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n4vgb
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« on: December 02, 2007, 11:42:10 PM »

Does anyone on here know anything about the Cubic CDR-3280 receiver?


Mack
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WA1GFZ
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« Reply #1 on: December 05, 2007, 09:16:18 PM »

My only DSP radio is a TCI/BR 8174 with 6 KHz the widest filter. Looks like a cubic designer did it. Again the S meter is very accurate. 3 conversions down to 5 KHz into an A/D / DSP it works pretty well but could use a better roofing filter in the first IF. Same set up as Harris/Racal Cubic 40.455 MHz to 455 KHz so many filter possibilities. It is in a 1U rack computer controlled. It would make a nice spectrum scanner with a lab view program. You can get at the low IF but not I/Q because it is generated in the DSP. My model does not have that option that takes a second DSP (that would be a cool radio as it also does the spectrum monitor)
As far as AM is concerned I2PHD seems a bit better than stock RA6830 sync detector under poor conditions. Flex is a distant third. I've spent many hours monitoring both in parallel and was very surprised with the Flex. I bet it is due to bill ware bloat. I also noticed somehing interesting with the boston buzzie on 160 last night. It pumps the noise floor of the flex and it takes a while to recover. I need to study this more to see if it was due to AGC release time. This also seems to happen when there is a lot of static.
I suggest good reading on Sherwood's site on DSP demodulation. He is a good guy I've had a number of emails with him over the years. I trust his test numbers.
Notice he has no data posted on either Flex. I know he has played with both of them.
I contacted the Flex software guys on my AM findings. They are very sharp but don't seem real interested in AM since most of their business is the I gotta have the latest rice box at the highest price gang. They are milking that like the afternoon cow. It is actually fun to watch. SDR1K is like a bugger stuck to their finger now.

I thought the 3280 had an I/Q output but maybe it is an option. Cubic makes some class stuff but Data is hard to come by. The 3500 series VHF/UHF stuff is beautiful but try and get schematics. A friend hit a dead end with Cubic. This new stuff might be easier but I bet you pay. If it belongs to uncle sam you might not be able to buy docs. I just completed a new R2307 chassis last week with all the right module numbers. It took 3 or 4 years to locate all the right part numbers.

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WA1GFZ
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« Reply #2 on: December 06, 2007, 08:34:52 AM »

Mack,
I started with an fT1000 AM demodulator and a Motorola DSP EVM module. Pete WA1SOV gave me some code and I hacked it to work. I was hooked after that. I know exactly your thought process because I've been there but I am also open to new things as long as they really work. SDR is getting better as we speak. I again suggest you invest about $15 in a softrock 6 kit and hang it off you 455 KHz IF and start to play. This is where I am but I homebrewed my I/Q converter to plug in as a module into my RA6830 for the same function. I duplicated the double balanced Tayloe and used the INA163 amps Flex used. I was lucky as a guy who bought an RX from me on the West coast made the PC boards and paid for the parts. I did the design, build and test.
Later I joined the HPSDR gang and bought the first modules that are superior to any sound card out there. The noise floor is so low you need special shielded cables to take full advantage of the dynamic range.
The smart guys there are getting ready to release a perselector driving an A/D sampling at 130 MHz or 170 MHz. Also a D/A making RF. 2 Tone IMD at -50 dB check out the HPSDR site.  We will see the real performance later but it has been interesting to follow these sharp guys. I usually ask stupid questions but try to shut up shutting up so as not to show my stupidity.
So far I agree the with you on hanging the SDR off a low IF but the dynamic range is limited by roofing filter performance and synthesizer phase noise.
 
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WA1GFZ
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« Reply #3 on: December 06, 2007, 04:58:57 PM »

All the 8174s came from the same place and all have a max bandwidth of 6 KHz. They work pretty well. I have the program and manual if you decide to buy it. Fun little radio. I would love to write a program to monitor HF spectrum real time. I paid $650 for mine. A number of guys wanted a second one after getting one of them.
DSP you are stuck with the software provided with the box. SDR software can be changed on the fly. Both use DSP functions for demodulation.
Too bad the 8174s didn't come with the second DSP installed.
This would also make a nice front end for a softrock.

