Re: QRP Labs Low Pass Filters
Mike,
I did the same using RFSim99, so the shift in the measured frequency
response must be down to capacitor tolerances, inductor values being
out, or, conceivably, stray capacitance added by the PCB.
It's surprising just how much variation there can be in the inductor
values. In addition to the Al tolerance of +/-10%, the winding
spacing makes a big difference. In Micrometals application note they
show the inductance of 10 turns of #20 wire on a T50-17 varying
between 0.22uH and 0.39uH depending on how the turns are spaced!
Also I note in the QRP labs table that at least two different
required inductor values are realised with the same number
of turns on the same core, so that introduces another
"approximation factor".
Steve G3TXQ
On 17/03/2017 22:25, K5ESS wrote:
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Steve,
I just entered the L and C values
that QRP Labs lists for the 20 meter LPF into AADE filter
Design.? The analysis shows only a .03 dB loss at 14.5 MHz
and doesn¡¯t exceed 1.5 dB until above 15.5 MHz.? I suspect
you¡¯ll have to measure and tweek your toroids to get close
to the values that QRP Labs calls out for their 20 meter
filter.
Mike
K5ESS
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Re: Using switching power supply....
I am using a switching supply and I have no noise. It is small and I
put it into the
case next to the PCB. Works great.
Ed
On 3/17/2017 2:15 AM, Yeonghwan Jun
wrote:
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I wish to use switching power supply.
because I don't have power supply yet. but I can find to buy
cheap switching power supply.
I had know that the switching power supply make a lot of noise.
So I will add RFC and Capacitor to reduce noise. if I will.
Is it possible?
I didn't received my BITX yet.
But I want to finish it before getting reach my BITX.
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Re: Changing frequency display
" I listened to the equipment, not the music. "
Amen to that. Sometimes we get so caught up in the perfection of equipment and the doodads, that we forget the whole purpose of the game in the first place.
Radio is for communications. Without using wires. Over considerable distances. And when we think about it, rather mysteriously. So is the internet. But you can't
talk directly from New York to Melbourne, AU without going through a lot of hoops controlled by others. You can on 40m one on one.
But, don't belittle your natural impulses. If making technologies work better is your thing, go for it. Sing it out. We all learn something from the community orchestra.
But the orchestra exists to play symphonies, not to exhibit the virtuoso flautist. It is a good thing to remember.
john
AD5YE
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Re: Changing frequency display
Yay Marco. There are so many hacks/mods on this simple little radio. I am hoping most will remember that this is a very good QRP radio. QRP in itself has it's own set of challenges and roadblocks. Many of the suggested mods won't change that. I'm for simple, inexpensive changes, that allow ham operators to more easily use and enjoy the Bitx. It's not an Elecraft, IC703 or FT817. I remember myself years ago as an audiophile. I listened to the equipment, not the music. Go ahead, try and break into a pile up, answer a lonely CQ'r, have fun. 73
Sent from Mike's iPad WA1MAD
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Rafel, See my comments below: On 17-03-2017 22:35, Rafa? Lichwa?a wrote: Hi Peter,
Thanks for this forwarded message!
So I noticed my first mistake: crystal filter has ~200 ohms Zin/Zout -
not 50, as I thought before.
Ok, so that means, attenuator has right Zin/Zout, but there is an
impedance mismatch between 1st AMP (just right after LPF) and mixer.
This AMP translates 50 ohms of the LPF to ~200 ohms, but mixer expects
50 ohms. Maybe that's why we can notice much improvement in the way
BITX works, when we remove that 1st AMP completely - then mixer has 50
ohms on all ports.
But I don't understand two things:
Second the terminal impedance of the crystal filter and the various
RF/IF amplifiers were optimized for 200 ohms the mixers are better at
50 ohms and there is no impedance matching to correct for that.
Yes, the lack of matching keeps the circuit simple but you pay the price of less than the best achievable performance from this circuit. In the real world you will need to measure and compare the results of both matched and unmatched circuits to see the performance difference and keep in mind that often what looks good on paper does not translate into a large practical (real world) difference, ie; the improvement may not be worth the added complexity. Why mixers are better at 50 ohms?
