Allison,
the filter will be only in the TX path, the roofing filter should also be in RX path.
why amplify all the mixes from the first mixer. A good change in the architecture of
uBitx.
Raj
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At 05-09-18, you wrote: Farhans method...
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.
Sounds like something that may seriously help. I tried a low pass filter there and it
did help but not enough. Time and other pressing things never got back to try a
band pass filter.
One I'd liked to have tried is just moving the filter to the other end of the amp.
What is the impact on RX performance?
Allison
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On Wednesday, September 5, 2018, 6:49:10 AM PDT, Ashhar Farhan <farhanbox@...> wrote:
If you guys want to try out the mod, i can have some spares shipped out. - f I'd like one if there are enough to go around
Jim (ab7vf)
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Re: stone soup ingredient list, what bands and modes are usable
Hi Dave,
This will get a signal into your scope.? But you won't be able to "see" splatter on it.? What you can do though is to input a 2-tone signal and then observe when flat-topping ocurrs.? When you can observe a good 2-tone pattern, then this will be the maximum power output level for the band.? The ARRL handbooks, and I'm sure others, often have pictures and procedures on how to do this -- just look up "SSB" or "two-tone test" in the index.? There are probably a bunch on youtube too.
73,
Mark.
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Raj,
Very cool that you found such an easy and cheap solution!
Though not so sure I was a part of it in any way.
So that 2.5mhz thing had nothing to do with the si5351, was caused by feedback from the power amp?
Very curious.? I have no idea how that 2.5mhz factor came about.
The extra 45mhz filter would solve the power amp feedback issue.
That was probably all the low frequency rumble in Warren's plots of a few weeks ago.
This would not be fixed by a LPF.
I had assumed that the 45mhz-DialFreq spur was generated inside the mixer at D1,D2.
But apparently the IF amp at Q20,21,22 was generating enough of a second harmonic?
that the resultant 90mhz energy minus the clk2 VFO was going straight on through
the mixer in the expected manner.? As Henning has stated previously.
I'm sure termination impedances around the new filter could be an issue somehow.
But if it works, I'm ok with that!
Passband ripple might not be much of an issue, as the filter is much wider than what we actually use.
Extra insertion loss may not be much of an issue either, especially with the crystal only in
the TX path since we have gain to burn there.? Less TX signal into the D1,D2 mixer is a good thing.
Good job!
Jerry, KE7ER
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On Wed, Sep 5, 2018 at 04:11 AM, Raj vu2zap wrote:
A a big thanks to Farhan, Allison and earlier to Jerry!
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I suppose, such overlay has never been published by Ashar farhan vu2ese
On Wed, Sep 5, 2018 at 8:07 PM ARNAB SEN VU2CMV < vu2cmv@...> wrote: Can anybody please provide PCB overlay of uBitx v3? Thanks and 73s
VU2CMV
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Re: stone soup ingredient list, what bands and modes are usable
On Wednesday, September 5, 2018, 1:58:06 AM PDT, David Wilcox via Groups.Io <Djwilcox01@...> wrote:
Does anyone have a simple method to take off the RF output from these rigs and safely input it to a scope to check the splatter? ?I have a 60 MHz scope but don't know how to use it correctly. ?That might help some of us reduce the spurs until we can learn how to do other mods. There are a lot of scopes out there to beg or borrow, mostly just sitting there in a shack or at a radio club. ?There are two sitting at our club but few know what to do with them. ?Sad story.
Dave K8WPE Try something like this (google Alan Yates Laboratory in category "test equipment"
Jim
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Can anybody please provide PCB overlay of uBitx v3? Thanks and 73s
VU2CMV
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Gould, ?If you see the schematic, especially the 45MHz filter section, you can see their values as Zero. ?Hence? it may not be called missing. all the best ?regards ?sarma vu3zmv
good afternoon all. Just a query please on the v4. on my board there are 2 capacitors missing. these are C210 and C215 is this correct? thanks in advance, PAUL M6feu
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Thanks again Tom for going to the trouble of replying, very much appreciated, and I WILL take your advice
on board.
