Re: stone soup ingredient list, what bands and modes are usable
On Thursday, September 6, 2018, 6:52:02 AM PDT, Tim Gorman <tgorman2@...> wrote:
Jim,
A two-tone test on an oscilloscope requires a subjective assessment of
the shape of the resultant waveform in order to determine if you are
generating splatter.
Increase power output till you see the output power increase
fall off on the power meter.
tim ab0wr
Back in the old days, that was called "compression"? ...I'm quite sure that is a LOT less subjective than the visual observation of a proper two-tone test ...reference : ARRL Lab Test Proceedures Manual
Jim
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Re: stone soup ingredient list, what bands and modes are usable
Jim, A two-tone test on an oscilloscope requires a subjective assessment of the shape of the resultant waveform in order to determine if you are generating splatter. It is *very* difficult to tell if the top of the waveform is actually flat-topped or not. By the time it becomes obvious you are probably already flat-topping. The same thing applies to assessing the "shape" of the waveform. Through decades of operation I have found that the most simple method to prevent distortion is just what I outlined. You can use any power meter, it doesn't even have to be accurate, just linear. Most any swr meter will work. You don't need a two-tone generator. Increase power output till you see the output power increase fall off on the power meter. If you have a 10db amp and a 1db increase in input power doesn't generate a 10db increase in power then you have maxed out your linear range of amplification. Mark the oscilloscope with that level. Adjust your mic level so your SSB signal never exceeds this level. You may not be getting the absolute most power out because of power supply capability for SSB use vs CW use but you *will* be generating far less splatter. tim ab0wr On Wed, 5 Sep 2018 18:03:36 +0000 (UTC) "jim via Groups.Io" <ab7vf@...> wrote: On Wednesday, September 5, 2018, 8:50:30 AM PDT, Tim Gorman
<tgorman2@...> wrote:
Jim,
There is no easy way to check for splatter on an oscilloscope.
Google "two-tone test" maybe old news or not
Jim
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Re: W0EB/W2CTX Firmware Source Code Sketches
#ubitx
Thank you! I was just looking at your web page yesterday and wondering about getting the sources.?
Ralph
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While waiting for my filters to arrive from eBay I decided see what effect would result from replacing R27 with a variable attenuator. I attached two short lengths of miniature coax, one the each end of the R27 pad with appropriate grounds. I then rolled in 1 dB of attenuation to replace the effect of R27 and set the drive level to produce 2 watts with -30 dBV of 1 KHz tone on the audio input. The purple trace shows that 12 meter output on an uncalibrated scale with the consequent 45 MHz minus carrier spur at 20.1 MHz. The difference in level between the spur and carrier is about -42 dB (Marker 1D).
I then increased the R27 attenuator by 10 dB to -11 dB and captured the blue trace. The spur to carrier delta at this level is -46 dB. So, reducing the 45 MHz drive to the mixer by 10 dB decreased the spur by 14 dB.
So I am not sure if it is the filter characteristics that are reducing the spurs or simply the attenuation that is added by putting a high impedance filter in line in a low impedance feed (point made by Henning).
One thing is pretty sure, and supported by Raj, output power is going to fall off dramatically with this mod unless subsequent (clean) gain is added to the chain to offset the insertion loss of the filter. In one way that would be good because the transmit chain as it stands produces unacceptable levels of IMD at SSB power levels above 2 watts.
Filters should be here an Monday and will check more.......
?
WA8TOD
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Both filter are identical as I cannibalized one from another uBitv3 for now.
In my case the reduced power is slight on 80/40/15/10 but for some reason 20 dropped. Something on 20 is behaving odd, when I touch the dummy load the power comes down. Haven't figured out what it could be. Probably a bad cable..
This evening I tried some 1:9 trifilar transformer to increase 50 to 450 but that did not help. The first mixer is fortunately happy with
650 ohms of 45M15 filter.
All my testing on my board is done with 1KHz modulation at 100mV. Power can be increased a little by shouting into the mic!
I think as more Bitxers try out this, we will have more idea and experiences to add to our own.
