Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
- BITX20
- Messages
Search
|
Re: si5351 crosstalk
#radiuno
Timothy Fidler
Your quote is Thomas Edison ???
toggle quoted message
Show quoted text
Timothy E. Fidler : Engineer BE Mech(1) Auckland , NDT specialist AINDT UT /RT3 , MT2 CB #2885,?
|
|
Re: si5351 crosstalk
#radiuno
Re 78 Fairchild Diode Data Book
In the old days the manufacturers really went all out with their data books.? They wanted the designer to know exactly what he was buying and how to use the thing.? In fact most data books had many application notes where they would lead the designer down the garden path to show how their part could be used in other ways, sometimes unexpected ways. National Semi was famous for this approach.? Their Op Amp data book was better than a graduate level course in Op Amp theory.? I still have my early 80's copy...dog eared...probably has 10 lbs of highlighter ink in it. -- "You see, wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only difference is that there is no cat." |
|
Re: si5351 crosstalk
#radiuno
Hey Glenn, So what were the results of adding the buffer stages??
Thanks Lyn -- "You see, wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only difference is that there is no cat." |
|
Re: Amplifier chain design - best practices
When I finish with my homemade SA, I made a list of a few things I'm going to try.
1). Improve ground layout. I plan on taking a Dremel tool and cut a line across the ground copper flow between the PA side and the IF amplifier side. Then I'll find a better common ground point for the two sides. This may reduce the ground loop from the PA feeding into the IF stages. 1a). Experiment to see if using an additional copper clad board, mounted under the uBITX, as a common ground island with various critical points of the circuitry grounded with short straps to the ground island helps at all. 2). Reduce the audio drive level to about where the uBITX currently puts out 1 watt on the lower bands. Then add an additional pre-driver stage before the PA to bring the power back up to around 10 watts. This may make life easier on the IF stages and the mixers. 3). Play more with moving the DC power feed points around.? 4). Rip up the filter relays (Allison's suggested filter fix) and rewire or just go with an external filter. 5). If I go with an external relay switched filler, I may buy a 10W amplifier kit, with a pre-driver, that only requires around 100 mW of drive, and tap into the TX drive chain ahead of the PA on the uBITX board. I'll do this at a point that provides enough gain so I can get 10 watts out with reduced audio drive. I might put both the amplifier and the relay switched filters in the same box. May use the Kees relay board with QRP Labs filters.? 6+) Whatever solutions that have been suggested on this forum that help solve the problems not address by the above list.? I'm willing to accept the current uBITX may not work on every band, and have other limitations, so I my not do every mod that comes along, if it only improves a band or mode I'm not interested in.? When a new uBITX revision comes out, I'll likely buy one. As the cost of two uBITX transceivers averaged together (one all bands and one a few bands) is still a pretty good price for two radios I the shack. I do hope any new uBITX will have the same form factor, so it can be dropped into any case people have already built for their current uBITX.? Tom, wb6b |
|
Re: I find This Shorted Circuit on Raduino, here the pics..plz Help?
#ubitx-help
Hi Fabian,
I really would like to help and I understand that you are not happy with the current uBITX situation. But without detailed information it¡¯s not easy and also not much fun. I already asked some questions and gave recommendations but didn¡¯t see answers. Yes concentrating first on fixing the receive part ?Baustelle¡° is a good idea. From what you¡¯ve described it looks to me that you possibly have changed already too much calibration ?screws¡°. If you cannot do the calibration with help of an AM radio station, you maybe can ask your local DARC ham club for help. They for sure have some frequency generator to help with the alignment and are willing to support a new ham doing his first steps in the ham radio world.Have you tried this? One other thing regarding the relais clicks in tx mode. What type of power supply are you using? Is it able to handle the amount of power your uBitx consumes in transmit mode? RV2 and RV3 aligned as described in?documentation?Calibration done? BFO? so please do yourself and us a favor and a chance to help and give us as much information you can about what you¡®ve already done or were you still have problems.? 73 Armin |
|
Re: Amplifier chain design - best practices
Howard,
toggle quoted message
Show quoted text