Take care and hope to talk to you again soon.
Paul
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Paul,
Originally I had thin audio, I installed the CEC firmware and played with the BFO calibration if I recall. The audio was much better after that. Specifically, on the V4 board, if you are referring to the audio from the new audio output circuit, I don't know directly. However, some people were doing a mod to improve the crossover distortion. Search the messages, you should find the fix.
Tom, wb6b
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Tom, Many thanks for that! Cant be too careful!! do you have poor rx audio with your v4
73
Paul M6FEU
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C210 and C216 are missing on my board (it is a older revision). I think that is normal.
Tom, wb6b
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Re: stone soup ingredient list, what bands and modes are usable
In my previous post, I would have more correct if I'd said splatter rather than spurs. The spurs are farther away, you could see them with a waterfall display if you tuned to where they are.
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good afternoon all. Just a query please on the v4. on my board there are 2 capacitors missing. these are C210 and C215 is this correct? thanks in advance, PAUL M6feu
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SM6MOJ
So I offer the challenge to those who know better than I do - please install metal shields round each individual filter and tell us what happens.
You haven't understood the issue or the cause.
Its the wiring under the relays and the way the relays are wired causing much of the grief.
There are pictures of that elsewhere in the forum.
Allison
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Lev,
I am also thinking heavily on a new design!
But what has t be done beforehand is to specify what we want!? I
already posted this requirement but only got minimal response. I
know for EE?s to write a spec is a task which is not welcome...
So some yo Your ideas stated below can be used as a first spec. I
want to include some more thoughts:
use diplexers especially on the IF port of mixers-- bandpass typ
(sereis resonator + parallel resonator) with a relative low loaded
Q (about 3).
I know there is an old paper "reactive loads the big mixer
meanace"? published in the 70?s . Unfortunately I do not have this
paper.
For the first mixer one more thought: in transmit mode the other
sideband (LO + 45 MHz) which has the same amplitude as the wanted
sideband is not terminated properly. So my idea is to put a
lowpass - high pass diplexer the hp side to be terminated into 50
ohms on the RF port of the mixer. ?
For the frist mixer: the configurattion should look like this:
RF port with LP- HP diplexer
IF port with BP diplexer but then a 90 deg hybrid with two xtal
filter branches summing up into a second 90 deg hybrid. In order
to get a good match both fitler branches should have equeal
amplitude (S21) and transmisson phase (Phi21) characteristics.
Then a first bidi amp (low noise would preferrable) but our
normal bidis with 6 dB NF could also work. We do not need a super
low overall NF!? For these bidis we should use appropriiate high
ft transistors as Allison already stated!?
In order to avoid? the still existing problem of the spur
genratoed within the mixer I chose a IF of 70 MHz. XTAL filters
were ordered.
So please have a look on my block diagrammes and total noise
calc.
Before a new pcb is routed (preferrably 100 * 100 mm) the new sub
modules should be characterized. I do have a good equipped home
lab with spectrum analyser, signa l gerator VNA ---).
Henning Weddig
DK5LV
Am 05.09.2018 um 14:59 schrieb Lev:
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So why don't we create a new design? Slightly
more expensive, but a good one. My thoughts:
1. Tuned IFs
2. Filter the output of the LOs
3. Push-pull preamplifier ()
4. RF transistors (BFS17P)
5. PA redesign (normal push pull design, two stage of
IRF530 ) use BFQ19S for drivers
6. More filters on the output
7. Maybe change of the mixers to JFET mixers
I started to put together my own design, so I have some
sketches. I can share if you interested.
On Tue, Sep 4, 2018 at 2:37 AM Warren Allgyer
< allgyer@...>
wrote:
Folks
I refer you to a famous story. It comes in many variations
and this is just one:
I am the last person to discourage experimentation.... it is
what I do, both for a living and for fun. But this is
getting ridiculous.
We have here a platform that literally does nothing well.
