¿ªÔÆÌåÓý

  1. BITX20
  2. Messages
Expanded Topics Messages Polls
Date
Re: a simple spur fix

 

To drastically increase the Q and thus the notch depending on whether the circuit is in series or in parallel one can lower or increase the impedance of the filters with impedance transformers at the input and the output of the filter. It would add complexity and likely lower the TX output.


Il 10/nov/2018 07:20, "iz oos" <and2oosiz2@...> ha scritto:

Right Brian, I don't really understand that as well. Maybe it might make sense but I should see how the schematics would be. The 91mhz might make sense to notch out the harmonics of 45mhz if this is the cause of the spur. Apart from the resonances I would look at the Q factor as well.


Il 09/nov/2018 21:49, "Brian L. Davis" <brianldavis@...> ha scritto:
10pf series with .3uhy - resonant about 91 MHz
47pf series with 5.0uhy resonant about 10.4 MHz
Is this correct?
Brian - WA5RDG

Re: a simple spur fix

 

Right Brian, I don't really understand that as well. Maybe it might make sense but I should see how the schematics would be. The 91mhz might make sense to notch out the harmonics of 45mhz if this is the cause of the spur. Apart from the resonances I would look at the Q factor as well.


Il 09/nov/2018 21:49, "Brian L. Davis" <brianldavis@...> ha scritto:
10pf series with .3uhy - resonant about 91 MHz
47pf series with 5.0uhy resonant about 10.4 MHz
Is this correct?
Brian - WA5RDG

Re: wanted: ND6T AGC kit

 

Received the circuit board from a group member! Thank you!

Darryl
Re: a simple spur fix

 

you are right jerry. i remember encountering this ... back to the bench to try this out...
- f

On Sat, 10 Nov 2018, 10:07 Jerry Gaffke via Groups.Io <jgaffke=[email protected] wrote:
How did you arrive at 47pF and 5uH for 12mhz?
freq = 1/(2*pi*sqrt(L*C)) = 1/(2*pi*sqrt(47e-12 * 5e-6)) =?10382123 Hz
Though that 30mhz LPF is a fairly complicated network to hang an LC trap on,
there may be more going on here.?

The 12mhz trap my not be needed if you reduce the loading on the si5351 clocks
since this would reduce crosstalk between clocks within the si5351.
?
Table 3, "DC Characteristics", in the si5351 datasheet says the output impedance is 50 ohms.
My best guess is that this means there is effectively a series 50 ohm resistor between the?
CMOS driver and the output pin.? If you then put a 50 ohm external load to ground on it and?
the driver is trying to drive high to 3v, then the expected current would be 3v/(50+50ohms) = 30ma.
But the output driver is limited to 8ma, so that output will be current starved.
And with three clocks all working hard as they possibly can, the crosstalk is pretty bad on the si5351.
So we want an external load that's more than 50 ohms on the si5351 clock pin,
but we want the mixer to see a 50 ohm source impedance to avoid reflections.
A pi network resistive attenuator is not a good choice.

I suggest each si5351 clock pin drive a series DC blocking cap and a series 100 ohm resistor
into the mixer port.? Assuming the si5351 has not hit its 8ma current limit, the mixer will
see a source impedance of 50 ohms (internal to the si5351) plus that 100 ohm resistor, so 150 ohms.
Add a 75 ohm resistor from mixer port to ground, that in parallel with 150 ohms makes
it a 50 ohm source impedance for the mixer.

Jerry, KE7ER

it?


On Fri, Nov 9, 2018 at 05:53 PM, Ashhar Farhan wrote:
allison and others,
?
the traps are capable of adding a notch of -20 db. so even if you don't hit the bottom precisely, a 10 db reduction is all that is necessary to clean it up to the required level.
?
these are meant to be fixes that work with existing boards : from v1 onwards. i tried to choose a method that was easy to do.
we will need a different post mix if amp design going forward
yes the traps are for 90 mhz and 12 mhz.
?
the 10 mhz insensitivity is something i will look into today, I havent experienced it. perhaps we should move the trap to tx filters for the 21 mhz to 28 mhz band? the 12 mhz is filtered for the lower bands in any case.
?
the other place to apply the 12 mhz trap would be the local oscillator output?
?
another simple mod to be applied is to change R26 and R46 from 470 ohms to 220. the darlington pair was having insufficient current adding to distortion woes.
?
Re: a simple spur fix

 

How did you arrive at 47pF and 5uH for 12mhz?
freq = 1/(2*pi*sqrt(L*C)) = 1/(2*pi*sqrt(47e-12 * 5e-6)) =?10382123 Hz
Though that 30mhz LPF is a fairly complicated network to hang an LC trap on,
there may be more going on here.?

