The AM Forum

The February 2007 issue of QST on page 1 has an ad for a new Icom receiver, the IC-R9500 “wide band receiver”.  It’s not approved or available in the U.S. yet.  It has been showing in Japan since this past August.  I think that the price will be about $11,000 U.S.

19” rack-mount type of box, 7” color LCD, 2 DSP processors, covers 5 kHz to 3335 MHz. so it’s not an RO version of the IC-7800 as I see it, but essentially a surveillance/scanner type of receiver. 
5 roofing filters from 240 kHz down to 3 kHz.  Up to quadruple conversion depending on frequency and mode selected.

It has 2 notch filters and synchronous AM detection, front panel bass and treble controls.  I counted 88 buttons and knobs.  Soft menu buttons along the left and bottom of the LCD.
DSP controlled noise blanking.

HF dynamic range is 110 db, +40 dBm 3rd order IMD input intercept.

4 antenna connectors – 2 are N, (1) SO-239, (1) phono.

Here is a link to a description of the receiver:
http://www.universal-radio.com/CATALOG/widerxvr/0095.html

Here is an product page with nice photos and full ICOM brochure.  Click on the link at the bottom of the page for the 1.4 MB .pdf brochure:
http://ndl-dx.se/icom_r9500/

Looks like the successor to the R9000.

it also has Ethernet, spdif and
USB connectors.
neat radio.

i just ordered 10 of them  ::)

The max bandwidth of 240 kHz limits is usefulness though.

Cascaded roofong filters provides enough ultimate attenuation to match the dynamic range. A single filter is good for about 80 dB max. Multiple bandwidths will help close in dynamic range.
$11K I would prefer the latest radio by Mr. Rohde for the same money.

I plan to be a door stop after I crap out when my kids cast my ashes with portland cement. I'll be cheaper than a useless 5 year old rice box missing 1 part of unobtanium

Icom still supports the 9000 and it's way more than 5 years old. Your comments are unfounded Phil.

Steve why would you want more than 240 KHz BW in the first IF. Bugs Bunny hasn't been on Saturday morning in years.

To put the receiver in the S20R emulation mode.

I don't see the oil/BTU topic.  I guess it went ballistic today and exploded.

Tell us how you really feel, Phil ;D

I know, and I miss Bugs!

Lots of wideband digital stuff out there now, like COFDM, etc.

Well I guess it won't handle GPS either. I would prefer less bandwidth options but cascaded filters. The Harris 590 and Racal 6790/6830 use cascaded filters to provide high ultimate rejection. This makes it easy to get high broadband dynamic range.
I guess I'm not interested in wb digital data but I'm sure there are people out there who want to get it. 

What's the deal with roofing filters.   In a lifetime of working in the electronics industry I have only seen this term used in ham radio ads.   I presume they are analog filters to correct for the problems with DSP filters, or antialiasing filters.   Or are they some type of filter yet to be described in older electronics literature?

A roofing filter is used in the first IF of an up conversion receiver to limit the bandwidth into the second mixer. An up conversion receiver throws the image into VHF band so a good roofing filter eliminates the image problem also. A single crystal filter eliminates the need for a tuned preselector RF stage
The roofing filter is a term that has been around since the 70s well before ham receivers used them. The WJ 8716 /8718 with Racal RA6790 and Harris were all doing this in mil receivers back in the 70s Harris and Racal use 2 roofing filters in cascade to get even better ultimate rejection. The Cat's butt is to have selectable bandwidths for roofing filters to limit the bandwidth into the second mixer improving close in dynamic range. They are usually in the 16 to 25 khz bandwidth range with some as tight as 8 KHz. Sherwood put a tight one in the R4 making it quite a RX for CW.

Thanks for the info.   I wasn't sure if it was just a marketing scheme or a technical term.   I am sure that my NC-183 doesn't have any, how about something like an IC-718 or some of the newer rigs that don't advertize that they have roofing filters?

