Re: uBITx v5 - with mods

Jerry Gaffke

Ravi,

Your equations look correct, though this might be a more concise description of the math involved:
https://groups.io/g/BITX20/message/44515

That was for a uBitx-v3, so had the 12mhz IF crystals, not 11.052mhz.
Those IF crystals get sorted at hfsignals into bins by frequency such that all crystals
used in any given rig are of the same frequency within perhaps 100hz or better.
Between rigs using crystals from different sorting bins, the 12mhz (or 11.0592mhz)
crystal filter can vary from rig to rig by a khz or so.
Some have found that the rig sounds better if the BFO is moved away
from its factory value by a few hundred hz.

Likewise, the center frequency of 45mhz filter might vary by a few khz,
but it is wide enough that you probably would not notice any reduced sensitivity
or change in audio quality without a direct A/B test.

An RF preamp may be needed to hear much if operating with a short whip.

Several here have played with different si5351 output drive levels and came to
different conclusions.  This can affect signal levels and birdies, but generally isn't critical.
The ideal settings might vary a bit from rig to rig, and your local incoming RF levels.

Posts 35235 and 54501 describe a calibration procedure that might be of interest.

Jerry, KE7ER

On Mon, Jun 10, 2019 at 06:09 AM, Ravi Miranda wrote:
Hi Sarma, Farhan, Curt,

Thank you all for replying so quickly. I have carried out the following:

a. I have used KD8CEC v1.20 for uBITx V5
b. The #define has been set for V5
c. I have an approx. 100mV signal now (10MHz) and injected that. On
hearing low output at the output, I proceeded to do the math to
calculate the values at each stage.

Here are the equations used. Assuming USB

1. IF_A_FREQ = VFO FREQ - INP_FREQ [IF_A_FREQ ---- should be a value
of 45MHz so that it can get through the 45 MHz crystal filter
+/-7.5Khz]
2. OP_FREQUENCY = IF_LOCAL_OSC - IF_A_FREQ [OP_FREQUENCY ---- should
be centred on 11.0592 000 (or thereabouts) to get through the Ladder
filter
3. AUDIO_OUT = BFO_FREQUENCY - OP_FREQUENCY [If both match correctly,
we get a ZERO Beat] if the BFO_FREQUENCY > OP_FREQUENCY we get LSB and
the other way we get USB.

Using these calculations, I arrived at a frequency difference of 6660
[strange number if you get the drift :-) ] No pun intended.

With no calibration, I got nothing, not surprising as the frequency was way off.

Using a frequency meter, I set the calibration of the XTAL from
25.000.000 to 25.003.090 (This value was found using
https://groups.io/g/BITX20/wiki/Si5351-Calibration-Sketch)
The pitch of the tone may have changed, not sure at this stage it was very late.

Using the IF Shift menu option I moved the IFShift to 6660, and the
tone was clearly there. [LOUD]

Having set this right (so far), I tried the whip antenna in the
balcony (sorry no dipole). There are no signals to be heard at all. So
I have the following questions.
1. Should I change the VFO base frequency to 45.005.000 (given that
the two inductances at both sides are pulling the crystal filter off?
If so what is the best value to set this to, and where in the program
2. Are the equations above correct
3. Instead of the IFShift of 6600 should I be thinking of changing the
#define SECOND_OSC_USB (56054200l)
#define SECOND_OSC_LSB (33940800l)
to better take into account the shift and therefore bring the shift
(as shown in pt.3 above to 0)
4. To improve reception of signals with my antenna, should I add an RF
preamp prior to the antenna input? This could be switched in via a
relay and not kept in the transmit path (not really sure here as I
haven't managed to test transmit section yet.
5. What are the effects of setting lower or higher current values for
SI5351(2,4,6,8)

Is there a worked example that has
a. BASE_VFO_FREQUENCY
b. USB_FREQUENCY
c. LSB_FREQUENCY
d. BFO_FREQUENCY

I can then use the calibration program to generate these three signals
and do measurements?

Many thanks for taking time to help me with this.

Best 73,

Ravi/M0RVI

Re: uBITx v5 - with mods

Ravi Miranda

Jerry/KE7ER

Many thanks for your help. Will have a look and report back.

Best 73,

Ravi/M0RVI

On Mon, 10 Jun 2019 at 16:51, Jerry Gaffke via Groups.Io
<jgaffke=yahoo.com@groups.io> wrote:

Ravi,

Your equations look correct, though this might be a more concise description of the math involved:
https://groups.io/g/BITX20/message/44515

That was for a uBitx-v3, so had the 12mhz IF crystals, not 11.052mhz.
Those IF crystals get sorted at hfsignals into bins by frequency such that all crystals
used in any given rig are of the same frequency within perhaps 100hz or better.
Between rigs using crystals from different sorting bins, the 12mhz (or 11.0592mhz)
crystal filter can vary from rig to rig by a khz or so.
Some have found that the rig sounds better if the BFO is moved away
from its factory value by a few hundred hz.