Future: Preselector directly into a real fast A/D for RX and D/A making RF with an output filter. Dats crankin if it really works.
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W1EUJ
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« Reply #4 on: December 06, 2007, 05:10:02 PM »

Where do you order the SoftRock 6? I have only been finding references to the 'sold out' SoftRock 4 and the 'upcoming' SoftRock 5 on the AMQRP website.

David Goncalves
W1EUJ
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WA1GFZ
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« Reply #5 on: December 06, 2007, 05:25:47 PM »

Contact Tony, Softrock 4 and 5 are long gone. Join the yahoo gang and just ask where to buy a softrock and Tony will respond within a day or so. The web site was never updated but the board has activity every day. There are piles of guys using his stuff. Price is cheap and quality is high. The only thing you have to be careful with is the through hole resistors. Measure each one because the color contrast isn't great even under a microscope. 
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WA1GFZ
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« Reply #6 on: December 06, 2007, 08:46:50 PM »

Wow 3150/4150 quite a machine. BTW 4150 manual is on cubic site....makes you even feel better doesn't it.
Any sound card will handle SDR functions. Some just better than others.
8174 I would not use the 5 KHz. 5 KHz would limit maximum AB bandwidth to about 9.8 KHz. It isn't I/Q so that is aproblem. I/Q is generated in the 8184 DSP as a math function and the basic radio like that model does not have it as an output. I would tap off the 455 KHz IF and interface a soft rock 6. I have one almost done for that purpose. All I need to do is break the seal on the radio and install a cable to bring 455 KHz out.
I'm one module shy of completing a new Cubic R2307 chassis and really want to get it done. Finally have all the right part numbers. Just need to get 1 more power supply module going. Yea it is analog but a brute.
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WA1GFZ
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« Reply #7 on: December 06, 2007, 09:08:46 PM »

Just checked the TCI. It has the extra BNC on the back my unit has a blunder button. I have more data as you see there are no schematics. I think I have all of the schematics. Looks like it came from the same batch as mine. BTW I located the control program and distributed it to the seller and all the guys who bought them. I found a TCI Rep who gave it to us.
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WA1GFZ
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« Reply #8 on: December 06, 2007, 09:22:59 PM »

The problem at first was the guy selling them had a funky control program. I never got it to work right. Install the one on ebay and chech it out. All you need is serial interface. I used RS232 but I think it also has RS422 and check it out pretty simple and easy to use. The radio configured as a dual DSP machine is pretty cool with a spectrum display. I tried to get some TCI hardware but they were out of production on that model. It was built in the '90s. One of the guys who does control software modified his code to control this unit. I forgot the guy but when a few dozen units hit the street a couple years ago there was a demand. The seller told me he was working on a contracting job and got the receivers as payment. He sold most of them.  Nice design but could use a better roofing filter. I have a nice WJ filter I may drop in my unit someday. The second IF has a 6 or 15 KHz 455 KHz filter. the 5 KHz if has RC filters. Then the DSP does the heavy lifting and demodulation.
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WA1GFZ
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« Reply #9 on: December 06, 2007, 09:47:32 PM »

ok you will be receiving some email
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WA1GFZ
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« Reply #10 on: December 06, 2007, 10:26:31 PM »

OK Mack I just sent you everything I had on a CD. Let me know if there is anything missing.  GN
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WA1GFZ
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« Reply #11 on: December 07, 2007, 09:06:42 AM »

I stayed up late to send it rather than make you wait a day. Yup a lot of data. the program may barf without a radio connected. Yes just dump the MS file and control program in a folder and it should run fine.
This model does not have tuning below HF. The preselector has to change and I think a different software version. I don't remember if mine tunes below HF. The S meter is very accurate. I checked it against the HP8640B. have fun 
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k7yoo
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« Reply #12 on: December 07, 2007, 11:41:41 AM »

