Over the years the author has intentionally sought out some of the top performing FM tuners for DX work. With this context in mind, it was pssible to empirically determine if the claims regarding the Sony XDR-F1HDI FM DX performance were true. The ideal setup for testing tuner sensitivity/selectivity is to have a stable weak signal (signal generator, or low powered local). A very weak low powered local area pirate TX on 90.0 MHz was a suitable stable signal source. Since there are strong local adjacent FM signals on 89.9 and 90.1 MHz, 90.0 MHz is an ideal even channel for selectivity testing.
Tuner Reception Observations
A standard Onkyo T-9090 II (5 x 150s) is completely swamped by 89.9 and 90.1 MHz adjacent channels. Even the T-9090 II (with 4 x 110s) is unable to detect any trace of the 90.0 MHz pirate TX. It is likely that a modified Yamaha T-85 (with 5 x 110s) would not detect the 90.0 signal.
The modified R-8500 wide FM mode (using 2 x 110s) as expected is swamped by 89.9 and 90.1. It should be noted that the T-9090 II selectivity is significantly ahead of the R-8500 (with 2 x 110s).
The Icom R-8500 (15 KHz nFM) is able to detect 90.0 MHz without any splash from 89.9 and 90.1. However, intelligibility is abysmal, hence only on/off modulation can be heard (very weak slush). This of course precludes any form of identification.
The Onkyo T-4970 (with DYNAS activated) can't lock on to the 90.0 signal. The signal breaks up, hence there is no intelligibility.
The KT-6040 (with stock filters) is swamped by 89.9 and 90.1.
The KT-6040 (with 4 x 110s) is able to resolve the 90.0 signal with moderate levels of splash.
The KT-6040 (with 2 x 110s + 4 x 80s) is able to resolve the 90.0 signal with no adjacent channel splash from 89.9 and 90.1. Although moderately distorted, the intelligibility is just adequate, especially when the signal strength increases.
The Sony XDR-F1HD (with stock DSP filter) is able to resolve the 90.0 signal with no adjacent channel splash from 89.9 and 90.1. Out of all the above tuners, the intelligibility is best on the XDR-F1HD.
With regards to selectivity / fidelity performance, the clear winners are the KT-6040 (80 KHz filters) and XDR-F1HD (stock DSP filter).
The KT-6040 (with 2 x 110s + 4 x 80s) is the ideal tuner for extremely weak scatter modes, (e.g. MS, AS, TS). The 110 KHz bandwidth is adequate for the stronger Es and tropo signals, but don't expect XDR-F1HD level selectivity.
The Sony XDR-F1HD (stock DSP filter) is the best tuner available for Es and tropo DX in congested areas (e.g. Europe, North America). The XDR-F1HD selectivity is equal to a modified KT-6040 (80 KHz bandwidth), but with much higher levels of intelligibility.
In terms of filter ultimate rejection and general IMD performance, the following tuners were ranked in the following order from worst to best:
Onkyo T-4970 (DYNAS DSP filter activated)
Onkyo T-9090 II (4 x 110 KHz filters)
Onkyo T-9090 II (stock 5 x 150 KHz filters)
Pioneer Supertuner IIID
Kenwood KT-6040 (4 x 80 KHz + 2 x 110 KHz filters)
Sony XDR-F1HD (stock DSP filter)
The XDR-F1HD is sometimes not suitable when operating in close proximity (< 7 km) to high powered FM transmitters. Most DXers will never experience XDR tuner AGC muting. The XDR-F1HD features automatic RF gain for the purpose of minimising overload and IMD. When confronted with several strong signals, the XDR attenuates all signals (including DX) to a high degree. When aiming into the local transmitters, the noise level on vacant FM channels drops considerably (this can be readily observed by connecting an AC multimeter to the XDR-F1HD speaker RCA output jack. The author's solution to this problem is to use a tuneable RF preamplifier which also acts as a low pass filter when tuning the low end of the 88-108 MHz band where most of the exotic channels lie. One other option is to use a T-9090 II or Yamaha T-85 when DX signals arrive from similar great circle bearings to the local transmitter site.
Onkyo T-9090 II: good overall performer for general Es and tropo DX for DXers not exposed to excessively strong local transmitters. Best ergonomics and overall functionality. Two RF inputs automatically select the strongest signal by using the APR function, 25 KHz tuning steps, 3 IF bandwidths, switchable mute.
Pioneer Supertuner IIID: highest selectivity, sensitivity, and IMD performance of any car FM tuner. AM sensitivity/selectivity also above average compared to other car tuners.
