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H4 F303 artwork updates(4.2 -> 4.2.1)

#nanovna-h4 #circuit #improvement

RFy All Messages By This Member #11976 H4 F303 variant PCB artwork updated to 4.2.1 : Update the schematic diagram, the impedance of ch1 is closer to pure 50 ohms H4_421changes.png
Dallas N4DDM All Messages By This Member #11981 That's not what my calculator says... 4.2 circuit:91 ohms in parallel with 51+11+51 take 1/91 + 1/113 = 1/x and that comes to 50.4068 ohms... When I do that to circuit 4.2.1 I come up with 50.64 ohms... 73 Dallas, KD4HNX Whatever you do, don’t fall victim to?“paralysis by analysis.” Go ahead and buy/build one and start? tinkering with it. This is a learn by doing hobby. No politician or scholar assured your freedoms. A Soldier, Sailor, Marine, or Airman did! toggle quoted message Show quoted text On Wednesday, March 25, 2020, 11:30:27 PM EDT, RFy <gpdxdveil@...> wrote: H4 F303 variant PCB artwork updated to 4.2.1 : Update the schematic diagram, the impedance of ch1 is closer to pure 50 ohms
John Baines All Messages By This Member #11982 These calculated values are correct if, and only if, the actual resistor values are exactly as marked which they will not be. 73 John M0JBA toggle quoted message Show quoted text On 26 Mar 2020, at 10:31, Dallas KD4HNX via Groups.Io <mylastname@...> wrote: That's not what my calculator says... 4.2 circuit:91 ohms in parallel with 51+11+51 take 1/91 + 1/113 = 1/x and that comes to 50.4068 ohms... When I do that to circuit 4.2.1 I come up with 50.64 ohms... 73 Dallas, KD4HNX Whatever you do, don’t fall victim to “paralysis by analysis.” Go ahead and buy/build one and start tinkering with it. This is a learn by doing hobby. No politician or scholar assured your freedoms. A Soldier, Sailor, Marine, or Airman did! On Wednesday, March 25, 2020, 11:30:27 PM EDT, RFy <gpdxdveil@...> wrote: H4 F303 variant PCB artwork updated to 4.2.1 : Update the schematic diagram, the impedance of ch1 is closer to pure 50 ohms
Erik Kaashoek All Messages By This Member #11983 4.2.1 is better because the input impedance of the SA602 (1.5kOhm//3pF per input) has less impact compared to 4.2 -- NanoVNA Wiki: /g/nanovna-users/wiki/home NanoVNA Files: /g/nanovna-users/files Erik, PD0EK
Dallas N4DDM All Messages By This Member #11984 I agree...? I'm just saying my calculator says the original circuit is closer... If I was to change anything I'd swap the 11-ohm resistor with an 8.97-ohm 1% and I'd have a 49.998 impedance... ? 73 Dallas, KD4HNX Whatever you do, don’t fall victim to?“paralysis by analysis.” Go ahead and buy/build one and start? tinkering with it. This is a learn by doing hobby. No politician or scholar assured your freedoms. A Soldier, Sailor, Marine, or Airman did! toggle quoted message Show quoted text On Thursday, March 26, 2020, 06:42:47 AM EDT, John Baines via Groups.Io <jbaines@...> wrote: These calculated values are correct if, and only if, the actual resistor values are exactly as marked which they will not be. 73 John M0JBA On 26 Mar 2020, at 10:31, Dallas KD4HNX via Groups.Io <mylastname@...> wrote: That's not what my calculator says... 4.2 circuit:91 ohms in parallel with 51+11+51 take 1/91 + 1/113 = 1/x and that comes to 50.4068 ohms... When I do that to circuit 4.2.1 I come up with 50.64 ohms... 73 Dallas, KD4HNX Whatever you do, don’t fall victim to “paralysis by analysis.” Go ahead and buy/build one and start tinkering with it. This is a learn by doing hobby. No politician or scholar assured your freedoms. A Soldier, Sailor, Marine, or Airman did! ? ? On Wednesday, March 25, 2020, 11:30:27 PM EDT, RFy <gpdxdveil@...> wrote: H4 F303 variant PCB artwork updated to 4.2.1 : Update the schematic diagram, the impedance of ch1 is closer to pure 50 ohms