The 12mhz trap my not be needed if you reduce the loading on the si5351 clocks
since this would reduce crosstalk between clocks within the si5351.
?
Table 3, "DC Characteristics", in the si5351 datasheet says the output impedance is 50 ohms.
My best guess is that this means there is effectively a series 50 ohm resistor between the?
CMOS driver and the output pin.? If you then put a 50 ohm external load to ground on it and?
the driver is trying to drive high to 3v, then the expected current would be 3v/(50+50ohms) = 30ma.
But the output driver is limited to 8ma, so that output will be current starved.
And with three clocks all working hard as they possibly can, the crosstalk is pretty bad on the si5351.
So we want an external load that's more than 50 ohms on the si5351 clock pin,
but we want the mixer to see a 50 ohm source impedance to avoid reflections.
A pi network resistive attenuator is not a good choice.

I suggest each si5351 clock pin drive a series DC blocking cap and a series 100 ohm resistor
into the mixer port.? Assuming the si5351 has not hit its 8ma current limit, the mixer will
see a source impedance of 50 ohms (internal to the si5351) plus that 100 ohm resistor, so 150 ohms.
Add a 75 ohm resistor from mixer port to ground, that in parallel with 150 ohms makes
it a 50 ohm source impedance for the mixer.

Jerry, KE7ER

it?


On Fri, Nov 9, 2018 at 05:53 PM, Ashhar Farhan wrote:
allison and others,
?
the traps are capable of adding a notch of -20 db. so even if you don't hit the bottom precisely, a 10 db reduction is all that is necessary to clean it up to the required level.
?
these are meant to be fixes that work with existing boards : from v1 onwards. i tried to choose a method that was easy to do.
we will need a different post mix if amp design going forward
yes the traps are for 90 mhz and 12 mhz.
?
the 10 mhz insensitivity is something i will look into today, I havent experienced it. perhaps we should move the trap to tx filters for the 21 mhz to 28 mhz band? the 12 mhz is filtered for the lower bands in any case.
?
the other place to apply the 12 mhz trap would be the local oscillator output?
?
another simple mod to be applied is to change R26 and R46 from 470 ohms to 220. the darlington pair was having insufficient current adding to distortion woes.
?
Re: a simple spur fix

 

allison and others,

the traps are capable of adding a notch of -20 db. so even if you don't hit the bottom precisely, a 10 db reduction is all that is necessary to clean it up to the required level.

these are meant to be fixes that work with existing boards : from v1 onwards. i tried to choose a method that was easy to do.
we will need a different post mix if amp design going forward
yes the traps are for 90 mhz and 12 mhz.

the 10 mhz insensitivity is something i will look into today, I havent experienced it. perhaps we should move the trap to tx filters for the 21 mhz to 28 mhz band? the 12 mhz is filtered for the lower bands in any case.

the other place to apply the 12 mhz trap would be the local oscillator output?

another simple mod to be applied is to change R26 and R46 from 470 ohms to 220. the darlington pair was having insufficient current adding to distortion woes.

- f


On Sat, 10 Nov 2018, 05:48 Mike Woods <mhwoods@... wrote:
My guess is that the two intended filter frequencies are:? 90Mhz (second harmonic of 45MHz 1st LO) and 12MHz (2nd LO).? The parts represent the right values for a filter at 90MHz, but it seems that 30M band would be wiped out by the second of the mods (which somebody has already observed).?? 12MHz should be being wiped out instead, so I suspect a typo.

Perhaps? either a 35pF capacitor and the 5?H inductor as stated or a 3.8?H inductor and the 47pF capacitor as stated being about right for getting the filter resonant just on the low side of 12MHz.?