I thought there is not much difference in mixing for different
impedances on mixer ports, but the point is to keep them EQUAL on each
port (nevermind if it is 50 ohm or 200 ohms - mixer will work fine as
long as those impedances are equal on each port). Is that correct? When I saw this question it caused me to think about how I have been using DBM's for many years now. In truth I have never considered operating them at impedance's other than 50 ohms, all the books and circuits said 50 ohms so thats what I did. However, (I am not into the basic physics of these things) my understanding is that for the DBM to be effective the diodes need to be switched hard on/off as quickly as possible. It seems to me that it is probably easier to achieve this if the DBM is being driven from a low impedance source which ensures maximum current flow through the diodes. And second thing: why RF/IF are optimized for 200ohms? You should ask the designer, Farhan is active on this group ask him. As it was explained by the author of that project, each AMP translates
impedance: 50ohms -> 220ohms and 220ohms -> 50ohms (for resistances
used in the circuit).
So I think there is no mismatch anywhere except this one between 1st
RF AMP and mixer. Is that correct? That is not my understanding of how the bi-lateral amps work, again talk to Farhan. Additional question at the end: is that a good idea to use ADE-1 (SMD
level 7 double balanced mixer) instead of those 1n4148 diodes and
"manual" transformers? This link was posted by a member of our group in the past and compares the performance of various DBM's. I was very happy to see that the homemade 1N4148 DBM's performed so well against the commercial DBM's. Of course you will have to be careful in how you build the homemade DBM, match the diodes and be careful with the transformers but if you do a good job the results can be quite good. See link below: Regards,
Rafal SP3GO Best regards, Peter VK1XP 18/03/2017
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Re: Rotary Encoder and latest sketch
Jack,
Thank you posting these two files. I was just starting to work my
way down the path of integrating a rotary encoder into my project.
Ashar's use of pot and ADC as a control for frequency is a very good
bit of creative lateral thinking. Very simple and sometimes simple
is all you need. I will have to spend some time playing with the
idea.
However, I think perhaps I would prefer a rotary encoder but perhaps
using a pot and ADC to implement a RIT function may work well.
Nothing ventured, nothing gained.
cheers, Graham ve3gtc
On 2017-03-17 19:46, Jack Purdum via
Groups.Io wrote:
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I just
uploaded:
and
which are the
rotary encoder articles I wrote for QRP Quarterly.
Perhaps those will help.
Jack,
W8TEE
I am
very confused. I find several sketches and many
references to using an encoder for tuning. Is there
a set of complete instructions for installing an
encoder (where to hook it up to which raduino pins
etc.) and can someone point me to the latest sketch
that incorporates code to operate the encoder? I am
very shaky and inexperienced with Arduino IDE and
programming and need some hand holding.
PJH
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Re: Fixing the galloping VFO problem
Bad link to YouTube video.
Roy WA0YMH
On Mar 17, 2017 4:40 PM, "KE0OG" < casler28@...> wrote: The VFO's "feature" of galloping up or down in 10kHz increments when the Raduino's VFO pot hits the stop is driving me crazy. I made a fix, picture attached . Also a video at??I may be reinventing the wheel here. Anyway, this goes in the YAM category (yet another mod). 73, Dave, KE?OG,
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I just designed an had PCBs made for tiny (.6x.8") 5351 board.?
It has 2 four pin connectors for power and I2C and then
output on the other side.??? I now have 40 oscillator modules?? I
only built one, worked the first time.
?
So, you would be SURPRISED on soldering in that little fellow.
Flux and some small solder braid and it went in like a breeze??
You need small tipped iorn and tweezers.
Some of the pins shorted, but you wipe the braid while heating
outwardly.
Actually the tiny crystal was a bigger problem.? You have to put
VIA holes so you? can solder from the reverse side.
Taking of the 5351 just use braid and iron tip.? Clean it up nice
with braid and then alcohol for the replacement?
Give it a try!? Mouser has the parts.
My Bitx40 is on the way!
Mike, WA6ISP
On 3/17/2017 1:50 PM, Brian Lewis
wrote:
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So Mark and I are having the exact same no receive problem.
