The Onkyo T-9090 II was released in 1988 and at the time was top of the range in the Integra FM tuner series. For distant reception of 87.5-108 MHz FM signals, the T-9090 II is arguably the best FM tuner that Onkyo has ever released in terms of selectivity, sensitivity and image rejection.

The T-9090 II tuner includes several key improvements over the earlier 1984 T-9090 model:

* Improved IF selectivity.
* More spohisticated Automatic Precision Reception (APR) system.
* Two 75 ohm antenna inputs.
* 25 KHz tuning steps.
* Three IF bandwidth settings.
* Improved front panel appearance.

Features

The T-9090 11 features 20 memories, which can be individually programmed with 5 reception modes: Antenna A/B, RF Mode DX/Local, IF Bandwidth (Wide/Narrow/Super Narrow), Hi-blend (On/Off) and Mode (Stereo/Mono). A computer controlled automatic precision system (APR) automatically sets the above 5 functions for optimum performance/reception quality. All modes can also be changed manually or by remote control if necessary.

Antenna Connections: The T-9090 II permits you to use 2 separate FM antennas. The APR system will then examine both antenna inputs and automatically select the stronger signal. You can also manually switch between the antennas.

This type of A/B antenna diversity reception can provide local or DX signals from different directions. For example, a 200 mile tropospheric signal may be present via antenna A, while a 1,400 mile sporadic E signal is present via antenna B.

Tuning: Tuning of this receiver is as follows:

1) 25kHz Tuning Steps: This feature is useful for de-tuning + or - 25 KHz from local stations to either avoid or minimize adjacent channel interference.

2) Automatic Tuning: This scans the dial and will stop when a station is present.

3) Manual Tuning: This allows the dial to be tuned manually.

4) All tuning is push button.

5) A center-tuned indicator is provided for tuning accuracy.

Multi-function Digital Display: The digital display of the T-9090 II presents station frequency, memory channel, signal strength in DBF (DB Femtowatts), and the tuning level threshold for scan tuning.

Scan Modes: Several scan modes are available, including memory scan, where the tuner will lock on to any available local or DX signal and then automatically store the 5 APR functions in the memory. Preset memory scan is useful, when 5 seconds of the 20 memory channels is required to be heard in sequence, before choosing the desired memory channel.

Selectable IF (Intermediate Frequency) Bandwidth: This is provided for locals (wide), semi-local (narrow) and DX (super narrow). The IF bandwidth can also be switched manually.

Technical

1) Antenna Inputs: Two switchable 75 ohm antenna inputs direct signals into a varactor tuned tuned RF bandpass filter. A Toshiba dual gate 3SK114 FET is used as the first RF Amplifier, which is followed by 3 varactor tuned bandpass filters, which are all track tuned by varicap diodes. Adjusting the tuning dial automatically adjusts the varicap diodes in the front end to resonate at the same frequency. This arrangement is effective for minimizing IMD problems, i.e., cross modulation and signal overload.

The Onkyo T-9090 II features a 3SK114 dual-gate Mosfet front-end. The static noise figure of the 3SK114 is specified as 1.4dB. For this reason, the sensitivity on the T-9090 II is very good, especially when the super narrow selectivity mode is selected.

The RF sensitivity of the T-9090 II can often be improved by careful re-alignment of the RF and IF coils. A T-9090 II service manual, plastic alignment tools, digital multimeter, and stable weak signal sources are the minimum requirements for re-alignment.

2) Local Oscillator: The local oscillator is well designed, with several amplifier buffer stages and a good output filter, which is also track tuned via varicap diodes. This means the local oscillator has minimal harmonics, hence minimal IF images and a low noise floor.

3) Mixer: The double balanced mixer consists of two 3SK114 dual gate Mosfets and from these signals go into the super narrow IF strip, which consists of 5 Murata 150 kHz ceramic IF filters in series, and various buffer stages to compensate for filter loss. The narrow and wide modes each use their own IF strip, with wider ceramic filters. Signals then go to the limiter amp and then a phase lock loop detector and finally into the multiplex demodulator stereo decoder.