Mike ZL1AXG

On 10/11/18 9:49 AM, Brian L. Davis wrote:
10pf series with .3uhy - resonant about 91 MHz
47pf series with 5.0uhy resonant about 10.4 MHz
Is this correct?
Brian - WA5RDG


--
Mike Woods
mhwoods@...
Re: a simple spur fix

 

¿ªÔÆÌåÓý

My guess is that the two intended filter frequencies are:? 90Mhz (second harmonic of 45MHz 1st LO) and 12MHz (2nd LO).? The parts represent the right values for a filter at 90MHz, but it seems that 30M band would be wiped out by the second of the mods (which somebody has already observed).?? 12MHz should be being wiped out instead, so I suspect a typo.

Perhaps? either a 35pF capacitor and the 5?H inductor as stated or a 3.8?H inductor and the 47pF capacitor as stated being about right for getting the filter resonant just on the low side of 12MHz.?

Mike ZL1AXG

On 10/11/18 9:49 AM, Brian L. Davis wrote:
10pf series with .3uhy - resonant about 91 MHz
47pf series with 5.0uhy resonant about 10.4 MHz
Is this correct?
Brian - WA5RDG


--
Mike Woods
mhwoods@...
Re: a simple spur fix

 

Allison,

I'm not 100% sure what his LC traps are doing, but they may not have to move around.
My best guess is that the one at TP13 (tuned to around 90mhz)
just removes the 2'd harmonic of the 45mhz IF that gets created by those 2n3904's
running flat out.? It doesn't have to move.

Example:? Transmitting at 21mhz, clk2 is at 45+21=66mhz.
If any 2*45=90mhz energy is present, it mixes with the 66mhz clk1 at D1,D2 to create a 90-66 = 24mhz spur.

Farhan suggests the second LC trap is to suppress the 12mhz BFO energy due to crosstalk between clk0 and clk2.
Though we have a report that this also sucks out 10mhz reception, so either that particular example is tuned
differently than Farhan's, or that's an awfully wide trap, or I don't know what's going on there.??

If these mods are easily reproducible for acceptable results, good enough by me.
We'll see.

Jerry


On Fri, Nov 9, 2018 at 02:45 PM, ajparent1/KB1GMX wrote:
Your doing what I tried back in June/July time frame, it failed then.

Reason first series traps good enough to suck out the spur at a given frequency
are narrow enough? to be only a spot frequency fix.? The 2IF-LO spur for 28mhz
BAND is between 17 to 16 mhz for 10M alone.? So you need a series trap that
can not do a band.

The other issue is the power amp.? At 80M and 10W out the gain is about 60db
but as you go up, at 20M the gain is down to ~56db, and at 10M the gain is maybe
~52DB.? ?So at the spur frequency you have more gain available than the desired
output frequency and the differential gain is enough to put that spur as shown at
-45db at more like -37db below 2W.

The fix has to be more comprehensive.? Also it must be field verifiable or factory
set to allow for 1 or 5% parts.

The 45mhz section needs:
? 45mhz filter inductors shielded or better that section relocated.
? Amplifier distortion clean up.
? Swap the 45mhz port and LO ports as IF ports are most sensitive to mismatch.

A thought to look into...
? Replace the TIA amp at 45mhz with a more common resistive feedback amp (typical 2n5109 amp)
? with 20db gain.? Here is the hint:? Often when that amp is shown due to the fact that changes at either
? port impact the opposing port they often have a 6db pad at the output.? However for the TX case that
? same pad can be at the input and it insures the 45mhz filter will have a good match for the network
? and the transistor with its input impedance stable will have output stability going to the mixer.

Allison
Re: a simple spur fix

 

Good!? Sounds like it's working!? ;-)
I for one am willing to give up 30m on what is mostly an SSB rig.

If you were planning to operate CW on 30m, you could put a couple pins and a jumper
in series with that C+L.? So with the jumper out, the mod is undone.
Transmitting CW we don't have trouble with spurs, since the BFO and clk1 are both shut down.
The only RF floating about the rig is clk2 at the transmit frequency.

Jerry, KE7ER


On Fri, Nov 9, 2018 at 03:03 PM, barry halterman wrote:
I installed the series trap across C202 in the LPF and it reduced the 30 meter sensitivity drastically.
Re: a simple spur fix

 

I installed the series trap across C202 in the LPF and it reduced the 30 meter sensitivity drastically.


