Ordered an sdr-iq...

[N2DTS]

I tried to use the HP8592L spectrum analyzer to look at the output of my signals and adjust the homebrew amplifier, but could not get a normal display on the thing, I did ssb with a 2 tone test, but got only one lobe on the display.
I also tried AM with one tone, same thing, it looks nothing like the pictures in books.
I tried every setting, and could see nothing that looks normal or useful.
I must be doing something wrong, but cant figure out what it is.

So I ordered the sdr-iq, that does have a very good spectrum display.
I also figure I can receive my own signals and record them in the software, and listen to them with various bandwidths set to get an idea of how to adjust the audio.
A different way to monitor your signal, by looking at the actual spectrum of your transmitted RF!

While the sdr-iq is a fair receiver, i think its great as a piece of test equipment...

Brett

[Steve - WB3HUZ]

What resolution bandwidth did you use on the HP.

[KL7OF]

Please report on the performance and your impressions of the sdr-iq after you have used it awhile...Curious minds want to know.......Thanks....Steve KL7OF

[w1vtp]

What resolution bandwidth did you use on the HP.

YES!  Some of this series didn't have narrow filters (RBW).  You need filters at least 1/3 the displayed modulation components -- forexample to see 1Kc, you would need to be able to set your RBW to at least 300 CPS - narrower the better.

The mfgr says  " Maximum display bandwidth of 196 KHz at an incredible 0.75 HZ RBW."

That should do the trick

But good luck on your purchase.  I'd be interested how this gadget works out

Al

[WA1GFZ]

8592L should work.  Scan width may have been too wide or BW too wide.
Maybe it is broken?? Sell it?

[N2DTS]

No, the spectrum analyzer is not broken, and its very useful when building things like VFO's where you can watch the levels and stability of the signal, even watch drift in Hz using the markers....
It may not go low enough in resolution to work, since it goes up to 21 Ghz...

I had an sdr-iq in the past but sold it to get something else.

It works very well, its the direct sample and downconvert type receiver, not like the flex system.
Its a great little box, powered by the usb port.
So a usb cable, an antenna and you are good to go from 500Hz (yes hertz) to 50Mhz I think.
The software was a bit clunky, no band buttons, band stacking registers, notch, but I think they are improving the software, and can make it do whatever they want in the future.
I think a new version is in the works, with lots more features.

One very interesting thing it can do is record the entire spectrum, from 500Hz to whatever, and you can play it back and tune around the bands just like it was live. No time limit other than what the hard drive can hold.

So I could record the entire heavy metal rally and listen to it whenever I want!

I plan on using it as a live monitor (spectrum) and to record my signal, then listen to it later adjusting filters to something like 6Kc and adjusting the audio till it sounds good....

As a receiver, its quite good, a little more background noise then the homebrew, the filters are very effective, and you can adjust them to whatever width you want.
Click tune on the spectrum display with the mouse, a VERY good detailed display of peoples bandwidth and modulation, its stunning.
Its smaller then a pack of smokes, and does not seem to need much of a computer to run fine, almost any computer with a usb port will likely work.

There are a few different programs that work with it, with more coming out I think.

I was going to wait for the flex 1500, but it might not be out for many months....


Brett


 

[N2DTS]

I looked, and the HP has 1KHz as the lowest resolution bandwidth....

I guess that is why I dont see the correct display.

Brett

[KF1Z]

The SDR-IQ is a pretty good RX.

I had one that came just as a bare board, before they sold them in a case.

You can record a maximum of 192khz chunk of band at a time.

(BTW  I  DID record the entire heavy metal rally on 75 meters.  250khz chunck of band from below 3700 to above 3900kc..  took just over 33Gb of disk space)


Good from about 3 kc up to 30Mc . max. ( the lower end was noisy, and unusable)


Brett has had one before, so he knows what he's getting...

For those who haven't it is a super step up from no SDR, or a softrock.

As far as performance vs price...  I think pretty good.
You'll spend twice as much to get a reciever better.

[KM1H]

The review in this months QST is pretty good and its obviously built as a piece of test equipment and not as a SWL radio. 
I may also get one.