Likewise, the center frequency of 45mhz filter might vary by a few khz,
but it is wide enough that you probably would not notice any reduced sensitivity
or change in audio quality without a direct A/B test.

An RF preamp may be needed to hear much if operating with a short whip.

Several here have played with different si5351 output drive levels and came to
different conclusions. This can affect signal levels and birdies, but generally isn't critical.
The ideal settings might vary a bit from rig to rig, and your local incoming RF levels.

Posts 35235 and 54501 describe a calibration procedure that might be of interest.

Jerry, KE7ER

On Mon, Jun 10, 2019 at 06:09 AM, Ravi Miranda wrote:

Hi Sarma, Farhan, Curt,

Thank you all for replying so quickly. I have carried out the following:

a. I have used KD8CEC v1.20 for uBITx V5
b. The #define has been set for V5
c. I have an approx. 100mV signal now (10MHz) and injected that. On
hearing low output at the output, I proceeded to do the math to
calculate the values at each stage.

Here are the equations used. Assuming USB

1. IF_A_FREQ = VFO FREQ - INP_FREQ [IF_A_FREQ ---- should be a value
of 45MHz so that it can get through the 45 MHz crystal filter
+/-7.5Khz]
2. OP_FREQUENCY = IF_LOCAL_OSC - IF_A_FREQ [OP_FREQUENCY ---- should
be centred on 11.0592 000 (or thereabouts) to get through the Ladder
filter
3. AUDIO_OUT = BFO_FREQUENCY - OP_FREQUENCY [If both match correctly,
we get a ZERO Beat] if the BFO_FREQUENCY > OP_FREQUENCY we get LSB and
the other way we get USB.

Using these calculations, I arrived at a frequency difference of 6660
[strange number if you get the drift :-) ] No pun intended.

With no calibration, I got nothing, not surprising as the frequency was way off.

Using a frequency meter, I set the calibration of the XTAL from
25.000.000 to 25.003.090 (This value was found using
https://groups.io/g/BITX20/wiki/Si5351-Calibration-Sketch)
The pitch of the tone may have changed, not sure at this stage it was very late.

Using the IF Shift menu option I moved the IFShift to 6660, and the
tone was clearly there. [LOUD]

Having set this right (so far), I tried the whip antenna in the
balcony (sorry no dipole). There are no signals to be heard at all. So
I have the following questions.
1. Should I change the VFO base frequency to 45.005.000 (given that
the two inductances at both sides are pulling the crystal filter off?
If so what is the best value to set this to, and where in the program
2. Are the equations above correct
3. Instead of the IFShift of 6600 should I be thinking of changing the
#define SECOND_OSC_USB (56054200l)
#define SECOND_OSC_LSB (33940800l)
to better take into account the shift and therefore bring the shift
(as shown in pt.3 above to 0)
4. To improve reception of signals with my antenna, should I add an RF
preamp prior to the antenna input? This could be switched in via a
relay and not kept in the transmit path (not really sure here as I
haven't managed to test transmit section yet.
5. What are the effects of setting lower or higher current values for
SI5351(2,4,6,8)

Is there a worked example that has
a. BASE_VFO_FREQUENCY
b. USB_FREQUENCY
c. LSB_FREQUENCY
d. BFO_FREQUENCY

I can then use the calibration program to generate these three signals
and do measurements?

Many thanks for taking time to help me with this.

Best 73,

Ravi/M0RVI

--
I'm here to add more value to the world than I'm using up.

Re: Mounting Low Pass Filter Relays On Bottom of Circuit Board

Nick VK4PP

IF you place them on the bottom, it makes re-wiring them as per Alisons wiki entry, for better routing and that makes a difference....
73 Nick VK4PP

Re: Installing BCI and Kit-Projects AGC

Joel Trenalone

Thanks so much for all the information :)

Now I understand how it works. I’m inclined to install the BCI before the AGC, except that the Kit-Projects board is designed so nice as to fit like a puzzle piece so nicely as the instructions show. There is really no other spot that works as good.

If i if I can figure out another point to intercept the receive rf for the BCI that puts it before the AGC I would do it, but I’m not seeing any good places.