On Fri, Nov 9, 2018, 5:46 PM ajparent1/KB1GMX <kb1gmx@... wrote:
Farhan,

Your doing what I tried back in June/July time frame, it failed then.

Reason first series traps good enough to suck out the spur at a given frequency
are narrow enough? to be only a spot frequency fix.? The 2IF-LO spur for 28mhz
BAND is between 17 to 16 mhz for 10M alone.? So you need a series trap that
can not do a band.

The other issue is the power amp.? At 80M and 10W out the gain is about 60db
but as you go up, at 20M the gain is down to ~56db, and at 10M the gain is maybe
~52DB.? ?So at the spur frequency you have more gain available than the desired
output frequency and the differential gain is enough to put that spur as shown at
-45db at more like -37db below 2W.

The fix has to be more comprehensive.? Also it must be field verifiable or factory
set to allow for 1 or 5% parts.

The 45mhz section needs:
? 45mhz filter inductors shielded or better that section relocated.
? Amplifier distortion clean up.
? Swap the 45mhz port and LO ports as IF ports are most sensitive to mismatch.

A thought to look into...
? Replace the TIA amp at 45mhz with a more common resistive feedback amp (typical 2n5109 amp)
? with 20db gain.? Here is the hint:? Often when that amp is shown due to the fact that changes at either
? port impact the opposing port they often have a 6db pad at the output.? However for the TX case that
? same pad can be at the input and it insures the 45mhz filter will have a good match for the network
? and the transistor with its input impedance stable will have output stability going to the mixer.

Allison
Re: uBITX AGC - Adafruit TPA2016, A Success! #ubitx

 

¿ªÔÆÌåÓý

I don't know. Check the T_DO and T_CS pins on the test set and see if one of the connected to the same input pin on the Teensy as the encoder SW.

On Nov 8, 2018, at 1:23 PM, John Scherer <jrsphoto@...> wrote:

Wow, just found this thread.? I currently?use the nd6t AGC?and as playing around with controlling the hang-time digitally, but it takes 6 pins.? I just placed an order for the TPA2016 so I'll be playing with this for sure.? It would be really awesome if KD8CEC (or anyone) could add a config page for this to the Nextion?display and support for it CEC firmware!? I'd take a stab at it but after looking at the graphics editor for the Nextion?display, I'll pass.? It'd take me weeks to figure that hot mess out ;-)

John - N0CTL?

Re: Transmit Problem

 

Hi Wayne,

Shielding can be added to the interior of those "attractive plastic boxes". I made my own steel box from new steel. But I have used the aluminum foil lining inside wood or plastic boxes, The heavier foil pans that are sold for baking or the ones frozen meals come in are much sturdier than the paper thin foil sold for wrapping food.

73,

Bill KU8H

On 11/9/18 5:20 PM, Lawrence Galea wrote:
Have you tried putting the amplifier on the back panel?
On Fri, Nov 9, 2018 at 5:59 AM Wayne Leake <wayneleake@... <mailto:wayneleake@...>> wrote:
?Regarding the shielded enclosures, yup, most good radios are
enclosed in metal cases.
?Receiver only is far less fussy.
?I was looking at a number of possible cases for my BITX, and
decided on a BUD enclosure, all aluminum
?It is big enough for the HF Signal BITX40, but turns out not for
another BITX I am assembling.
?Boards too wide to fit both exciter and PA boards in it.
?I see all these great looking plastic cases, but figured that I do
not want to go with no shielding.
?Hence the one that will go into a cassette? deck case will have
shielding.
?The ferrite beads have their places, but don't take the place of
good shielding, which may also help prevent images and harmonics ,
plus spurs, from escaping.
?YMMV
?Wayne WA2YNE
--
bark less - wag more
Re: a simple spur fix

 

Farhan,

Your doing what I tried back in June/July time frame, it failed then.

Reason first series traps good enough to suck out the spur at a given frequency
are narrow enough? to be only a spot frequency fix.? The 2IF-LO spur for 28mhz
BAND is between 17 to 16 mhz for 10M alone.? So you need a series trap that
can not do a band.

