RF source  - Page 1
Forum section: electronics / testgear

author: real69
author_rank: Newbie
timestamp: March 04, 2017, 02:44:24 pm
content: hi guys,Could anyone suggest a good 3GHz(<2.5GHz)( Rf source (0dBm will do...).my first choice is Signalhound's VSG25A. 2nd one is gw instek USG LF44. as i looked into the rf sources are the quite expensive. Even rigole cost ~3.6K.My question is what is the best priced RF source in sub $1000? (my measurement dont need to be ultra precise). Did any one found problem while using VSG or USG . another question is if i want to measure 3rd Order Intercept Point can i do it with multitone gen of the VSG (in the book they used 2 rf source and a power combiner).

author: daqq
author_rank: Super Contributor
timestamp: March 04, 2017, 02:48:47 pm
content: You could try buying an old unit or a refurbished unit of ebay. They are generally much more affordable than a new device.

author: PA0PBZ
author_rank: Super Contributor
timestamp: March 04, 2017, 02:58:14 pm
content: Have a look at the HP/Agilent ESG series.http://www.ebay.com/sch/RF-Signal-Generators/181994/i.html?_from=R40&_nkw=ESG&_sop=15

author: asadullah mir
author_rank: Newbie
timestamp: March 04, 2017, 03:18:40 pm
content: I found a board with an ADF4351 on Aliexpress and even wrote an assembly program ( for a stand alone instrument) to output a single frequency or sweep over any arbitrary range. I probably have it some place.It is an interesting chip with a wide range PLL on board.Look for ADF4351 board. on Aliexpress, could still be available. It was only 43 $.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: March 04, 2017, 03:25:06 pm
content: RF Explorer gen. 24-6000MHz. Cheap. +Forms SNA with RFEx Rx unit.

author: real69
author_rank: Newbie
timestamp: March 04, 2017, 03:59:15 pm
content: thank you for your reply. :)What do you think about the signal hound; signal gen?

author: DaJMasta
author_rank: Super Contributor
timestamp: March 04, 2017, 04:37:05 pm
content: The HP ESG series generators are pretty nice, there's also the Rohde & Schwarz versions, the SMT03 or SMIQ3, the Marconi/IFC/Aeroflex 2030 or similar, or the older HP 8664 - all of these older models would probably be good choices and are available used, but it's a struggle to find a cheap RF generator with more than a couple GHz of bandwidth. These units often come with modulation inputs and options, an extremely wide output range, and high stability and accuracy timebases... they are solid instruments, though depending on your application, they may be overkill. These older generators also tend to be very large, so they take up space on the bench and are heavy to ship. There's considerable advantage (at least for me) to have a physical interface on the instrument, though. Having a quick way to access settings and change things without having to plug into a computer is helpful for most of my usages, and using one of these benchtop generators usually give you a lot more input and output options - instead of automatically generating your modulation signal in the unit, one of these larger ones can also take in external signals to be used - depending on the application, this can be quite useful.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: March 04, 2017, 05:06:42 pm
content: Quote from: MrW0lf on March 04, 2017, 03:25:06 pmDo they have firmware that lets you set frequency by digit (like every other function/signal gen on earth) or are they still forcing you to step through the entire frequency range step by tiny step?

author: saturation
author_rank: Super Contributor
timestamp: March 04, 2017, 09:53:31 pm
content: Low cost models, several variants each:http://www.rf-consultant.com/simple-signal-generator/https://windfreaktech.com/product/usb-rf-signal-generator/There are also cheaper Chinese versions of unknown spec based on the ADF4351 chip, just eBay search it, typically under $70 and well, buyer beware. Some of these were discussed on eevblog some years ago as well as on EDN magazines.'Budget' RF sources have pros and cons, so its important the spec sheet is true so you can determine if what it does meets your need. For example, output per frequency may not be flat, but usually the included software can normalize output :RF Explorer Signal Generator, RFE6GEN, is based on the Maxim MAX2870 see its spec sheet for details. It does a similar thing with its output curve following its internal attenuator profile, when on.These low cost generators out of box do not have enough spectral purity for calculating TOI without additional filtering, and you'd need 2 sources at least. Noise Power Ratio, NPR, is built into Signal Hound's software and saves additional work.