Carl
KM1H

[WB2EMS]

I got an SDR-IQ back at the end of December (thanks Santa!) and have been enjoying it since then. It comes with it's own software, Spectravue, but there is an alternative software being developed by Simon, the same fellow who wrote Ham Radio Deluxe, called SDR-RADIO at sdr-radio.com. He's currently offering what he calls technology previews as he works up the software. I don't like the display on it as much as on Spectravue, it's slower and blockier, and I don't like the tuning method as much, but it does have band buttons and provisions for keyboard entry of frequency and such. He's just working on noise reduction routines today and will be adding features as he goes along. He seems to have developed a working relationship with the RFspace guys who make the SDR-IQ.

One very nice feature is that it also includes a separate server program that will drive the receiver and make the audio and control available over the internet. It automatically lists the receiver on a central server site that can be seen and selected off the regular sdr-radio console (select Input Source, then Remote Via network, a window will pop up - choose browse web and look for an open receiver. Be sure to click start after you make the connection and then off and then disconnect when you are done so you don't hang the server) Mine is currently plugged into an 80 meter loop and available for listening that way. I was just listening to Tim on the SBE with it from my desk at work. 

As a receiver, I'm pretty impressed. I'm not sure it's quite as sensitive as some of my other receivers, but I seem to be able to hear everything that I can on the TS2000. It's very interesting to be able to see the spectrum and find signals with it. I was looking for some AM action last night and the window was dead, and scanning around with it I found an AM carrier down around 3705 - clicked on it and found K4KYV tuning and testing and fired up the TS2000 and had a nice chat with him. I probably would have missed him without the ability to scan the spectrum and see an AM signal pop up.

The sdr-radio software doesn't allow you to record the whole chunk of spectrum like spectravue does, but it does let you click on an mp3 recording button and record the demodulated signal to an mp3 file.

I'm enjoying the heck out of mine. Download the free sdr-radio software and you can enjoy it too! 

[w1vtp]

I looked, and the HP has 1KHz as the lowest resolution bandwidth....

I guess that is why I dont see the correct display.

Brett

Yep -- you're right.  You can begin to see 3 KC SB components.  Anything lower than that begins to dissolve into the carrier or other SB components.

I used to accept / calibrate those beasties here at Raytheon.  We stopped buying that particular model because we needed better filters (RBW) -- like down to 1 CPS.

Where that unit will shine would be to check harmonics.  You can go into the zero span mode and dink around with the filters and video filtering and use it as an AM detector.  Even FM if you slope detect.  If I recall things right, there is a volume control and a little speaker in the thing.  The output linearity is pretty good and you can use it as a sort of power meter.

Al

[KF1Z]

You can also use Winrad with SDR-IQ and SDR-14.

I'd suggest giving that a try as well.

[WB2EMS]

I didn't realize you could run winrad with it. I did give it a quick try and didn't get anywhere, I'll have to revisit it. Apparently you can also get powersdr to run with it by setting up spectravue to make an 11khz output and turn off the demodulation and then point powersdr at the 11khz stream. I haven't tried that yet but saw some directions for it.

I'm new to all this and just getting my feet wet but I'm having fun.

Got an sdr-1000 coming next week as the next step of the learning curve.

[KF1Z]

You need to install "support files" to run the SDR-IQ and SDR-14 with winrad...

They are Here:

http://www.winrad.org/bin/SDR14-IQ.zip

[K1JJ]

"A different way to monitor your signal, by looking at the actual spectrum of your transmitted RF!"


Yes, a very important point.  Monitoring our own signal at the 1500 watt RF  level is what it's all about. Watching our own transmit I.F. is meaningless cuz it's gonna be clean no matter how bad the power amplification system is ahead.  For example, I understand the Flex TX  spec is about -25db IMD, so this wud be a problem driving a big amp in a congested area like the DX window .

Question: Do the common Flex rigs look at the high level RF output or the I.F. on transmit - or do they even have an option to input this external (1500w) signal into the spec display?

BTW, I'm still digesting the SoftRock 6.2 info and will need to order a xtal.  Thanks for the info and help, Bruce and Frank.  I may look into your SDR-IQ idea, Bruce, before I proceed too far with this.


Oh, on your spec analyzer problem:  When you input the two-tone into the ssb rig, does the standard o'scope show a modulated sinewave-type RF envelope? Unless the two tones beat properly, you may get just a carrier. If good, then try inputting (splitter) a sig gen into the same spec analyzer and see if you can see the "bug" next to the ssb signal.  How does a standard AM signal look on the spec analyzer when a 1kc tone is injected into the rig?  These should shed some light.

