Re: Harmonics and Relay Replacement

Howard Fidel

That is a great find! It means the capacitance is lower on those relays.


On 10/8/2018 4:22 PM, Mike Doty via Groups.Io wrote:
Thanks Jack.  I wish I could say that I discovered this intentionally but, to be honest, it was completely accidental.  I had removed the original relays from my first uBiTX while looking for a solution to the harmonics issue.  In doing so, I broke a pin on one of the original relays.  I had some of the Axicom relays in the junk box so I ended up sticking those in as replacements for all 5 of the relays.  When I put things back together and looked at the output I saw that the harmonics were all down below -50dB.  I still had 4 of the Axicom relays left in the junk box so I replaced the 4 relays on my second Ver 3 rig, leaving K1 in place.  I saw the same results.  To be sure that there wasn't something else involved before posting to the group, I ordered more relays and replaced the same 4 relays in my Ver 4 uBiTX.  Again, the same results.  I've attached pictures of the spectrum analyzer results for both of my Ver 3 rigs so you can see that it wasn't just coincidental. Unfortunately I didn't take pictures of the other two rigs before replacing the relays but they both originally had harmonics around -35dB before the relay swaps.  All of the spectrum analyzer results for each rig shown are on 40 meters at 10 watts with the SA span from 1 MHz to 100MHz but I cannot see any harmonics above -50dB on any band, 80 - 10. 
--73-- Mike

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