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Homebrew SBITX LPF board

 

Well waiting for my 12MHz crystal to come in from Mouser I decided to build the switched low pass filter board. I spent some time looking at the schematic and reading all the notes about how the diode switching works and I decided it was just too complicated for him my needs. So I went with a simple relay switched board.

Manhattan style as always...

Waiting for a couple of caps to finish one of the filters but other than that the board is finished.

This is the last major board for the full transceiver. I'm going to try and make Dx contacts on all bands that are active this weekend during the contest.

73,
Dean
KK4DAS
 

You also need a 30mhz cut off LPF at the mixer output


On Sat, Mar 2, 2024, 8:01 AM Dean Souleles <dsouleles@...> wrote:
Well waiting for my 12MHz crystal to come in from Mouser I decided to build the switched low pass filter board. I spent some time looking at the schematic and reading all the notes about how the diode switching works and I decided it was just too complicated for him my needs. So I went with a simple relay switched board.

Manhattan style as always...

Waiting for a couple of caps to finish one of the filters but other than that the board is finished.

This is the last major board for the full transceiver. I'm going to try and make Dx contacts on all bands that are active this weekend during the contest.

73,
Dean
KK4DAS
 

Thanks Farhan, I have that as well and after I chat last week it is now in line on both TX and RX.
 

Well, I am impressed.? My homebrew experience from scratch is quite limited. Sourcing parts is so much different now than when I began ham radio. No more local radio shack stores, but internet parts stores worldwide. Enjoy!

Scotty

Scotty
 

On Sat, Mar 2, 2024 at 08:05 AM, Scotty R wrote:
No more local radio shack stores, but internet parts stores worldwide
All true... But I think there is no better time to do homebrew radio electronics than ever. Sites like Mouser and Digikey have a vast array of components of all types. Common components are available on Amazon ship to your door the next day. The internet is full of useful to tutorials, videos, projects, etc.? heck, you can even email the designer and the high likelihood is they will answer. Thank you, Farhan.??

I've had so much fun and learned so much over the last few years building rigs and leading our clubs maker's group. I highly encourage anyone with an interest to try building some things on their own.??

73,
Dean
KK4DAS?
 

Update on the LPF board... I did not have relays on both the input and output and learn very quickly that that did not work.? ?The open ended filters were interfering with each other.

I reconfigured the board so that both the LPF inputs and outputs are switched.? Now the problem is I have a very significant loss across the filter module on all bands.? Each individual filter tested fine separately.

More debugging to do..
 

Do you have sweeps for each filter?
- f

On Thu, Mar 7, 2024, 3:23 AM Dean Souleles <dsouleles@...> wrote:
Update on the LPF board... I did not have relays on both the input and output and learn very quickly that that did not work.? ?The open ended filters were interfering with each other.

I reconfigured the board so that both the LPF inputs and outputs are switched.? Now the problem is I have a very significant loss across the filter module on all bands.? Each individual filter tested fine separately.

More debugging to do..
 

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I¡¯m ts also common to ground both ends of unused filters. ?


Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

?

Owner - Operator

Big Signal Ranch ¨C K9ZC

Staunton, Illinois

?

Owner ¨C Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com


email:??bill@...

?


On Mar 6, 2024, at 8:26?PM, Ashhar Farhan <farhanbox@...> wrote:

?
Do you have sweeps for each filter?
- f

On Thu, Mar 7, 2024, 3:23 AM Dean Souleles <dsouleles@...> wrote:
Update on the LPF board... I did not have relays on both the input and output and learn very quickly that that did not work.? ?The open ended filters were interfering with each other.

I reconfigured the board so that both the LPF inputs and outputs are switched.? Now the problem is I have a very significant loss across the filter module on all bands.? Each individual filter tested fine separately.

More debugging to do..

<PXL_20240306_025334369.jpg>
 

On Wed, Mar 6, 2024 at 09:53 PM, K9HZ wrote:
I¡¯m ts also common to ground both ends of unused filters. ?
Thanks Bill - that is easy enough to do - I'm using SPDT relays and the NC pins are currently floating.? I'll ground them and see if things improve.??