I have followed your high end Rx conversations for awhile and one thought caught may attention (paraphrased):
"Use a good quality analog Rx and send the 455 (or 40 Mhz,) out put to a DSP or SDR"
This has been rattling around in my hollow state consciousness for some time and I would like some advice on how to implement it.
My main Rx are WJ 8716/18 and R-390 & 390A. The AGC on the WJ is annoying but it is otherwise quiet & solid. The 390 series is OK but dated. Both of these Rx series are adequate for my use but I would like to put their bulletproof front ends in front of a "smoke & mirrors" computer radio. Like you guys, I do not lust after the latest bells and whistles--I just want to hear, and do it well. I considered something as simple as purchasing one the the SDR packages and feeding the IF into it. Is is that simple?
Tell me how to go about this.
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VE7 Kilohertz
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« Reply #13 on: December 07, 2007, 12:15:45 PM »

Isn't the Collins HF-2050 a DSP radio? My manuals are all packed away so not sure what it has for outputs.  Would this RX be usable for what we are playing with here?

Paul
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« Reply #14 on: December 07, 2007, 12:43:00 PM »

The TCI 8174 is basically what you are talking about but you can't modify the software. I was in the same boat a year ago when I homebrewed a I/Q converter. The Softrock 4s were sold out so had to roll my own and it cost a lot more. Get yourself a soft rock 6 order it for a 455 KHz IF. The OP amp gain will be a bit high so you just need to reduce 2 resistor values or put a step attenuator ahead of the module. I also changed the design of the input transformer making it better suited for 455KHz. Then you just download free flex software or I2PHD or Rocky. For a $15 investment and about 4 hours work you have SDR demodulation to learn how it works. The coolest part is the spectrum display. You will never go back to a sweep type spectrum monitor after using an FFT spectrum display. The output of softrock goes into the line in of your sound card. Then you just have to get the levels right so you don't over drive the sound card. Then you can run SDR demodulation in parallel with any stock radio and compare performance. You get used to the processing delay after a while. The better the sound card the greater the dynamic range. You just have to look at the levels coming out of the rX you want to use. The 6730 is at -13 dBM and i'm sure the 6790 is about the same level. This is way too high for the softrock 6. Solution build a pad or put a step attenuator between them. The softrock noise floor is almost the  same as the receiver so there will be too much gain. My stock Dell sound card had a noise floor around -120 dBM so at -13 and a bunch of gain in the softrock you quickly saturate the sound card. I found the op amps want to be set at X6 to X10 gain when operating as an IF demodulator and you still need to knock the input down. A 3 resistor pad will handle that. Say with no signal you have -50 dBM coming out of the radio then you will need about 50 dB of attenuation to get the lavels for maximum dynamic range of SDR. This takes a bit of cut and try but no worse than setting audio levels right because I and q are audio if you think about it. The sound card doesn't like much above 0 dB audio so X10 opamps do the math. The sound card is usually the first thing to saturate and it makes a pile of distortion on the display. It is best to build the board and throw it on a signal generator with AM modulation so you can see the effects of level changes at the noise floor and saturation point. You have to shift the operating dynamic range of the softrock up to handle the RX output level while staying below the saturation point of the sound card. Again giving you the best dynamic range in the SDR section. I can easily see hum on a signal at 1 % modulation with my set up.
  
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WA1GFZ
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« Reply #15 on: December 07, 2007, 12:44:23 PM »

yes the 2050 is early DSP I don't remember the IF. fc
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k7yoo
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« Reply #16 on: December 07, 2007, 01:05:12 PM »

I went to Softrock 40 website and it is not immediately apparent where/what to order.
Perhaps you could E-mail some links to to assist me on this.

k7yoo@yahoo.com

tnx
Skip
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VE7 Kilohertz
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« Reply #17 on: December 07, 2007, 03:10:30 PM »

Just realized something, when I operate AM I always have to shut off my computer because of EMI/RFI interference from the computer gettig into the radio.

What have you guys done to alleviate this? It may be the switcher or maybe the processor??

