, delivered a signal that was closer to equal on both radios, with maybe a slight edge to the E1. (both used the 4.0kHz filter, and both used AM SYNC best setting)

How about sensitivity when using an external antenna? Like most communications receivers, the E1 has a low impedance external antenna input; the 2010, however, has a higher impedance antenna input, fine for direct connection to a random wire, but which can degrade the radio’s apparent sensitivity somewhat when driven by a low impedance antenna. The usual antenna for these tests was a 1m square ALA100 loop antenna, which has a low impedance output. These tests took place when conditions were poorer, and Asiatics were not audible using the internal antennas of the portable receivers; the Drake R8 was included in the comparisons. In addition, some daytime tests were done on weak domestic stations. All radios were driven from a single antenna through a Mini-Circuits four-way splitter

It was quickly discovered that the E1 with its preamp “off” (non-DX mode) was roughly equivalent in sensitivity to the 2010 in DX mode, when external antennas were used. At this location, using the E1’s DX mode was not a good idea, even with the relatively low output ALA100 (remember that Wellbrook recommends a considerably larger loop than 1 meter for the ALA100), as scratchy unidentifiable audio often interfered with the desired station, indicating overload. Although the 2010’s sensitivity could be improved markedly by the old trick of partially pulling out the external antenna plug, this was not used in the tests, as it too often caused overload, and the comparison was to be between “stock” radios.

JOBB-828 was weakly audible on the R8 during these tests, but was only a carrier on the E1 and 2010. A similar observation was made with KSWB-840 in the daytime (1 kw at 300km), and on KKPZ-1330 (5kw at 300km), though in that case, there might have been a hint of music heard on the two portables, through playing with the AM SYNC.

The R8 dug out the signal in AM mode alone, however. In spite of these observations, there were definitely situations where a difference was noted in external antenna sensitivity between the E1 and 2010, always in favour of the E1.

• 1280 is fairly clear from splatter in the daytime here, and was showing a mix of two stations, mostly KIT. These came in fine on R8, were barely audible on 2010 in DX mode, but were quite readable on the E1 without DX mode, though not at R8 level

• 960 in the daytime, likely KALE, had barely readable audio on the R8; could just tell on E1, with the preamp disabled, that a woman was talking, but there was very little audio at all on the 2010.

• JOUB-774 generally had a pretty poor signal the morning of the comparison, using a northerly facing Flag antenna rather than the ALA100; the Flag also has a low impedance output. The 4.0 kHz selectivity (“narrow” on the 2010) and the best AM SYNC setting was used on both receivers. Unlike the earlier test using internal antennas, the E1 signal recovery was slightly better than on the 2010, and the E1 really shone compared with the 2010 when the 2.3 rather than the 4.0 kHz filter was used. This seemed to have more to do with improved signal to splatter ratio, rather than any improved raw sensitivity, but the narrow filter is an important tool for the DXer that is lacking on the stock 2010. However, the R8 with the same antenna and using ECSS (enhanced carrier selectable sideband) delivered clearer and more readable audio than the E1 did with this station.

A later test with the ALA100 and the two radios seemed to indicate that the sensitivity gap between the two sets could be narrowed almost completely using a 1:6 matching transformer in the antenna line between the ALA100 and the 2010, with the caveat that the E1 had its unusable (at this location) DX setting disabled. In an area with no strong locals, where the DX setting could be used, the E1 would likely continue to have the sensitivity advantage when using an external antenna.

Note that the R8’s AM SYNC is not in the same class as the synchronous detector on the two portables, so exalted carrier selectable sideband (ECSS) techniques were used on the R8 for comparison if AM SYNC was used on the portables. However, at this point, it’s difficult to tell if we’re testing raw sensitivity or other characteristics of the radios. The readability of a signal used for these sensitivity tests, especially at night, was affected by such things as IF filter bandwidth and overall audio quality delivered by the radios on weaker signals.

At this location, the internal antenna in each radio was more than capable of delivering signals on all domestic channels at night; in the daytime, a number of channels could benefit from an external antenna, and reception of foreign stations generally required an external antenna.

Selectivity

Selectivity of the E1 was pretty much as advertised; it was tested by tuning past CKWX-1130 (a strong semi-local) and CKMO-900 kHz (a local), noting at what frequency the demodulated signal started to become sideband splatter.

The E1’s 2.3kHz setting uses a nice sharp filter, which could split off the beacon on 529 from the TIS’s and RVC on 530, in AM mode, by detuning below 529, though 529 had to have a reasonable strength signal to do this, i.e. an external antenna was needed. Detuning alone wouldn't do that with the 2010's narrow filter, though the LSB SYNC worked fine on that radio to get the same effect. Note that the 2010’s narrow filter is considered “about 4 kHz”, though it is not actually specified in the manual. In fact, using the above test, I found that the 2010 delivered audio on CKMO-900 from 897.6 to 902.6 kHz, so it seemed to be somewhat narrower than the E1’s 4.0 kHz filter.

