Gigahertz frequency generator - Page 1
Forum section: electronics / testgear

author: smbaker
author_rank: Regular Contributor
timestamp: January 03, 2016, 06:32:27 pm
content: I have a frequency counter project that I'm building, and I wanted something that I can use to exercise the counter out to about 2.4 Ghz. I have lots of frequency generators, but the best of them tops out around 200 Mhz, so I need something that covers the range of 200 Mhz to 2.4 Ghz. I'm looking to spend on the order of $100. I don't need a laboratory grade instrument (certainly not at this price), just something to serve as a proof of concept. I've found this contraption on eBay:http://www.ebay.com/itm/138MHz-4-4GHz-USB-SMA-Source-Signal-Generator-Simple-Spectrum-Analyzer-138M-4-4G-/311103300023Are there any notable pieces of used test equipment that I should be looking for? HP8614A Seems like a possibility, although it looks like it would consume a fair bit of lab/storage space. I was looking for something smaller.

author: dom0
author_rank: Super Contributor
timestamp: January 03, 2016, 06:38:11 pm
content: The Chinese sell RF oscillators for a couple bucks. Just to see if your trigger amplifier works they should work just fine.http://www.ebay.com/itm/2-4GHz-OSC-Oscillator-VCO-Frequency-Source-Noise-Figure-3dB-/281777704128?hash=item419b428cc0:g:Z0oAAOSw9N1V1Nca

author: dadler
author_rank: Unknown
timestamp: January 03, 2016, 08:49:54 pm
content: I used to have this model, until I upgraded to the next model up (the manufacturer is nice and accommodating, and let me trade the lower model in for the higher):http://www.rf-consultant.com/simple-signal-generator/You can sometimes find them on eBay (same seller) for a discount. A bit over your price range, but the product works well. Square wave output only.

author: awallin
author_rank: Frequent Contributor
timestamp: January 03, 2016, 09:35:15 pm
content: Quote from: dadler on January 03, 2016, 08:49:54 pmhave you taken it apart?frequency range sounds like ADF4350 or ADF4351 or a similar PLL chip with integrated VCO?AD has eval kits for these e.g. digikey EVAL-ADF4351EB1Z-ND

author: chris_leyson
author_rank: Super Contributor
timestamp: January 03, 2016, 11:17:06 pm
content: Couldn't stop laughing dom0,with 3dB noise figure, snake oil radiofoolery:-DD

author: dadler
author_rank: Unknown
timestamp: January 03, 2016, 11:24:02 pm
content: Quote from: awallin on January 03, 2016, 09:35:15 pmYes, it's based on the ADF4351.http://www.edn.com/electronics-blogs/the-emc-blog/4423710/Review--inexpensive-RF-generator

author: smbaker
author_rank: Regular Contributor
timestamp: January 04, 2016, 01:04:37 am
content: Quote from: dadler on January 03, 2016, 08:49:54 pmThat's certainly what I wish I had. I'll have to see if I can justify stretching the budget. It's not a big stretch, but is still a little more than I was hoping to pay.I might pick up the $7 Chinese 2.4Ghz oscillator, to serve as another data point, to see how my counter handles it compared to the commercial counter I have.

author: tggzzz
author_rank: Super Contributor
timestamp: January 04, 2016, 01:17:54 am
content: Quote from: smbaker on January 04, 2016, 01:04:37 amhttp://www.ebay.co.uk/itm/181728458478I have one, have not evaluated it fully, and eventually managed to get useful documentation from the seller. The software runs in Linux under Wine.

author: G0HZU
author_rank: Super Contributor
timestamp: January 04, 2016, 01:36:45 am
content: QuoteI suspect that the VCO will drift and jump around a lot. It will be much worse if it is left exposed (not screened) as it will be very erratic if you move your body near it. Also, it will need a stable supply and tuning voltage. But I guess you can't grumble at the low price of $7Maybe this won't matter because you just want to get the counter to show something at 2GHz, but it could jump/drift around in chunks of something like 100kHz every few seconds.The other option is to make your own oscillator or fudge the $7 version to replace the varactor tuning with a fixed capacitor and stick it in a box and power it from a clean battery supply as this should help with stability if you just have it as a free running oscillator.But if you want to compare counters in terms of triggering/count stability, you really should be looking at a stable synthesised frequency source.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 04, 2016, 02:09:54 am
content: Seems doable. How low of a signal are you trying to measure?Could you just use an old router. Maybe a cordless phone?

author: babysitter
author_rank: Frequent Contributor
timestamp: January 04, 2016, 09:35:07 am
content: Maybe getting a Realtek DVB USB Dongle and listening to the LO would be a great thing to do?With the advantage of having a RTL-SDR capable radio.

author: Mr Simpleton
author_rank: Unknown
timestamp: January 04, 2016, 06:51:39 pm
content: Signal sources based on ADF4351 or similar are pretty OK but usually they lack filtering i.e. very rich on overtones. And most are without any adjustable attenuator. Still, can be very useful...

author: smbaker
author_rank: Regular Contributor
timestamp: January 04, 2016, 09:45:09 pm
content: Quote from: dadler on January 03, 2016, 08:49:54 pmI ended up deciding to spend the extra money and buy this. It seems like it'll be a useful tool for the bench. I opted for the one with the ook modulation option. More than I wanted to spend, but it felt good supporting something produced locally rather than something made in China.Thanks for the recommendation!

author: dadler
author_rank: Unknown
timestamp: January 04, 2016, 11:14:13 pm
content: Quote from: smbaker on January 04, 2016, 09:45:09 pmNo problem. I find mine quite useful. The software is pretty good too, and the engineer that designed it is quick to answer email/question.I traded up to the calibrated version, once I realized how solid of a tool it was.Square wave only, but I was able to get my 53132A to count its output up to 4Ghz (53132A only rated to 3Ghz) with the amplitude set high enough.The Chinese clones are similar, but I prefer a supported product in a nice enclosure.

author: smbaker
author_rank: Regular Contributor
timestamp: January 05, 2016, 12:00:45 am
content: Quote from: dadler on January 04, 2016, 11:14:13 pmIt looks like he has taken the time to put together some nice software for it too. I can definitely see the value in his product as compared to the Chinese units that I saw listed on ebay.