Subjective Operation

The T-9090 11 selectivity is rated as 95db for alternative channels +/- 400kHz, and 80db for channels +/- 300kHz. Hence, the T-9090 II will easily separate a DX station from a 200 KHz adjacent local, e.g., 104.7 next to 104.9MHz.

In the super narrow position, it is often possible to hear adjacent DX stations 100kHz away from a local by slight de-tuning, e.g., 93.0 next to 92.9 or 93.1 MHz. Sensitivity is optimum when the super narrow IF bandwidth is selected and this is the best setting for weak DX signals. Daily signals via tropospheric propagation are present out to about 200-280 miles. Meteor bursts also being common. With two external antennas on separate masts, the A/B antenna switch is useful when receiving DX signals from different directions, or when selecting different polarisation.

To help set a context, the Sony XDR-F1HD exhibits unprecedented selectivity performance (80 dB @ +/- 200 KHz), which is significantly better than a modified T-9090 II. For this reason, the author now primarily uses the T-9090 II and XDR-F1HD for different DX reception applications.

FM DXers in the USA have compared the T-9090 II to the legendary McINTOSH MR-78 FM tuner. They found that the selectivity was equal on both tuners. However, the T-9090 II with its digital frequency display was the preferred tuner.

The Onkyo in Comparison to the TEAC T-515 Tuner: The Teac selectivity specification is 60db for stations plus or minus 300kHz. In some cases, the Teac cannot receive a weaker signal between two more powerful signals. The Onkyo completely separates adjacent channels, leaving the weaker signal in between possible to receive. In areas with congested high power transmitters such as the northern suburbs of Sydney NSW, the Teac tends to overload, however the Onkyo is free of images in these same areas. The Onkyo T-9090 II was designed for city areas, hence image rejection is excellent. The Onkyo uses push button tuning and has digital readout, where the Teac uses a tuning dial with analogue readout.

Onkyo T-9090 II block diagram and schematic diagram

Click here to view the Onkyo T-9090 II block diagram.

Click here to view the Onkyo T-9090 II partial circuit diagram (only front-end and IF strip).

Conclusion

The Onkyo T-9090 II has enabled 88-108 MHz FM reception from all Australian states and seven overseas countries to be heard from Sydney. With the recent addition of 4 110 KHz Murata IF filters, the selectivity performance is even better. When the 4 110 KHz filters are switched in, I suspect the +/- 300 KHz selectivity specification is now around 85-90 dB.

T-9090 11 specifications

Tuning range: 87.5 - 108.0 MHz

(AUTO MODE 50 KHz steps,

MANUAL MODE 25 KHz steps)

Usable sensitivity: Mono: 0.8uV (S/N 26 dB, 40 KHz Deviation.) DIN

Stereo: 20uV, (S/N 46 dB, 40 KHz Deviation.) DIN

50dB Quieting Sensitivity: Mono: 15.8dBf, 1.7uV

Stereo: 37.2dBf, 20uV

Capture Ratio: 1dB

Image Rejection Ratio: 100dB

IF Rejection Ratio: 100dB

Signal -to -Noise -Ratio: Mono: 95dB (IHF)

Stereo: 85dB (IHF)

Selectivity:

(+/-200 KHz, IF super narrow) 45dB.
(+/-300 KHz, IF: super narrow) 80dB DIN.
(+/-400 KHz, IF super narrow) 95dB.

AM Suppression Ratio: 60dB

Total Harmonic Distortion: Mono: 0.009% (IF: wide)

Onkyo T-9090 11 filter IF modifications

My advice is to leave the five 150 KHz Murata MZ2 filters (super narrow IF setting) were they are. This filter combination is excellent for high selectivity/fidelity.

