This article features synthesized scanning receivers that are recommended for effective monitoring of VHF/UHF television and FM radio DX signals. Although they are among the most expensive range of wide-band scanners available, their outstanding performance is well worth the investment.

After I purchased my first AOR-AR3000 VHF/UHF scanning receiver back in 1991, VHF DX reception considerably increased. In fact, I now consider scanning receivers the most important part of my VHF/UHF DX receiving system.

Programming memory channels

I initially check the memory channels on the Icom scanners for signs of DX TV signals before switching on a TV set. Scanner receivers will detect the presence of extremely weak TV signals - typically down to ~ 0.1uV - long before they are strong enough to produce images on a TV screen.

Approximately 60 memory channels, including 50-52 MHz 6 meter beacons, and 45-108 MHz TV video and sound carriers are programmed into my Icom R-7000 and R-8500 scanners. USB mode 2.4 KHz bandwidth is used to detect weak AM video carriers. Narrow 15 KHz and wide 100 KHz FM modes are used for monitoring TV audio.

To facilitate programming of scanner memory channels, obtain an allocation table for all television video and audio frequencies. For example, US TV DXers would program all video and audio channels for channels A2-A13.

For optimum reception, tune approximately 1 KHz below the AM video carrier. For example, memory channels are usually as follows:

M1: 55.2390 MHz USB.
M2: 55.2490 MHz USB.
M3: 55.2590 MHz USB.

Depending on what channels are received, the audio frequency can also be programmed into memory. For example:

M1: 55.2390 MHz USB.
M2: 59.740 MHz NFM.
M3: 55.2490 MHz USB.
M4: 59.750 MHz NFM.
M5: 55.2590 MHz USB.
M6: 59.76 MHz NFM.

EME and radio astronomy applications for the Icom R-8500

EME (earth-moon-earth) VHF DX hams chase extremely weak CW signals. These signal levels are typically only a fraction of a microvolt. To improve the S/N (signal to noise ratio), narrow bandpass audio filters are used to detect moon bounce signals. Some DX TV operators have employed narrow band receiving systems for detection of signals that would otherwise go unnoticed.

All of the receivers described on this page, feature AM, NBFM, WBFM, USB and LSB detectors, with an audio output suitable for connecting to the sound card line input for driving most PC frequency spectrum analyzer programs.

For monitoring extremely weak AM video carriers, a 20 Hz tunable audio bandpass filter is used by the author. For circuit details, go to http://www.geocities.com/icdx_australia/audio_bandpass_filter.htm.

Most amateur radio astronomy pages recommend the Icom R7000, R7100, or R8500. They do state that the R8500 is the best receiver available for their SETI experiments. This is perhaps because the sensitivity and noise floor on the R8500 is superior to the R7000 and R7100. However, the only drawback for radio astronomy is that the R8500 doesn't have a switchable AGC. It is possible to switch off the AGC by simply cutting a single wire on the R8500 main circuit board. One could easily mount a on/off switch at the back of the set for bypassing the AGC. See: Disabling AGC in the ICOM Microwave Receivers: http://www.setileague.org/hardware/8500agc.htm

The R8500 instruction manual also includes detail of a command code to toggle the AGC on and off. This is listed on page 35 of the R8500 owners manual.

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Icom IC-R7000.

The ICOM model 7000 receiver, which is no longer available new, is an all-mode, synthesized VHF and UHF receiver tuning 25 to 2000 MHz. It contains AM, NBFM, WBFM, USB and LSB detectors. It has been largely replaced by the model 7100, which has similar capabilities except that reception of the 800 - 900 MHz cellular telephone band has been left out.

The R-7000 receiver was first released around 1986. It is only available second-hand. However, it has impressive performance, and is probably the most cost effective professional grade scanning receiver for the VHF DXer.

Icom R-7000 specifications.



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Icom IC-R7100.


This receiver was released around 1992, and came after the R-7000. Performance for DX is similar to the R7000. The main advantage over the R7000 is 900 more memory channels.

Icom R-7100 specifications.



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Icom IC-R8500.


The Icom IC-R8500 is my current primary scanning receiver. The R-8500 has a significant improvement in performance, compared to the R-7000 and R-7100. The R-8500's specifications and performance are equal or almost equal to the Icom IC-R9000. The R-8500 also represents better value for your money.

Below 1000 MHz, the IC-R8500 has exhibited better intermodulation immunity than any of the VHF/UHF scanners I've previously used. In fact, there is no sign of any intermodulation below 88 MHz!

Icom R-8500 specifications.