The R390A has a L/C roofing filter and it tunes with the radio. I think it is up conversion on the low bands. This was back before they could make filters work above 30 MHz. Most modern receivers do up conversion to eliminate the need for a tunable preselector. Some roofing filters are simple and don't have the performance of a mil receiver. The better the roofing filter the less crud gets into the second mixer. Racal an dHarris mounted the two filters in different modules for best isolation. You don't get 100 dB of ultimate rejection when mounted on a single board. They have to be in shielded enclosures using good coax in and out.
Racal uses this cool double shielded 1/8 inch teflon coax and still it is hard to get much over 100 dB of isolation.

Roofing filters are used in receivers that are double conversion or more conversions.  As Frank said they are placed before the second mixer.  The idea is to have a filter right away with enough selectivity to eliminate signals that are outside the final i.f. filter bandwidth so that the intermodulation distortion products generated in all of the earlier i.f amplifiers is greatly reduced.

The Kenwood TS-820S for example, circa 1977?, is single-conversion receive, so the roofing filter does not apply with this and other single-conversion receivers. 

The Drake R-7 triple-conversion receiver, circa 1979, has a roofing filter “nominal bandwidth of 8 - 12 kHz.”  Implemented with (2) two-pole crystal filters and L-C circuits at the first i.f. of 48.05 MHz.  The widest 2nd i.f.  selectable crystal filter bandwidth offered was 6 kHz. for AM.

The Kenwood TS-430S double and triple-conversion receiver, circa 1982, has a roofing filter with specifications of greater than or equal to 19.2 kHz. at -3 dB and less than or equal to 56 kHz. at -10 dB.  Implemented with (1) monolithic ceramic filter at the first i.f. of 48.055 MHz.  The -430 receives narrow-band FM, so the roofing filter must be greater than 15 kHz. wide.

These older receivers used one roofing filter only.  The newest receivers with greater dynamic range switch multiple roofing filters, more expense, but greater performance.

The National NC-183 was single-conversion.  The NC-183D was single and dual-conversion, dual above 4 MHz.  I don’t have the schematic on hand, but I believe there is some L-C selectivity in the first i.f. when dual conversion.  There is enough selectivity for sufficient image rejection for the second conversion, but I don’t think it qualifies to be called a roofing filter because the selectivity does not approach the final application bandwidth intended.

Searching the internet, I found that the IC-718 circa 2000, is double conversion receive and has a 7 kHz. bandwidth roofing filter.

There's already a Yahoo Group for this receiver:
http://groups.yahoo.com/group/R9500/

I used a KVG 7 KHz roofing filter in my homebrew RX. It does 96 dB of dynamic range. The tighest 40.455 MHz roofing filter I've seen it 8 KHz used in WJ and Racal receivers. The 10 KHz filter used in Cubic receivers is also quite good. Harris has a 12 KJz unit that is pretty fair. 40.455 Mhz. is a standard first IF in many mil receivers built in the 70s through 2000. I've also seen them as wide as 200 KHz in special applications.
My hot rod racal has a pair of 8 KHz roofers. It does 100 dB dynamic range at 10 khz spacing.

In Robert Sherwood's latest rankings of HF receiver dynamic range, the Ten-Tec Orion heads the list at 92 dB., as determined by the 2 kHz spacing results.  The Orion had a 1 kHz. bandwidth roofing filter installed to achieve this number.

I see also that Sherwood offers a cooling kit for the R9000!  I can't find any mention of the actual power consumption of the R9000 however. 

The R9500's power consumption is listed as "70 VA typ.".  It does appear to have a fan in the rear.

Two things kill close in dynamic range. Synthesizer phase noise and excessive gain ahead of the second mixer.  A DDS lo like in the flex sdr1000 can claim  great close in dynamic range but at the expense of spurs down only 70 dB. A good synthesizer needs phase noise below the dynamic range floor. This is hard to do inside 5 KHz dBc.
The second mixer actually needs to be stronger than the first to handle the gain required in maintaining the noise figure.

Most crystal and mechanical filters have a dynamic range around 100 dB. The only way to improve that is to run 2 filters in a parallel path with quad hybrids. It boils down to the maximum power a filter can handle without distorting.

It's been a while since I've used a 9000, but I don't recall them having a fan. And, yes, they did get quite warm!

