This guy is cheaper (N2CBU ?) but shipping to India is
expensive..
Raj
At 05-09-18, you wrote:
toggle quoted message
Show quoted text
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
|
Re: Grounding shematic for a Metal Chassis, which is the right way to wire up?
I think the optimal solution is an entire metal case. I can talk only about what I did and my case is hybrid, it's metal except for the front and the back panels that are plastic. Why did I choose that? Simply it was nice, the right size and I had it some years taking dust. All connectors are mounted either on the front or on the back panel. I kept things as simple as possible, so the heatsinks are the originals and the board is mounted inside so I don't use the case for thermal cooling. Unless you are certain how to keep insulated the tabs of the finals (which have DC voltage if I am correct) I wouldn't mount the finals to the metal chassis. But that depends also on how you want to use the uBitx. If you use it for RTTY or digital modes, you might need a better cooling, drill holes on the chassis and/or add a vent. I mostly use SSB and CW and what I did was not optimal but adequate. In the case my finals would fail, I will spend 2 euros and half an hour to replace them.
Il 05/set/2018 12:15, "sdr freak" < sdrfreak55@...> ha scritto: @ iz oos
ok, good to hear this, but a few more answer to the problem that i ask for was better ;D
@ WA5ZTD
i was talking about the heatsink from the IRF510, so i read it in this shematic uploaded here in forum, the v.1.9...
i have no picture or shematic for the grounding should be, that's what i ask for! my problem is that i doesn't have one! i need a couple of information about this whole things about, like grouding the metal case, what about avoid grounding loops and for important the wire up with the jacks and their sleeves in front of the grounded case.. these are my problems, when i say it shortly,... today i've tried to say it shortly
so please have anyone a few info about, please?
|
Re: CW PTT attack time to slow
#ubitx
Joop and all, yes, that is the proper value to set it. ?When that software was written we didn't think that the uBITX would be used for contesting and we have now been proven wrong - LOL. ?Making that number smaller shortens the transition time between TX and RX, larger lengthens the time. ?You don't want to get it too short though as that will overwork the relays. ?Remember, the uBITX is NOT capable of full break-in (QSK) on CW because relays are being used for T/R switching. ?Get that delay too short and your relays won't last long using CW.
Jim Sheldon for the TSW team
------ Original Message ------
Sent: 9/5/2018 6:05:06 AM
Subject: Re: [BITX20] CW PTT attack time to slow #ubitx
Howdy,
today I have had a go at W0EB¡¯s firmware version together with a I2C LCD display. Using the I2C bus frees up a number of digital and analog lines. A dedicated digital line is used for straight key input (I am using an external keyer). Also, using software interrupts improves keying responsiveness. I no longer have missing dits and dahs¡
One thing I am missing in this firmware version: there is no way to set PTT delay, that is the time it takes to go from transmit to receiver. It is much to long, especially for contesting.
It looks like it is hardcoded: #define CW_TIMEOUT (350l) in ubitx.h
Regards, Joop PG4I
Op 1 sep. 2018, om 04:10 heeft W2CTX < w2ctx@...> het volgende geschreven:
On??webpage is NANO software that implements interrupt driven CW generation.? Also
eliminates the voltage divider scheme.? Also eliminates the need to switch between straight key?
and paddle as both are always active.
rOn
|
Warren has a point and an opinion. He has raised an issue and we are trying to fix it. His way of saying i probably rufflea some feathers, but lets do a minmal reading of how he is saying it and hear what he is saying.. It is upto each of us to fix the harmonics and spurs.? Raj has found a way to fix the spurs. I have independently confirmed it. So, we are one down and one to go. Harmonics will be an easier fix. My parenta health issuea continue to eat into my bench time, hopefully we will be able ride this out and get back on the bench in a few days more.?
73, and get some of the awesome weather.?
- f
On Wed, 5 Sep 2018, 17:26 Praba Karan, < vu3dxr@...> wrote: Typical colonial thinking....
On Tue, Sep 4, 2018, 6:07 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
|
Typical colonial thinking....
On Tue, Sep 4, 2018, 6:07 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
|
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
|
Further experimentation with Farhan's method,
Instead of removing R27 47Ohms and putting the filter there. I removed
C22
and soldered the filter there.
