Topics

spurs & harmonics, whew!

Ashhar Farhan
 

there seems to be a light at the end of this tunnel now, i have been talking in the group and off the group with a number of you: Raj, Jerry, Allison, BIll (Meara) and this represents the consolidated output of this group. i have taken editorial liberties to leave some changes out and incorporate others in.

1. The spurs were cause by the harmonic distortion in the 45 MHz IF amplifier. This resulted in a 90 MHz harmonic that mixed with the local oscillator to produce a spur. the local oscillator was at 45 Mhz + tuned freq. The spur was as 90 MHz - local oscillator, that is 90 - (45 + tuned freq) = 45 - tuned frequency. Hence for 21 MHz ,we had a spur at 45-21 = 24 MHz, etc.
The cure was to increase the current in the amp by decreasing R26 from 470 ohms to 220 and introducing a low pass filter between the front-end mixer and the 45 MHz IF amplifier. This consists of L31, C205 and L32. A little snick and solder job can do this on existing boards. WIth these mods, the spurs are well under control. This hack was due to the preliminary work that Raj did followed by taking 50 odd readings of how the spurs moved and analyzing them. in the end, a two variable equation out of a 7th grade algebra book could point out this problem; but we never knew. 

2. The harmonics at below 14 MHz were due to the bad routing in the LPF relays. Allison provided a simpler and far better option. The unfortunate part is that the existing boards can't do this. The other tragedy is that the way these relays are wired . The 28 MHz filter permanantely in the tx output path and the other three LPFs switch in, in series with it. So, the Arduino code for these LPFs is going to be different too.

3. Change of 2nd IF frequency. I am moving the 2nd IF to 11.059 MHz from 12 MHz. This will avoid the frequent problem of having the the 16 mhz oscillator generating spurs inside the IF pass band. The new filter is also a little broader, it is about 2.7 KHz. The audio sounds better, at least I personally prefer it so. Hence, the crystal filters' caps are changed from 100pf to 68 pf.

4. The LM386 returns. This is an unfortunate decision. I am regretting it already. The audio amplifier is now the old frenemy of hams, the LM386. We had to do this because it is the only one that is readily available to manufacture as well as to those who are going to scratch build. This is an open source project that must use easily available components and also strive for a minimum complexity. Using an op-amp with a complementary npn-pnp pair could have worked, but the complexity would have had us to use a bigger board. We wanted to keep the board size same, to allow others to upgrade as well.

5. It is vital that the output above 14 Mhz must be kept to 5 watts. Over-driving this rig will certainly lead to the spurs. Check out the captures of 21 MHz. One is with a 5 watts output, the other has it over-driven to 10 watts.  It will stay within the legal limits wiht the supplied electret mic. 

Check out the pictures. The green line across the screen is drawn at -43 dbc, the legal limit. I adjusted the RF attenuator so that the transmitted power stayed at -20dbc. See how the distortion adds to the spurs in the two 21 Mhz captures.

If things look good, we will roll with this as v5 board.

73, f.

Cameron McKay
 

Ashhar,

Thanks for the update and the team's efforts on this however I have one query. Below item 5 below you state that the spurs are to be -43dBc.

In Australia (and I'm not about to push Australian requirements onto the rest of the world or this project) - our legislation requires spurious emissions to be the lessor of:

a) 43+10log(PEP)dB (which for 5W PEP would be just under 50dB below transmitted emissions) , or

b) 50dB

(refer Clause 7A of http://www.wia.org.au/licenses/assessor/documentation/documents/Radiocommunications_Licence%20Conditions_Amateur_Licence_Determination_2015.pdf). This requirement is a condition on our licences and enforceable 'in law'.

Now, this isn't actually an Australian-centric criteria. It is sourced from the ITU-R recommendations stated in Table 1 of ITU-R SM.329.7 under the Service Category 'Amateur service operating below 30MHz (including with SSB)'.

As such, targeting 50dBc would appear to be a pragmatic solution and given the nature of the ITU-R recommendations most jurisdictions would probably use this as their reference source (I recall one JA operator who has previously commented in this group and discussion about having to get his *BitX 'tested and approved' for use).


Best Regards,


Cameron McKay - VK2CKP




On 9/01/2019 9:32 pm, Ashhar Farhan wrote:
there seems to be a light at the end of this tunnel now, i have been talking in the group and off the group with a number of you: Raj, Jerry, Allison, BIll (Meara) and this represents the consolidated output of this group. i have taken editorial liberties to leave some changes out and incorporate others in.

1. The spurs were cause by the harmonic distortion in the 45 MHz IF amplifier. This resulted in a 90 MHz harmonic that mixed with the local oscillator to produce a spur. the local oscillator was at 45 Mhz + tuned freq. The spur was as 90 MHz - local oscillator, that is 90 - (45 + tuned freq) = 45 - tuned frequency. Hence for 21 MHz ,we had a spur at 45-21 = 24 MHz, etc.
The cure was to increase the current in the amp by decreasing R26 from 470 ohms to 220 and introducing a low pass filter between the front-end mixer and the 45 MHz IF amplifier. This consists of L31, C205 and L32. A little snick and solder job can do this on existing boards. WIth these mods, the spurs are well under control. This hack was due to the preliminary work that Raj did followed by taking 50 odd readings of how the spurs moved and analyzing them. in the end, a two variable equation out of a 7th grade algebra book could point out this problem; but we never knew. 