Yes, there are problems up front around the first and second IF's that create harmonics and spurs. Yes, replacing the 30mhz LPF with band specific filters could help with both spurs and harmonics during transmit, though does complicate what is trying to be a simple rig. Here's my take on a couple of your points. Unfortunately, I have not found time to do any experimenting on this stuff myself. > To date most everyone has blamed the poor output filters. We could also fix this problem > by insuring we always drive the transmitter section with a sine wave to begin with.? The output LPF's are fine, it's just board layout and how the relays got wired up that allows way too much blow-by.? When the board is hacked to clean this up, transmissions are fine with respect to harmonics.? The power amp will generate some harmonics (and IMD) on its own, especially when pushing for more power on the upper bands.? Many CW rigs operate class C (so a square wave at the final), simple output LPF's work fine even then. ? > This clock comes from the infamous SI5351 chip that is also causing the spurs. The primary cause of spurs seems to be in the diode ring mixers,? too much signal and not enough local oscillator. The fix is less IF gain and higher local oscillator levels into the mixers. The Si5351 is having a hard time dealing with the 50 ohm 6dB pads it's trying to drive, but otherwise doing pretty good.? Crosstalk due to the heavy loading is causing some carrier leakage and perhaps a few extra spurs.?? Would be interesting to know if anyone's tried this:??/g/BITX20/message/35206 discussed further here:??/g/BITX20/message/59220 Unfortunately, I have not found the time (or the logic analyzer) to evaluate it. Do dig in if you can and let us know if you find some new tricks to help clean the rig up. Jerry, KE7ER On Fri, Sep 21, 2018 at 07:35 PM, Howard Fidel wrote:
I've been sitting here on the sidelines for a while. I was hoping to have a complete solution finished by now. However, life gets in the way. I unexpectedly got 2 consulting jobs, plus my teaching job has eaten up most of my free time. However, I think it is worth putting? my 2 cents in now. |
|
Re: Dynamic mic on ubitx
Especially it is intelligibility that we need in ssb? amateur HF radios. Thanks for agreeing to my way of thinking, Michael Shreeve regards sarma vu3zmv On Sat, Sep 22, 2018 at 8:30 AM Michael Shreeve <shreevester@...> wrote:
|
|
BCI Filter
Joe Puma
¿ªÔÆÌåÓýI didn¡¯t see anything mentioned about this filter but I own the RTL-SDR Blog BCI filter.Filter Type:?LC High Pass Filter 3 dB Cutoff:?2.5 ¨C 2.6 MHz Attenuation:?~60dB Pass band I.L:?Typically well below 2 dB Power Levels:?RX power only, cannot pass DC The one I have got fried from a local 100 watt radio close to a receive antenna so I cant try it but I was wondering if it would make a good BCI filter for the uBit. I already read about Nick Pullens solution but I don¡¯t see where I can get one built already. I¡¯m up for winding torrids and all as it would be my first time but I rather get to the point if this other one would work. I know it did a good job filtering BCI with my SDR radios. Joe kd2nfc |
|
Re: Dynamic mic on ubitx
Thankyou. I agree. The radio should be heard farther, it isn't a dancing appliance.? On Fri, Sep 21, 2018 at 7:36 PM Mvs Sarma <mvssarma@...> wrote: Dynamic Mics are Great for music and performance. -- Michael Shreeve N6GRG |
|
Re: Amplifier chain design - best practices
¿ªÔÆÌåÓýI've been sitting here on the sidelines for a while. I was hoping to have a complete solution finished by now. However, life gets in the way. I unexpectedly got 2 consulting jobs, plus my teaching job has eaten up most of my free time. However, I think it is worth putting? my 2 cents in now.I will address the harmonics issue. We need to look at the root cause of the problem. The harmonics occurs in CW because it is direct conversion (or no conversion?) CLK 2 runs at the operating frequency. This clock comes from the infamous SI5351 chip that is also causing the spurs. Well, this clock is a square wave. The mixer it drives is unbalanced in CW and the clock just passes through and goes through a lowpass filter. (L1-L4 etc.) This removes frequencies above the 10 meter band. As most of you know, a square wave is made up of only odd harmonics, so we have the 1st, 3rd, 5 th etc. harmonics coming out. So for the 80 meter band operation many harmonics will pass through this lowpass filter get amplified and need to be filtered out by the output lowpass filter. We see fewer harmonics from 40 meters, mainly the 3rd since the others are removed by the first lowpass filter. At 20 meters and above the signal coming out of this filter looks like a sine wave, it has all the harmonics removed, hence there are no harmonics coming out of the transmitter. Garbage in garbage out. There are many ways to solve this problem. To date most everyone has blamed the poor output filters. We could also fix this problem by insuring we always drive the transmitter section with a sine wave to begin with. So, we could modify the L1-L4 so that its cuttoff frequency is about 8 MHz for use on the 80 and 40 meter bands and stays what it is for the other bands. This will remove the harmonics earlier in the chain. ?Another, easier? way is to heterodyne in CW as well and go through the 45 MHz filter. So we need to move the unbalance circuit from the above mentioned mixer to the CLK1 mixer. Drive this mixer at 45 MHz and clk2 would would be the same frequency as we use for SSB and the harmonics would be gone. To do this all we need to do is lift R105 and so it stands up on the C1 side pad and place a jumper wire from the open end of the resistor to pin 6 of T4. Of course the software needs to be updated, but now without any filter changes, and with a very simple hardware change the harmonics are history! Howard |
