Re: Harmonics and Relay Replacement

Jim Sheldon
 

Finally got the >500 mW Axicom relays in - they got misrouted in the mail and have been riding the airways all over the US.  Don't know what happened as Digi-Key addressed them correctly - USPS just screwed up the shipping - LOL.

I plugged these into my V4 test bed built up on aluminum open chassis.  Sockets are mica filled 2mm thick with silver plated flat contacts.

That leaves the relays 2mm above the PC board and hopefully reduced the capacitive and with the >500mW coils (less turns) the inductive coupling as well.  Unfortunately this does not appear to be the case.  I got almost exactly the same results as with the 400 mW relays mounted the same way.

40 meters is still just barely in spec with the 3rd harmonic being -43.8 dBC.  The others are also in spec but not much better with 3rd harmonic varying from -46 dBC on 10 meters, -44.5 dBC on 12 & 15 meters , -44.7 dBC on 20 meters and -57.3 dBC on 80 meters.  I don't use 60 meters so it wasn't tested.

The relays help, but I can only vouch for my own uBITX boards and really recommend the LP Filters be re-worked as well to be absolutely certain you get clean output.  Allison has the right idea and I believe Kees has a really nice set of LPF rework PC Boards in the mill.

Sorry it took so long to get the final results but the US Postal Service lost the last set of relays for a time and I just got them yesterday.

To the person who called some of us "phoneys" I suggest you take a long look at your own background and refrain from attacking people you know nothing about -- nuff said.

My technical credentials aren't quite as impressive as Allison's, but I taught electronic theory for the US Army Security Agency for the last half of my 20 year Army career and have many letters of commendation in my files for quality instruction on the various subjects taught.  I DO have an associate degree in electrical engineering, I hold an FCC GROL Commercial license, an Extra Class Amateur Radio License (dating back to 1966 when the test had to be in an FCC office, administered by an FCC engineer) and a Master Electrician's License as well.  I think I'm qualified enough to perform the required tests and I do have the required test equipment (IFR 8000A Spectrum analyzer, IFR-1200 Radio Service monitor, both with their frequency standard inputs provided by a 10 MHz GPS Disciplined Oscillator) and a 100 MHz Digital Storage Oscilloscope by OWON.

Jim Sheldon, W0EB

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