Dallas N4DDM All Messages By This Member #11991 ASSUMING the SA602 inputs are 1.5K each for a total of 3K my calculations come up with changing the 11 ohm 1% resistor with a 13.2 ohm 1% resistor from Digi-Key...?? 1 over 1/3000 + 1/91 + 1/115.2 = 49.992 ohms Only one part needs to be changed vs swapping out all 4... The 4.2.1 ckt math would be: 1 over?1/3000 + 1/56 + 1/529.9 = 49.806 ohms 73 Dallas, KD4HNX Whatever you do, don’t fall victim to?“paralysis by analysis.” Go ahead and buy/build one and start? tinkering with it. This is a learn by doing hobby. No politician or scholar assured your freedoms. A Soldier, Sailor, Marine, or Airman did! toggle quoted message Show quoted text On Thursday, March 26, 2020, 07:58:21 AM EDT, erik@... <erik@...> wrote: 4.2.1 is better because the input impedance of the SA602 (1.5kOhm//3pF per input) has less impact compared to 4.2 -- NanoVNA Wiki: /g/nanovna-users/wiki/home NanoVNA Files: /g/nanovna-users/files Erik, PD0EK
Erik Kaashoek All Messages By This Member #11992 Did you do a calculation over the total frequency range or only DC? The impedance mismatch was most prominent at higher frequencies due to SA602 input capacitance. Increasing R22 and R23 reduced this problem. -- NanoVNA Wiki: /g/nanovna-users/wiki/home NanoVNA Files: /g/nanovna-users/files Erik, PD0EK
EB4APL All Messages By This Member #11993 You say that because you never lived under a military dictatorship. These political comments (included mine) should be avoided, they are not good for the good health of the group. Ignacio, EB4APL toggle quoted message Show quoted text El 26/03/2020 a las 11:31, Dallas KD4HNX via Groups.Io escribió: That's not what my calculator says... 4.2 circuit:91 ohms in parallel with 51+11+51 take 1/91 + 1/113 = 1/x and that comes to 50.4068 ohms... When I do that to circuit 4.2.1 I come up with 50.64 ohms... 73 Dallas, KD4HNX Whatever you do, don’t fall victim to?“paralysis by analysis.” Go ahead and buy/build one and start tinkering with it. This is a learn by doing hobby. No politician or scholar assured your freedoms. A Soldier, Sailor, Marine, or Airman did! -- El software de antivirus Avast ha analizado este correo electrónico en busca de virus.
Erik Kaashoek All Messages By This Member #11994 Sincere apologies for something I must have done wrong. Please help me to understand how I should have explained the problem is most prominent at higher frequencies, much more then the 0.1 ohm differences at DC. -- NanoVNA Wiki: /g/nanovna-users/wiki/home NanoVNA Files: /g/nanovna-users/files Erik, PD0EK
CT2FZI All Messages By This Member #11996 Hola Ignacio, Es solo un mensaje de "firma" agregado automáticamente después de cualquier texto (arriba) que no tiene nada que ver con el tema en discusión ... Por favor ignora jaja @Eric@ he was mentioning the KD4HNX email signature. Please ignore :)
Hugen All Messages By This Member #12006 Another solution comes from the suggestion of Massimo. Changing the input of SA612A to single-ended can eliminate the influence of the capacitance of one of the input pins. Maybe this modification is more appropriate, I am testing. “ R22 = 68 ohm 0603 1% resistor R23 = 0ohm 0603 shunt R24 = 120ohm 0603 1% resistor R25 = 22ohm Note that it has changed form differential to single ended, just because it was a nonsense. The driving signal of the SA612D mixer was in-phase on both sides of R25, so there was no advantages using that configuration. I found this configuration less noisy indeed and best matching the CH1 input port impedance for higher frequencies, that thanks to the higher value of R22 that is the one which influence more the capacitive behaviour of the CH1 input port trought the mixer input capacitance. ” hugen
Erik Kaashoek All Messages By This Member #12010 Hugen Can I suggest you use the same values of R25 and R24 in the attenuator circuit for the CH1 input as those used in for the reference SA612? And then set R22 to come to 50 ohm? This will reduce the amount of calibration deduced compensation needed for S21 measurements and thus noise. Interesting you found the unbalance less noisy. In my experiments I found the balanced less noisy. Not sure why????. Possibly because I was doing experiments on an unshielded PCB and we have rather strong DAB and mobile phone signals here and in a balanced configuration these could be eliminated because of the SA612 differential input???? -- NanoVNA Wiki: /g/nanovna-users/wiki/home NanoVNA Files: /g/nanovna-users/files Erik, PD0EK

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