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Author Topic: Icom IC-R8600 Wideband Receiver  (Read 48846 times)
AA7AS
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Posts: 3




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« Reply #30 on: August 11, 2017, 06:09:49 AM »

The IC-R8600 is using the same FPGA as the IC-7300, so I'll guess the noise blanker / waterfall performs identically.

That's not 100% definitive; FPGA traditionally means "Field Programmable Gate Array", and if that's what the chip is, then the reprogramming required is trivial - a very high performance blanker requires only level detection, a switched multiplier/data gate, and a counter. It's where it is in the data processing that makes or breaks the waterfall / spectrum in the presence of noise. The same chip could be programmed differently for the ICR8600. And for future releases of the IC-7300, for that matter (which really needs such a fix... I cannot possibly emphasize enough that the way it works now is the wrong way.)

Also, based on the IC-7300's performance, the noise blanker implementation may not be in the FPGA at all. If the FPGA is doing the FFT for the spectrum, then they'd have to add it in there. However, if the FPGA is providing the baseband RF for the spectrum, then it can also be implemented in the CPU. From the block diagram, it's unclear exactly what data the FPGA is producing.

So, to recap, there are two possible ways the noise blanker could be done properly in the IC-R8600:

1) If the S/W FFT is done in the FPGA, the first is different FPGA programming, which may not change the FPGA designation.

2) If the S/W FFT is being done by the CPU, the second is only a very small CPU code change and doesn't affect the FPGA.

The only way to know short of an ICOM engineer stepping in here and telling us, is to observe the radio's actual performance.
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OH6I
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Posts: 42




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« Reply #31 on: August 23, 2017, 11:19:47 PM »

http://webpages.charter.net/n9ewo2/icr8600.html
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PITSWL
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Posts: 176




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« Reply #32 on: September 19, 2017, 09:19:32 AM »


Incredibly informative review; many thanks!
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"Section 97.101(d) prohibits ALL amateur licensees from causing harmful interference, and does not provide ANY exception for interference caused to other amateurs whom the interferer believes have violated a Commission rule." - DA 16-877 at 17
N0YXB
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Posts: 1137




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« Reply #33 on: September 19, 2017, 01:32:26 PM »

Indeed, thanks for the link!
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VR2AX
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Posts: 803




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« Reply #34 on: September 20, 2017, 01:59:14 AM »

Wonder whether anyone here has tested one? The positive comparison to the IC-9500 certainly makes this tempting at USD2K.

Does anyone understand the reference to deployment with 2 receivers on a 19 inch rack here?

http://www.icomamerica.com/en/products/amateur/receivers/r8600/default.aspx

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KC2NLT
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Posts: 93




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« Reply #35 on: September 28, 2017, 02:39:11 PM »

Sensitivity in the VHF band in AM mode appears to be 15 dBμ. That translates to 5.6µV.

Am I wrong in saying that it seems this receiver will practically be deaf in the VHF band? That seems like a pretty high figure.

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VE3WGO
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Posts: 161




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« Reply #36 on: September 28, 2017, 05:16:18 PM »

Yes, I agree, the 15 dBμ number seems a bit high, but that's not far from the general range for many AM receivers over the years.  With the rapid disappearance of AM transmission mode overall, I imagine it became a lower priority than say FM or SSB/CW performance. 

I suppose it doesn't matter much, as on the VHF and UHF bands it's generally a good idea to use an outboard broadband preamp anyway, possibly mounted at or near the antenna, and that will set the noise figure and sensitivity of the radio for those frequencies.

But the spec is better in the HF band, 7 dB better in fact, so that's about 2.5 μV. That will be plenty sensitive to hear the AM crowd on the HF bands, actually better than all but the most serious AM receivers of the past.

73, Ed VE3WGO
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ZENKI
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Posts: 1439




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« Reply #37 on: September 29, 2017, 11:08:57 PM »

Anyone have a better explanation of Icoms  S-meter meter scales in on the R8600?

I can understand the Dbm Scale, but what is their scaled called "DbUV EMF"

Most professional receivers either have calibrated Dbm or DbuV scales. What is DbUv EMF?
The manual offers little explanation on what the R8600 is measuring and if the scale is fully calibrated.

The Dbm scale is nice to have and so is a true DbUv scale. It would have also been nice if the S-meter was calibrated and they supported something like Quasi Peak in a calibrated 9khz bandwidth which would have been  made the R8600 popular as a EMC pre-compliance  receiver which is a pity. Icom could have  sold thousands of R8600's as pre-compliance receivers if they just stick to the conventional industry standards rather than not having the not invented here mentality. It ruins the appeal of the R8600 which can be achieved for far less using a radio like the SDRPLAY.
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KC2NLT
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Posts: 93




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« Reply #38 on: October 06, 2017, 04:50:54 PM »

Yes, I agree, the 15 dBμ number seems a bit high, but that's not far from the general range for many AM receivers over the years. 

I suppose it doesn't matter much, as on the VHF and UHF bands it's generally a good idea to use an outboard broadband preamp anyway, possibly mounted at or near the antenna, and that will set the noise figure and sensitivity of the radio for those frequencies.

73, Ed VE3WGO

So given that the selectivity is really good in the AM mode in VHF, you're saying that sensitivity can be easily improved with a good preamp?

