Here are snapshots for 20 and 10 meters after the relays were replaced with the Axicom components. Sorry, I didn¡¯t capture the harmonics profile at 14.2 and 28.8 Mhz before the relay change but there nothing exceeding the -43 dB threshold for FCC compliance. Once again Yellow = SSB and magenta is CW
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Picture 1 is of harmonics and spurs on 28.8 Mhz
Picture 2 is the harmonic profile at 14.2 Mhz
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A couple of other notes: using a 12 volt 50 watt power supply my power out is 10 watts on 80, 40, and 20 meters, dropping down to 8 watts on 15 meters and 6 watts at 10 meters.
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Ripley
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Sent from for Windows 10
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From: Ripley
Sent: Sunday, October 14, 2018 7:52 PM
To: [email protected]
Subject: RE: [BITX20] Harmonics and Relay Replacement
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Hello All,
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I installed the Axicom relays in my uBITX (ver 4) test bed this afternoon and ran tests 3.8, 7.2, and 14.2 Mhz. Here are the before and after snapshots. Yellow is SSB and magenta CW.
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Pic #1 is 7.2 MHz before relay change
Pic #2; 7.2 Mhz after relay change. Note that the CW third order harmonic was brought down by about 7 dBs but still exceeds the -43 dBs threshold for FCC compliance
Pic #3; 3.8Mhz before relay change
Pic #4; 3.8 Mhz after relay change
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The biggest drops were in SSB mode as others have pointed out already.
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So you know the base line of my build. The 45 Mhz crystal for spur reduction has been installed but only the crystal itself. Driver transistors Q92, Q93, Q96, Q97 were replaced with metal can 2N2222A and the emitter resistor changed to 11 ohms. AGC was added along with a manual RF gain control.
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Ripley
KD8UYQ
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Sent from for Windows 10
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From: Joe Puma
Sent: Sunday, October 14, 2018 5:57 PM
To: [email protected]
Subject: Re: [BITX20] Harmonics and Relay Replacement
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Yea but changing the relays looks like the real winner here.?
Joe
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Looking at pic #2 seems to me that adding a 47nF capacitor to ground at each coil terminal as Arv hypothesized would make the uBitx a leap close to be legal compliant with respect to the harmonics.
Il 14/ott/2018 20:31, "Kees T" <windy10605@...> ha scritto:
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> Plots of the coupling between N/C contacts on either side of the relay (which will include the armature) and what they look like with the addition of a 47nF capacitor to ground at each coil terminal.? You can see the dB of isolation improvement.
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> #1 HK16F-SHG "16 pin" relay (like the original uBITX relays)
> #2? same as #1 but with the 2 capacitors added (see less coupling ....a good thing).
> #3 NAIS TQ2-H "10 pin" smaller relay which does not have the long armature
> #4 same as #3 but with the 2 capacitors added (less coupling .....a good thing)
> #5 Axicom .....TBD waiting for the relays.
> #6 same as #5 but with the 2 capacitors added (less coupling .....a good thing)
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> 73 Kees K5BCQ
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