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More BPF Results

 

I just uploaded the results of a T41 BPF redesign, the salient features of which are as follows:
1) All filters were re-simulated in ELSIE using AI6YM kit capacitor values (which differ slightly from K9HZ values as shown in the attached file).
2) ARRL and Toroid.Info toroid material recommended frequency ranges and tolerances were taken into consideration.
3) No Type 0 (phenolic) material toroids were used. At least for me, these produce inductance values all over the place.
4) Air coils were used for all very small values of inductance.
5) All toroids were wound with 28 gauge wire. Heavier gauge (22 or 24) was used for air core inductors.
6) Inductor values were checked with LCR meter and ¡°pre-tuned¡± prior to insertion. In some cases a turn had to be added or removed from the calculated number in order to obtain a better value.
7) The filter as a whole was then tuned until loss was less than at least 3 dBm for entire range.
8) Filter performance was measured with calibrated and normalized DSA832-TG spectrum analyzer, then saved.
9) Filter ELSIE simulated vs. measured performance was displayed using custom Python program.
10) Design details and resulting performance are in the posted file. I expect that even better performance is possible with more fussing.
Design files available upon request.
?
73,
John Bennett
AE0AM
?
?
 

That is very nice filter performance, and even better documentation! Thank you for sharing it.

On Tuesday, April 1st, 2025 at 1:15 PM, John Bennett via groups.io <jkb@...> wrote:

I just uploaded the results of a T41 BPF redesign, the salient features of which are as follows:
1) All filters were re-simulated in ELSIE using AI6YM kit capacitor values (which differ slightly from K9HZ values as shown in the attached file).
2) ARRL and Toroid.Info toroid material recommended frequency ranges and tolerances were taken into consideration.
3) No Type 0 (phenolic) material toroids were used. At least for me, these produce inductance values all over the place.
4) Air coils were used for all very small values of inductance.
5) All toroids were wound with 28 gauge wire. Heavier gauge (22 or 24) was used for air core inductors.
6) Inductor values were checked with LCR meter and ¡°pre-tuned¡± prior to insertion. In some cases a turn had to be added or removed from the calculated number in order to obtain a better value.
7) The filter as a whole was then tuned until loss was less than at least 3 dBm for entire range.
8) Filter performance was measured with calibrated and normalized DSA832-TG spectrum analyzer, then saved.
9) Filter ELSIE simulated vs. measured performance was displayed using custom Python program.
10) Design details and resulting performance are in the posted file. I expect that even better performance is possible with more fussing.
Design files available upon request.
?
73,
John Bennett
AE0AM
?
?
 

Excellent report John.? One question; does your measured response include the RF Switches?? Attached are my notes on the BPF.
dave, n3ds

On Tue, Apr 1, 2025 at 5:03?PM John Bennett via <jkb=[email protected]> wrote:
I just uploaded the results of a T41 BPF redesign, the salient features of which are as follows:
1) All filters were re-simulated in ELSIE using AI6YM kit capacitor values (which differ slightly from K9HZ values as shown in the attached file).
2) ARRL and Toroid.Info toroid material recommended frequency ranges and tolerances were taken into consideration.
3) No Type 0 (phenolic) material toroids were used. At least for me, these produce inductance values all over the place.
4) Air coils were used for all very small values of inductance.
5) All toroids were wound with 28 gauge wire. Heavier gauge (22 or 24) was used for air core inductors.
6) Inductor values were checked with LCR meter and ¡°pre-tuned¡± prior to insertion. In some cases a turn had to be added or removed from the calculated number in order to obtain a better value.
7) The filter as a whole was then tuned until loss was less than at least 3 dBm for entire range.
8) Filter performance was measured with calibrated and normalized DSA832-TG spectrum analyzer, then saved.
9) Filter ELSIE simulated vs. measured performance was displayed using custom Python program.
10) Design details and resulting performance are in the posted file. I expect that even better performance is possible with more fussing.
Design files available upon request.
?
73,
John Bennett
AE0AM
?
?

20240827 T41 Bandpass Filter Report.pdf
20240827 T41 Bandpass Filter Report.pdf

 

Nice work John
?
Where did you find t37-7 cores seem to be very scarce.
Tim W4YN
 

I got the T37-7s from Power Magnetics in the UK:
They offer fast and reliable shipping to the States.
73,
john
 

¿ªÔÆÌåÓý

This company carries them in the USA:

?

?

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch ¨C K9ZC

Staunton, Illinois

?

Owner ¨C Operator

Villa Grand Piton ¨C J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

?

From: [email protected] <[email protected]> On Behalf Of John Bennett via groups.io
Sent: Wednesday, April 2, 2025 10:09 AM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] More BPF Results

?

I got the T37-7s from Power Magnetics in the UK:

They offer fast and reliable shipping to the States.

73,

john
 

¿ªÔÆÌåÓý

?

This one too¡­

?

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch ¨C K9ZC

Staunton, Illinois

?

Owner ¨C Operator

Villa Grand Piton ¨C J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

?

From: [email protected] <[email protected]> On Behalf Of K9HZ
Sent: Wednesday, April 2, 2025 10:38 AM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] More BPF Results

?

This company carries them in the USA:

?

?

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch ¨C K9ZC

Staunton, Illinois

?

Owner ¨C Operator

Villa Grand Piton ¨C J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

?