author: saturation
author_rank: Super Contributor
timestamp: March 04, 2017, 10:08:22 pm
content: You set any frequency randomly but on the hand held all inputs are done with the limited arrow keys interface, there is no keypad; scroll left right, up down through each position and set numbers for each position: 0000.000 MHz.Quote from: jjoonathan on March 04, 2017, 05:06:42 pm

author: MrW0lf
author_rank: Frequent Contributor
timestamp: March 04, 2017, 11:55:16 pm
content: I just got it. For initial tests used PC software. Can set frequency, sweep etc over USB. Main drawback - no smooth amplitude setting but discrete steps.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: March 05, 2017, 12:15:48 am
content: That's not how mine works (FW 1.15). There *is* a "increment/decrement any digit" frequency setting but it's squirreled away in a submenu between 4 and 7 clicks away from the main screen depending on which menu was last accessed. Since it remembers, you can't just memorize the keystrokes either. I've gone back and read the manual. It documents the behavior that I observe: *only* fixed-step frequency increases and decreases from the main screen, and although you can change the step size, it takes so many button presses to do it you might as well just sit there and press the right arrow 50 times. To add insult to injury, the buttons don't auto-repeat when you hold them down, either.Oh, and if you're near one edge of the frequency range and overshoot, it wraps around, and refuses to let you wrap around in the other direction, forcing you to smash that button even moreMy goal here isn't to rag on the RFExplorer Handheld RF Signal Generator. My preferred outcome is to find out that I'm wrong. Barring that, I want to make sure others are aware of the caveat before they buy.Quote from: saturation on March 04, 2017, 10:08:22 pm

author: saturation
author_rank: Super Contributor
timestamp: March 05, 2017, 12:45:24 pm
content: Its a primitive menu, but its consistent and easy to learn and optimize. I have the same FW, as its the latest. It remembers the last menu item before 'return' so long as it powered on, so its only 1 click to the desired menu setting. So, its 1 click to frequency setting from "menu", 1 click to engage CW adjust, then one click for each digit setting and click per digit. Likewise its 1 click to get to the amplitude output menu if I'm using it then 1 click to each adjust menu. Scroll goes from 0<->9 but it will increment or decrement the next significant digit like a counter, so if you wish to set 600MHz, set digits to under that say working from Left to right 588.88n so that if you overshoot it will not cause too far a change then touch it up going R to L when you're done to hit the setting you wish.Good luck, but you should post on RF Explorer forum rather than here if you want it improved. Aracholl is quick to reply when he's not away.Quote from: jjoonathan on March 05, 2017, 12:15:48 am

author: MrW0lf
author_rank: Frequent Contributor
timestamp: March 05, 2017, 12:48:46 pm
content: Quote from: jjoonathan on March 05, 2017, 12:15:48 amJust connect it to PC, it will work much betterAlmost any device like this is pretty much guaranteed to be pain if there is no numeric keypad section. Strange design decisions because many same form factor comms radios have these.I bought mine for mainly stationary lab use, and mainly for horizontal timing testing, for which it is adequate with 0.5ppm frequency stability. Might not suit application where vertical dynamics are important.

author: saturation
author_rank: Super Contributor
timestamp: March 05, 2017, 02:03:46 pm
content: Yes, for both RF Explorer and Generator, you can get more 'features,' improved functionality and speed using the PC software. Plus, no bugs I can findI am running RF Explorer and Signal Gen on Win 7 Pro 64 bit, its flawless.Compared to its competitors [ that I linked] its primitive on-device interface allows some stand alone handheld use or as USB device, whereas most others are dedicated USB devices. Also, the RF Gen and other sources I linked have good software support; on the GWInstek dongle posted by the OP, there are few reports of driver problems and poor response from Instek to solving it, and it runs $400 but it has better phase noise vs RFGen at least on its data sheet.Aracholl does not have published phase noise on their products but I asked for nominal values after I did some self measurements. They are on par with mine and here is my worse case interpolation so you can compare. The SG380 is a quality low cost RF generator from SRS that begins at $4000. I use this graph to compare against other curves. E6 is RF EXplorer at ~ 6 GHz, E1 is Explorer at 1 GHz, S1 is Signal Generator at 1 GHz, actual data points.Note this only phase noise, if spectral purity is of concern to you harmonic as well as RF leakage or spur data is not provided on basic RFGen datasheets.Quote from: MrW0lf on March 05, 2017, 12:48:46 pm.

author: joeqsmith
author_rank: Super Contributor
timestamp: March 05, 2017, 04:14:51 pm
content: Quote from: real69 on March 04, 2017, 02:44:24 pmI assume you need a vector generator. Maybe start by listing what modulation techniques you need.