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For lower current needs, there are some transformers available from minicircuits too. I haven't used them, though.
- f
On Sun, Mar 5, 2017 at 11:06 AM, Ashhar Farhan <farhanbox@...> wrote: buy the cores from W8DIZ and wind them yourself.
- f
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Hi Mr. Farhan,
I glad that you finish to design new uBITX. If you do not finish to design PCB. Can you make Header pattern on your PCB for IF signal. Because I wish to connect your new uBITX with RTL-SDR receiver. I think It will be very useful gear to operation HF. please refer above link...
Thanks to read it. 73.
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Excellent suggestion. I will try adding this. We need a break in the if chain anyway - f
On 5 Mar 2017 4:17 p.m., "Yeonghwan Jun" < ds5siz@...> wrote: Hi Mr. Farhan,
I glad that you finish to design new uBITX. If you do not finish to design PCB. Can you make Header pattern on your PCB for IF signal. Because I wish to connect your new uBITX with RTL-SDR receiver. I think It will be very useful gear to operation HF. please refer above link...
Thanks to read it. 73.
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T10 and T11 look like all the other trifilar FT37-43 transformers but as they are both handling power I assume they need something bigger. Ashar, what cores did you use?
Also the top capacitors in the PA LPFs dont have values... c241, c245, ?c231, c235... are these required??
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T10 is same. T11 is not really a trifilar transformer. Instead, it is an 8t:10t transformer on an ft3743. As there is no dc through T11, it can handle 10 watts of rf. - f
On 5 Mar 2017 5:21 p.m., "VK3HN" < prt459@...> wrote: T10 and T11 look like all the other trifilar FT37-43 transformers but as they are both handling power I assume they need something bigger. Ashar, what cores did you use?
Also the top capacitors in the PA LPFs dont have values... c241, c245, ?c231, c235... are these required??
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Ashhar,?I noticed some differences in the first amplifier of the TIA circuit. Looks like you are biasing it for more current, perhaps to improve strong signal handling. Or maybe this is necessary for operation at 45MHz. Can you comment on this?
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I have biased all the four amps to exactly the same current. the current is a little high, that is to improve the signal handling.
- f
On Sun, Mar 5, 2017 at 10:09 PM, W0PWE <j.b.hall@...> wrote: Ashhar,?I noticed some differences in the first amplifier of the TIA circuit. Looks like you are biasing it for more current, perhaps to improve strong signal handling. Or maybe this is necessary for operation at 45MHz. Can you comment on this?
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You pretty much addressed Allison's entire list of things to improve on the Bitx with this new uBitx design, and did so before she put out her list. ?I like how you chose to do CW. ? A few questions and comments: How much of a compromise is the Si5351 on the uBitx? ?Would you expect to hear significant difference between an Si5351 and going to three Si570's due to phase noise or crosstalk between channels? ? Perhaps put pads down for the Si5338 as a stuffing option, the Si5351's higher performance big brother. Would a four FET H mixer or similar give better performance up front on receive? ?If one were to chase this path, would it be best to have separate transmit and receive mixers? This might be an interesting option for a high performance first IF filter: ?? ?They say typically 3db loss, but we might find a 3khz slice that is even less. ?Are those diode ring mixers and BiDi amps good enough at 87mhz? How close are we to being legal on the second harmonic using just the two transmit LPF's? ?I'm ok with offboard filters in the antenna line, perhaps have a suggested antenna tuner for use with an end-fed-half-wave. For shielding, I'm looking at 1.25 inch diameter thin walled copper pipe at the local hardware stores. ?Perhaps cut it into 1/4 inch high pieces, have four ground test points in a square around each RF section of the board such that the pipe fits just inside the test points. ?When complete, a stiff cover of PCB material gets bolted down on top of the copper pipe sections, use conductive foam sheet as gasket material.? I'd prefer the Si5351 on the main board, keeps the Arduino processor and display choices flexible. ?Also, use board mount connectors and pots and switches as much as possible, all with panel mount bushings for sturdy mechanical support so they don't rip up PCB pads with use. ?Those that want different panel arrangements can choose not to stuff them, and run wires to their chosen connectors and pots and switches. ?Most Bitx40's are getting built with an ugly mess of wires boiling up off the board, a significant part of the problem around birdies and clicks and such. Keep in mind any checkout aids you can include in the design. ?I'm thinking AF and RF signal sources with appropriate attenuators, diode RF probe, voltmeter through the Arduino ADC that normally just monitors battery voltage. Some kind of SWR monitor would be nice, and perhaps a temp sensor that shuts down the IRF510 bias. ?Would save lots of people lots of grief. Jerry, KE7ER ?