The spurs on 20 dropped even lower @5W the spurs were -55 to -60dbm!
With proper termination the results may be better!
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.
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.
|
A a big thanks to Farhan, Allison and earlier to Jerry!
Cheers
Raj
At 05-09-18, you wrote:
toggle quoted message
Show quoted text
I have tried the spur-zap fix.
It really works. We need a big shout out to Raj, VU2ZAP. He has endlessly
measured, tabulated but never given up on hunting this spur down.
I have tried it this morning too. Here are my results. I took out the
R27, it is the 47 ohm series resistor that connects the tx side IF p to
the front end mixer. In its place, i soldered the two ends of a spare 45
mhz filter. The ground pin of the filter was soldered to the ground end
of C11.
73, f.?
On Wed, 5 Sep 2018, 14:28 Lev,
<leventelist@...>
wrote:
- Would that be a good solution to make the IF amplifier tuned? Like
this? Also, change the transistors to BFS17P, this is more suited to
RF.
- 73s de HA5OGL
- On Wed, Sep 5, 2018 at 10:46 AM Raj vu2zap
<
rajendrakumargg@...> wrote:
- 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!
- --
- Raj, vu2zap
- Bengaluru, South India.
|
It is a idea to try Lev.. will give it a thought.
Raj
At 05-09-18, you wrote:
toggle quoted message
Show quoted text
Would that be a good solution to
make the IF amplifier tuned? Like this? Also, change the transistors to
BFS17P, this is more suited to RF.
73s de HA5OGL
On Wed, Sep 5, 2018 at 10:46 AM Raj vu2zap
<
rajendrakumargg@...> wrote:
- 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!
- --
- Raj, vu2zap
- Bengaluru, South India.
Content-Type: application/pdf; name="if_amp-if_amp.pdf"
Content-Disposition: attachment;
filename="if_amp-if_amp.pdf"
Content-ID: <f_jlowtrh20>
X-Attachment-Id: f_jlowtrh20
|
Hi Henning,
I did try a filter but did not help much, I guess this issue needed a
filter with greater end stop.
Allison said she tried a filter and found improvement.
I originally visualized a pad with LC matching with xtal conditioning
filter. The pad would keep
the mixer peaceful and the BiDi will be happy with LC. Have to try this
in the next days.
What I felt is that the BiDi was amping the TX signal that it picked up
and sending to the
first mixer. When I lowered th power the spurs came down much more..
The spurs were moving together and apart in 3x 4x and 5x of the change in
VFO freq.
They came together every 2.5 Mhz and were worst behaved at 15MHz and
22.5MHz
Raj
At 05-09-18, you wrote:
toggle quoted message
Show quoted text
Raj,
Your mod verifies my suspicion: apart form the mixing products within the
mixer harmonics of the TX Bidi amp in front of the mixer also contribute
to the problem, i.e. the first harmonic of the BiDI amp (2*45 MHz = 90
MHz!!!).
Placing an xtal filter directly into the path without any impedance
transformation is a bad idea, the filter itself wants to see a higher
impedance than 50 ohms. If this filter is not terminated correctly its
insertion loss and passband ripple will be "ugly".
In addition: the connection from R27 to the transformer T2 will produce a
source impedance close to 50 ohms. The output of the emitter follower Q21
is low impedance. PLUS: any complex load (especially capacitive) can
cause Q21 to oscillate! A coure would then be a series resistor ( e.g.
100 ohms or so) to the base of Q21 .???
As the bidiamp produces harmoncis it would be easier to place a low pass
filter (corner freq. a bit larger than 45 Mhz but "good"???
attenaution at 90 MHz). A small pcb with good grounding should do--???
please test this small pcb for real attenuation @90 MHz or if available a
"commercial low pass filter e.g. from Mini Circuits could also do
the trick for just a test.
A" fast design" using RFSIM99 for a 50 MHz five pole low pass
filter (chebychev, 0.1 dB ripple, 50 ohm impedance)??? C-L-C-L-C gives
the following component values: 73 pF 218 nH 125 pF 218 nH 73 pf. The
simulated attenuation at 90 MHz is 30 dB.???
73
Henning Weddig
DK5LV???