Raj
toggle quoted message
Show quoted text
Not sure if Raj replaced both filters, but if not, might T X power be 8mproved with a 'matched pair^ with identical pass and if the existing filter was replaced?
Brent
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I found a Chinese supplier 45MHz filter supplier here
I'll try and search for others Ali Express proves negative at the moment, but they could be listed under something else?
73 Steve
G1KQH
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Re: Grounding shematic for a Metal Chassis, which is the right way to wire up?
Yes Fabian with 'finals' I mean the power amplifier transistors, the IRF510. My UBitx had the heatsinks just put on the back of IRF510. If I had used a metal case in place of the heatsink I could not just screw (sounds bad hihi) the IRF510 on the metal case. There are small plastic kits to DC isolate the transistors and allow heat dissipation at the same time. If you live in Germany, Conrad shops should have them for sure. I haven't found ground loop issues with my Ubitx, but ground loops depend on the things, accessories, PC, connected to the Ubitx. I have had ground loops problems other times. Once with a German 10.7Mhz IF sdr receiver. The antenna ground was connected with the ground of PC and generated any sort of noise. To solve that completely I used a small conventional RF 1:1 transformer at the antenna input. It happens, when you see an increase of noise it may be due to ground loops.
Il 05/set/2018 19:31, "sdr freak" < sdrfreak55@...> ha scritto: Hello again!
First thanks, i'm anytime be glad for answer! And these kind of answer is still hepl me. So thanks.
ok, sorry but what is the word "Finals" ,in your post, mean for? Do you mean the IRF510? The heatsink and the metal case doesn't have contact but when this was corectly built up, so is there more insulation at anypoint a must be? like the board screw holes when mounted on bottom alumium plate, like other conections there?? For real its only the concact between the heatsink of both IRF510 to the back plate and when it's securly built up, then it should be all fine, or does i missed up anything?
The ventilation in my case is on bottom many little holes and on back plate are ventilation lines milled, in the hight of the 2 heatsinks. I work on the idea to install a little processor fan.
But in my workshop room it's caos.. (When you look at my profile pic, and make bit larger you can see the workshop room a little bit, ok not much you can see on it, but the milling machine should be able to see. I have in times before come to HAM, learned Metal-Worker Job and it was a interest to make little things from metal with mill and lathe or other machine.. But now when then ubitx works anyday i want to build a few Antenna and Variable Capacitor for Mag Loop with the mill, so i was lucky to bought these machine and hasn't do waste the money for party or so, in years ago, when have the job and was able to bought this things for look at future. Now i'm proud about that i was think so and see a chance for work with this things on HAM homebrew build things...) Just a story about this..
ok back to topic..
These things like Ground Loops and Grounding a was better understand if i see a shematic which descripe this.
The modes i want do, is SSB mainly and CW in next time when learned this better... But a important thing for me is to make WSPR in next time..This was very nice for me to do it self one day..
ok i hope you can descripe the insulation of the heatsink to the metal case, a little more information for this from your mind was nice.
regards Fabian
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and in addition duen to the mismatch of the filter (it is high iompedance so acts as an attenuator). BUT: if this is true then the drive Level to the mixer is also reduced thereby redusing the mixer internal generatores spurs!
Henning?
?
?
-----Urspr¨¹ngliche Mitteilung-----
Von: Raj vu2zap <rajendrakumargg@...>
An: BITX20 < [email protected]>
Verschickt: Do, 6. Sept 2018 9:40
Betreff: Re: [BITX20] Simple spur fix
McAfee-Webkontrolle ¨C Warnung
Diese E-Mail-Nachricht enth?lt potenziell unsichere Links zu den folgenden Sites:
http://ubitx.net/-
I forgot the caveat!
Your transmit power comes down due to loss of the filter.
Raj
At 05-09-18, you wrote:
toggle quoted message
Show quoted text
This fix reduced the spurs by up
to 10 db? and requires ONLY ONE part to be added.
There is big change above 10MHz in the board. There is some improvement
below also.
The way I did it, CW may not work anymore will
need some more mods for CW:
1. T2 - desolder the transformer wires that go to pin 3 and 5. Pin 1
has a square pad.
2. Bring out the two wires above board and join them together and
solder.