If you want to install 110 KHz filters, replace the (wide) 180 and 230 KHz filters. The table below will clarify how the T-9090 II IF filters are configured.

WIDE: (250 KHz) Filter X101: sfe10.7MXKA+ X104 sfe10.7MXKA

Narrow:

(180 KHz) Filter X101: sfe10.7MXKA + X102: sfe10.7MS3GKYA + X103: sfe10.7MS3GKYA + X104: sfe10.7MXKA

Super narrow:

(150 KHz) Filters: X151-X154 sfe10.7MZ2KA, and X155: sfe10.7MJKA

I have replaced the 180 and 250 KHz filters(X101,X102,X103,X104) with sfe10.7MHY-A 110 KHz filters.

Ask a qualified technician to remove filters (X101, X102, X103, X104), and replace them with Murata sfe10.7MHY-A 110 KHz filters.

Murata 80 KHz, 110 KHz and 150 KHz filters are currently available in small quantities from the FM and TV DX plaza.

Comparison of Onkyo T-9090 and T-9090 11.

T-9090: 50 KHz steps, two IF bandwidth settings, 4 APR functions, 1 antenna input.

T-9090 11: 25 KHz steps, 5 APR functions, 2 antenna inputs, three IF bandwidth settings, improved selectivity over T-9090 (according to the brochure), remote control unit.

T-9090 II modified with four Murata 110 KHz filters

The author's Onkyo T-9090 II FM tuner has five 150 KHz filters (original super narrow IF). The wide 180 and 230 KHz filters were replaced with four 110 KHz Murata filters.

When the T-9090 II was purchased, the stock five 150 KHz filters were adequate for receiving adjacent channels 200 KHz away from locals. Since that time, most of local stations have increased their tx power, and more stations are on the air, hence the five 150s are not fully rejecting adjacent channel sideband splatter. The four 110s make a significant difference. In fact, unless the DX station is at least 300 KHz from a local, it is necessary to use four 110s.

Five or six Murata 110 KHz filters is the practical limit for high selectivity on FM tuners. Any more than 5-6 filters, is asking for trouble in terms of excessive 10.7 MHz IF amp noise.

A small quantity Toshiba IC amps (from the Onkyo T-4711) were purchased. These IC amps are ideal for DIY IF board modifications. When too many IC amps are placed in series, the signal-to-noise ratio is degraded. As more filters are used, the shape factor and stop band attenuation improves. However, like most things, the law of diminishing returns prevents one from using more than 6 filters placed in series.

Onkyo T-4711

In addition to the Onkyo T-9090 II, I also recommend a Onkyo T-4711. The T-4711 features similar specifications to the T-9090 II, but also includes a rotary tuning dial.

T-4711 Selectivity specification
70dB DIN(+/- 300kHz, 40kHz dev).

Other recommended Onkyo Integra FM tuners:

* Onkyo T-4970 RDS tuner (1993) - European version of the T-488F. 25KHz/50KHz tuning steps, MOS-FET Varactor front-end, wide/narrow/super narrow/Dynas IF bandwidths, two antenna inputs, 100dB image rejection.
* Onkyo T-9990 (1988) - European version of the T-9090 II.
* Onkyo T-4670 (1991) RDS tuner, 25/50 KHz tuning steps, MOS-FET Varactor front-end, 100dB image rejection, two antenna inputs.
* Onkyo T-4850 RDS tuner (1991), 25/50 KHz tuning steps, MOS-FET Varactor front-end, one antenna input, 90dB image rejection.
* Onkyo T-488F RDS tuner (1993), 25KHz steps, MOS-FET Varactor front-end, wide/narrow/Dynas bandwidths, two antenna inputs.

Note: the Onkyo T-9900 is the European version of the 1985 T-9090. The Onkyo T-9990 is the European version of the 1988 T-9090 II.

Onkyo T-9090 II alignment instructions.

Onkyo T-9090 II brochure (page1).

Onkyo T-9090 II brochure (page2).