Topics

Value of the 45mhz filter?

Gérard <kabupos@...>
 

Hello
Request information about filter 45mhz

What is the bandwidth of the (of) 45mhz filters. + /- 7.5 khz or +/- 15khz. thanks
It's for future modification for spurs
https://ubitx.net/tag/spurs/
It's write: "The filter is a 45MHz 15Khz type filter identical to the existing roofing filter in the µBITx and replacing R27 in the original circuit"
I am making my one: https://ubitx.net/2018/07/02/homebrew-ubitx-with-through-hole-components/
If some one have 2 to sell (I am in france) or where to find it.
cdt

Curt
 

Gerard

Any decent 45 MHz crystal filter should work, it has 2 sections. Whether it is 15 or 30 kHz should not be a huge factor under most conditions,  of course narrower is better except for possibly higher loss.

Earlier when an extra one was added to address transmit spurious,  close alignment to the original is desired. I myself would be so tempted in a homebrew build to put the entire 45 MHz filter with its matching inductors into a metal box, to minimize leakage. This of course would be impractical for a production build, but one could wonder what Asshar did for his original prototype?

Curt

MVS Sarma
 

I suppose yout can get here
With all shipping constraints due to pandemic. 
Sarma vu3zmv

On Mon, 18 May 2020, 1:14 pm Gérard, <kabupos@...> wrote:
Hello
Request information about filter 45mhz

What is the bandwidth of the (of) 45mhz filters. + /- 7.5 khz or +/- 15khz. thanks
It's for future modification for spurs
https://ubitx.net/tag/spurs/
It's write: "The filter is a 45MHz 15Khz type filter identical to the existing roofing filter in the µBITx and replacing R27 in the original circuit"
I am making my one: https://ubitx.net/2018/07/02/homebrew-ubitx-with-through-hole-components/
If some one have 2 to sell (I am in france) or where to find it.
cdt

John Kirk
 

Gérard <kabupos@...>
 

Hello Curt
Thank's for your answer.

Here for pb of spurs (You may add second filter, if you want) Nothing shielder.
https://ubitx.net/tag/spurs/
If you look on original PCB, no shield. See files.

On the M0THY model, for band filters, it looks more like modules that can be soldered.
https://ubitx.net/2018/07/02/homebrew-ubitx-with-through-hole-components/
So i can do this prototype and shield quartz filter (45mhz). And also do you think if it's good idea enclosure band filters in shied?
tinned iron cookie boxes bottom of good shielding

I have also  ordered axicom relays, they are better for spur.
I got the epoxy, I need to burn the PCB.
cdt

Curt
 

Gerard

Shielding of the band filters seems unimportant,  unless they are placed closer than the board arrangement.

Coupling into the inductors of the 45 MHz xtal filter from several circuits is a well known and discussed problem. Those better relays should help.

Enjoy your build of a nice rig.

Curt wb8yyy