Thanks

Paul
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WA1GFZ
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« Reply #18 on: December 07, 2007, 03:20:45 PM »

I don't have any RFI issues with my computer. My 160 meter antenna goes over the house. How about some beads on the power leads.
It could be your power supply or it could even be the monitor.
I'm using a Dell Demension 220 1 Ghz machine in the shack and an old 17 inch monitor. I didn't do anything special.
Check the quality of your RX coax.
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WA1GFZ
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« Reply #19 on: December 07, 2007, 05:06:52 PM »

It is very doable. and cheap if you have a computer. It doesn't take a wizz bang machine to get started either. If I was going to use a 6790 as a front end I would go to an unused filter position. There is a series 4.7 K resistor feeding the input of the filter. I would add a 47 or 51 ohm resistor to ground then connect some small coax across the new resistor to drive the softrock. This will give a wide band input of the first IF roofing filters usually around 20 KHz. Also the level would be a lot lower. You don't need all that gain anyway. Then the RX would operate as normal and the sdr will get a good signal. I did this in my 6830 before I built a dedicated chassis with DF hardware. The DF hardware has no AGC but has higher dynamic range than stock Racal hardware. The Fixed gain allows me to calibrate the Flex S meter. The 6790 AGC will introduce S meter error in the Flex above anout -83 dBM signal input because this is the point where the first IF agc kicks in reducing the level to the IF filters. You can get around this by running in manual agc mode but the second mixer could overload on a strong signal.This is something you will have to play with. Another option is build a HD second mixer and pick off a little first IF and 40 MHz for the LO. There were a few 6790 DF units made but very rare. I'm actually using a very rare second mixer form a RA6840 modified to work in the 6830. It has a dynamic range higher than the first roofing filter.
Go for it the spectrum display makes it worth it. Heck you can even measure RX phase noise real time with the flex software if you have a good sound card. If you just use the 455 khz output on the back your output will be the bandwidth selected and the level will be held to a fixed point by the whole RC agc loop. Still it is very usable to get you started.
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WA1GFZ
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« Reply #20 on: December 07, 2007, 09:17:17 PM »

about a year ago I decided to roll my own converter and see for myself.
Just a year later Soft Rock Tony has provided a high quality kit that doesn't cost an arm and leg to get into SDR. he has been pumping them out since spring. This is a great investment if for only the spectrum monitor.
A crystal Local Oscillator Tayloe converter has phase noise performance better than anything in my shack including the HP8640Bs. This allows me to measure performance I only guessed about. Heck it is the first tool that I have that lets me null the  analog compensation of the racal fractional N synthesizer real time while looking at a good chunk of spectrum.
Flex software is configured to interface to the softrock so every function works except wide band tuning which the RX takes care of.
I think the Key to a good SDR system is the bandwidth going into it based on everything I have measured and seen......HMMM wasn't this the same problem back in TRF radio days. So you need a good preselector or an sdr dynamic range about 20 db than us nonmil people can afford or even buy. Flex has neither yet. HPSDR mercury looks interesting and I have a couple high performance preselectors so that is what I'm waiting for.
 
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WA1GFZ
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« Reply #21 on: December 08, 2007, 11:20:24 AM »

I've had a number of emails with Rohde. He is a cool guy and quite helpful.
BTW check out the latest R&S SDR ....no you can't afford it if you hang with us losers.
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W1DAN
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« Reply #22 on: December 08, 2007, 12:54:15 PM »

Frank:

Thanks for all the discussion here.

Does the SoftRock6 come with a 455kc input? I see all ham band input stuff on their web site.

Not that I have a PC with USB 2!

Thanks,
Dan
W1DAN

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Steve - WB3HUZ
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« Reply #23 on: December 08, 2007, 01:28:36 PM »

You have to special order it, but you can get one with a 455 kc input. I have one awaiting assembly (yea, I'm lazy and scroteless). If you plan to hook it up to an older receiver, you must order a 455 kc input. If you plan to use it with a newer receiver, you must order a 455 kHz input.
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WA1GFZ
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« Reply #24 on: December 08, 2007, 07:21:43 PM »

many of the guys who bought one  were wanting a second one. I'm surprised it lasted as long as it did. You will learn more with a softrock.
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