Robert Sherwood Sherwood Engineering did some tests on the Icom R8500:

Noise Floor = -135 dBm (SSB filter).
Sensitivity = .011uV.
Dynamic range= 81 dB wide (20khz) 59 dB narrow (2 Khz).
100KHz blocking 130dB.
AGC threshold 0.45m uV.

The noise floor and sensitivity specifications are excellent, but dynamic range is mediocre.

The dynamic range for the AOR 5000 is inferior compared to the R-8500. Out of all the receivers tested by Robert Sherwood, the AOR 5000 has one of the poorest dynamic range specifications.

Receiver specification comparison chart by Robert Sherwood

RECEIVER TEST DATA

Device
Under Test
Noise
Floor
AGC
Threshold
dB 100kHz
Blocking
Sensitivity LO
Noise
Spacing
KHz Front End
Selectivity
Filter
Ultimate
Dynamic Range
Wide Spaced
KHz Dynamic Range
Narrow Spaced
KHz
Icom R-8500 -135# 0.45 3 132 0.11 131 10 B 0.5 Octave 75 81 20 59 5
Icom R-9000 -131# 0.8 3 129 0.15 128 10 B 0.5 Octave 90 93 20 71 5
AOR 5000 -124/-130#* 0.9/1.8 3 118 0.2/0.35 103 10 B 0.5 Octave 60 58 50 ^ 5

Notes on Receiver Table Legend

# = Measured with SSB filter.
* = Built-in preamplifier actuated.
^ = Measurement was phase-noise limited rather than intermodulation limited.

Notch filter options for the Icom R-8500

During the recent southern hemisphere F2 openings, I have experienced an annoying strong heterodyne on 50.11 MHz. Even though my Icom R- 8500 receiver is an all round excellent performer, it needs a tunable audio or IF notch filter. While the R-8500's IF shift facility offers some improvement, other options should be considered:

1. Build an out board tunable audio notch filter, for connection between the front panel line-out socket and a tape deck and/or audio amplifier. An example is the circuit at: http://www.keirle.fsnet.co.uk/notch.htm

2. Buy a commercial unit. For example, see: http://www.wsplc.co.uk/acatalog/Online_Catalogue_Audio___Filters_36.ht ml or http://www.universal-radio.com/catalog/filters/1124.html

3. For those with technical skills, a notch filter circuit could be added to the receiver's internal circuits.

4. The approach I decided is to use another high grade HF receiver as a tunable IF. For example, my Drake R8B and Icom R71E receivers, feature excellent tunable notch filters. By feeding the 10.7 MHz IF output from the IC-8500 into the RF input of the Drake R8B, the SSB audio is monitored by tuning to 10.7 MHz.

Make sure there is no DC voltage from the output of the R-8500 (use a ceramic capacitor to block any DC voltage). The Drake's audio notch filter can then be used to eliminate or minimize any offending heterodynes.

R-8500 technical overview

The R-8500 produces performance, coverage and sophistication rarely seen in other models. Covering 100 kHz to 1999.99 MHz (less cellular), this receiver does cover it all; and more importantly; it does it well throughout this extraordinary range. Most wideband receivers tend to perform only modestly below 30 MHz. The R-8500 (and R-9000) are clear exceptions to this rule. Reception modes include AM, LSB, USB, CW, FM-N and FM-W. This receiver is equipped with IF Shift and Auto Peak Filter functions ... a first for receivers in this class. The IF shift effectively rejects nearby signals in the SSB modes. The APF can select between two bandwidths and serves as a tone control in the FM mode and can also selectivity boost signals in the CW mode.

Triple conversion and Advanced RF circuits achieve an improved dynamic range of 107 dB and an intercept point of 27.5 dBm. Separate band pass filters minimize cross modulation and provide high sensitivity in the .1 to 30 MHz range. The R-8500 employs a newly designed PLL circuit which provides tuning and readout resolution to an amazing 10 Hz. A host of tuning steps are featured: 10, 50, 100 Hz, 1, 2.5, 5, 9, 10, 12.5, 20, 25, 100 kHz and 1 MHz. In addition you can program your own tuning step (.5-199.5 kHz). And what a memory system! 1000 channels are available organized in 20 banks of 40 channels, plus 100 skip channels and 100 Auto Write Memories. Other refinements include: Noise Blanker, S and Center Tune Meter, RF Attenuator, LCD Dimmer, Clock-Timer, Record Jack and Recorder Activation Jack, Selectable AGC and Main Dial Tension adjustment. The rear panel features three separate antenna inputs (covering two ranges: .1-30 and 30-2000 MHz). Other rear panel jacks include: IF Output (10.7 MHz), Remote Jack, AGC Out Jack, External Speaker and RS-232C (DB25) Jack. The R-8500 is supplied with an AD-55A AC adapter or may be run from 12 VDC with the supplied DC cord.