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Mr Ashhar, Would you consider providing a list of the ?winding details ?and cores used for the ? Ubitx ...
Regards
On Fri, 3 Mar 2017 at 5:58, Ashhar Farhan <farhanbox@...> wrote: It has been more than a decade since the BITX20 was first built. In these years, we have had many ideas knocking around. After looking hard at these, it became evident to me that a full reboot of the bitx series was needed to incorporate these.
Raduino has been a game changer in many ways. It would have been unimaginable even a few years ago that for a dollar, you would be able to buy a single chip with three clock outputs for less than a dollar.
Anyway, here is the new uBITX (I pronounce it as microBITX). I hope you all find it interesting. Unlike the Minima this is full tested and ready to be built.?
You can read about it on . It hasn't still made it to my home page. If you find any typos or anything that is not clear, push the reply button on this mail thread and I will fix it before it goes out to the world outside the
There is no kit for it. As usual, the circuit is free for you to build, write about, forward and publish it wherever. However, commercial production of PCBs and kits is prohibited for now.?
Will HFsigs kit it? I am not sure. They are already swamped with a backlog of the bitx40 orders. I will have a conversation with the team and ask them about it.
It goes without saying that without the help of so many of you this rig would never been possible. It is a joint effort of several people who have been helping along with things big and small.? Curiously, this rig derived much of its theory from an older text : Introduction to RF Design by Hayward. Hence, you will see it in the pictures of the rig too.?
- f
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Paul, ? Ashhar, please correct any errors in my message. ? I believe the two lowpass/notch filters used by Ashhar in the transmitter output are based on the the W3NQN filter design described in the article. “Second-Harmonic Optimized Low-Pass Filters”.? The article is available at: The filter can be designed using the ELSIE software that is available for free for hobbyists at: ? The values of C241, C245, C231 and C235 are listed as 0 as they are not used in this filter. ? This looks like a great project and I am collecting parts J ? 73, Dale? K9NN ?
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From: [email protected] [mailto:[email protected]] On Behalf Of VK3HN
Sent: Sunday, March 05, 2017 6:51 AM
To: [email protected]
Subject: Re: [BITX20] uBITX - A reboot of the old BITX ? T10 and T11 look like all the other trifilar FT37-43 transformers but as they are both handling power I assume they need something bigger. Ashar, what cores did you use? ? Also the top capacitors in the PA LPFs dont have values... c241, c245, ?c231, c235... are these required??
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That QST article suggests the return loss might not be acceptable across more than one band. ?The topology agrees but Ashhar's values differ significantly from those recommended, might be something more going on here.
On Sun, Mar 5, 2017 at 03:45 pm, dvhammer_99 wrote:
I believe the two lowpass/notch filters used by Ashhar in the transmitter output are based on the the W3NQN filter design described in the article. “Second-Harmonic Optimized Low-Pass Filters”.? The article is available at:
?
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Just out of curiosity, Ash, why are L8 and L9 separate?
Is it topography or is there a reason not to use an UNUN
here?
john
AD5YE
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Damb you Ashhar... now I have another project to add to the ever growing list.... uBitx looks like a very interesting rig, I am sure it will evolve a bit in the next few months so it is probably lucky I have 3 other rigs partly completed that I need to finish first. Thanks Ashhar and the others involved with this project it looks to be an excellent piece of home brew work that many will replicate.
