PSG9080 Counter not calibrated to signal generator - Page 1
Forum section: electronics / testgear

author: Mike Oglesby
author_rank: Newbie
timestamp: February 15, 2023, 04:28:39 pm
content: Newbie here but have searched the forum to no avail. My Juntek Psg9080 is gpsDO calibrated to a frequency of 10Mhz, but measures 67hz high when fed to the frequency counter. I have the Freq fine tuning set to 63 which calibrates the signal generator to my gpsDO using my two channel o-scope. Has anyone figured out how to calibrate the frequency counter to match the signal generator? All I know to do at this point is to always subtract 67hz from frequency counter reading.

author: wasedadoc
author_rank: Super Contributor
timestamp: February 15, 2023, 05:21:40 pm
content: Quote from: Mike Oglesby on February 15, 2023, 04:28:39 pmWell you are off to a bad start there. You do not subtract 67Hz. You need to scale all readings (ie multiply or divide) by some number close to 1.If you input 10 MHz and the reading is 10,000,067 then you should divide by 1.0000067 or multiply by the inverse of that.

author: Mike Oglesby
author_rank: Newbie
timestamp: February 16, 2023, 02:50:06 am
content: Thanks for the heads up, I should have thought of that since scaling over many frequencies. I still hope someone has information on how to calibrate the frequency counter separate from the signal generator. Maybe it can be done in firmware?

author: BillyO
author_rank: Super Contributor
timestamp: February 16, 2023, 03:44:41 am
content: Do you mean you replaced the internal oscillator with a GPSDO?

author: Mike Oglesby
author_rank: Newbie
timestamp: February 17, 2023, 08:47:34 pm
content: No, I used the gpsDO as a reference to fine tune the signal generator oscillator output at 10Hhz. The signal generator now agrees with the gpsDO at 10Mhz, but when I hook signal generator part to the frequency counter, the frequency counter counts about 66 hz high. I hope someone can figure out the PSG9080 circuits well enough to figure out how to calibrate the signal generator to match the frequency counter. I emailed the Juntek website with this problem but have no response so far.

author: Mike Oglesby
author_rank: Newbie
timestamp: February 17, 2023, 09:33:59 pm
content: A little more playing with the PSG9080 I find if set the fine tune at 50 which it comes shipped at, the frequency counter and signal generator track within 0.1 hz at 10Mhz. Using my RSP1A sdr and SDRPlay, I was able to calibrate the Rsp1a to WWV at 10Mhz. By zooming out on the signal display I can get an accuracy within a few htz. The gpsDO is accurate using this method to with in a couple of hz but the PSG9080 signal generator reads high by 64hz. I would assume from this that the CTS brand pll oscillator is off by this much. Does any of this make since? Any tips on diagnosing the oscillator and changing its frequency by this much? Do I just need to buy and install a better crystal oscillator? I do know about the external oscillator mod, but would rather not go this route at this time.

author: BillyO
author_rank: Super Contributor
timestamp: February 17, 2023, 10:50:01 pm
content: First, it seems to me to a bit strange that they have a different time base for the the generator and the counter. To me, that's just wrong.Next, if the PSG9080 does not use at least an OCXO for it's time base it makes no real sense to expect it to match the GPSDO over any great length of time or ambient temperature range.

author: radiolistener
author_rank: Super Contributor
timestamp: March 18, 2023, 12:39:12 pm
content: fine tune of PSG9080 doesn't affect frequency counter readings. Also fine tune has too high steps, and noticeable temperature drift, so there is no sense to use GPSDO for tuning it. If you want precise tune, it's better way to replace onboard cheap and small TCXO with a good OCXO

author: Mike Oglesby
author_rank: Newbie
timestamp: June 21, 2025, 08:14:46 pm
content: Two years later and I am finally following up for anyone interested. I bought and replaced the TCO chip with a more stable tCXO board and it mostly fixed the problem. Now when the Channel 1 frequency is set to 10,000,000 Hz (10 MHz) the counter reads 10MHz. When connected to the GPSDO the counter switches between 9,999,998 and 9,999,999 which is close enough for my work.