And Farhan - yes - I swept all the filters as I built them and they looked fine.? ?The caps are all good NP0s from Mouser.

73,
Dean
KK4DAS
 

Hello Dean,
as I thought, that it would be too cumbersome to build the PA LPF as a Manhattan or ugly build, I designed a PCB for the PA LPF, that fits on top of the PA.
The schematic is taken over from the sBitx and includes
  • the RX / TX PIN diode (1N4007/MRA4007) switching
  • PA LPFs with PIN diode switching
  • the SWR-bridge and the ATTiny85 for measuring the FWD and RFL power:

I used SMD components wherever possible. At the left end (antenna) I have allowed for either an SMA edge connector or a BNC connector.

This LPF filter board is mounted on top of the K9HZ RD16HHF1 PA.
It has the same width as the PA PCB and at the rear end the mounting holes are in the same distance as on the PA PCB, to allow a mechanical connection:


I am planning to use this combination of PA and LPF filters also in other transceivers like the T41-EP or the EdenDSP/TRX.
If I would make the LPF PCB as long as the PA PCB it should then even be possible to add a 6m LP filter.

BTW: I don't intend to share the KiCAD design or the gerbers, to avoid any impact to the official sBitx sales.?
--
73, Joerg - DB2OO
Jack, W8TEE
 

Very nice!

Jack, W8TEE

On Monday, March 11, 2024 at 02:14:10 PM EDT, Joerg DB2OO <db2oo.ju@...> wrote:


Hello Dean,
as I thought, that it would be too cumbersome to build the PA LPF as a Manhattan or ugly build, I designed a PCB for the PA LPF, that fits on top of the PA.
The schematic is taken over from the sBitx and includes
  • the RX / TX PIN diode (1N4007/MRA4007) switching
  • PA LPFs with PIN diode switching
  • the SWR-bridge and the ATTiny85 for measuring the FWD and RFL power:

I used SMD components wherever possible. At the left end (antenna) I have allowed for either an SMA edge connector or a BNC connector.

This LPF filter board is mounted on top of the K9HZ RD16HHF1 PA.
It has the same width as the PA PCB and at the rear end the mounting holes are in the same distance as on the PA PCB, to allow a mechanical connection:


I am planning to use this combination of PA and LPF filters also in other transceivers like the T41-EP or the EdenDSP/TRX.
If I would make the LPF PCB as long as the PA PCB it should then even be possible to add a 6m LP filter.

BTW: I don't intend to share the KiCAD design or the gerbers, to avoid any impact to the official sBitx sales.?
--
73, Joerg - DB2OO

--
Jack, W8TEE
 

Joerg,

Your boards look great.? You seem to be doing a great job with the PCBs and service mount parts.

As far as making your boards available, It's totally up to you. It's an open source design and your call.

73,
Dean
 

Can you share the PCB files?with me?

de VU2UPX

On Mon, 11 Mar, 2024, 11:44 pm Joerg DB2OO, <db2oo.ju@...> wrote:
Hello Dean,
as I thought, that it would be too cumbersome to build the PA LPF as a Manhattan or ugly build, I designed a PCB for the PA LPF, that fits on top of the PA.
The schematic is taken over from the sBitx and includes
  • the RX / TX PIN diode (1N4007/MRA4007) switching
  • PA LPFs with PIN diode switching
  • the SWR-bridge and the ATTiny85 for measuring the FWD and RFL power:

I used SMD components wherever possible. At the left end (antenna) I have allowed for either an SMA edge connector or a BNC connector.

This LPF filter board is mounted on top of the K9HZ RD16HHF1 PA.
It has the same width as the PA PCB and at the rear end the mounting holes are in the same distance as on the PA PCB, to allow a mechanical connection:


I am planning to use this combination of PA and LPF filters also in other transceivers like the T41-EP or the EdenDSP/TRX.
If I would make the LPF PCB as long as the PA PCB it should then even be possible to add a 6m LP filter.

BTW: I don't intend to share the KiCAD design or the gerbers, to avoid any impact to the official sBitx sales.?
--
73, Joerg - DB2OO

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