What value components do I need to make a Band Pass filter to receive two stations at 8.5 Mhz and 9.11 Mhz? That would have a center Frequency of 8.8 Mhz.
Hi,Not an easy answer that can be done without some significant calculation and modeling. There are several methods to do this (and I am not going to do it for you). The video involved the use of packaged transformers which are no longer available. Thus the only option is to build the band pass network from scratch. You have a requirement to have at least 600 kHz of pass frequencies with a base frequency of 8.8 MHz.One way is to hand calculate the component values using methodology shown in a publication entitled Solid State Design for the Radio Amateur by Wes Hayward. That calculations are not that difficult but may require you to make a couple of runs at it. A second method is to use free software programs that let you adjust values so that you can get a centered filter with a specific band pass. Two such programs are LT Spice (free) from Linear Technology. and the second is Elsie ( free from Tonne Software). Both programs let you simulate the filter and you can visually see the band pass. By making several runs you can finally arrive at the desired filter. Keep in mind these are simulations and that what you build in practice may have some effects from physical layout and stray capacitance.What was shown in the video had a smaller band width like 300 KHz and was a bit of a stretch for the packaged units. For a larger bandwidth (like 600 kHz) you will probably need to do the calculation. Another publication called EMRFD (Experimental Methods In RF Design) has programs to design BPF's --this is not a favorite publication of mine. My 1st choice would actually be a combination (and how I do it) of first hand calculating the component values and then use LT Spice to validate the design. The video was associated with a published project and was intended to provide a design that used standard components (now not available) so that the builder could just slap something together without having to do some serious engineering. Now you will have to engineer the answer. If you can actually find the specified transformers you can trial and error the values. The coupling caps most likely would be in the 1 to 2 PF range and since the transformer original design was 10.7 MHz and was moved down to 7.2 MHz with 68 PF --something in the 22 PF to 39 PF range should move it down to the range you want but making it do 600 KHz is very likely not a reality -- you will get several hundred kHz of pass but most likely not 600 kHz. To meet your specifications will require the rigorous calculation as described in the publication cited.Good luck with your project.73'sPete N6QW
Hi Pete, I'm looking into building your project and i'm trying to find sources for all the components. For the most part its really straightforward, but those IF transformers your using arn't stocked at Mouser any more. Do you have an alternate source for them, or can you suggest a suitable alternative? I'm thinking of gutting an old radio for IF transformers, but I don't know how to get them resonant at 6.989Mhz
Check the webpage for this project here www.jessystems.com/LBS_Detail.html There are two options we have listed: an alternate source for the transformers "Kit and Parts" or you can roll your own by building your own band pass filter. Kits and parts is also a source for the toroids used in the homebrew filter. Thank you for your interest in this project. Pete N6QW
Hi Peter, The 42IF123 IF Cans but disappeared from the world and so now I am forced to use discrete coils and caps. LT Spice the simulation program (free) from Linear Technology sure makes that task easier. I have one design developed using that program where with the addition or removal of two 150 PF caps the network can be tuned to either 40 or 20 Meters. See my searchable blog n6qw.blogspot.com and you can see the component values. also my website www.n6qw.com and look at the Sudden Transceiver project for the values. Thanks for your posting. 73's Pete N6QW
kiriakos k Hi -- Thanks for your email. If you can buy the 42IF123 transformers then it would take about 15 minutes to build as it only requires three capacitors and the two IF cans. The cost could be around $10 USD depending if you have to buy everything. The version with discrete components would cost only slightly more and perhaps 1/2 to 1 hour to build depending on your skill level. Either is fairly simple to build. 73's Pete N6QW
great video I am learning a lot from yourself and Charlie Morris
Thanks for watching the video. Charlie Morris is a friend and undoubtedly a superb engineer. He has built some really great rigs.
73's
Pete N6QW
What value components do I need to make a Band Pass filter to receive two stations at 8.5 Mhz and 9.11 Mhz? That would have a center Frequency of 8.8 Mhz.
Hi,Not an easy answer that can be done without some significant calculation and modeling. There are several methods to do this (and I am not going to do it for you). The video involved the use of packaged transformers which are no longer available. Thus the only option is to build the band pass network from scratch. You have a requirement to have at least 600 kHz of pass frequencies with a base frequency of 8.8 MHz.One way is to hand calculate the component values using methodology shown in a publication entitled Solid State Design for the Radio Amateur by Wes Hayward. That calculations are not that difficult but may require you to make a couple of runs at it. A second method is to use free software programs that let you adjust values so that you can get a centered filter with a specific band pass. Two such programs are LT Spice (free) from Linear Technology. and the second is Elsie ( free from Tonne Software). Both programs let you simulate the filter and you can visually see the band pass. By making several runs you can finally arrive at the desired filter. Keep in mind these are simulations and that what you build in practice may have some effects from physical layout and stray capacitance.What was shown in the video had a smaller band width like 300 KHz and was a bit of a stretch for the packaged units. For a larger bandwidth (like 600 kHz) you will probably need to do the calculation. Another publication called EMRFD (Experimental Methods In RF Design) has programs to design BPF's --this is not a favorite publication of mine. My 1st choice would actually be a combination (and how I do it) of first hand calculating the component values and then use LT Spice to validate the design. The video was associated with a published project and was intended to provide a design that used standard components (now not available) so that the builder could just slap something together without having to do some serious engineering. Now you will have to engineer the answer. If you can actually find the specified transformers you can trial and error the values. The coupling caps most likely would be in the 1 to 2 PF range and since the transformer original design was 10.7 MHz and was moved down to 7.2 MHz with 68 PF --something in the 22 PF to 39 PF range should move it down to the range you want but making it do 600 KHz is very likely not a reality -- you will get several hundred kHz of pass but most likely not 600 kHz. To meet your specifications will require the rigorous calculation as described in the publication cited.Good luck with your project.73'sPete N6QW
Hi Pete, I'm looking into building your project and i'm trying to find sources for all the components. For the most part its really straightforward, but those IF transformers your using arn't stocked at Mouser any more. Do you have an alternate source for them, or can you suggest a suitable alternative?
I'm thinking of gutting an old radio for IF transformers, but I don't know how to get them resonant at 6.989Mhz
Check the webpage for this project here www.jessystems.com/LBS_Detail.html There are two options we have listed: an alternate source for the transformers "Kit and Parts" or you can roll your own by building your own band pass filter. Kits and parts is also a source for the toroids used in the homebrew filter. Thank you for your interest in this project.
Pete N6QW
Excellent video pete, like yourself i prefere to use this method its easy to tune up and gives a good proportion use of the 40meter band. thanks pete.
Hi Peter,
The 42IF123 IF Cans but disappeared from the world and so now I am forced to use discrete coils and caps. LT Spice the simulation program (free) from Linear Technology sure makes that task easier. I have one design developed using that program where with the addition or removal of two 150 PF caps the network can be tuned to either 40 or 20 Meters. See my searchable blog n6qw.blogspot.com and you can see the component values. also my website www.n6qw.com and look at the Sudden Transceiver project for the values. Thanks for your posting.
73's
Pete N6QW
hello
can someone please tell me how much time and money does ti take to make this filter ?
thank you
kiriakos k Hi -- Thanks for your email. If you can buy the 42IF123 transformers then it would take about 15 minutes to build as it only requires three capacitors and the two IF cans. The cost could be around $10 USD depending if you have to buy everything. The version with discrete components would cost only slightly more and perhaps 1/2 to 1 hour to build depending on your skill level. Either is fairly simple to build. 73's Pete N6QW
Pete Juliano thank you a lot