Rohde & Schwarz SMIQ Series Vector Signal Generators - Page 1
Forum section: electronics / testgear

author: KungFuJosh
author_rank: Super Contributor
timestamp: July 03, 2025, 03:42:37 pm
content: This thread is for the Rohde & Schwarz SMIQ Series Vector Signal Generators SMIQ02B, SMIQ03B, SMIQ03HD, SMIQ04B, SMIQ06B, and SMIQ06ATE.I have a great SMIQ06B that had a mediocre screen (typical dimming with the green "frame"), so I bought an SMIQ02B parts unit that had a great screen, but needs the error 110 fixed (I have the part and will probably repair it).Anyway, the 02B has the SMIQB14 Fading Simulator option.Should I keep the B14 option for some reason and install it in the 06B, or leave it in the 02B unit (which I might sell)? I can't think of a reason I would need that, but maybe you can?Thanks,Josh

author: KungFuJosh
author_rank: Super Contributor
timestamp: July 04, 2025, 07:54:48 pm
content: The SMIQ06B I bought came with Option B19...which Ihate. The screen worked, but it was a little dark with the green tint on the edges that some of these get. So, I bought a SMIQ02B with a nice screen, and an OCXO, and I swapped some stuff around.Now my 06B doesn't have B19 (woohoo!), it has B1 OCXO, and the screen looks great:As Rene pointed out to me, the RF output cable, for some dumbass reason, is not the same in the 02B/03B models as it is in the 04B/06B models. So, after a couple failed attempts at other ideas, I grabbed the RF output cable from my SML03 parts unit. It worked!I did a power sweep, using the same RF power meter, before and after the change. That's definitely a win. There's a tiny bit less output, but all well within spec:Thanks,JoshPS. The SML03 and SMIQ02B parts units are both for sale for best offer + shipping.

author: KungFuJosh
author_rank: Super Contributor
timestamp: July 21, 2025, 01:39:38 am
content: I made a definition driver file for the 53132A for TestController, and did a quick frequency sweep test with the SMIQ. Channel 3 on my 53132A is (currently) rated for 100MHz to 3GHz, but it did well enough all the way down to 10MHz.This is probably the most interesting chart ever made.Thanks,Josh

author: BillyGo
author_rank: Contributor
timestamp: July 21, 2025, 03:53:03 am
content: Quote from: KungFuJosh on July 04, 2025, 07:54:48 pmThat looks quite readable. I'm trying to redo the optical bonding on mine before resorting to sacrificing a poor CMD55

author: KungFuJosh
author_rank: Super Contributor
timestamp: July 21, 2025, 03:05:06 pm
content: Quote from: BillyGo on July 21, 2025, 03:53:03 amWhich part is it that you're repairing?

author: BillyGo
author_rank: Contributor
timestamp: July 21, 2025, 11:14:13 pm
content: Quote from: KungFuJosh on July 21, 2025, 03:05:06 pmI am dealing with the original lcd display

author: KungFuJosh
author_rank: Super Contributor
timestamp: July 21, 2025, 11:25:49 pm
content: Quote from: BillyGo on July 21, 2025, 11:14:13 pmOhh, you're adventurous.How's it going so far?

author: RK9ALC
author_rank: Newbie
timestamp: August 22, 2025, 09:07:21 am
content: Hello, guys! I have SMIQ03B but without SM-B5 option (FM modulation). Recently I bought this module from another SMIQ03B. After installing and recalibrating an error message has appeared: "130 FM Modulator VCO unlocked" and there is no FM signal on output. Though all other modulations work correct.The readings of test points are:TP500 = -0.2 mVTP501 = +4.4 mV (should be 2÷13 V)TP502 = +0.3 mV (should be 0.1÷0.5 V)TP503 = +220 mVTP504 = +198 mVTP505 = 0 mVDid I miss something or is this module just faulty?

author: 44kgk1lkf6u
author_rank: Regular Contributor
timestamp: September 27, 2025, 05:54:12 pm
content: Has anyone measured its modulation bandwidth? The data sheet says that the frequency response is <3 dB at 30 MHz for the I and Q inputs. That is, there is a total of 60 MHz in both side bands. But my unit seems to have a total of 125 MHz. It is a 2.2 GHz SMIQ 02B with the SMIQB14 fading simulation option.

