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Zbitx at 12vdc
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I would like to run my zbitx at 12vdc and up to 14vdc. ?I already swapped the linear regulator and the finals and re biased. ?It works great up to about 10vdc over that the receiver starts to attenuate. ?I am assuming this is because of the switching design for the bpf. ?I remember Farhan mentioning that there were components that could be swapped to allow for running up at 12vdc. ?Is it possible to get a rough list as to what these components are?
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Ryan
KK6DZB
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I've been looking into building an RF quiet DC/DC converter for the zBitx.? I've found some ICs that might fit the bill.? But after April 5, not sure I would be able to make them at a price that people would pay.? I've been trying to find the time to get the
design complete and boards sent for fab, but don't think I'm going to make it before the de minimus execption is removed.? Cheapest US based board house I can find is 2-3x more than what I was getting.
Jeff KF7YDU
From: [email protected] <[email protected]> on behalf of WP3DN via groups.io <3voltios@...>
Sent: Thursday, April 17, 2025 8:35 AM To: [email protected] <[email protected]> Subject: Re: [BITX20] Zbitx at 12vdc ?
Ryan,?
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Looking at the schematic, what if you separate the 9v input for the finals drain and feed 14v to it. That way you can use just one 8v regulator to the rest of the system.
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Juan WP3DN
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Jeff,
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I have a tiny drok in it now. ?3amp. ?It¡¯s woking fine and cuts the current draw on receive in half. ?I didn¡¯t notice any substantial increase in the noise floor. ?I do have an rf quite switcher evaluation board for another project. ?Its awesome and has 2 outputs. ?You can combine them together both at 5vdc and it¡¯s good for 8 amps! ?The actual IC and aux components are tiny. ?
Also I need to recheck but I am pretty sure the finals are already on the 12v rail not on the regulator. ?The linear regulator would not be able to handle the current of the finals. ?The problem seems to be in the way the bpf switching happens. ?It needs to likely be rebiased. ?I would need confirmation from farhan. ?At 13vdc with different finals that have been re biased I get 10w out on all bands including 10m. ?But it¡¯s still not right.
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Ryan
KK6DZB |
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Thanks Juan. ?
I knew this to be the case. ?Tx on higher voltage is fine. ?Rx is the issue. ?As the unit doesn¡¯t use relays for bpf switching I am only assuming that the issue is the higher voltage messing with the bpf switching scheme. ?Last night on 80m had a long qso at 5w at 9vdc on zbitx with mods. ?They said it sounded great. ?
Ryan |
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I am bumping this back to the top. ?Any idea why the zbitx receiver begins to go deaf over 11vdc? ?I have different finals and a switching 5v regulator no no issues there. ?So looking into what I need to change to get the receiver to not go deaf over 11vdc. ?Looking to run as high as 13.8vdc.
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Ryan
KK6DZB |
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Ryan l, it might be your switching regulator going into a different gear at that voltage. Can you try it with a linear regulator instead? You can risk a minute of heat. On Sat, 26 Apr, 2025, 8:36?am Ryan Wesolowski via , <cosmo1stgen=[email protected]> wrote:
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Ashar,
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I have tried both. ?Did it with the linear before going to the switcher same issue. ?I switched to the switcher for heat and it cut the receive current down. At 13vdc switcher is still at 5.2vdc. ? Works great to 11vdc. ?After that signal drops. ?Thought it might have something to do with the lpf switching scheme. I do get 10-12w though on transmit at 13vdc just the receiver goes almost deaf.
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Ryan
KK6DZB |
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