The other issue is the power amp.? At 80M and 10W out the gain is about 60db
but as you go up, at 20M the gain is down to ~56db, and at 10M the gain is maybe
~52DB.? ?So at the spur frequency you have more gain available than the desired
output frequency and the differential gain is enough to put that spur as shown at
-45db at more like -37db below 2W.

The fix has to be more comprehensive.? Also it must be field verifiable or factory
set to allow for 1 or 5% parts.

The 45mhz section needs:
? 45mhz filter inductors shielded or better that section relocated.
? Amplifier distortion clean up.
? Swap the 45mhz port and LO ports as IF ports are most sensitive to mismatch.

A thought to look into...
? Replace the TIA amp at 45mhz with a more common resistive feedback amp (typical 2n5109 amp)
? with 20db gain.? Here is the hint:? Often when that amp is shown due to the fact that changes at either
? port impact the opposing port they often have a 6db pad at the output.? However for the TX case that
? same pad can be at the input and it insures the 45mhz filter will have a good match for the network
? and the transistor with its input impedance stable will have output stability going to the mixer.

Allison
Re: Transmit Problem

 

Have you tried putting the amplifier on the back panel?


On Fri, Nov 9, 2018 at 5:59 AM Wayne Leake <wayneleake@...> wrote:
?Regarding the shielded enclosures, yup, most good radios are enclosed in metal cases.
?Receiver only is far less fussy.
?I was looking at a number of possible cases for my BITX, and decided on a BUD enclosure, all aluminum
?It is big enough for the HF Signal BITX40, but turns out not for another BITX I am assembling.
?Boards too wide to fit both exciter and PA boards in it.
?I see all these great looking plastic cases, but figured that I do not want to go with no shielding.
?Hence the one that will go into a cassette? deck case will have shielding.
?The ferrite beads have their places, but don't take the place of good shielding, which may also help prevent images and harmonics , plus spurs, from escaping.
?YMMV
?Wayne WA2YNE
Re: DIGITAL FREQUENCY READOUT

 

I WANT TO BUY? "The Raduino board with Si5351, Arduino Nano. Fully tested AND PROGRAMMED." I DON'T NEED THE LCD READOUT.

HOW MUCH AND WHERE CAN I ORDER?

WILLIAM

On 11/9/2018 1:32 PM, MONEYSMITH wrote:
THANK YOU

On 11/9/2018 1:21 PM, Vince Vielhaber wrote:
The crystal is on the green board under the display.? Unplug the display and you'll see it.

Vince.


On 11/09/2018 03:26 PM, MONEYSMITH wrote:
THIS BOARD HAS A MEGA328P CHIP. I HAVE NO INFORMATION ON THE BOARD.

I FOUND NO SI5351A CHIP?

PHOTOS ATTACHED.

W4NFR

On 11/9/2018 11:42 AM, Arv Evans wrote:
Bill W4NFR

The picture you provided is the back side of an Arduino Nano board.
The crystals on this PCB
have nothing to do with the transmitting frequency of your
transceiver.? The SI5351a frequency
synthesizer is a small 10-pin MSOP IC, or 20-pin QFN IC.? It should be
clearly labeled on the
top as an Si5351A device.? Do you have a picture of the Raduino board
with its Si5351A chip
and crystal?

Arv? K7HKL
_._


On Fri, Nov 9, 2018 at 11:20 AM MONEYSMITH <w4nfr@...
<mailto:w4nfr@...>> wrote:

??? HERE IS A PHOTO OF BOARD AND CRYSTAL.

??? W4NFR

??? On 11/9/2018 9:57 AM, Mvs Sarma wrote:
??? OMG. acidentally crept in perhaps .
??? could you please share a? photo please, !!!!!

??? regards
??? sarma
???? vu3zmv

??? On Fri, Nov 9, 2018 at 10:50 PM MONEYSMITH <w4nfr@...
??? <mailto:w4nfr@...>> wrote:

??????? I OPENED UP MY uBITX? AND TOOK A LOOK AT THE S1535A BOARD.
??????? THE CRYSTAL HAS 20.0 STAMPED ON IT INSTEAD OF 25.0 MHZ?