I think the specs on Icom's website already mention that the sensitivity figures are with the preamp on.

How does the noise floor fit into this entire discussion? Is it going to increase to the point that it's better to get a more sensitive receiver or is a dedicated low noise figure preamp a better solution in your opinion?
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VE3WGO
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Posts: 161




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« Reply #39 on: October 06, 2017, 07:18:50 PM »

yes, for sure, get a preamp.  Even the very best receiver has to sit at the end of a cable that connects it to an antenna, and that's where the story begins......

An outboard preamp will be the biggest single item in the receiving setup that would determine the signal to noise ratio (ie, the apparent sensitivity) for the whole system.  A good quality, low noise preamp, with a high overload point and wide enough bandwidth for your frequencies of interest, would be perfect. 

A low noise preamp with perhaps 10 or more dB gain will actually be the defining component of the receiver's noise floor.  It will therefore make a vast improvement especially at higher frequencies where the cable between the antenna and receiver will have increased signal losses (losses rise with frequency), since the preamp will amplify the received signals more cleanly when it is placed near the antenna, before the signals have to travel through the lossy cable to the receiver where that signal has to compete with the receiver's own noise floor.

I would suggest that above 200 MHz or so (perhaps 50 MHz if you are looking for perfection) an external preamp, mounted very near the antenna, becomes almost a necessity for any serious signal hunting.

If you want to build one, a google search for something like low noise wideband preamp would yield many hits, both store-bought units and home-built construction plans.  Preamps are pretty compact and far simpler than in days gone by, since almost all of the circuitry is now included inside a single integrated circuit.  See for example a nice home-built one that is easy to build at http://gridtoys.com/preamp/preamp.html . Places to buy ready-made ones are numerous, for a couple of examples see http://lna4all.blogspot.ca/2013/04/lna-for-all-low-noise-amplifier-for.html  or  http://janielectronics.com/index.php?route=product/category&path=20_62 . I have not built or bought any of these mentioned, so I can't tell how well they work, but they seem reputable.  My preamp is getting old, and was built for the former TV VHF-UHF bands, but it still seems to have a low enough noise floor to make a difference.

If you buy a preamp that has no cover, you will want to add a metal one to keep static electricity away from the interior components of the unit, and if you want to mount it outdoors say near the antenna, get a sealed cover to protect it from weather.

I am seriously considering buying an IC-R8600.  If I do, I will definitely be adding a new preamp in front of the input.

73, Ed VE3WGO
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W6RZ
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Posts: 161




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« Reply #40 on: October 06, 2017, 10:38:12 PM »

The IC-R8600 is reviewed in November QST. The AM sensitivity figures seem a lot better than the Icom figures. 1.64 microvolts with the preamp off and 0.68 microvolts with the preamp on at 120 MHZ.
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KC2NLT
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Posts: 93




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« Reply #41 on: October 08, 2017, 05:45:10 PM »

Thank you for the informative responses.

If you were only interested in analog, which would you get, a barely used Icom IC-R9000 or the 8600?

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VE3WGO
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Posts: 161




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« Reply #42 on: October 09, 2017, 06:37:15 AM »

Deciding between the R9000 and R8600 is tough, without knowing the price and condition of the 9000.  Depends on the price difference for you, and how heavily and long you intend to use the radio. 

The 9000 is beautiful radio, and probably 20 or so years old I would think.  Repairing it might be a little difficult if that's ever needed, but if you will be a light user that probably won't matter at all.  Is the one you can buy the LCD (9000L) or CRT (9000E) version?

If you intend to do a lot of signal hunting and frequent monitoring over many frequency bands, in other words be a heavy radio user, then you probably want to consider the 8600.
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KC2NLT
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Posts: 93




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« Reply #43 on: October 09, 2017, 11:37:03 PM »

I do like the 9000 for its vintage look. It will be for light use, not heavy use. Parts and repairs are a consideration. While I do like the light weight and small footprint of the 8600, including the waterfall display, I wonder if the 9000 is better built and a better performer. You know, something along the lines of, “They don’t make’em like they used to.” 
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VR2AX
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Posts: 803




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« Reply #44 on: October 11, 2017, 04:15:00 AM »

I had a R9000 some years ago which I parted with reluctantly. It is a classic in terms of design and build quality for its time (1989). That said there are some cons which are summarized on the Sherwood site.

http://www.sherweng.com/radios.html

I don't have a 8600 but am tempted after reading some of the reviews referred to above. That said it is said to be similar to a 7300 on HF at least. Reading that reminded me I had a 7300 under the bed in the spare room so I have been test running the 7300 on receive the past few weeks. Location is city centre high rise with much man made noise. I acquired a AOR LA400 magnetic loop antenna to try to minimise that stuff.

The noise blanker on the 9000 was vastly superior to the NB on the 7300. The noise reduction on the 7300 is a personal choice at least for me. It does reduce background hiss but I am undecided whether that makes copy better, or just gives copy with less background hiss.

The AM selectivity choices on the 7300 are better than the 9000.

The 9000 can be a pain to ship. properly packed and boxed the box is likely to tip slightly over 50 pounds which many carriers will turn away.

Anyway this is a continuing study from this side. Good luck.
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