|
Re: Newbie Help
Ed
I am thinking the stock firmware is not a significant factor in CW operating.? I would suggest using a CW audio filter with the uBITX.? One candidate is the hypermite from 4stateQRP - there is at least one you tube video demonstrating its usefulness in the uBITX.? I understand there are at least 2 different widely used alternatives, but I suggest using the uBITX as is to discover factors you think need improving to find the best fit.? Enjoy your rig.? Curt |
|
Re: Amplifier chain design - best practices
On Fri, Sep 21, 2018 at 02:58 PM, Jeff Omundson wrote:
It is a little hard that parts become obsolete and so the projects might be difficult to build as is.? I have booth books and more even old copies of HamRadio, 73, CQ, Pop'tronics.? Its rare I find a circuit that can't be built because the device usually a transistor or tube is unobtainium. As a experimenter that's part of the game to figure out what part that is available might be a good match.? For the most parts Diodes are easy, most transistors are not magic either. I still pull down SSD and play with ideas.? Spice, rarely and I've driven that and many others, then again I can drive sim or a slide rule its just numbers and if you don't understand what their significance its data not information. The rest of the parts are coils, caps, and resistors and they are fare from rare.? There may be exceptions but they are far from the rule.?? True thing that ubitx would take people into parts of tech they would never have gone. Playing with the user interface (raduino firmware) has been the big fun for me.? I was shocked how few understand superhet radio being a near 90 years old and well understood.? I suspect that from it being new to people that have never worked with it. So they get to learn it and all the little things that go with it. Allison |
|
Re: Amplifier chain design - best practices
jim
thats my take on the uBitx ...Simple ie cheap parts ..Easy to work on ..Its all right on top ..spread out with BIG surface mount parts ... Play to your hearts content
Jim ?
On Friday, September 21, 2018, 12:21:03 PM PDT, Curt via Groups.Io <wb8yyy@...> wrote:
I was only citing K2 as example, yes now unobtainable or costly parts as I alluded to. Some of its circuits, like the uBITX, have legacy to discussion in those 2 W7ZOI et al books. The older one has lots of interesting concepts, but many unobtainium parts. What we can get cheap enough can change rather quickly. I respect many folk around the world cannot afford a K2, hence the uBITX paradigm. Lets see how that new QSX related IRF510 PA works when it comes out. 73 curt |
|
Re: Ubitx - using Amateurradiokits.in AGC
#ubitx
I¡¯ve taken a look at this circuit, too. I think Sunil is talking about the power to the first bi-directional amplifier (receive +) before the mixer. I don¡¯t know how well that would work, but I guess it could be worth a try. I¡¯ve added a manual RF gain control to my Bitx using Fig. 6.42 from EMRFD. It could be connected to something like that and probably work.
|
|
Re: Amplifier chain design - best practices
Thank you for the thoughtful responses!? Great ideas to digest.? I have the Solid State Design book but have not worked my way through it.? May be that is homework :-)? The explanation at the start for biasing transistors always made more sense to me than what I read in other books, including EMRD.? It is a little hard that parts become obsolete and so the projects might be difficult to build as is.? I suppose it could be broken down into smaller bits and then modelled in SPICE with best guesses at replacements for hard to find bits.
I thought buying the uBitx would be kind of a simple and unchallenging project radio.? I bet a lot of people didn't expect it to take us where it has!I haven't done any of the work to make it better, but I appreciate all the work that is being done.? It has prompted me to think deeper about multi band transceivers and it has been interesting to observe the community (and certain individuals in particular) work out solutions.? I think we are all learning more than if we were content to just play radio on the major commercial offerings. Thank you to Ashar and all of you who have spent so much time working on this and sharing the knowledge! -Jeff AG7NW |
|
Re: Ubitx - using Amateurradiokits.in AGC
#ubitx
Jon Titus, KZ1G
I find clarity and precision of instructions--if any--sadly lacking from many electronic kits and projects.? The same goes for illustrations that lack important details such as part locations, pinouts, part numbers, flow charts, etc.? Some of our good ham writers and editors might offer to help, but it's an uphill battle.
-- Jon Titus, KZ1G Herriman, UT USA |
|
Re: V3 uBitx Very Shrill Audio
Hi everyone. I¡¯m up and running and the radio sounds good!
I went in and did a Set Calibration and then Set BFO and all is good. Boy you can really get this thing out of whack if you¡¯re not careful! I¡¯ve already had my first QSO between my home QTH near Pittsburgh, PA and Winfield, MO, which is nearly 600 miles. The guy was running a net and said that he was impressed that I could make it that far today on nearly QRP power.? Thanks for for your help.? Curt |
Michael Shreeve
to navigate to use esc to dismiss