Re: Harmonic performance - SSB vs CW

Gordon Gibby <ggibby@...>
 

"Without adding other relays like omrI on g5 g6 and alike, maybe some might prefer just connect the outputs of the four filters to separate antenna outputs, one for each filter. Isn't more simple? Would it solve the harmonics issue?"


A simple-minded solution that will likely work for the one or more that I'll be using "manually" will be a SPDT switch on the outside end of each filter.   Cut the loooong return traces, rewire existing relays as needed, tiny little perfboard off to the side to hold 3 or 4 switches (depending on how many bands I really care about) and wire the outputs with some coax back into the circuit.   Rewrite software if needed to activate desired relays after a bit of rewiring.   Done   



A slightly more exotic solution would be small printed circuit board off to the side instead of the switches;  wire the output of each filter to another (cheap) relay there;   perhaps add one additional 2n3904 to drive those relays, so the existing 2n3904 isn't overtaxed---but now only 2 relays in filter needed at any time....   Can even put in inductors to the coils or in the power line to prevent signal escaping that way.   Might even add an LED so i can see which filter is in use.   

In both cases, ground the unused filter output when not used.   


Full blown solution is new filter assembly completely, but the above solutions will probably handle my existing boards....  When I had heathkits there were ALWAYS modifications being developed to fix this or that problem with the units.   I have a few DOCUMENTS full of them to refer to when refurbishing those units.



In the long run, likely the bandpass filters (at least a stage or so) prior to power amplifier is probaby a good idea and then a redesign of the output filtering --- a version 5 of this wonderful kit transceiver!



Someone criticized the bitx40 filter or something as "not being enough" -- remember, that if the harmonic is already down 15 dB.....that is 15 dB less filtering required.   Same thing as with desense isolation required for duplexers---cleaner transmitter and hardier receivers require less of the duplexer filters!   


Got to get me a step-attenuator box.....or an HF spectrum analyzer....just got a simpleton VHF/UHF analyzer for $110 and able to see duplexer performance for the first time.    


Cheers,

gordon






From: BITX20@groups.io <BITX20@groups.io> on behalf of iz oos <and2oosiz2@...>
Sent: Tuesday, August 7, 2018 3:25 AM
To: BITX20@...
Subject: Re: [BITX20] Harmonic performance - SSB vs CW
 

Without adding other relays like omron g5 g6 and alike, maybe some might prefer just connect the outputs of the four filters to separate antenna outputs, one for each filter. Isn't more simple? Would it solve the harmonics issue?


Il 07/ago/2018 08:56, "m5fra2 via Groups.Io" <m5fra2=btinternet.com@groups.io> ha scritto:

That is excellent Glenn, I never ceased to be amazed by this group.

 

Colin – M5FRA

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Glenn
Sent: 06 August 2018 23:42
To: BITX20@groups.io
Subject: Re: [BITX20] Harmonic performance - SSB vs CW

 

More to see if it's possible rather than anything else, I was working on a PCB that would fit in same space as the original LPF area, but switching on both ends of each filter. (ie 3 more relays)  I didn't alter the actual switching sequence just added the extra relays controlled in the same manner as the original ones. Picture is of the PCB. No switching transistors are on the PCB, yet.  You can see space either side though.

This is not all routed as you can see, just the RF paths in and out of the relays. (The inductors are shown with 4 holes, just because i  had that part in my LIB.) Orientations may change.

glenn vk3pe

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