Am 05.09.2018 um 10:46 schrieb Raj vu2zap:
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!
--
Raj, vu2zap
Bengaluru, South India.
|
Re: CW PTT attack time to slow
#ubitx
Howdy,
today I have had a go at W0EB¡¯s firmware version together with a I2C LCD display. Using the I2C bus frees up a number of digital and analog lines. A dedicated digital line is used for straight key input (I am using an external keyer). Also, using software interrupts improves keying responsiveness. I no longer have missing dits and dahs¡
One thing I am missing in this firmware version: there is no way to set PTT delay, that is the time it takes to go from transmit to receiver. It is much to long, especially for contesting.
It looks like it is hardcoded: #define CW_TIMEOUT (350l) in ubitx.h
Regards, Joop PG4I
toggle quoted message
Show quoted text
Op 1 sep. 2018, om 04:10 heeft W2CTX < w2ctx@...> het volgende geschreven:
On??webpage is NANO software that implements interrupt driven CW generation.? Also
eliminates the voltage divider scheme.? Also eliminates the need to switch between straight key?
and paddle as both are always active.
rOn
|
Raj,
Your mod verifies my suspicion: apart form the mixing products
within the mixer harmonics of the TX Bidi amp in front of the
mixer also contribute to the problem, i.e. the first harmonic of
the BiDI amp (2*45 MHz = 90 MHz!!!).
Placing an xtal filter directly into the path without any
impedance transformation is a bad idea, the filter itself wants to
see a higher impedance than 50 ohms. If this filter is not
terminated correctly its insertion loss and passband ripple will
be "ugly".
In addition: the connection from R27 to the transformer T2 will
produce a source impedance close to 50 ohms. The output of the
emitter follower Q21 is low impedance. PLUS: any complex load
(especially capacitive) can cause Q21 to oscillate! A coure would
then be a series resistor ( e.g. 100 ohms or so) to the base of
Q21 .???
As the bidiamp produces harmoncis it would be easier to place a
low pass filter (corner freq. a bit larger than 45 Mhz but "good"???
attenaution at 90 MHz). A small pcb with good grounding should
do--??? please test this small pcb for real attenuation @90 MHz or
if available a "commercial low pass filter e.g. from Mini Circuits
could also do the trick for just a test.
A" fast design" using RFSIM99 for a 50 MHz five pole low pass
filter (chebychev, 0.1 dB ripple, 50 ohm impedance)??? C-L-C-L-C
gives the following component values: 73 pF 218 nH 125 pF 218 nH
73 pf. The simulated attenuation at 90 MHz is 30 dB.???
73
Henning Weddig
DK5LV???
Am 05.09.2018 um 10:46 schrieb Raj
vu2zap:
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!
--
Raj, vu2zap
Bengaluru, South India.
|
Re: stone soup ingredient list, what bands and modes are usable
On Tue, 04 Sep 2018 19:54:11 -0700 "Tom, wb6b" <wb6b@...> wrote: Thanks Tom, great tips. Saved this email for future reference. Joe On Tue, Sep 4, 2018 at 07:42 AM, ajparent1/KB1GMX wrote:
########################
80m harmonics, use external low pass filter
60m harmonics, use external low pass filter
40m harmonics, use external low pass filter
30m should be ok cw and SSB-digital
20m should be ok all modes
17m should be ok all modes.
15m CW ok, SSB has spur
12m CW ok, SSB has spur
10m CW ok, SSB has spur?
##########################
This is great, it means the two bands I'm interested in, 30m and 20m, are good to go.?
If I followed the various threads correctly, on 80 through 40 meters, CW was the big offender for harmonics, but SSB was not much better.
If people overdrive the TX on SSB, that is not the radio's fault. I imagine there are people overdriving and splattering all over the place with their multi grand super deluxe transceivers, by attaching all manner of add-on microphone audio processors to get more "punch".
Without any expensive equipment at all, there are multiple ways to see if you are overdriving the transmitter.
An SWR/Power meter. Increase audio until power increase flattens out and back off 20 percent.
Use a lightbulb (24+ volts, low current in parallel with a dummy load [or gasp -- antenna]) and do the same judging from the lightbulb brightness.?
Do basically the same measuring the RF voltage.