Kenwood KT-6040 (modified with 4 x 80 KHz + 2 x 110 KHz filters): when used with MosFET or GaAsFET RF preamp, best tuner for extremely weak signal modes (aircraft scatter, meteor scatter). Low noise RF preamp + 80 KHz bandwidth equates to the highest sensitivity performance obtained on any tuner. Without preamp inline, RF sensitivity slightly down compared to the Onkyo T-9090 II / T-4970. The KT-6040 110 KHz wide FM selectivity somewhat better than T-9090 II 110 KHz selectivity. Relatively poor construction quality - more likely to develop technical fault compared to all tuners listed above. 80 KHz IF bandwidth audio quality relatively distorted - especially on pop/rock stations featuring wide deviation.
Onkyo T-4970 (DYNAS DSP filter activated): high sensitivity and selectivity combination performance for DXers who desire high fidelity audio response on DX signals. When listening 200 KHz below a local signal, selectivity performance is equal to the Sony XDR- F1HD. However, the DYNAS DSP asymmetrical filter response often means the T-4970 will have difficulty locking on to a DX signal above or in between the local signal(s). The T-4970 features two RF inputs, 25 KHz tuning steps, switchable mute. Applications include 100 KHz adjacent channel DX.
Sony XDR-F1HD (stock DSP filter): highest selectivity and IMD performance for any tuner available. Especially suitable for DXers who desire high fidelity audio response on DX signals, but with 82dB adjacent channel rejection. Applications include 100 KHz adjacent channel DX, and superior IMD immunity in very high RF areas. Without a preamp, the soft mute can sometimes mask extremely weak signals. However, having said that, the XDR-F1HD 50 dB quieting RF sensitivity is so low that most meteor scatter signals are readily received despite the soft mute. Threshold extension and adaptive noise reduction technology means that noise is 50 dB down for an unmodulated 13.5-dBf stereo signal. With low noise RF preamp added, the 50 dB quieting level is only ~ 1 uV. This means that weak signals rapidly increase to full quieting.
Low Noise Preamplifiers and the XDR-F1HD
At a quiet rural listening location, some sensitivity tests were conducted using three 88-108 MHz preamplifiers with the Sony XDR-F1HD. The results were as follows:
The German manufactured and designed Amiwima ULNA 3013 88-108 MHz 0.3 dB NF 20 dB gain preamp was the best overall preamp in terms of noise performance. We all agreed the S/N improvement was significant when the ULNA 3013 was inserted inline with the Sony XDR-F1HD. Without a doubt this is the most sensitive tuner/preamplifier FM DX combination we have ever seen.
The Jim Dietrich UA-701 GaAsFET 40-230 MHz wideband preamp was the second overall performer which produced useful improvement on most signals.
My BF981 MosFET tunable 88-108 MHz home-constructed preamp was the third overall performer in terms of S/N improvement. The relatively low sensitivity improvement obtained with this preamp could be due to impedance mismatching on the input stage. IMD performance was best due to the high Q narrowband tuning. The BF981 preamp is not recommended for rural locations, but essential (for most) in metro/city locations.
The ULNA 3013 is the overall best performer provided the preamp is operating in rural or semi-rural areas that feature minimal high power transmitters.
Sony XDR-S3HD vs XDR-F1HD Comparison Report
Test conditions: Triax FM-8 aimed 110 degrees east. No RF preamp connected.
Overload / IMD: none experienced.
Sensitivity: equal to XDR-F1HD.
Selectivity: equal to XDR-F1HD.
Overload / IMD: 88.1 MHz (3 bars of IMD), 88.9 MHz (2 bard of IMD), 89.3 MHz (0 bars - weak IMD), 89.7 MHz (1 bar IMD), 90.5 MHz (1 bar IMD), 91.3 MHz (0 bars - weak IMD, cant hear Campbelltown FM).
IMD was concentrated near the low end of the band (i.e. 87.6 - 92 MHz).
Sensitivity: equal to XDR-S3HD.
Selectivity: equal to XDR-S3HD.