T

[W9GT]

I really like the SDR-IQ.  I'm using it with the companion IF-2000 board and SpectraVue software to monitor/control the FT-2000 transceiver.  However, Tom is right.  If I just use it to look at the IF of the FT-2000, I can't see what is really going on with my own signal.  If you use it in close proximity to your own rig, make sure you protect the input!  Use a couple of back to back diodes across the input to swamp out any excessive RF.  You can even make-up a more elaborate front-end protector with diodes and a series lamp.  Lots of guys on the SDR-IQ and FT-2000 bulletin board sites have reported wiping out the front end, if not protected.

73,  Jack, W9GT

[w1vtp]

"A different way to monitor your signal, by looking at the actual spectrum of your transmitted RF!"


<SNIP>...  For example, I understand the Flex TX  spec is about -25db IMD, so this wud be a problem driving a big amp in a congested area like the DX window .

Question: Do the common Flex rigs look at the high level RF output or the I.F. on transmit - or do they even have an option to input this external (1500w) signal into the spec display?

<snip>


T

On the first point - dunno where that -25 IMD spec came from but all the Flex's I see on the band have an amazing drop off at the transmitter AF bandedge setting and drop like white cliffs of Dover.  I've included a PDF of some screen shots I took a while ago.  The first page was a screen shot taken of a local station running a 5000a into a HB linear putting out legal limit.  You can only see the first 25 dB due to band noise which accumulated because I was on peak hold but I'll wager that without that noise that station's IMD would be quite acceptable.  This guy cannot be heard outside that window at all.

On the second question - no - the Flex only looks at what's going on inside the box and I'm not sure where it takes off the sig.  However, one could hook up to RX input from a coupler/sampler to a regular xmtr output and look at the products but the 5000 would have to remain in the RX mode to do that - I think.  Now that I think of it - I do have the second RX board installed - it does have its own RX input.  Anyone out there know if it could be used to monitor the output of a linear while transmitting -- that might be possible.    Might be an interesting experiment -- one that I intend to try some time.  It really is just like a S/A

Al

[N2DTS]

Spectraview, winrad, and there was another program that worked with the sdr-iq, but I forget what it was, and now the new sdr-radio.
Most of the stuff was sort of simple and crude compaired to power sdr, but that will likely change over time...

While I will likely use the sdr-iq as a receiver in the den, you can post here, get email, and listen on 3880 at the same time on a slow laptop, I think it will mostly be used as a TX monitor.

The flex 1500 might work a bit better as a receiver, maybe not, but its only got a 48KHz display, and it might not be avalable for 6 months....

Brett

[Steve - WB3HUZ]

I don't think any of the newer radios are better than about -30 or -32 dB IMD. This is almost 10 db worse than some of the better tube rigs of the past.

You cannot determine the IMD performance with on-air test with voice input. You can make relative comparisons but that's about it.

[N2DTS]

I plan on just using a little (3 inch) antenna on the sdr-iq in tx monitor mode, or maybe no antenna at all, I will just set the level adjusting the antenna size/location.

The flex looks at its TX signal past the power amp I think, but not what comes out of an amplifier.
The 2nd receiver might be able to do so.
They are also working on the receiver sampling the TX output and correcting imd and so on.
Maybe they will be able to include an amplifier in that?

Brett

[N2DTS]

The flex stuff has tone generator stuff built in, 2 tone, sweep, triangle, saw tooth, maybe square wave.
I was doing (trying to) the 2 tone test and looking at the spectrum analyzer, with the flex in ssb going through the amplifier.
If I set the two tones much wider, say 200Hz and 4000 Hz, would that work?
Is there some sort of formula for the frequencies of the two tones?
What would you do with a sawtooth or triangle waveform, look for the waveform on a scope, to see if it looks like a triangle or saw tooth?
It seems it would be hard to measure distortion that way, with 2 tones, you get the 2 tones, and anything else is distortion which you can see and measure the level of....