Nothing. Its only claims to fame are 1) It is inexpensive
and 2) it is software configurable. The uBitx is a horrible
transmitter, perhaps a worse receiver, bereft of simple
operating niceties like AGC, ALC, preselection filtering,
etc. As it comes out of the box it is illegal for air
operations in most countries in the world. Its receiver has
no front end, no filtering, miserly overall gain, and lousy
audio. The transmitter cannot be put on the air legally and
maintained without thousands of dollars of lab grade test
equipment. Even as a core SSB generator it is 1960's
technology executed badly.
And all of that would not be so bad if it were not for the
fact that it IS put on the air, in the vast majority of
cases, without the necessary lab equipment and testing
simply because it does a lot of bands very inexpensively.
This is the Twinkie offered to a starving child, the
shipping container begging to become a multimillion dollar
condominium,? the tricycle with dreams of winning the Indy
500. All possible..... but all ultimately futile for all but
a persistent, doggedly stubborn few. And the others who try
will simply add to the noise and junk that has become HF
around the world.
Even the narrative that this represents employment for needy
women in a third world country.... even that does not
justify foisting this on amateur radio operators around the
world. Producing garbage does not lift a segment out of
poverty..... it just makes more garbage. It is very, very
disappointing to see the hobby I have loved for 50 years be
reduced to this.
If there was ever an electronic analogue for "Stone Soup",
it is uBitx.
WA8TOD
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The idea of tunable traps is impractical.?
Another example of its simple, it will fix everything. NOT!
Unless you have a inline spec ana how do you know its properly tuned and?
adeqauate suppression????
At best its a poorly applied bandaid, at worst a bad hack.
What does work is a band pass filter as it passes what we know we want.
Another approach is suppress the trash getting into the IF and contributing?
signals we do not want.? See the posting Raj has made it goes more aggressively
down a path I tried and has a significant impact.
Allison
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Farhans method...
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.
Sounds like something that may seriously help. I tried a low pass filter there and it
did help but not enough.? Time and other pressing things never got back to try a
band pass filter.
One I'd liked to have tried is just moving the filter to the other end of the amp.
What is the impact on RX performance?
Allison
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If you guys want to try out the mod, i can have some spares shipped out. - f
On Wed, 5 Sep 2018, 19:06 Gordon Gibby, < ggibby@...> wrote:
?I ordered the pair.? ?Interesting and exciting development.
gordon
Filters suitable (I believe) for this mod are available here for $5.99 for a pair:?
If this solves the spur problem then it is also a very positive step toward solving the overall PA filter issue. Absent the spurs, and with the board layout problems addressed, the existing four filters should be adequate. I am about to receive a prototype
4 filter board that can accept the existing components for testing.?
Very nice work!
WA8TOD
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Re: stone soup ingredient list, what bands and modes are usable
Hi Dave, Gordon created a voltage divider attenuator for his dummy load so he could check harmonics with another receiver, here are the messages where he describes this.? /g/BITX20/message/57979/g/BITX20/message/57974In your case you are trying to feed this into your scope rather than a receiver, so the 16K resistor may be more resistance than you want. You may want to try 5k and 50 ohms so you can still use a 1/4 watt resistor. ?You don't need to put the resistors on a dummy load, you can connect the 50 ohm resistor to the ground of your antenna out and the 5k resistor to the center pin wire of your uBITX antenna output. Although if you are testing, doing so into a dummy load is a good idea.? Looking at the spurs directly requires a spectrum analyzer or a receiver with a waterfall display. That can be a newer transceiver or a SDR dongle. However, you will still see things like the RF waveform flattening or distorting in other ways when the TX RF out is overdriving. So, your scope should be informative and useful for monitoring your TX output. You will get the most reliable display if you first try with a single tone fed into the microphone input rather than a more complex signal like voice. But, you will get a feel for it, as you experiment. I have a little tiny scope that will at least work up to 80m and I'm planning on doing the same thing, just to see what I can see.? Tom, wb6b
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Raj vu2zap
ARNAB SEN VU2CMV