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Icom IC-R9000.


The IC-R9000 was first released around 1986 and is top of the range in the Icom VHF/UHF wideband receiver series. It has received excellent reviews for its DX and weak signal receiver performance. Even though the IC-R9000 is possibly the best wideband VHF/UHF receiver ever produced, most DXers can't justify paying over $3,000+. However, second-hand IC-R9000 receivers occasionally appear on eBay. A second-hand IC-R9000 is about the same price as a new IC-R8500.

The IC-R9000 excels in several areas. For example, the IC-R9000 has track tuned BPF's (varactor diodes) in the RF front end (VHF/UHF only). This means the IMD - Intermodulation performance is excellent. The R-9000's dynamic range figures are also very good - 20 kHz dynamic range averages 96 dB. The 5 kHz dynamic ranges averages 74 dB.

Icom R-9000 review by Robert Sherwood, NC0B

Icom R-9000 specifications.


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AR-5000+3 AOR High Performance Receiver



Frequency Range: 10kHz to 2.6GHz * Modes: AM, Synchronous AM (USB, LSB &
DSB), FM, USB, LSB & CW * AFC * Noise Blanker * 1,000 memories ( 100 Ch x 10
banks) * 45 Ch per sec. scan speed * 20 search banks * 45 increments per
sec. search speed * 2,100 PASS frequencies * DTMF decoder * RS-232 port *
Aerial input N-type & SO239 * Audio 1.7W (8 Ohms) * Supply 12V DC @ 1A *
Size 217 x 100 x 260mm * Weight 3.5kg


The AR-5000+3 awarded four stars in 1999 by both the authoritative Passport to World Band Radio and the World Radio & TV Handbook. The AR-5000 used by professional monitors, government departments, armed forces throughout the world and top-end hobbyists, has an unparalleled high performance, amazing flexible operating system, high build quality and yet remains very compact and relatively light weight.

The AR-5000 was first released in 1996, and is the top receiver in AOR's range. The AR-5000 is almost impossible to find second-hand. It is also more expensive than it's nearest competitor, the Icom IC-R8500.

One feature of interest to TVDXers is the wide range of FM bandwidths:
1. 15 KHz for standard NFM utility broadcasts.
2. 30 KHz for NTSC TV audio, and 270 MHz band satellite audio.
3. 110 KHz for FM and TV wide-FM audio.
4. 230 KHz for strong local FM and TV broadcasts. I would suggest the 230 KHz filter could be replaced with a 50 KHz Murata filter.

AOR AR-5000 specifications.

R-8500 vs R-7000 comparison results by T Emslie

I did some comparison tests for my Icom R-7000 and R-8500 scanning receivers. Considering there is a 10 year gap between the two radios, you would expect some differences. RF technology can change a lot in 10 years. However, even though the R-8500 looks nicer, and has better audio quality, the DX potential of both receivers are equal. Here are my basic subjective test results:

Intermodulation (overload and image rejection, etc):

With a vertical Triax 8 element 86-108 MHz yagi aiming north, the following intermod was noted on 40-88 MHz.

R-7000: 75.5 MHz, 76.35 MHz (image from 97.7 MHz SBS), 80.3 MHz, (image from 101.7 MHz 2WS), 82.7 MHz, 83.5 MHz, 84.325 MHz, 85.15 MHz. All these images were from the 88-108 MHz FM band. Even though they were fairly strong, none of them moved the S meter.

R-8500: 85.2 MHz very weak FM image.

Conclusion: The R-8500 has the best intermod performance. Bear in mind that the R-7000 has good intermod performance, compared to most scanners.

Wide FM (110 KHz) selectivity:

R-7000: 88 MHz relatively clear with minor splash next to 88.1 MHz. 88.7 MHz relatively clear with minor splash from 88.5 MHz. 92.7 MHz clear with very weak splash from 92.9 MHz.

R-8500: 88 MHz faint signal buried under strong splash from 88.1 MHz. 88.7 MHz signal mostly buried under strong splash from 88.5 MHz. 92.9 MHz 2ABC FM spreads down to 92.475 MHz! Not totally clear until 92.45 MHz!

Conclusion: The R-7000 has the best wide FM selectivity. In fact, considerably better than the R-8500. Switching to 15 KHz narrow FM cleaned up any adjacent splash. The nFM selectivity was equal on both receivers. This indicates that the RF front-end is not responsible. The difference lies in the wide FM IF strip. Both receivers were modified with two Murata 110 KHz ceramic filters. I suspect that because the R- 8500 originally used surface mount filters, the impedance is different, hence not optimum for 330 ohm filters. The other possibility is slightly inferior Murata filters. In any case, 92.9 spreading down to 92.475 is a real concern. I remember that some of the local Darwin FM tx's also had relatively wide spread.

