Modifying / Adding a Frequency Counter to a Vintage Signal Generator - Page 1
Forum section: electronics / beginners

author: Glassman
author_rank: Contributor
timestamp: October 30, 2022, 06:23:44 am
content: I would like to add a frequency counter to my old Trio SG 402 Signal Generator similar to whats been done in this video and hopefully make it a bit more accurate as I'd like to eventually align some old Transistor Radios & CB radio's etcI have SDR radio on my lap top and it picks up the tone coming from the Sig Gen so I know it works and that the analogue adjustment is slightly out, also- For some reason my SDR doesn't go below 10mhz and need to know I'm generating a tone at 455khz- I have found that the Frequency Counter fluctuates / doesn't lock- The difference between the analogue display and frequency counter increases the further down in frequency I go.- I then tried using an RF amp set up similar to whats been done in this next video and the counter seem to stabalise and lock around 25mhz - 30mhz with the Sig Gen set to High and full RF gain.Am I wasting my time trying to attempt this?Should I look at a better frequency counter than the one I got off AliExpress? Is there an SDR that goes down to 455khz? Is the RF amp a bit of gimmick?Admittedly I didn't do the greatest job putting everything together i.e. long wires & no coax used, just wanted to see if the amp would make a difference which it did but not as good as what I hoped for.Trio manual, schematic and external & internal photos & RF amphttps://mega.nz/folder/ZxEWRDYR#SHJYkWr2b_1hyvyD5Bth2QThanks for taking the time to view this

author: David Hess
author_rank: Super Contributor
timestamp: October 31, 2022, 02:00:19 am
content: It makes perfect sense to do that. Two of my signal generators work exactly like that.The frequency counter probably has an AC coupled input causing its sensitivity to decrease at low frequencies.

author: Glassman
author_rank: Contributor
timestamp: October 31, 2022, 03:08:05 am
content: Thanks for you reply David.Did you modify the signal generators yourself and if so what sort of Frequency Counters did you use?

author: David Hess
author_rank: Super Contributor
timestamp: October 31, 2022, 04:25:27 pm
content: Quote from: Glassman on October 31, 2022, 03:08:05 amThese had the frequency counter built in, but worked in the way you describe. They were not synthesized, so the generator was completely analog with a separate digital frequency counter.I am sure the problems you are having are because the frequency counter from AliExpress is not suited to what you are trying to do, but I do not have any better suggestions. Some units are better than others.On my other analog function generators, I use an external frequency counter as needed. What you might do is add a frequency generator output to your signal generator which is constant amplitude to drive an external general purpose frequency generator.

author: Terry Bites
author_rank: Super Contributor
timestamp: October 31, 2022, 05:47:55 pm
content: this kind of thingwww.ebay.co.uk/itm/363267216826?hash=item549469d5ba:g:XEEAAOSwkz9gB~gC&amdata=enc%3AAQAHAAAA8LyClbjoAt2VXnonfNX6ByGQioTvjOdQ%2FUta%2FQ6gwbgdHlcqV4FdK1Ys8vDwnC7cWkb4cLPyfdaaGoXR0c%2FLAH4vk5TuCLrHYO%2F35bUnhFv%2BZuawmLUiDczEL9porccfwKIm0SaARHF65LyRkv8cm7XqzrVSyBBCvbsIParQ%2Brwh%2BNt2krRWnTZarNyEh4QK7qA7%2BjU1oGA3mACIBb2jgGS5oOfQDGYg%2FVupB0pE0zwMCdScOyZW%2BtsgrQZ3QXTO5kRlYutLmWFZk%2ByQdAEpi4ld74mwJ1AIy7MO2Qw%2FYlTfvWTClDSuvLABpxmJatZV7g%3D%3D%7Ctkp%3ABFBMnMTZ8IVhWorth a punt.They claim to use a 13MHz ± 2.5 ppm TCXO (really?). You need to test that againt a known source. Get a GPS disciplined 10MHz box- a must fot your lab.