I've reprogrammed my nano thinking maybe something was amiss but
that didn't help. Mark replaced his 5351 board including the
nano with a known good part and now his works. Is there any way
to replacement for these boards? ?There's no way I can replace
the smd 5351 chip which I believe to be the culprit. ? Brian
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Re: Changing frequency display
Simple and elegant solution.? I like how this works.? Seeing it in action, it makes more sense.? Time to get some push button switches.
Marco - KG5PRT?
On Mar 17, 2017 5:04 PM, "Michael Davis" < maddmd818@...> wrote: This is what I tried to explain. Thanks to Dave Casler KE0OG. See
Sent from Mike's iPad WA1MAD
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Re: QRP Labs Low Pass Filters
Steve, I just entered the L and C values that QRP Labs lists for the 20 meter LPF into AADE filter Design.? The analysis shows only a .03 dB loss at 14.5 MHz and doesn¡¯t exceed 1.5 dB until above 15.5 MHz.? I suspect you¡¯ll have to measure and tweek your toroids to get close to the values that QRP Labs calls out for their 20 meter filter. Mike K5ESS ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Steve Hunt
Sent: Friday, March 17, 2017 4:51 PM
To: [email protected]
Subject: Re: [BITX20] QRP Labs Low Pass Filters ? Hans - thanks for that. Maybe I just got unlucky with a combination of capacitor and toroid Al tolerances. I think I've seen the figure of 10% quoted by Micrometals for the Type-6 material. ? Steve G3TXQ
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Re: Changing frequency display
This is what I tried to explain. Thanks to Dave Casler KE0OG. See
Sent from Mike's iPad WA1MAD
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Re: QRP Labs Low Pass Filters
Hans - thanks for that. Maybe I just got unlucky with a combination of capacitor and toroid Al tolerances. I think I've seen the figure of 10% quoted by Micrometals for the Type-6 material.
Steve G3TXQ
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Re: QRP Labs Low Pass Filters
Hi Steve
I don't think that there is any design error. Most of the band designs come originally from the G-QRP technical pages, which in turn got the component values from the legendary design by Ed Whetherhold W3NQN. The exception to this are the bands 2200m, 600m, 60m, 4m, 2m and 222MHz which are all added later.?
Over 30,000 of the QRP Labs LPF kits are in use in 69 countries and normally without any issues.?
It's a great and reasonably repeatable design. Sharper filters or filters with fewer poles can be built. But this design can usually be built successfully by people without access to exotic test equipment, just by counting turns and installing the right components in the right places.?
That said - there will always be some variations in component tolerances, and winding style, and even the complete measurement system. If you think the cut-offs are uncomfortably close to the band edges then I suggest just removing a turn or two from each inductor.
73 Hans G0UPL? ?
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Fixing the galloping VFO problem
The VFO's "feature" of galloping up or down in 10kHz increments when the Raduino's VFO pot hits the stop is driving me crazy. I made a fix, picture attached . Also a video at??I may be reinventing the wheel here. Anyway, this goes in the YAM category (yet another mod). 73, Dave, KE?OG, youtube.com/davidcasler
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QRP Labs Low Pass Filters
I wonder if anyone in the group has experience with QRP Labs Low Pass Filter kits? I recently built 10 of them - one for each band 160m thru 10m - and found that on some bands the "knee" of the filter response is very close to the upper band edge. It's particularly bad on 20m and 12m where the tops of the bands are at a point 1.5dB down the filter slope.
I've checked and double-checked the capacitor values and the number of turns on the inductors; I've also spaced the turns on the toroids carefully so as to minimize the inductance. But -1.5dB is the best I can achieve at the 20m and 12m upper band edges. Measurements were made using a 2-port VNA and checked with a TG/SA.
I guess I can reduce the number of turns on the inductors, but wondered if anyone else has experienced the same thing, and if it is a design error?
Steve G3TXQ
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Brian, I'm going to replace the 25mHz crystal on the SI5351 board and see if that's the culprit. ?If so, I'll let you know. ?I had to order 5 of them so if it works I'll send you one to try. Mark W5MCU
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So Mark and I are having the exact same no receive problem. I've reprogrammed my nano thinking maybe something was amiss but that didn't help. Mark replaced his 5351 board including the nano with a known good part and now his works. Is there any way to replacement for these boards? ?There's no way I can replace the smd 5351 chip which I believe to be the culprit. ? Brian
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