Re: Harmonics and Relay Replacement

iz oos
 

That's unbelievable! Wasn't the bad board layout causing it? Do the new version 4 have different relays and/or a different board layout?


Il 08/ott/2018 23:18, "Jim Sheldon" <w0eb@...> ha scritto:
I sent Mike a private email asking if these were pin for pin compatible.  While waiting for an answer I did some more research and find they ARE pin for pin.  They are also available at Digi-Key under the part# PB1055-ND for a couple of pennies less plus a bit cheaper shipping.  They are $2.81 each singly and $2.633 apiece in quantities of 10 each (enough to replace all 5 relays in 2 radios for $26.33 plus shipping.

I ordered 10 of them from Digi-Key and will replace all 5 relays in both of my V4 boards.  I'll run spectrum analysis on mine once I get that done and hopefully will duplicate Mike's indications.  Might be the simplest fix at least for the harmonic problem anyway.  Since I operate only CW, I'm not concerned with the SSB spurs anyway.

BTW, right now, both my V4 boards DO meet FCC spec with all harmonics -45 to -48 dBC on both boards.  I have NOT adjusted the factory set PA bias or the power controls as prior experience showed me that doing so was a great way to get the rig out of spec for sure.  

After changing the relays I'll do a complete bias adjustment on the PA transistors per the HF signals website instructions and check harmonics again.  If they are still in spec after that I'll play around with the power control while watching the spectrum analyzer to see what, if any changes occur.

I was recently given the use of an IFR A-8000 spectrum analyzer that was calibrated less than a month ago so I think the tests will be pretty accurate (after I learn how to use the beast! - LOL)

Jim Sheldon, W0EB

------ Original Message ------
From: "Mike Doty via Groups.Io" <mikedoty@...>
Sent: 10/8/2018 2:53:49 PM
Subject: [BITX20] Harmonics and Relay Replacement

I thought I would pass this along, for whatever it is worth.  I have two Ver 3 and one Ver 4 uBiTX rigs.  I have replaced K3, KT1, KT2, and KT3 relays with Axicom relays which has knocked down the 3rd, 5th, and 7th harmonic levels from -35dB to below -50dB on all 3 rigs without any board modifications to the LPF circuits.  This may be anecdotal but with 3 rigs showing the same results it may be something to consider.  I purchased the relays from Mouser - part # 655-V23105A5403A201.  Cost was $2.89 per relay plus shipping.  I've attached photos (sorry for the blurriness) showing the before and after results on my Ver 4 rig.
--73--  Mike  --  W0MNE

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