3. Take a 45Mhz filter- 45M15 or? similar 2 pole - one xtal only.
Solder one end of filter
to the wires of T2 pulled out. The center filter wire to ground at one
end of R26. You will
see a ground via there.
4. Solder the third wire of filter to C10/R27 junction.
Thats it! This prevents the leaked TX signal that gets amplified by the
1st BiDi from getting into
the first mixer and creating havoc.
Farhan method of the same..much simpler and CW will work.
1. Remove R27
2. Solder the 45Mhz filter two extreme ends to the pads of the
resistor.
3. Solder the center lead of the filter to the nearest ground. R13 is
very near with a ground via.
The first method the extra filter will work in RX mode also and may help!
In the second the
filter is only in the TX path..
Folks with DSA815 or better please share your feed back. The filter may
work better properly
terminated etc.
Have fun!
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Link to ebay.ca for any VE hams wanting the filters
Ordered a pair last night. Not sure if Raj replaced both filters, but if not, might T X power be 8mproved with a 'matched pair^ with identical pass and if the existing filter was replaced?
Brent
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Hi,
I am really pleased to see the 45 MHz crystal filter solution to the spur problems. I am writing up a MicroBitX article for our club - Michigan QRP Club - and this is a welcome last minute edit of the article in the section about warts. I am ordering some of those filters for myself. I have been planning to use them in homebrew projects anyway. If the people with the Rigols etc do the measurements and publish good results I will use one of the filters to update mine.
This and the lowpass filter work are examples of "open source" at it's best.
73,
Bill KU8H
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Hi Glenn
> Right now, the only way i can see to use multiple? > (10pin) Si5351's in a rig is to have say, an ATtiny or > similar 8 pin uP to program it on power up. Or as > commanded by the master uP.
It is not difficult to program a second (or third etc) firmware-emulated I2C port on the microcontroller. The inbuilt I2C/TWI peripheral isn't the only way to do it. I have code examples in the pages below .?
This way, you can program multiple Si5351A from the same microcontroller. You need only one additional I/O pin per device since all Si5351A can share the same SDA pin. Only SCL needs to be unique per device.?
However in my opinion this is a somewhat complicated solution to the problem.?
In many situations there is NO problem. You may not be using multiple Si5351A outputs concurrently. The spurs may not be on frequencies that matter, in the design. Or the spurs may be at a neglible level.
The last point is important. The spurs are worse the lower the impedance of the load on the Si5351A outputs. I think that this is entirely expected within chip, but it is very nice to see it quantified.
The easy solution is don't load the outputs heavily. Use a buffer with a high impedance input. Then the spurs disappear into the noise floor. In most cases this solution is probably cheaper and easier than multiple Si5351A.
73 Hans G0UPL? ?
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Re: Adjustment the RV1 and RV3 Resitor on Ubitx 3
If he does not have? an RF powr meter he can put in a 10 W 50 R non inductive load and add a a two diode RF probe and measure the peak DC on a DVM. There are? passive? RF probe designs all over the internet .. some are right some look suspect.? ? Go to?? on page 15 of the manual there is an RF probe.? It should have say a 15K load on RHS to make it responsive rather than letting the DVM bleed it down.? .. that is all you need to pseudo measure power as peak RF .?
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Re: Adjustment the RV1 and RV3 Resitor on Ubitx 3
hi, cool to see you again here in post, can we make a call in german "relay station"? when you have echolink, you can call the "th¨¹ringen link-node" and we can speak over this, that was really nice if we can me a little qso in german language?
to the post, ok the RV1 is the drive level, yes a read a few other post with this declaration but not the correct position.. but i've adjust at all RV1,2 and 3 when i was such for the first right alligment...
on this way i can set RV2 and RV3 at 100ma, each one.. but the RV1 level is not able to be set without the real messuarment device? for this i recommend a power watt meter, right?
thanks for your help and you can look for the qso conversation at the th¨¹ringen link node if you want, just a correct time we need.
regards Fabian
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I forgot the caveat!
Your transmit power comes down due to loss of the filter.
