开云体育

  1. BITX20
  2. Topics

A more stable Bitx40 (fun with ceramic resonators)

 

If you don't wish to add a DDS to the Bitx40 (eg need low current consumption) I now have an alternative.?

A cheap as chips 4.92 MHz ceramic resonator can be substituted for L4 in the VFO and be pulled by over 100 kHz. ?

I discuss and demonstrate the ins and outs of this and other VXO approaches in this video.?




This would only have been possible due to a stroke of serendipity. ?Farhan opting for a 12 MHz IF, and someone deciding that 4.92 MHz was a good frequency to make some cheap ceramic resonators.?

73, Peter VK3YE
 

Nice idea Peter!

Increase in value of C96 will give you a little more range. I will try adding a parallel MV209 to D9 to increase the tuning capacitance range. I have a bunch of them in the box!

Cheers
Raj (vu2zap)

At 26-12-2016, you wrote:

?

If you don't wish to add a DDS to the Bitx40 (eg need low current consumption) I now have an alternative.

A cheap as chips 4.92 MHz ceramic resonator can be substituted for L4 in the VFO and be pulled by over 100 kHz.?

I discuss and demonstrate the ins and outs of this and other VXO approaches in this video.





This would only have been possible due to a stroke of serendipity.? Farhan opting for a 12 MHz IF, and someone deciding that 4.92 MHz was a good frequency to make some cheap ceramic resonators.

73, Peter VK3YE
 

开云体育

Peter,

That is a really good idea. If I could find a CR around 4.7 to 4.8MHz to get it in the upper portion of the US 40 meter band it would be perfect. Thanks for the idea.

Joel?
KB6QVI

On Dec 26, 2016, at 1:24 AM, parkerp@... [BITX20] <BITX20@...> wrote:

?

If you don't wish to add a DDS to the Bitx40 (eg need low current consumption) I now have an alternative.?

A cheap as chips 4.92 MHz ceramic resonator can be substituted for L4 in the VFO and be pulled by over 100 kHz. ?

I discuss and demonstrate the ins and outs of this and other VXO approaches in this video.?




This would only have been possible due to a stroke of serendipity. ?Farhan opting for a 12 MHz IF, and someone deciding that 4.92 MHz was a good frequency to make some cheap ceramic resonators.?

73, Peter VK3YE
 

I have posted this hack to the bitxhacks blog.

- f

On Mon, Dec 26, 2016 at 10:09 PM, Joel Caulkins caulktel@... [BITX20] <BITX20@...> wrote:
?

Peter,

That is a really good idea. If I could find a CR around 4.7 to 4.8MHz to get it in the upper portion of the US 40 meter band it would be perfect. Thanks for the idea.

Joel?
KB6QVI

On Dec 26, 2016, at 1:24 AM, parkerp@... [BITX20] <BITX20@...> wrote:

?

If you don't wish to add a DDS to the Bitx40 (eg need low current consumption) I now have an alternative.?

A cheap as chips 4.92 MHz ceramic resonator can be substituted for L4 in the VFO and be pulled by over 100 kHz. ?

I discuss and demonstrate the ins and outs of this and other VXO approaches in this video.?




This would only have been possible due to a stroke of serendipity.? Farhan opting for a 12 MHz IF, and someone deciding that 4.92 MHz was a good frequency to make some cheap ceramic resonators.?

73, Peter VK3YE
 

What is a good source in the US for a ceramic resonator?
 

The usual suspects: Mouser, Digikey, Farnell, and Jameco.

Todd K7TFC


On Dec 27, 2016 5:08 PM, "cruisenewsnet@... [BITX20]" <BITX20@...> wrote:
?

What is a good source in the US for a ceramic resonator?
 

开云体育

This is where i get mine,?

Joel KB6QVI

On Dec 27, 2016, at 5:08 PM, cruisenewsnet@... [BITX20] <BITX20@...> wrote:

?

What is a good source in the US for a ceramic resonator?
 

Looks like Mouser has a 4.8mhz Ceramic Resonator, which would put it at 7200khz.?

?

?and also a 4.75mhz xtal to put it at 7225khz:



Not a lot of wiggle room with a crystal but you could get between 7222 and 7225 with a trim cap.The frequency would at least be "rock solid" if you'll pardon the pun.
 

Would this one work?



?
 

You'd have to pull it pretty far to get it into the US 40m phone band
12.000 - 4.915 = 7.085 MHz.



---In BITX20@..., <cruisenewsnet@...> wrote :
Would this one work??
 

开云体育

I have found that most three leg ceramic resonators are resistant to frequency pulling due to the two internal caps, some will pull further than others. YMMV.

Joel Caulkins
KB6QVI

On Dec 27, 2016, at 6:19 PM, geocrasher@... [BITX20] <BITX20@...> wrote:

?

Looks like Mouser has a 4.8mhz Ceramic Resonator, which would put it at 7200khz.?


?

?and also a 4.75mhz xtal to put it at 7225khz:



Not a lot of wiggle room with a crystal but you could get between 7222 and 7225 with a trim cap.The frequency would at least be "rock solid" if you'll pardon the pun.
 

?Actually, some xtals can be warped a lot more, though it may depend on the frequency and type of oscillatorI know of a model of CB SSB unit that could go quite a lot more when its "clarifier" was modified.
?just a bit of food for thought.

? Wayne WA2YNE
 

The 4.92 MHz resonator with C94 & C95 not removed gives about 4.8 MHz. ?The problem is that there's little variation since the varactor's capacitance swing is masked by the 100pF. ?I give some ideas for overcoming this in the video. Or maybe use a big old variable capacitor with all gangs connected together.?

As for the crystal option, two crystals in parallel in a super VXO should give a lot more than 3 kHz swing in a properly optimised VXO with the right inductance. More like 10 or 15 kHz. ?Again ideas in the video. So the 4.75 MHz crystal could be a good option if you can't get the resonator. ?

73, Peter VK3YE

1 - 13 of 13