Re: Installing BCI and Kit-Projects AGC

KE2GKB

Which BCI are you using? I can take a look my self! I sadly know the layout acceptable well for now :)

-- Tim Keller - KE2GKB https://shop.kit-projects.com

Re: Installing BCI and Kit-Projects AGC

Joel Trenalone

I have ordered the qrpme kit here (haven’t received it yet):
http://qrpme.com/?p=product&id=BCI

And by the way the AM interference is pretty strong, enough that I can’t really use the radio until I get it filtered.

Re: Installing BCI and Kit-Projects AGC

Curt

Joel

obviously test the filter to see how well it works before working hard to integrate it.  and take advantage of natural integration of the AGC board.  I am confident you would find a way somehow.  also okay to experiment to 'prove' I am wrong with my recommendation.

Tim

Its the intermodulation of huge signals that reach the MOSFETs up front in the AGC that would concern me.  When they get a strong bias to be completely on or off they may have okay performance, but a bias voltage in between often makes it more susceptible.  yes the mosfets behave like a resistor, but there is also a transistor junction there that can operate like a mixer - not the behavior we want.  I imagine in the vast majority of cases the ubitx operator may not need a BCI filter - but in Joel's case he clearly thinks he needs it.

Experiment on.  Results are generally 'numeric' and actual operation will tell the truth.

Curt

Re: Installing BCI and Kit-Projects AGC

KE2GKB

Curt we are on the same page! I actually have a rather loud SWL station near me at 7.300 that loves to blow out my front end. My comments were more on the unless it gets through into the audio output the agc will not react specifically to the loud adjacent station in the IF passband!

-- Tim Keller - KE2GKB https://shop.kit-projects.com

Re: Installing BCI and Kit-Projects AGC

Jack, W8TEE

If the AM is domestic, the BCI filter I used works well. Here is the schematic:

and the response plot:

Insertion loss is small and I used axial inductors purchased from Tayda Electronics. I think the total cost was under \$1 for a QRP version. For a 100W model, I used toroids and silver mica caps; details at A Cheap and Easy BCI Filter, CQ Magazine, August, 2016.

Jack, W8TEE

On Monday, June 10, 2019, 9:08:30 PM EDT, Joel Trenalone via Groups.Io <jtrenalone@...> wrote:

I have ordered the qrpme kit here (haven’t received it yet):
http://qrpme.com/?p=product&id=BCI

And by the way the AM interference is pretty strong, enough that I can’t really use the radio until I get it filtered.

Re: Installing BCI and Kit-Projects AGC

Joel Trenalone

Curt,
I think I will take your advice and install the Kit-Projects AGC in the location it is supposed to go. Then I’ll try the BCI after the AGC and see how it works. The local broadcast only interferes when the antenna is hooked up, so maybe it will be fine. But if not I can see if there is another location ahead of the AGC to put it.

Jack,
thanks for the schematic. If the filter I ordered is not enough I will try yours. Hopefully ill I’ll get the filter this week and try it out.

I do have fun experimenting, but I just don’t want to break anything :)

AGC Circuit for uBITX Featured in July 2019 QST Magazine

Dennis Zabawa

On page 45 of the July 2019 issue of QST magazine there is an article on an AGC Circuit for uBITX.  The circuit replaces the uBITX audio amp and adds the AGC functionality.

Re: AGC Circuit for uBITX Featured in July 2019 QST Magazine

Curt

Cool maybe.  Remember this list is global -- many in India, Europe, Asia, South America, even Canada don't have access to QST (nor do I - my copy hasn't arrived yet) --

can you at least mention the type of audio amplifier, how they are implementing AGC and anything else that is different about this mechanization?

please think global -- the US may be 'central' to me -- but not everyone here.

Curt

Re: AGC Circuit for uBITX Featured in July 2019 QST Magazine

pat griffin

I have only glanced at the circuit but it appears similar to the various ubitx agc circuits we have seen with some nice enhancements.  In fact, the author, K1BQT (email: k1bqt at arrl dot net), built it for a ubitx.  It uses 2n5486, 2N7000 and LM386.
73, AA4PG

http://www.cahabatechnology.com/aa4pg.html

From: BITX20@groups.io <BITX20@groups.io> on behalf of Curt via Groups.Io <wb8yyy@...>
Sent: Tuesday, June 11, 2019 6:37 AM
To: BITX20@groups.io
Subject: Re: [BITX20] AGC Circuit for uBITX Featured in July 2019 QST Magazine

Cool maybe.  Remember this list is global -- many in India, Europe, Asia, South America, even Canada don't have access to QST (nor do I - my copy hasn't arrived yet) --

can you at least mention the type of audio amplifier, how they are implementing AGC and anything else that is different about this mechanization?

please think global -- the US may be 'central' to me -- but not everyone here.