Brett

[w1vtp]

The flex stuff has tone generator stuff built in, 2 tone, sweep, triangle, saw tooth, maybe square wave.
I was doing (trying to) the 2 tone test and looking at the spectrum analyzer, with the flex in ssb going through the amplifier.
If I set the two tones much wider, say 200Hz and 4000 Hz, would that work?
Is there some sort of formula for the frequencies of the two tones?
What would you do with a sawtooth or triangle waveform, look for the waveform on a scope, to see if it looks like a triangle or saw tooth?
It seems it would be hard to measure distortion that way, with 2 tones, you get the 2 tones, and anything else is distortion which you can see and measure the level of....

Brett

The triangle wave form would be an easy way to look at the envelop in the time domain and look for flattening.  Sort of like the trapezoid approach.  Triangle, sawtooth and square wave have their use in measuring amplifiers.  Not sure what use they would have in AM mod service except to show low freq response of transformer coupling or ringing to indicate strange stuff going on in the upper mod freqs.. By definition, it would be difficult to make meaningful measurements using these waveforms because freq response limitations of, say, 5 KC would remove much of the harmonic content needed to measure performance of an amp... Might be useful in checking the lows tho'.. (I'm repeating myself here)  But then, a good S/A would do the same thing -- the current topic of this thread.

[WB2EMS]

I plan on just using a little (3 inch) antenna on the sdr-iq in tx monitor mode, or maybe no antenna at all, I will just set the level adjusting the antenna size/location.

When I got on with K4KYV last night, I disconnected the SDR-IQ but left it running. I could see some of my signal pop up on the display, but not a lot of it with just the empty connector. I think a couple of inches of antenna might work well enough for a monitor. I'll give that a try some night soon.

I am also planning to build up an input protection board. Got a couple of husky diodes and a teeny little lamp at RS to cob one together. I'm also going to have to come up with a more foolproof switching arrangement on the antennas so I don't have the SDR on one loop while I'm transmitting on the other. The feed points are only about 10 feet apart and the 75 meter loop is inside of the 160 meter loop. With the amp on I'm going to be putting substantial signal into the 'off band' antenna. I should plug the scope onto it and take a look just to see some evening.

Powersdr does look to have the most horsepower and features. I'll have to look into how that interfaces with the sdr-iq. I also need to figure out how much CPU and mobo I need for a dedicated flex computer.

[KF1Z]

With my QS1R, I short the antenna terminals on transmit, and have PLENTY of signal to monitor myself... and there is no "front-end" ( no filter, pre-amps etc).

You might consider a BNC plug, with a 50 ohm resistor across it, with a little piece of wire attached....

It's those pre-amps in the SDR-IQ you need to worry about.



Tom,
The IQ's pop up on the used market quite often.... though nice to get new....warrantee etc...

Of course, considerably more investment but WAY more useful than the softrock...

[K1JJ]

"On the first point - dunno where that -25 IMD spec came from but all the Flex's I see on the band have an amazing drop off at the transmitter AF bandedge setting and drop like white cliffs of Dover. "

Yes, all the Flex's I've heard were clean on the air too.  If you do a Google search for "IMD Flex" you will come across threads about this specific problem in the past, but maybe the new ones have been squared away.  

I would like to see someone do a scientific two-tone test on ssb to see what the real numbers are from the output of the final amplifier. The ARRL has, but I'd like to see an off-shelf test done by one of us with no axe to grind. I know that Chuck, who has a Flex 5000, said his was not as clean as his FT-1000D and planned to use the Flex just for RX and the 1000D for TX. This was about a month ago. (The 1000D specs are -32db for 200w and -36db IMD 3rd for 150w output, which is acceptable.)  I use my 1000D at 40w pep to drive a heavily loaded tube amp with low plate voltage that produces even better numbers than this. The result is about 250w output pep of super clean ssb or AM to use for whatever..

The chat here about putting a stub antenna on the input to sample TX RF is a big step and should begin a new trend towards monitoring our own signals "on the air."  That's the main reason I'm pursuing it myself.

When the HuzMan stopped by here last Oct with a hi-tech spectrum analyzer, it showed me my solid state IPA was poor. It also showed that Dr.Love was an exceptionally clean linear. I was able to build upon that information and improve things even more as a result..

There ARE sweet spots when adjusting all the many parameters of an amplifier chain to become extra-clean- that's what a spectrum analyzer will tell us through trial and error testing. It's well worth the extra effort to set up..

T