--
Mike VK3XL
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Farhan Sir, C107 gndref near BPO mizer xfrmr .1uf seems typo to me, will it be .001 ?? -- Please encourage recycling, reuse or repairing of E-waste. ?7?3? ?d?e? ?V?U?3?S?X?T?
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Hi Sandeep jee, ?The capacitor under discussion is for carrier removal and Audio in/ out can happily work even with 0.1uF value, I suppose, sir.
sarma ?vu3zmv
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Jerry, I am pretty sure the component values used by Ashhar for the transmit filters agree with this article as I used to ELSIE program to display the frequency response using the values listed on the Microbitx schematic.? The resulting plot agreed exactly with the desired low pass response of 7 Mhz with a notch at 10.5Mhz and the other filter of a low pass response of 28 Mhz with a notch at 42 Mhz. ??I believe Ashhar picked the values as a compromise to allow a filter to be used for multiple bands, versus the values used in the article which were picked for single band harmonic suppression. ? Now I need to figure out how to use the ELSIE program to calculate the desired component values from scratch as Ashhar did J ? 73, Dale? K9NN ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Sunday, March 05, 2017 7:25 PM
To: [email protected]
Subject: Re: [BITX20] uBITX - A reboot of the old BITX ? That QST article suggests the return loss might not be acceptable across more than one band. ?The topology agrees but Ashhar's values differ significantly from those recommended, might be something more going on here. On Sun, Mar 5, 2017 at 03:45 pm, dvhammer_99 wrote: I believe the two lowpass/notch filters used by Ashhar in the transmitter output are based on the the W3NQN filter design described in the article. “Second-Harmonic Optimized Low-Pass Filters”.? The article is available at:
?
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I couldnt use the Elsie as Linux wine emulator crashes when i run it. I used the good ol LTSpice starting with a standard low pass filter and modifying it with the capacitor to create the notch. The trick is to keep the parallel inductor and the caps reactance same as the original inductor at the cut of frequency. One coukd spend days playing simulations. Gradually, a pattern of images emerge that we call spherical, cheychev, Butterworth, etc. They are all about various ratios that do things to the passband. - f
On 6 Mar 2017 4:59 p.m., "dvhammer_99" < DaleHammer@...> wrote: Jerry, I am pretty sure the component values used by Ashhar for the transmit filters agree with this article as I used to ELSIE program to display the frequency response using the values listed on the Microbitx schematic.? The resulting plot agreed exactly with the desired low pass response of 7 Mhz with a notch at 10.5Mhz and the other filter of a low pass response of 28 Mhz with a notch at 42 Mhz. ??I believe Ashhar picked the values as a compromise to allow a filter to be used for multiple bands, versus the values used in the article which were picked for single band harmonic suppression. ? Now I need to figure out how to use the ELSIE program to calculate the desired component values from scratch as Ashhar did J ? 73, Dale? K9NN ? From: [email protected] [mailto:[email protected]] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Sunday, March 05, 2017 7:25 PM
To: [email protected]
Subject: Re: [BITX20] uBITX - A reboot of the old BITX ? That QST article suggests the return loss might not be acceptable across more than one band.? The topology agrees but Ashhar's values differ significantly from those recommended, might be something more going on here. On Sun, Mar 5, 2017 at 03:45 pm, dvhammer_99 wrote: I believe the two lowpass/notch filters used by Ashhar in the transmitter output are based on the the W3NQN filter design described in the article. “Second-Harmonic Optimized Low-Pass Filters”.? The article is available at:
?
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Does anyone have any winding details for the torroids for the UBITX .... Thanks .
Regards
On Mon, 6 Mar 2017 at 12:15, Ashhar Farhan <farhanbox@...> wrote: I couldnt use the Elsie as Linux wine emulator crashes when i run it. I used the good ol LTSpice starting with a standard low pass filter and modifying it with the capacitor to create the notch. The trick is to keep the parallel inductor and the caps reactance same as the original inductor at the cut of frequency. One coukd spend days playing simulations. Gradually, a pattern of images emerge that we call spherical, cheychev, Butterworth, etc. They are all about various ratios that do things to the passband. - f
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VK3HN
Marc Jones