??????? On 11/8/2018 5:59 PM, RCC WB5YYM wrote:
??????? The crystal is not "bad"


------------------------------------------------------------------------

??????? AVG logo <>

??????? This email has been checked for viruses by AVG antivirus
??????? software.
??????? www.avg.com <>


<#m_4175695945886965737_m_2844835715575407798_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
---
This email has been checked for viruses by AVG.
Re: DIGITAL FREQUENCY READOUT

 

THANK YOU

On 11/9/2018 1:21 PM, Vince Vielhaber wrote:
The crystal is on the green board under the display.? Unplug the display and you'll see it.

Vince.


On 11/09/2018 03:26 PM, MONEYSMITH wrote:
THIS BOARD HAS A MEGA328P CHIP. I HAVE NO INFORMATION ON THE BOARD.

I FOUND NO SI5351A CHIP?

PHOTOS ATTACHED.

W4NFR

On 11/9/2018 11:42 AM, Arv Evans wrote:
Bill W4NFR

The picture you provided is the back side of an Arduino Nano board.
The crystals on this PCB
have nothing to do with the transmitting frequency of your
transceiver.? The SI5351a frequency
synthesizer is a small 10-pin MSOP IC, or 20-pin QFN IC.? It should be
clearly labeled on the
top as an Si5351A device.? Do you have a picture of the Raduino board
with its Si5351A chip
and crystal?

Arv? K7HKL
_._


On Fri, Nov 9, 2018 at 11:20 AM MONEYSMITH <w4nfr@...
<mailto:w4nfr@...>> wrote:

??? HERE IS A PHOTO OF BOARD AND CRYSTAL.

??? W4NFR

??? On 11/9/2018 9:57 AM, Mvs Sarma wrote:
??? OMG. acidentally crept in perhaps .
??? could you please share a? photo please, !!!!!

??? regards
??? sarma
???? vu3zmv

??? On Fri, Nov 9, 2018 at 10:50 PM MONEYSMITH <w4nfr@...
??? <mailto:w4nfr@...>> wrote:

??????? I OPENED UP MY uBITX? AND TOOK A LOOK AT THE S1535A BOARD.
??????? THE CRYSTAL HAS 20.0 STAMPED ON IT INSTEAD OF 25.0 MHZ?

??????? On 11/8/2018 5:59 PM, RCC WB5YYM wrote:
??????? The crystal is not "bad"


------------------------------------------------------------------------

??????? AVG logo <>

??????? This email has been checked for viruses by AVG antivirus
??????? software.
??????? www.avg.com <>


<#m_4175695945886965737_m_2844835715575407798_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
---
This email has been checked for viruses by AVG.
Re: DIGITAL FREQUENCY READOUT

Vince Vielhaber
 

The crystal is on the green board under the display. Unplug the display and you'll see it.

Vince.

On 11/09/2018 03:26 PM, MONEYSMITH wrote:
THIS BOARD HAS A MEGA328P CHIP. I HAVE NO INFORMATION ON THE BOARD.

I FOUND NO SI5351A CHIP?

PHOTOS ATTACHED.

W4NFR

On 11/9/2018 11:42 AM, Arv Evans wrote:
Bill W4NFR

The picture you provided is the back side of an Arduino Nano board.
The crystals on this PCB
have nothing to do with the transmitting frequency of your
transceiver. The SI5351a frequency
synthesizer is a small 10-pin MSOP IC, or 20-pin QFN IC. It should be
clearly labeled on the
top as an Si5351A device. Do you have a picture of the Raduino board
with its Si5351A chip
and crystal?

Arv K7HKL
_._


On Fri, Nov 9, 2018 at 11:20 AM MONEYSMITH <w4nfr@...
<mailto:w4nfr@...>> wrote:

HERE IS A PHOTO OF BOARD AND CRYSTAL.

W4NFR

On 11/9/2018 9:57 AM, Mvs Sarma wrote:
OMG. acidentally crept in perhaps .
could you please share a photo please, !!!!!

regards
sarma
vu3zmv

On Fri, Nov 9, 2018 at 10:50 PM MONEYSMITH <w4nfr@...
<mailto:w4nfr@...>> wrote:

I OPENED UP MY uBITX AND TOOK A LOOK AT THE S1535A BOARD.
THE CRYSTAL HAS 20.0 STAMPED ON IT INSTEAD OF 25.0 MHZ?