In domestic DXing, signal handling and demodulation capabilities came into play at least as much as selectivity, because all the IF filters in either receiver seemed capable of handling the domestic channel separation of 10 kHz, even next to my locals.

When using the E1, KKSN-910 was readable at night, next to my local on 900, especially using AM SYNC USB, but that station was also heard on the 2010 and with crisper sound quality. I could just hear CJDC-890 when using LSB AM SYNC on either radio, but the 2010’s audio was not so readable, even with its crisper sound. Oddly, however, the 2010 could hear 890 in the AM setting with the narrow filter, while the E1 could not, even with its 2.3 kHz filter; there was too much splatter.

Next to my other local on 1070, the E1 was able to hear CKMX-1060 using AM only, and reception got better with AM SYNC; the 2010 in contrast had more problem with 1070 splatter but improved markedly when the DX/local switch was set to local. But the E1 produced quite a good signal whether its preamp was on or off. Again, oddly, given the preceding observation, KWJJ-1080 on the other side of my local was only audible using the 2.3 kHz IF filter on the E1, even though the 2010 was delivering a signal using its narrow filter. Using its 4.0 kHz filter, the E1 couldn't match the 2010, and couldn't even find the AM sync lock until the 2.3 kHz filter was used, and then, not always reliably. When the lock was found, wider filters could then be switched in while continuing to use AM SYNC mode. Incidentally, using either radio, AM (no sync) demodulated better as one detuned above 1080, but again, I suspect this had less to do with the IF filter than with the fact that less splatter was heard as one tuned away from 1070.

Especially when trying to find split channels, it seemed best to tune around on the E1 using the 2.3 kHz filter for first indication of signal, then switch to the 4kHz filter when the signal faded up. Having said that, most of the extra audio frequencies heard when using the 4 kHz filter seemed to be from splatter rather than adding to the overall readability of the DX.

Strong signal handling

At this location, I have a couple of test channels for intermodulation products produced by my locals. For example, the combined sound of the two locals can turn up on 170 kHz; this was heard on both the 2010 and the E1 (170 kHz is a second order product from 900 and 1070). Some of this spur may be produced externally, as it's hard to defeat it completely with either attenuation or with antenna tuners. Another second order product is on 1970 kHz, but that was noted only on the E1. 1240 kHz can show a third order product (2*1070-900) at this location. It was audible on the 2010, but could be killed by using the “local “ switch (antenna attenuation), leaving KGY alone on the channel. Switching off the RF preamplifier on the E1 didn't kill that spur unfortunately, but then, as noted, that mode on the E1 is equivalent in sensitivity to the 2010 “DX” setting. These overload products were noted using internal antennas. Unless an antenna tuner is used, an external antenna could increase the likelihood of spurious signals on either receiver depending on one’s location.

A situation that may have indicated a problem with signal handling was the following: KPNW-1120, nearly 500km away, is a good test for daytime sensitivity here. It was heard on the 2010 with readable audio though the splatter from semi-locals on 1110 and 1130 was a problem; SYNC was little help here. But, no matter what I did, there was just splatter on E1, and even an external antenna didn't show any signal on 1120, just splatter. It seemed that strong splatter from both sides of the desired signal defeated the E1 in this situation, though whether it is a signal handling or demodulation problem, I’m not sure.

There were no obvious internal spurs on the E1 when tuning across MW band with the antenna fully collapsed.

Demodulation

The E1 sound quality was always full and bassy when using the speaker, even with the 7kHz IF bandwidth; on good headphones, the sound was not quite so bassy, but still "full" without the crispness of the 2010’s audio. When using the 2.3 kHz filter, the sound was bassy as expected, but, as noted above, switching in the 4.0 kHz filter often just added splatter highs, with no further clarity to the signal. The E1 has bass and treble controls, but I always ran the radio at full treble when DXing, sometimes with minimum on the bass control as well, so these controls were not much help in hearing a signal better. For DXing, I almost always preferred the brighter sound from the 2010, but for program listening, the E1 was very good.

When signals were at low level, even with AM SYNC switched in, the sound got bassier yet, and a bit "furry" sounding. This is often a problem when trying to hear weak signals on any receiver, but it seemed a bit more pronounced on the E1. For example, when testing an external antenna in the daytime, the TIS on 530 from Hurricane Ridge, WA was slightly weaker on the 2010 than on the E1, using the AM mode, yet its signal was crisper and more readable. In general, the AM only mode on the 2010 seemed to deliver a more readable signal than the E1 did in that mode, unless the signal was reasonably strong.