From: [email protected] <[email protected]> On Behalf Of John Bennett via groups.io
Sent: Wednesday, April 2, 2025 10:09 AM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] More BPF Results

?

I got the T37-7s from Power Magnetics in the UK:

They offer fast and reliable shipping to the States.

73,

john
 

My 4 poles mesh filters results :

Mesh_results.pdf
Mesh_results.pdf

 

¿ªÔÆÌåÓý

Hey John¡­ what did you do with the extra 3-5pf and a few tenths of a micro henry provided by the boards in the ELSIE plot generation?? Obviously, its in the SA plots¡­

?

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch ¨C K9ZC

Staunton, Illinois

?

Owner ¨C Operator

Villa Grand Piton ¨C J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

?

From: [email protected] <[email protected]> On Behalf Of John Bennett via groups.io
Sent: Tuesday, April 1, 2025 12:16 PM
To: [email protected]
Subject: [AmateurRadioBuilders] More BPF Results

?

I just uploaded the results of a T41 BPF redesign, the salient features of which are as follows:

1) All filters were re-simulated in ELSIE using AI6YM kit capacitor values (which differ slightly from K9HZ values as shown in the attached file).

2) ARRL and Toroid.Info toroid material recommended frequency ranges and tolerances were taken into consideration.

3) No Type 0 (phenolic) material toroids were used. At least for me, these produce inductance values all over the place.

4) Air coils were used for all very small values of inductance.

5) All toroids were wound with 28 gauge wire. Heavier gauge (22 or 24) was used for air core inductors.

6) Inductor values were checked with LCR meter and ¡°pre-tuned¡± prior to insertion. In some cases a turn had to be added or removed from the calculated number in order to obtain a better value.

7) The filter as a whole was then tuned until loss was less than at least 3 dBm for entire range.

8) Filter performance was measured with calibrated and normalized DSA832-TG spectrum analyzer, then saved.

9) Filter ELSIE simulated vs. measured performance was displayed using custom Python program.

10) Design details and resulting performance are in the posted file. I expect that even better performance is possible with more fussing.

Design files available upon request.

?

73,

John Bennett

AE0AM

?

?
 

Hi Bill,
For each ELSIE file I made sure that the C values matched the schematic, then adjusted L values to tune each stage to the center frequency of the band (for the 6M filter I tuned to a higher value). Here is an example for the 40M filter:
?
?
I attach all of my ELSIE files. I used the attached spreadsheet to design inductors that matched those values, taking into account recommended frequencies, tolerances, and my aversion to Type 0 material cores. Then I tried to build inductors that matched those values. I appreciate that this is very much a "measure with a micrometer, cut with a chain saw" kind of endeavor, but like a lot of experimental radio, the journey is at least as much fun as the destination. Of course this process was greatly facilitated by your gracious sharing of the details of your design.
73,
john AE0AM

AE0AM T41 BPF Design.xlsx
AE0AM T41 BPF Design.xlsx
AE0AM_T41_BPF_Design_Files.zip
AE0AM_T41_BPF_Design_Files.zip

 

¿ªÔÆÌåÓý

Hi John, thanks for these¡­ I¡¯ll put them out in the GITHUB so that others can do the same analysis if they want.

?

What I was illuding to was that there is a small amount of capacitance and inductance generated by the traces on the PCB that is not included in the analysis.?? I proved early on that it made little if any difference on the 180M-15M filters¡­ but we did see some influence for the 10M and 6M filters¡­ just a few pf of capacitance (hard to measure but its between 0-5pf) and a tiny bit of inductance.? That¡¯s not in the modeling but it is in the actual performance.? It¡¯s taken care of by tuning the filters¡­ trimming the caps and the inductors as you did

?

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch ¨C K9ZC

Staunton, Illinois

?

Owner ¨C Operator

Villa Grand Piton ¨C J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

?

From: [email protected] <[email protected]> On Behalf Of John Bennett via groups.io
Sent: Sunday, April 6, 2025 11:43 AM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] More BPF Results

?

Hi Bill,

For each ELSIE file I made sure that the C values matched the schematic, then adjusted L values to tune each stage to the center frequency of the band (for the 6M filter I tuned to a higher value). Here is an example for the 40M filter:

?

?

I attach all of my ELSIE files. I used the attached spreadsheet to design inductors that matched those values, taking into account recommended frequencies, tolerances, and my aversion to Type 0 material cores. Then I tried to build inductors that matched those values. I appreciate that this is very much a "measure with a micrometer, cut with a chain saw" kind of endeavor, but like a lot of experimental radio, the journey is at least as much fun as the destination. Of course this process was greatly facilitated by your gracious sharing of the details of your design.

73,

john AE0AM
 

Hi Bill,
Yes. The pass bands are wide enough that things were fine just tuning to center frequency until 6M. There I tuned 2Mhz high (to 54MHz) to to account for PCB effects. I neglected to include that ELSIE file; it's attached below.

AE0AM-6-54MHz.LCT
AE0AM-6-54MHz.LCT

 

I used Oliver's BPFTest.ino. I first self-calibrated the SA with nothing attached, then connected the BPF and normalized to the bypass setting (which included all cables, connectors, etc.). Without normalization, the BPF set on bypass (plus hookup) had a little over 10 dBm loss. All reported results were obtained with normalization turned on.
73,
john
AE0AM

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