Curt

Re: AGC Circuit for uBITX Featured in July 2019 QST Magazine

Jack, W8TEE

The JackAl circuit has both audio and IF AGC, is Open Source, and designed for the µBITX. The manuals can be downloaded from QRP Guys. Anyone who wants to build it is free to do so. See attached.

Jack, W8TEE

On Tuesday, June 11, 2019, 9:59:21 AM EDT, pat griffin <patgriffin@...> wrote:

I have only glanced at the circuit but it appears similar to the various ubitx agc circuits we have seen with some nice enhancements.  In fact, the author, K1BQT (email: k1bqt at arrl dot net), built it for a ubitx.  It uses 2n5486, 2N7000 and LM386.
73, AA4PG

_._,_._,_

jsternmd

Just got the beautiful, high quality UBitx case for 5: Nextion and assembling.  One thing I notice is that for the many panel mounted components (pots, Mic, Key, Power, etc) there is no ground to the metal case to act as a single ground point.   I am tempted to grind away inside the panels to bare metal and then make sure the UBitx is mounted with an adequate ground to the case.  Has anyone NOT bothered to do this and how is your performance?  No looking for shortcuts but grinding to bare metal will take a lot of time and dust!

TIA  Jerry NY2KW

Ravi Miranda

Hi Jerry,

https://petetest2017.files.wordpress.com/2018/11/grounding-modification.pdf

Hope this helps?

Ravi/M0RVI

On Tue, 11 Jun 2019 at 16:47, jsternmd <jsternmd@...> wrote:

Just got the beautiful, high quality UBitx case for 5: Nextion and assembling. One thing I notice is that for the many panel mounted components (pots, Mic, Key, Power, etc) there is no ground to the metal case to act as a single ground point. I am tempted to grind away inside the panels to bare metal and then make sure the UBitx is mounted with an adequate ground to the case. Has anyone NOT bothered to do this and how is your performance? No looking for shortcuts but grinding to bare metal will take a lot of time and dust!

TIA Jerry NY2KW
--
I'm here to add more value to the world than I'm using up.

Joe Puma

I have done this. Using a dremel I grinded around  the screw holes from inside for all the case parts and grinded the holes where jacks, pots, antenna ports connect. I did notice a before and after while dong it as far as noise from raduino, nextion screen and RF issues.

Definitely worth doing. I suggested to Sunil to have these contact points tapped off before painting. From what I understand, it’s not so simple. Dremel away.

Joe
Kd2nfc

On Jun 11, 2019, at 11:47 AM, jsternmd <jsternmd@...> wrote:

Just got the beautiful, high quality UBitx case for 5: Nextion and assembling.  One thing I notice is that for the many panel mounted components (pots, Mic, Key, Power, etc) there is no ground to the metal case to act as a single ground point.   I am tempted to grind away inside the panels to bare metal and then make sure the UBitx is mounted with an adequate ground to the case.  Has anyone NOT bothered to do this and how is your performance?  No looking for shortcuts but grinding to bare metal will take a lot of time and dust!

TIA  Jerry NY2KW

Re: AGC Circuit for uBITX Featured in July 2019 QST Magazine

The advantage of the JackAL is that it is a true AGC, controlling the gain of the AF and RF stages of the radio… and thus preventing overload and distortion of the RF stages before the audio gain adjustment.  The circuit in the in QST is just a simple volume control/ limiter that could work on “any audio line” to keep the volume below a specified point.

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Jack Purdum via Groups.Io
Sent: Tuesday, June 11, 2019 9:11 AM
To: BITX20@groups.io
Subject: Re: [BITX20] AGC Circuit for uBITX Featured in July 2019 QST Magazine

The JackAl circuit has both audio and IF AGC, is Open Source, and designed for the µBITX. The manuals can be downloaded from QRP Guys. Anyone who wants to build it is free to do so. See attached.

Jack, W8TEE

On Tuesday, June 11, 2019, 9:59:21 AM EDT, pat griffin <patgriffin@...> wrote:

I have only glanced at the circuit but it appears similar to the various ubitx agc circuits we have seen with some nice enhancements.  In fact, the author, K1BQT (email: k1bqt at arrl dot net), built it for a ubitx.  It uses 2n5486, 2N7000 and LM386.

73, AA4PG

 Virus-free. www.avg.com

--

…_. _._

Curt

Ravi, Joe - good info - I remember doing something to expose some metal on the nice case.

remember this is a DIY project -- Sunil would be happy to have us expose some metal wherever we deem suitable!  we have the technology (use a drill bit slightly larger than the hole or whatever one might have).

enjoy the nice hardware, from India and other parts of the globe!

Curt