Least expensive way of looking at 2.7 GHz - Page 1
Forum section: electronics / rf-microwave

author: PaulAm
author_rank: Frequent Contributor
timestamp: June 16, 2019, 07:54:03 pm
content: I have an issue that keeps cropping up in an LTE connection and I need some way to visualize the signal. All of my RF equipment tops out around 1.5 GHz (8568b sa and 8754a vna) My signal generator is a 1 GHz 8640b.What's the least expensive way of being able to look at the 2.7 GHz band? I can't directly use my current equipment and I don't want to spend thousands on a more capable SA (budget is more like a couple hundred USD).I'm not adverse to cobbling something together but I have limited time for large projects.I ran across modifying a $5 SUP 2400 Direct upconverter into a downconverter to cover up to 4.5 GHz. Maybe that in front of my SA?Ideas?thanks

author: Radiosonde
author_rank: Contributor
timestamp: June 16, 2019, 08:00:12 pm
content: If you are lucky you can get a CMU200 for under 500 bucks.Thats a SA and SA to 2.7GhzRegards

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 16, 2019, 08:58:37 pm
content: maybe a mixer like this...ADL5350-Module-Low-frequency-10M-4GHz-high-linearity-Mixer-RF-IF-LO-portsince you have 1GHz gen, you can see something 2.7 - 1 = 1.7GHz with your equipments. if that still pushing the limit, you need gen or source that can produce 1.5 - 2 GHz to see 1.2 - 0.7 GHz IF-. this one is cheapest grade with built in monitor...2018-RF-signal-generator-with-sweep-function-RF-signal-generator-140MHz-4-4GHzyou are going to need good BPF as well.. ymmv.

author: PaulAm
author_rank: Frequent Contributor
timestamp: June 16, 2019, 10:46:31 pm
content: Thanks, that looks very interesting.I snagged a listing on the SUP 2400. For $5 and an hour's work, it was worth a shot; that would get me 2.5-3.9 GHz. Not optimal, but probably good enough if it works.

author: David Hess
author_rank: Super Contributor
timestamp: June 18, 2019, 12:31:41 am
content: Hack together a preselector, mixer, and local oscillator to translate the band you want to a range your existing spectrum analyzer can monitor.

author: DaJMasta
author_rank: Super Contributor
timestamp: June 18, 2019, 02:10:58 am
content: Absolute cheapest is probably a frequency doubler for your RF gen and a mixer for downconversion, but you're going to want filtering for conditioning the doubler output to minimize harmonics that make a mess of your mixer output and then probably filtering after the mixer, so it's a pretty DIY and custom tuning sort of setup.Do you need much dynamic range? If 8 bits or so suffices, a SDR with the capability can probably be had for a pretty reasonable sum.There are also downconverting modules for various bands available secondhand. Could be tough to find datasheets, but if you can find a brick with a built in LO or a lower frequency input to a built in LO multiplier, you could probably find a combo mixer/LO/filtering for your band of interest.

author: German_EE
author_rank: Super Contributor
timestamp: June 18, 2019, 08:53:31 am
content: Add a high pass filter on the input stage of your mixer and, if possible, a low pass filter on the output. This will remove image artifacts from the mixing process.

author: 9aplus
author_rank: Regular Contributor
timestamp: June 18, 2019, 09:42:58 am
content: Two things coming on my mind...1) Lime SDR mini for 200 $ going up to 3.5 GHz2) Look for DBMs for higher freq, once I managed to purchaseone Anaren up to 4 GHz and one WJ up to 15 GHz for 100$ both.Than double your sig gen to 2 GHz and you can see enough on bare DBM input.Sometimes I am doing the same trick with my Agilent E7495B

author: chrisl
author_rank: Regular Contributor
timestamp: June 18, 2019, 10:26:02 pm
content: Agilent E4406A VSA can be had for just few $100's. I bought mine for only $300 a few years ago, and it came with many options.The possible drawback is the 10MHz SPAN limitation which can be extended with some of measurement options.

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 19, 2019, 10:21:29 am
content: QuoteHackRF from Ebay and China.

author: radiolistener
author_rank: Super Contributor
timestamp: June 19, 2019, 10:22:53 pm
content: You can try this one:https://www.aliexpress.com/item/32973380394.html

author: PaulAm
author_rank: Frequent Contributor
timestamp: June 20, 2019, 03:38:47 pm
content: Some great ideas, thanks!I'm going to try the modified SUP 2400 downconverter option first since that's the cheapest option and one's on it's way. Might be interesting to see if I can swap the internal 2.4GHz LO to a 2GHz one, but for $5 it's hard to go wrong. The E4406A looks really interesting plus that it's portable compared to my 70kg SA (another piece of obsolete test gear? what's not to like?)