author: KungFuJosh
author_rank: Super Contributor
timestamp: September 27, 2025, 06:30:11 pm
content: Quote from: 44kgk1lkf6u on September 27, 2025, 05:54:12 pmIt sounds like you got it working? If so, congrats! Did you repair or replace the IQ/Mod unit?How did you setup your bandwidth test?Thanks,Josh

author: 44kgk1lkf6u
author_rank: Regular Contributor
timestamp: September 27, 2025, 11:31:27 pm
content: I repaired it. An IC was broken. 2 resistors were missing. I bought the IC. The resistor values were available in the service manual. It took less effort than replacing the LCD back light and moving the connectors to the front.The I input was connected to a network analyzer. The Q input was connected to a dust cap. The output was connected to another port of the network analyzer. The amplitude was 16 dBm. The center frequency was 2 GHz. Vector modulation was enabled. The other settings were what the preset button gave. On the network analyzer, the output amplitude was 4 dBm. The sweep was 1000 points linearly between 100 kHz and 100 MHz swept in 40 ms. The frequency offset was 2 GHz. The multiplier was 1. It measured the upper side band. Calibration was not run on the network analyzer. Each instrument used its internal clock source.

author: KungFuJosh
author_rank: Super Contributor
timestamp: September 28, 2025, 12:05:46 am
content: Nice work! You replaced the backlight too? How's it look now?I don't have a real VNA to test with.@KeBeNemight be a good person to ask.Thanks,Josh

author: 44kgk1lkf6u
author_rank: Regular Contributor
timestamp: September 28, 2025, 12:27:03 am
content: Now it is easy to read the screen whether the light in the room is on or off. The periphery of the screen is of a different color from the center. It seems to be due to the liquid crystal being heated unevenly during the lifetime of the original back light.If you feel like it, there is probably a way to measure the band width with stuff that you have. A spectrum analyzer or oscilloscope can look at the output. A function generator can generate a swept frequency sine wave or square wave into the modulation input.

author: KungFuJosh
author_rank: Super Contributor
timestamp: September 28, 2025, 12:38:32 am
content: AFAIK, the discoloration on the edges of the LCD is an RF blocking screen sandwiched in the LCD glass. Some people have gotten rid of the green by removing the screen, and the smarter ones replaced it (the RF blocking screen) with something else.When I have some time, I may try and set something up. I do have a scope and sig gens.Thanks,Josh

author: KeBeNe
author_rank: Regular Contributor
timestamp: October 05, 2025, 04:40:56 am
content: Hi all,Sorry for the late reply, I didn't notice this at all.SM-B5 must also be connected to the system with a coaxial cable, not just plugged in.My TP's:Settings: FM MOD DEV 10Khz, LFGEN1, MOD ONTP500 = -0,1mVTP501 = +6,412VTP502 = +272,9mVTP503 = +175,6mVTP504 = +233,7mVTP505 = +/- round 210mVWhen the B5 is installed, the calibration of the LF-Gen may be interrupted.This is due to the slightly reduced level caused by the increased load on the internal LF-Gen.Older models of the A240 had a potentiometer, but this was later omitted, requiring some tinkering as the level of the NF DAC is specified by the EEPROM value.Did you convert the LCD to LED?regards René

author: RK9ALC
author_rank: Newbie
timestamp: October 06, 2025, 11:09:19 am
content: I defeated this problem. There was broken capacitor C339 - it was giving 5 kΩ leakage and output voltage was lower than required -12 volts. After replacing everything works fine.

author: 44kgk1lkf6u
author_rank: Regular Contributor
timestamp: October 07, 2025, 03:02:52 pm
content: Quote from: KeBeNe on October 05, 2025, 04:40:56 amI converted the LCD back light to LED. Each CCFL was replaced with 28 of 3030 size 6 V LED's. They were connected to the 6 V to 10 V power supply with a 15 Ω resistor in series. The 2 resistors occupied the room for the original high voltage power supply. I used GW QSLPS1.PM-L1L4-XX52-1-150-R18 LED's. The screen was bright enough even when the brightness was set to the minimum. So I probably could have used larger resistors to help the LED's stay cooler. Attached is the circuit board.

author: KungFuJosh
author_rank: Super Contributor
timestamp: October 07, 2025, 03:13:07 pm
content: Nice work! If I ever need to replace the backlight, I'll probably go that route.Thanks,Josh