Newbie
Joined: 21/10/2025
Location: AustraliaPosts: 6
| Posted: 02:51am 23 Dec 2025 |
Hi Doug,
I have built one and even though it works as described i have found a couple of problems.
1. The sensitivity of the BNC input at low frequencies especially below 100KHz to be very poor. It even starts dropping off from about 1MHz. the lower you go you end up driving the input up to 2-3V sine wave to get any accurate reading. There is no problem with a square wave. Thinking it may be noise from the supply upsetting the TL3016I IC6 as there is some switching noise present which is raising the noise floor of the input.
2. The mmbasic code had some divide by 0 errors which caused the program to hang with the GPS attached after 15 minutes. The program is a bit of a minefield and being not very good with mmbasic I fed it through ChatGPT. To its credit it did find all the problems eventually with a bit of prompting. So now at least it runs constantly with the GPS. This has improved the accuracy greatly but not quite as i hopped.
I have one of the Tamed GPS oscillators with a 10MHz output and using it as the GPS source via the NMEA serial and 1PPS I can plug that into the counter. It eventually after an hour it settles down adjusting the TCXO too much and reads around 10KHz high. The revised code still does a small glitch every 15min or so which surprisingly gets the counter within about 1-2Khz but it slowly drifts out, maybe temperature related, so I will have to look into that.
Anyway i will keep plodding away. If anything its a good learning experience.
As far as finding any other info available, i have had no luck other than your post.
See a couple of pics for interest. and the revised code
Cheers peter.
FreqCounter6GHz_Fixed_GPS_Hangs.bas.zip
Edited 2025-12-23 12:59 by walshpj64