For TV DXers, the R-8500's poorer wide FM selectivity will not degrade TV audio. This is because TV DXers don't need to worry about 200 KHz adjacent channels. Only FM DXers will complain.

Sensitivity:

57.26 MHz ABSQ1 Warwick, QLD via daily tropospheric scatter, and monitored using the 2.4 KHz SSB filter, is equal on both receivers. Not surprising considering the high external noise levels.

A weak 86.25 MHz video carrier, monitored in nFM, had slightly less noise on the R-8500, but still very close. A 91.08 heterodyne was also slightly stronger on the R-8500.

UHF sensitivity is roughly equal, as indicated by a weak heterodyne on 709.25 MHz. But even if there was a difference, no serious UHF DXer is going to use a 7-8dB noise figure receiver, considering that 2dB preamps are readily available.

Conclusion: The R-8500 is generally slightly more sensitive than the R-7000. This difference will not be of any consequence during good DX openings. Because the 30-70 MHz band has high external noise levels, no difference will usually be noted between the two receivers.

Noise blanker:

While helpful on the R-7000, not equal to the R-8500. For example, with some types of noise, the R-7000's noise banker made no difference, while R-8500's NB did.

Interference:

The R-8500's IF shift facility was able to remove a interfering heterodyne. Of course, other than switching to another sideband, nothing more could be done on the R-7000.

Audio quality:

R-7000 has a more tinny midrange type audio quality. The R-8500 has more bass and a generally mellow type audio quality.

Conclusion: A secondhand R-7000 still represents the best overall DX performance verses price ratio. The next step down (a big step!) is a Realistic Pro-2006 for around $300 secondhand. However, the Pro-2006 has no SSB, and the intermodulation performance is inferior to the R-7000.

The R-8500 has equal performance to the R-9000, minus a few 'bells and whistles'. The R-8500 looks better than the R-7000, has better audio quality, decent HF performance, and excellent intermodulation performance. If you have $3,300, the R-8500 is generally better than the R-7000. However, as stated earlier, the DX performance is generally equal on both receivers.

Receiver modifications and upgrades

The Icom R-9000, R-7000, 7100, and 8500 receivers requires some minor additions and modifications to enhance the wide-FM selectivity. I suggest the following additions and modifications be made for wide-FM reception of DX TV and FM signals:

Replace the two Wide 230 KHz Murata FM filters with Murata SFE 10.7 MHY-A 110 KHz ceramic IF filters.

If you are mainly interested in TVDX audio, I suggest that the Murata SFE10.7MTE 80 KHz filters are ideal. The SFE10.7MTE filters have good spurious performance of 48 dB (9 ~ 12 MHz). Also, the -3dB bandwidth (80 KHz) of these filters is halfway between NTSC TV audio -3dB bandwidth (50 KHz), and system B audio -3dB bandwidth (100 KHz).

The Icom R-8500 has two small surface mount chip 230 KHz Murata filters which are used for wide FM reception.

Ian Roberts, ZS6BTE, provided the following details:

"A DXer sent me a couple of 110 kHz SFE10.7MHY-A 10.7 MHz Muratas for the wide band FM filtering which I have already installed by cutting across the existing 230 kHz Murata ceramics, and simply soldering the three pin new ones across the skeletons left. To remove the old SMT filters requires a stream of hot air, which will also loosen nearby components, which I did not want to do.

The 230 KHz SFECA 10.7MS2-A Murata filters are located at the rear center right, they don't look like ceramic filters, as I remember it they are also not IDed on the PCB mask...don't make the mistake of replacing the more obvious narrow band 15 KHz FM filters, more to the left when the front of the rig is towards you.

I chopped through the ceramic filters each in two places between the poles of each filter. A more elegant way would be to grind those spots with a Dremel moto tool or similar. Make sure to get within about .5 mm of the PCB to take the filter substrate out of play. The tatty pieces of metal left are the new soldering points."

"Note that increased IF filter losses have no effect on the sensitivity of receivers - assuming that they have sufficient RF gain and first IF gain in front of the IF filter(s).

The noise-to-noise ratio of a receiver - derived from KTB - is bandwidth related, so reducing bandwidth from 230 to 110 kHz will increase sensitivity by 10log 230/110 = 3.2 dB. The visual effect is a possible reduced "s"-meter reading of ~3 dB, depending on where the "s"-meter senses the IF level. This reduction may be erroneously interpreted by the user to mean lower sensitivity.