Raj
At 05-09-18, you wrote:
toggle quoted message
Show quoted text
This fix reduced the spurs by up
to 10 db? and requires ONLY ONE part to be added.
There is big change above 10MHz in the board. There is some improvement
below also.
The way I did it, CW may not work anymore will
need some more mods for CW:
1. T2 - desolder the transformer wires that go to pin 3 and 5. Pin 1
has a square pad.
2. Bring out the two wires above board and join them together and
solder.
3. Take a 45Mhz filter- 45M15 or? similar 2 pole - one xtal only.
Solder one end of filter
to the wires of T2 pulled out. The center filter wire to ground at one
end of R26. You will
see a ground via there.
4. Solder the third wire of filter to C10/R27 junction.
Thats it! This prevents the leaked TX signal that gets amplified by the
1st BiDi from getting into
the first mixer and creating havoc.
Farhan method of the same..much simpler and CW will work.
1. Remove R27
2. Solder the 45Mhz filter two extreme ends to the pads of the
resistor.
3. Solder the center lead of the filter to the nearest ground. R13 is
very near with a ground via.
The first method the extra filter will work in RX mode also and may help!
In the second the
filter is only in the TX path..
Folks with DSA815 or better please share your feed back. The filter may
work better properly
terminated etc.
Have fun!
|
Congratulations to Allison and the rest for all their trouble shooting and discoveries. Regards
On Thu, Sep 6, 2018 at 8:04 AM VK3HN < prt459@...> wrote: Ray, that has to be the best shielded homebrew rx I think I've ever seen!? And SMAs everywhere. I bet there isn't a sniff of RF anywhere within a mile of your receiver.? ?Congratulations!
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He'll everyone i have problem with s meter i try to do it more than one time and it's doesn't work i followed the steps LM385? and LM386 can i find some s meter ready to use ? I need something that similar to LM385 because i use nextion lcd?
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Ray, that has to be the best shielded homebrew rx I think I've ever seen!? And SMAs everywhere. I bet there isn't a sniff of RF anywhere within a mile of your receiver.? ?Congratulations!
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Changed the bias on the PA drivers ...Q90 - R 81 changed to 2700 ohms Q911,912 - R85 changed to 220 ohms, R 86 changed to 2200 0hms Q 92,93 - R 90 changed to 220 ohms, R 92 changed to 2200 0hms Q 96,97 - R 93 changed to 220 ohms, R 95 changed to 2200 ohms All this to redistribute Emitter current across the drivers ..Q90 now has 8,5 ma current , each Q911,912 have 10 ma, each Q 92,93 have 10 ma. and Q 96,97 now have 10 ma each..? stage 1= 8.5 ma, stage 2 20 ma, stage e 40 ma ...to keep each stage progressively amplifying without overloading from the previous stage. Ran some scans of overall passband from input to the low-pass filter (after the last mixer) through to dummy load as well as individual band output...I'll put the bulk of the pictures in a Photo Folder called PA MOD ..     
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The real killer with trying to use a 45mhz crystal is that it will almost
certainly be an overtone crystal.? And I believe it would not
be suitable as a filter at other than it's fundamental frequency.
This ebay ad for some 45mhz filters similar to what is stuffed at Y1
? ??
Note that they are selling "matched pairs".
That suggests to me that if you buy a 45mhz filter off ebay it may not match
the frequency of what's already installed at Y1.? So buy two, preferably matched.
toggle quoted message
Show quoted text
On Wed, Sep 5, 2018 at 09:17 PM, Jerry Gaffke wrote:
It's not a given that some 45mhz quartz crystal from ebay patched in using Raj's instructions
for a filter module will just work.
?
Perhaps the series resonant frequency won't quite agree with Y1.
Impedance matching may be an issue.
May have a very high insertion loss.
Most forum readers don't have the tools to plot the passband of their new filter.
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Maker spaces are great. I was a member some years ago at Tech Shop in Menlo Park, Ca. Enjoyed it, but for example, I wanted to look at the output of an inverter generator I had and needed to find, fix and recalibrate enough scope probes before I could get started.?
Tom, wb6b
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Raj vu2zap
Brent Seres/ VE3CUS
sdr freak
VK3HN