Tom,
The Tentec has quite a cool looking synthesizer design. The close in phase noise is very good. My hot rod racal is in the 80s at 2 KHz but since I've found a way to improve it with an additional voltage regulator that supplies power to the synthesizer 5 volt regulator.  I don't think it will get me to 90 because the synthesizer phase noise is slipping through -90 dBc at around 2 KHz.

It would be interesting to see the Orion synthesizer schematic then.

At the dynamic range numbers Sherwood is quotng now, I would think that the measurement and number assignment is getting quite...."hairy".

The other corresponding thing is how much does the DR vary from receiver to receiver in priduction?  In other words, is it actually tested on every unit.  My gut feel is that the actual DR can vary quite a bit, especially if the synthesizer and other l.o.s aren't critically looked at. 

At the DRs you are talking about Frank, you mention that the filters are at their DR limit too.  Does anyone check that before popping them into the high DR radios?

Tom,
Once you get above 95 dB of dynamic range I have found a number of things happen. First you have to worry about interaction between generators. I use a pair of HP8640Bs and they really need an isolation amplifier on the outputs to trust numbers above 95 dB. I need to build a pair of push pull nortons to provide better isolation. Also as the synthesizer warms up in the RA6830 phase noise changes it also changes slightly as you change frequency. Up around 100 dB I can see plus or minus 5 dB from test to test on different days. I never trust a measurment unless I see it 5 or 6 times on different days.
The crystals in crystal filters start having problems when they see about 10 mw of power. Even SAW filters have problems with transducers at that power. When I was working ar Andersen Labs they were trying to come up with a transducer that would take more power without hurting insertion loss.
Collins mechanical filters are rated at 30 dBM IP3.
I tested the Racal roofing filters and find them to run 100 to 105 dB dynamic range. I built a homebrew second mixer module with high dynamic range norton amplifiers and was surprised to only get 105 dB DR. The stand alone amps were better.
The guy who designed the H mode mixer ran into the same problem and used two filters in parallel driven by quad hybrids and phased 90 degrees from each other. He measured IP3 above plus 40 dB.
When it comes to receiver specs I'm from Missouri.
I'll see if I have the synthesizer schematics for the ten tec and send them to you. fc

240 kc bandwidth would be great for radio astronomy.  Put an integrator (simple RC stretch, diode det. and op amp DC amplifier) on the output and listen to Jupiter ! 

In years of sun-spot lows like right now, 18 Mhz is a very good receiption freq. for Jupiter's lightning storms. -All very mysterious back in the day before the cause was proven.  If memory serves correctly, "Sky and Telescope" had an article about a radiometer complete with stacked yagi design, etc. some years ago.

I tried a watered down version with an HQ 110 on 15 meters, picked off the IF to a diode and RC integrator to a Rustrack recoder. I think I got a 24 hour cycle as Jupiter transited.  But not sure, heh, heh, Could have been anything.  For a real thrill use 27 Mhz; integrate that!

Those Sherwood and other numbers are interesting but no context is provide. Just how many more DX contacts can one make with a receiver rated for a DR of 92 dB versus on with 91 dB. It's somewhat like the horsepower thing with cars. The number used alone is nearly meaningless.

40 meters battle mode with broadcashers you need 100 dB of dynamic range to play hardball.
90 dB of dynamic range is pretty good for 75 meters most of the time.
The numbers mean nothing unless you understand what is going on.
I trust Sherwood's numbers and have verified them on a few different receivers,
unlike the marginal specs in rice box ads.

Close in dynamic range is a big deal and there you want to be 70 dB or better.
Consider trying to work a guy S6 with a slop bucket 45 over next door.

Horsepower, like rigs never enough limited by ability to feed the beast.

Like I said, no hard data showing real world results. Sure, more is always better, but where are the measured and real world verified break over points. Too much anecdotal stuff and not enough legitimate measurements. This is typical of hams. "Yea, I put up a JS 123 antenna and worked 10 DX stations in 2 minutes on 20 meters. Conclusion: the JS 123 antenna is a great DX antenna." Never mind this was done at the peak of the sunspot cycle when everyone and their brother was working 10 DX stations in 2 minutes on 20 meters.

I just spent a ton of money on this yealowood and I know it is the best a slop bucketer told me

Heh, heh. Indeed. ;D