On 11/8/2018 5:59 PM, RCC WB5YYM wrote:
The crystal is not "bad"


------------------------------------------------------------------------
AVG logo <>

This email has been checked for viruses by AVG antivirus
software.
www.avg.com <>


<#m_4175695945886965737_m_2844835715575407798_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
--
K8ZW

Re: a simple spur fix

Timothy Fidler
 

Yup.? it is correct.? The easiest way to get the units right is? L in uH , C in uF and result will be in Mhz? ie recip of sqrt of micro x micro .

But remember when you are working at VHF with 5 percent capacitors and air wound coils,? even Tiny errors or tolerances? will put you off by 100s of KHz.? Ditto temperature effects on components.

?

Timothy E. Fidler : Engineer BE Mech(1) Auckland , NDT specialist AINDT UT /RT3 , MT2 CB #2885,?
Telephone Whangarei?? 022? 691 8405
e: Engstr@...



----- Original Message -----

To:
<[email protected]>
Cc:

Sent:
Fri, 09 Nov 2018 12:49:44 -0800
Subject:
Re: [BITX20] a simple spur fix


10pf series with .3uhy - resonant about 91 MHz
47pf series with 5.0uhy resonant about 10.4 MHz
Is this correct?
Brian - WA5RDG

Re: a simple spur fix

 

¿ªÔÆÌåÓý

Ashhar:

?

You give the number of turns necessary, and the core IDs, but what is the gauge of wire used???

?

David A Posthuma, WD8PUO

1 (616) 283-7703

?

From: [email protected] <[email protected]> On Behalf Of Ashhar Farhan
Sent: Friday, November 09, 2018 10:35 AM
To: [email protected]
Subject: [BITX20] a simple spur fix

?

so, there is one spur fix that is now consistently working for me.

among rhe solutions, i was looking for one that would be easy to apply.

first, the distortion in the 45 mhz amp is creating harmonic distortion. so a 0.3uh in series with a 10 pf is used across TP13 (output of the 45 MHz IF amp going to the front end mixer). 8 turns on T30-6 gives you 300nh.

second, there is a cross talk inside the Si5351 where the 12 mhz from the bfo leaks into the local oscillator. A 5uh in series with a 47 pf across C202 of the LPF will suppress it. 35 turns on T30-6 gives you 5uh.

- f

?
Re: DIGITAL FREQUENCY READOUT

 

The Si5351 is on the back side of the board in the first picture, between the display and the board that the ATmeg board plugs into.? The board with the plug is the Raduino board.


On Fri, Nov 9, 2018 at 2:27 PM MONEYSMITH <w4nfr@...> wrote:

THIS BOARD HAS A MEGA328P CHIP. I HAVE NO INFORMATION ON THE BOARD.

I FOUND NO SI5351A CHIP?

PHOTOS ATTACHED.

W4NFR

On 11/9/2018 11:42 AM, Arv Evans wrote:
Bill W4NFR

The picture you provided is the back side of an Arduino Nano board.? The crystals on this PCB
have nothing to do with the transmitting frequency of your transceiver.? The SI5351a frequency
synthesizer is a small 10-pin MSOP IC, or 20-pin QFN IC.? It should be clearly labeled on the
top as an Si5351A device.? Do you have a picture of the Raduino board with its Si5351A chip
and crystal?

Arv? K7HKL
_._


On Fri, Nov 9, 2018 at 11:20 AM MONEYSMITH <w4nfr@...> wrote:

HERE IS A PHOTO OF BOARD AND CRYSTAL.

W4NFR

On 11/9/2018 9:57 AM, Mvs Sarma wrote:
OMG. acidentally crept in perhaps .
could you please share a? photo please, !!!!!

regards
sarma
?vu3zmv

On Fri, Nov 9, 2018 at 10:50 PM MONEYSMITH <w4nfr@...> wrote:

I OPENED UP MY uBITX? AND TOOK A LOOK AT THE S1535A BOARD. THE CRYSTAL HAS 20.0 STAMPED ON IT INSTEAD OF 25.0 MHZ?

On 11/8/2018 5:59 PM, RCC WB5YYM wrote:
The crystal is not "bad"?


This email has been checked for viruses by AVG antivirus software.


56021 - 56040 of 117075