Use a nearby SDR dongle, with antenna disconnected, and look at your signal output and see where the spurs and splatter start to increase and back off the audio level.
Tom, wb6b
|
At last, my ?BITX is configured and I can use it for local contacts on 80 m, together with a Pi-filter antenna matcher and a G5RV antenna. The band is quiet at 09.00 local time and I am not likely to annoy anybody with spurious emissions.
The discussions about filters and spurious emissions go right over my head, since I do not have access to a lot of expensive lab gear. This can be left to those who have access to equipment and better knowledge than I have.
I bought a Wehrmacht receiver about 20 years ago. Although it was then about 50 years old, its calibration was still spot-on. It was quite simple, electrically, but was ruggedized and field-serviceable. Many of the components were located in individual diecast aluminium enclosures. Thinking about the discussion about ?BITX filters, I realised that it would be reasonable to assume that the cross-talk etc. that people complain about could be cured or reduced by putting each filter unit in its own metal box.
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.
While you are at it, you could also test rigs like the HW-7 or HW-8 and tell us about their spurious emissions.
|
Re: Ubitx version 4 speaker impedance?
|
Re: Ubitx version 4 speaker impedance?
I went ahead and just ordered them. For that price it's worth the shot. I also found these little grills that should work. Should look better than drilling a bunch of holes for a $1.33
--
Barrett
K5SSO
|
Re: Grounding shematic for a Metal Chassis, which is the right way to wire up?
@ iz oos
ok, good to hear this, but a few more answer to the problem that i ask for was better ;D
@ WA5ZTD
i was talking about the heatsink from the IRF510, so i read it in this shematic uploaded here in forum, the v.1.9...
i have no picture or shematic for the grounding should be, that's what i ask for! my problem is that i doesn't have one! i need a couple of information about this whole things about, like grouding the metal case, what about avoid grounding loops and for important the wire up with the jacks and their sleeves in front of the grounded case.. these are my problems, when i say it shortly,... today i've tried to say it shortly
so please have anyone a few info about, please?
|
I have tried the spur-zap fix. It really works. We need a big shout out to Raj, VU2ZAP. He has endlessly measured, tabulated but never given up on hunting this spur down. I have tried it this morning too. Here are my results. I took out the R27, it is the 47 ohm series resistor that connects the tx side IF p to the front end mixer. In its place, i soldered the two ends of a spare 45 mhz filter. The ground pin of the filter was soldered to the ground end of C11.
73, f.?
Would that be a good solution to make the IF amplifier tuned? Like this? Also, change the transistors to BFS17P, this is more suited to RF.
73s de HA5OGL
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!
--
Raj, vu2zap
Bengaluru, South India.
|
Would that be a good solution to make the IF amplifier tuned? Like this? Also, change the transistors to BFS17P, this is more suited to RF.
73s de HA5OGL
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!
--
Raj, vu2zap
Bengaluru, South India.
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Re: stone soup ingredient list, what bands and modes are usable
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
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On Sep 4, 2018, at 3:13 PM, Jerry Gaffke via Groups.Io < jgaffke@...> wrote: We should have some way to indicate when too much mike gain is applied. A diode, cap and resistor watching either audio or IF or RF peak signal levels, sending that to a Nano analog pin should be sufficient.? Firmware shows a warning in the LCD if level exceeded. I'd go with that, and a pot for mike gain. If you insist on ALC:? /g/BITX20/message/56796? Jerry On Tue, Sep 4, 2018 at 10:45 AM, Warren Allgyer wrote:
Your analysis is true so long as the tones, or the voice if that is your mode, do not overmodulate either the audio or the RF chain. In the case of the uBitx running 10 watts of SSB, whether it is voice or tones, one or both of those stages are significantly over-modulated to the extent they put splatter into the adjacent channels on either side. This splatter will not affect anyone listening to the SSB channel but will dramatically affect those 3 KHz up and down from that channel. The effect is far worse than on a full-featured SSB transceiver in that there is no ALC or compression to control the level.
My unit, a sample of one, over-modulates at any power level greater than 1.5 watts. Most do not care as you can hear most days on 7200 KHz..... but for those who do, you are on notice.
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Raj vu2zap
Jim Sheldon
sdr freak
