Sinad meter project
Chris Smith
Dear members
As some of you will know I have an interest in making and using Sinad meters for aligning FM radio receivers, transceivers, PMR radios and CB's. I wanted to buy one but they rarely come up for sale and if they do they are often sold at over £200. So a couple of years ago I bread boarded one up on Veroboard and entered it in the last construction contest. I was awarded joint second place with Denis G4KWT. The meter worked well and has been in use at the JTN shack ever since.
Surprisingly there is nobody out there anymore producing these meters in kits or ready built. The original company Helper instruments closed down around 1998.
These original meters were produced in the 80’s and there were lots of companies manufacturing them all to the same basic circuit design, however most designs had errors and most were not actually built to the published circuit.
The most common and simplest design is the original Sinadadder SD101. Working with Simon M0ZSU we have redrawn the schematic and laid out the PCB design in Kicad. This new PCB board is a 4 layer PCB which is far in advance of any board that could be produced back in the 80s. Although this is loosely a copy of the design we have improved and corrected some basic errors in the original design. Especially in the area of the power supply, notch filtering and AGC circuit. Using modern components, what we have now I believe is probably the most reliable and repeatable design ever produced.
To date a small batch of boards has been produced and they have all worked straight out of the box. So far four meters have been made, calibrated and completed by club members.
It was decided that it would now be nice to make this a club project.
So if you think you might like to build one, have no idea why you might need one, think it is too difficult or just not sure how to use it, download and have a read of the attached PDF and see what you think.
The cost would be about £50 to build the complete meter (most of that is in the cost of the 50uA meter and the case). PCB cost would work out at about £5 for the PCB and £10 for the components. The design uses standard through hole components (not SMD) so no fiddly soldering. You can source your own components and case from Ebay or CPC and assemble the meter yourself. Alternatively, we could have a small build it group at the construction meetings where together we can help each other and check the boards together as you build. I am happy to get a batch of boards made if you don’t want to get involved with all those “Gerber” files and Kicad stuff like the “Geeks” do. I can also supply the FET’s and the Op-amps that are needed if you have trouble finding them yourself.
Simply having fun together, building a very useful piece of test gear for the shack is what it is all about.
If you are interested, please reply to this message, drop me an email or see me at the next meeting and we will get things going.
Kind regards
Chris (G0JTN)
Chris Smith MIET (G0JTN)
35 Allendale Road
Earley
Reading
RG6 7PD
Mobile 07809707056
Home 0118 966 1075
email: christophe...@gmail.com
Mike Gathergood
Hi all.
I finally managed to excape from the decorating long enough to finish the SINAD meter, and I’m pleased to report that it worked first time, thanks to Chris’ PCB and instructions.
I’ve posted a video here of it with and FT-227R, using the internal 1kHz tone from the Marconi 2019A signal generator.
https://www.youtube.com/shorts/8f8hTuH2oUQ
73
Mike G4KFK
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