BG7TBL RF Signal Gen Quick Teardown and first impressions. - Page 1
Forum section: electronics / rf-microwave

author: Insatman
author_rank: Frequent Contributor
timestamp: February 15, 2018, 07:32:05 am
content: Hi...This unit arrived a couple of days ago and today I tested it and did a quick teardown. Build quality was decent. Only one minor bodge spotted. I'm not an expert on RF gear by any means. I wanted this unit to generate signals above 500Mhz where my old HP8654A runs out of gas. I needed something at least up to 2GHz where my spectrum analyzer limits and preferably 3Ghz where the SA should be hackable too (SA3021X). The unit was bought from Ebay at a reasonable cost and free shipping. It looked similar in construction to my GPSDO which has performed flawlessly...maybe the same designer perhaps? The BG7TBL is spec'd at 35Mhz to 4.4GHz and outputs from -45dBm to +17dBm.I only tested it at relatively low frequencies thus far. It has an extermal 10Mhz reference in and out. Tests were done using the internal reference and measured on an HP5370B 16digit counter with an external GPSDO reference. Accuracy was better than expected. At 50Mhz the unit was high by 0.5Hz. The 10MHz reference out was off by less than 0.1Hz. The unit had been warmed up overnight before tests. Waveform display at 50MHz on my Hacked Rigol DS1054Z (-3dB at 150MHz) looked OK. The unit does not output a sinewave, rather squarish wave which varies with amplitude settings somewhat. See photos. I was able to go down to slightly under 33Mhz so it meets the low end of the range. No way to test the high end at present.It comes with a tiny CD on which is a lot of manuals and software for the various products this outfit must make. The manual was ok for a Chinese product of this type. A photo of the table of contents below. The software worked well enough and a screenshot is below. It is quite simple but does everything I would need. The unit does have a calibration mode which can be accessed via software out on the front panel using boot-Key combinations shown in the manual.I paid $135 including shipping but the cost has gone up just a tad when I looked at the latest Ebay listinghttps://www.ebay.com/itm/35M-4-4G-Signal-Generator-Signal-Source-Simple-Spectrum-Analyzer-LCD-display/263409595668?hash=item3d546f7514:g:NO8AAOSwOA1aRhSH.Overall I am pretty pleased with this unit.

author: Insatman
author_rank: Frequent Contributor
timestamp: February 16, 2018, 03:12:23 am
content: Quote from: Mechatrommer on February 15, 2018, 10:12:32 amI considered some of those but I like enclosed test gear. Given my prior good experience with the GPSDO and the fact that they look built by the same outfit, I decided to pull the trigger on the unit shown.

author: w2aew
author_rank: Super Contributor
timestamp: February 16, 2018, 03:47:04 am
content: Did you have the scope input set to 50 ohms, or using a 50ohm thru terminator? Maybe the waveform would clean up a bit when properly terminated...

author: Insatman
author_rank: Frequent Contributor
timestamp: February 16, 2018, 04:44:25 am
content: Quote from: w2aew on February 16, 2018, 03:47:04 amA 50 ohm feedthru terminator was used. Without it the waveform is a little worse but nearly double in amplitude.

author: German_EE
author_rank: Super Contributor
timestamp: February 16, 2018, 06:39:12 pm
content: I was interested up t the point where you told us that the minimum frequency was 35 MHz. Ummmm, no, an RF generator needs to go a lot lower than that, preferably to 1 MHz

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 16, 2018, 07:50:33 pm
content: Quote from: German_EE on February 16, 2018, 06:39:12 pmthere are 2nd hand rf generators in ebay that can do that such asthis. or buy another AD9850 based lower frequency SG for cheap arse like us. the bg7tbl generator is based onADF4351 Synthesizerwhich can only go down to 35MHz in single chip, you get what you pay...

author: rhb
author_rank: Super Contributor
timestamp: February 17, 2018, 02:07:25 am
content: Thanks for the post. It looks like a pretty decent unit. I've got an ADF4351 module, but that's all it is, a module. No display MCU or anything else. So some assembly (and C) required which I've not got around to yet. With the JDS6600 and the FY6600 going to 60 MHz, I don't really have a problem with 35 MHz as the lower limit. The fact that the waveform is a quasi square wave is more of an issue. But that's what the ADF4351 is designed to produce.The JDS/FY6600 AWGs are remarkably clean. Biggest issue is FeelTech's unwillingness to resolve FW issues in shipped units.I'm considering using two ADF4351 modules with low pass filters and a mixer to get a clean sine wave from a few Hz up to 2 GHz by running both in the 2.4-4.4 GHz range.

author: Insatman
author_rank: Frequent Contributor
timestamp: February 17, 2018, 04:50:10 am
content: Quote from: rhb on February 17, 2018, 02:07:25 amYeah...35Mhz wasn't an issue because I own both the JDS6600 and a new FY6600 (v3.2). Both the BG7TBL and FY6600 showed up on the same weekly trip to the P.O. I've had the JDS6600 for awhile now. It has proven a decent performer with a good user interface. It's frequency stability is 10x better than the FY6600 at 0.5Hz on 10Mhz setting. I've been thinking of buying some low-pass filters to create sinewaves at specific frequencies, namely 1Ghz and 100Mhz, on the BG7TBL.

author: Insatman
author_rank: Frequent Contributor
timestamp: February 17, 2018, 04:52:11 am
content: Quote from: German_EE on February 16, 2018, 06:39:12 pmInteresting outlook...My old HP8654A classic RF generator went from 10Mhz to 500Mhz. As stated in prior message I have other generators to cover the lower frequencies.