AM SYNC Observations

Synchronous AM detection is a major selling point of both the E1 and 2010, as it allows one to tune to the opposite sideband from an interfering signal, and reduce heterodynes and sideband splatter to a large degree. The E1 has USB and LSB AM SYNC like the 2010 does, but the E1 also includes double sideband AM SYNC; however, I didn’t find the latter much use for DXing.

The AM SYNC on the E1 has been regarded as superior to the 2010’s by other reviewers. Certainly, it is quite fast to lock, and appears to lock on weaker signals than the 2010 does. In addition it has a wide lock range, for example tuning to 910kHz using the 7kHz IF filter, and detuning to get away from the local splatter from 900, I found I could lock to 910, even when tuning out to 915 kHz, where stations on 920 then took over locking the detector). This wide locking range caused difficulties using the E1 when trying to zero in on a presumed Fiji on 639 using AM SYNC LSB and the 2.3kHz IF filter; it locked onto the stronger station on 640 instead. It was necessary to tune further below 639 until the stronger 640 kHz signal dropped off the filter passband skirts. This is mentioned in the manual, so is something that the user should be aware of. No such problem existed with the 2010’s +/- .7 kHz locking range for AM SYNC, it would lock on 639 as soon as one tuned more than 0.7 kHz below 640 kHz.

Signal recovery in “AM SYNC” was superior to “AM” for DXing in almost all cases on the E1, especially if selecting the least QRM’d sideband. A couple of examples:

• HLAZ-1566: there was a better chance of listenable audio from this station using AM SYNC rather than simple AM, especially when the signal was just on edge of audibility. It had a "punchier" sound with more clarity compared with a more diffuse sound in AM. Splatter avoidance using USB/LSB sync of course was also helpful, though splatter on this channel is not too big a problem at this location.

• JOUB-774: AM SYNC was almost always viable with the E1 if there was any audible signal at all in the AM setting, and as with HLAZ, improved the clarity, especially in USB AM SYNC, rejecting splatter from my semi-local on 770. The 2010 would not indicate any lock on the LED on such a weak signal. However, it was found that the 2010 SYNC often locked before the LED indicator lit, so was actually more sensitive than first thought, though still not as sensitive as the E1. Although audio quality on the E1 was improved by using AM SYNC, I found that the 2010, for the most part, had a “crisper” sound if it was successful locking on to weak signals.

Although clarity of weak signals improves in AM SYNC using the E1, the process can actually add a low frequency hiss to the recovered audio in some cases.

Other features

• It’s wonderful to have PBT on a portable receiver, but it’s really only useful on SSB on the E1; it is just a frequency shift in the AM modes, and the manual is quite clear on this.

• Carrier spotting, using SSB modes, was easier with the E1 than with the 2010. This may be partly due to the 10Hz tuning steps of the E1. Surprisingly, however, in spite of the relatively small tuning steps, ECSS did not seem very successful on the E1. It was hardly any better than the 2010 with its 100 Hz tuning steps, and quite inferior to the R8, which also has 10 Hz steps.

• The S-meter has reasonable resolution (20 divisions up to S9+60 dB). A quick test with a signal generator at the low end of the MW band showed S2 to be indicated with a –103dBm input signal and –90 dBm indicating S7. “6dB per S-unit” doesn’t seem to apply below S7, but above this point, the signal strength readings are relatively accurate. Although the S-meter is quite responsive it is not as swift on nulls and tuning peaks as the analog meter of the R8

• On domestic channels at night , “pumping” was noticed with fast AGC due to multiple stations on the channel being separated by only a few Hertz. Selectable AGC was quite useful here, and the “auto” setting would smooth out the sound in most cases, as would manual selection of slow AGC.

Conclusion

The E1 is a worthy successor to the Sony ICF2010, with added features useful for the MW DXer, the most noteworthy of which are the 2.3 kHz IF filter, a capable AM synchronous detector, and somewhat better sensitivity when using an external antenna, especially in areas when strong signal overload is not a problem. However, it is not as portable as the 2010, especially when the internal antenna is used, and its overall demodulation, especially in AM mode, produced an audio that was somewhat bassier than this DXer’s ears would like.

The E1 is not a substitute for a communications receiver, and if (relative) portability is not desired, then better DXing capability will likely still be found in table-top receivers, though usually at a premium price. {mos_sb_discuss:12}

Nick Hall-Patch is a Victoria resident and author. His work with the IRCA Technical Guide, over the years, has earned him many accolades. He continues this fine work in earnest as well as maintaining a day job with Ocean Sciences Canada.