Guessing, it seems that ICOM uses ~230 kHz WFM filters to enable users to make use of the 10 MHz output on the 10MHz/AGC voltage connector on the rear panel (of the IC-R8500, also IC7000?) for external stereo decoding. The receivers themselves do not decode stereo so there is every reason to reduce the WIDE FM bandwidth. Mono TV sound has a deviation or around ~50 kHz and mono FM broadcasts ~75 kHz. The additional deviation due to stereo and information subcarriers can be dumped in the narrower 110 kHz filters without harming the DX performance of the receiver. Also, services such as satellite APT (WEFAX) require 50 kHz at most. One would have thought decent filters for these ICOM receivers would have been:
15 kHz standard communications FM,
50 kHz TV sound/WEFAX/weak TEP broadcast FM, etc and
110 kHz for strong FM mono broadcasts."

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

Yupiteru hand-held scanners

The Yupiteru 7100, 7200, and 9000 series of portable hand-held scanners are considered to be the best choice for mobile monitoring of DX TV signals. The 7100 is probably the most sensitive on the 40-88 TV band.

The MVT-7200 & (MVT-9000) use a CFJ455K5 2.4kHz SSB filter and whilst this is not the whole story it does give much better HF/SSB performance. Also, performance would be better for close spaced video carriers. With the exception of the MVT-7200, which uses the same filter there is no better wide band scanner available at the moment on HF/SSB than the MVT-9000. If this is not a priority then the MVT-7100 remains a good choice.

Tony Mann (Perth) recently tried his Yupiteru 7100, during a 2Es opening to the eastern states of Australia. The 7100 was connected to an outdoor yagi antenna. While ABMN0 Wagga was received at excellent levels on the 7100, their was some spurious signals around 45 and 55 MHz.

Receivers such as the Icom 7000/7100/8500, AOR 5000, etc have several bandpass filters in the first RF stage. This keeps images and cross-modulation to a minimum.

We concluded that the Yupiteru's RF front end was too broad, and hence needed an external RF low pass filter, with a cut off frequency of ~ 88 MHz (FM band) or 64 MHz (local ch2 TV). This only applies to DXers who connect their Yupiteru scanners to large outdoor DXTV antennas, and live in major cities, with several high power local TV and FM tx's. In rural and semi-rural areas, Yupiteru scanners are generally free from any overload problems.

Assuming overload is present on a Yupiteru 7100, the first step is to determine the source(s) of the RF overload. It could be 49 MHz baby monitors, local band 1 TV, or 88-108 MHz local FM, etc. Strong local 88-108 MHZ FM stations mainly cause my own overload receiver problems. To minimize overload, I use a small Hills FC658084 88-108 MHz FM trap (40dB attenuation). The filter's in and out use F connectors. Use BNC/F adaptor connectors. For a hand-held scanner such as the Yupiteru 7100, the Hills filter will easily fit between the chassis and whip antenna. This will give a much cleaner response over 30-88 MHz.

Small hand-held scanners, such as the Yupi 7100, although excellent for their size, are a compromise in terms of input RF bandpass filtering. Large size scanners, such as the Icom R7000/8500, AOR AR5000, etc, have several filters in the front end, hence overload and image rejection are excellent. Another problem is the very high sensitivity of certain hand-held scanners. This can be a problem if a high strength local signal causes desensitization. For example, a strong local 50 MHz beacon can cause overload, thus the RF amplifier loses the ability to properly amplify.

Some DXers have mentioned overload problems when the Yupiteru 7100 is connected to an outdoor antenna. When using outdoor antennas, I suggest that a 88-108 FM trap filter should be permanently left in line for 30-88 MHz DX. Also, you could try using opposite polarisation, relative to the interference sources. A variable RF attenuator could also help to minimise RF overload.

I don't recommend that a commercially available pre-amp (including switchable RF filtering), should be used with a hand-held scanner.

Another possibility is a fixed 30-70 MHz RF bandpass filter. Designs can be scaled from other amateur band filters. The ARRL handbooks are a good source of designs.

The Yupiteru 7100 can be found for around $250-$300 (Australian) second hand. The 7200 is around $350-$400.

For DXers on a tight budget, the Realistic Pro-2004 scanner is a good choice. Although the 2004 doesn't feature SSB modes, it does have NFM (5 KHz steps), AM, and wide FM. The sensitivity and image rejection specs are also reasonably good.

Realistic Pro-2004 scanner

Links

Precise measuring of video offsets on VHF/UHF scanning receivers.

Copyright © 2005 Todd Emslie