With the Triax FM-8 aimed at 110 degrees, local signals are approaching maximum strength, yet the high powered 93.7 MHz FBI FM only indicates 2 bars (XDR-F1HD + XDR-S3HD). 96.1 MHz One FM flashes 0 to 1 bar on the XDR-S3HD! The XDR-F1HD indicates 1 bar on 96.1 MHz. Both XDR tuners are exhibiting high AGC RF attenuation. Seeing that the XDR-S3HD is indicates lower signal on 96.1 MHz One FM, there could be marginally increased AGC RF attenuation compared to the XDR-F1HD; hence lower IMD. Whatever the cause, the XDR-F1HD suffers from increased overload on several channels compared to the XDR-S3HD. Will Renton's XDR-F1HD featured less IMD compared to my XDR-F1HD; hence my unit could be a one-off anomaly? In any case, the XDR-S3HD is now the preferred tuner for serious DX work at my QTH.
The XDR series tuner feature high levels of AGC attenuation to (partially) combat the lack of RF front end pre-selection. The high-end Onlyo Integra series tuners all feature varactor-tuned RF front-end pre-selection; hence there is no need for savage AGC attenuation. DXers residing in very close proximity to high power local transmitters (less than 8 km), will benefit from using tuners featuring track-tuned RF pre-selection (e.g. Yamaha T-85, Onkyo T-9090 II, Onkyo T-4970, Kenwood KT-6040). By comparison, the XDR series tuners are relatively insensitive when aiming toward local high powered signals. Savage AGC attenuation is good design feature for non-DXers. However, DXers can circumnavigate the XDR AGC attenuation issue by using tuneable narrowband MosFET RF preamps.
XDR-S3HD Digital Display Issue
The XDR-S3HD digital display features roughly 25% less brightness compared to the XDR-F1HD. My 50 watt Jaycar power supply (50 Hz/60Hz converter) is probably the cause. The 50 watt power supply does not in any way impact reception performance. Robert Copeman purchased a 100 watt P/S from Jaycar, with resultant full brightness noted on the display. However, I save $100 by sticking with the existing 50 watt P/S.
No Internal Heating Issues Noted on the XDR-S3HD:
Because the XDR-S3HD employs an external power transformer, internal heating effects are not an issue. This is a welcome design feature (the Icom R-8500 scanner also features an external power transformer). However, due to the internal transformer, the XDR-F1HD can potentially overheat during prolonged periods of use on very hot summer days.
XDR-S3HD Superior Ergonomics
The XDR-S3HD features a rotary tuning dial. The whole 87.6-107.9 dial can be rapidly tuned using the rotary dial in literally seconds. By comparison, the XDR-F1HD can only be tuned via the remote control, while the tuning rate is slower. Note that the XDR-S3HD can also be tuned via remote control. The XDR-S3HD also includes an external rotary volume control. The XDR-S3HD digital display is marginally bigger compared to the XDR-F1HD.
The XDR-F1HD is probably more suited for DXpeditions (especially if a small headphone amplifier is brought along to save space). The XDR-S3HD is ideal for home use.
The Sony XDR-S3HD appears to be marginally more sensitive re RDS locking. Also, additional RDS information (e.g. scrolling text) is displayed compared to the XDR-F1HD.
I intend to use my XDR-F1HD exclusively for DX TV audio monitoring when connected to the HS D100 TV tuner/converter. The TV audio weak sensitivity is better than any other arrangement. Garry Smith was using this approach from the late 1970s onwards, which explains why DX TV audio is so clear on his video recordings from the same period.
Another potential approach is to make up an IF to RF upconverter circuit to convert the Icom R series 10.7 MHz IF output to ~ 100 MHz. The D100's upconverter circuit could be used as a model with the appropriate inductor values changed.
The XDR-S3HD includes its own inbuilt speaker. When you include the average mini stereo amplifier and two speakers, the XDR-F1HD takes up approximately as much physical space as the XDR-S3HD.
One Australian FM DXer reports that the XDR-S3HD features marginally higher selectivity performance compared to a modified Kenwood KT-6040 (4 x 80 KHz + 2 x 110 KHz filters).
With the introduction of the new Sony XDR-F1HD and XDR-S3HD DSP FM tuners, IF selectivity / audio fidelity performance has reached a pinnacle. For many DXers, portable radios, ceramic filter tuner modifications and most other available tuners will be largely uneccesary. However, ceramic IF filter modifications are still useful with high performance tuners such as the Onkyo T-9090 II and Kenwood KT-6040. Serious DX installations usually incorporate a range of receivers and tuners for specific requirements. The Sony XDR FM tuner series will be an important component of any serious DX installation.
The XDR-S3HD is likely the best tuner available anywhere for serious DX work, while the XDR-F1HD comes second. With the XDR-S3HD, Sony have incorporated the world's best tuner with a rotary tuning dial, volume control, internal speaker, and external power transformer.