2. The harmonics at below 14 MHz were due to the bad routing in the LPF relays. Allison provided a simpler and far better option. The unfortunate part is that the existing boards can't do this. The other tragedy is that the way these relays are wired . The 28 MHz filter permanantely in the tx output path and the other three LPFs switch in, in series with it. So, the Arduino code for these LPFs is going to be different too.

3. Change of 2nd IF frequency. I am moving the 2nd IF to 11.059 MHz from 12 MHz. This will avoid the frequent problem of having the the 16 mhz oscillator generating spurs inside the IF pass band. The new filter is also a little broader, it is about 2.7 KHz. The audio sounds better, at least I personally prefer it so. Hence, the crystal filters' caps are changed from 100pf to 68 pf.

4. The LM386 returns. This is an unfortunate decision. I am regretting it already. The audio amplifier is now the old frenemy of hams, the LM386. We had to do this because it is the only one that is readily available to manufacture as well as to those who are going to scratch build. This is an open source project that must use easily available components and also strive for a minimum complexity. Using an op-amp with a complementary npn-pnp pair could have worked, but the complexity would have had us to use a bigger board. We wanted to keep the board size same, to allow others to upgrade as well.

5. It is vital that the output above 14 Mhz must be kept to 5 watts. Over-driving this rig will certainly lead to the spurs. Check out the captures of 21 MHz. One is with a 5 watts output, the other has it over-driven to 10 watts.  It will stay within the legal limits wiht the supplied electret mic. 

Check out the pictures. The green line across the screen is drawn at -43 dbc, the legal limit. I adjusted the RF attenuator so that the transmitted power stayed at -20dbc. See how the distortion adds to the spurs in the two 21 Mhz captures.

If things look good, we will roll with this as v5 board.

73, f.

Bob Lunsford <nocrud222@...>
 

Hello Ashhar...

I am happy such great strides have been achieved in removing
some of the problems with the uBitx. I consider it a great move
forward. However, I have two questions:

1) What band or bands do you recommend holding down the
output power to 5W? Or does it mean that ALL bands must be
held to this or lower power?

2) When do you project that V5 will be the normal purchase
issue? Is it weeks or months away? Curious only at this point.

I have plans to get the 40M radio soon but also plan to get
another uBitx relatively soon thereafter. Thus my question #2.

Bob — KK5R

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

On Wed, 1/9/19, Ashhar Farhan <farhanbox@...> wrote:

Subject: [BITX20] spurs & harmonics, whew!
To: bitx20@groups.io
Date: Wednesday, January 9, 2019, 5:32 AM

there seems to
be a light at the end of this tunnel now, i have been
talking in the group and off the group with a number of you:
Raj, Jerry, Allison, BIll (Meara) and this represents the
consolidated output of this group. i have taken editorial
liberties to leave some changes out and incorporate others
in.
1. The spurs were cause by the harmonic
distortion in the 45 MHz IF amplifier. This resulted in a 90
MHz harmonic that mixed with the local oscillator to produce
a spur. the local oscillator was at 45 Mhz + tuned freq.
The spur was as 90 MHz - local oscillator, that is 90 -
(45 + tuned freq) = 45 - tuned frequency. Hence for 21 MHz
,we had a spur at 45-21 = 24 MHz, etc.The cure
was to increase the current in the amp by decreasing R26
from 470 ohms to 220 and introducing a low pass filter
between the front-end mixer and the 45 MHz IF amplifier.
This consists of L31, C205 and L32. A little snick and
solder job can do this on existing boards. WIth these mods,
the spurs are well under control. This hack was due to the
preliminary work that Raj did followed by taking 50 odd
readings of how the spurs moved and analyzing them. in the
end, a two variable equation out of a 7th grade algebra book
could point out this problem; but we never
knew. 
2. The harmonics at below 14 MHz were due to the
bad routing in the LPF relays. Allison provided a simpler
and far better option. The unfortunate part is that the
existing boards can't do this. The other tragedy is that
the way these relays are wired . The 28 MHz filter
permanantely in the tx output path and the other three LPFs
switch in, in series with it. So, the Arduino code for these
LPFs is going to be different too.
3. Change of 2nd IF frequency. I am moving the
2nd IF to 11.059 MHz from 12 MHz. This will avoid the
frequent problem of having the the 16 mhz oscillator
generating spurs inside the IF pass band. The new filter is
also a little broader, it is about 2.7 KHz. The audio sounds
better, at least I personally prefer it so. Hence, the
crystal filters' caps are changed from 100pf to 68
pf.
4. The LM386 returns. This is an unfortunate
decision. I am regretting it already. The audio amplifier is
now the old frenemy of hams, the LM386. We had to do this
because it is the only one that is readily available to
manufacture as well as to those who are going to scratch
build. This is an open source project that must use easily
available components and also strive for a minimum
complexity. Using an op-amp with a complementary npn-pnp
pair could have worked, but the complexity would have had us
to use a bigger board. We wanted to keep the board size
same, to allow others to upgrade as well.
5. It is vital that the output above 14 Mhz must
be kept to 5 watts. Over-driving this rig will certainly
lead to the spurs. Check out the captures of 21 MHz. One is
with a 5 watts output, the other has it over-driven to 10
watts.  It will stay within the legal limits wiht the
supplied electret mic. 
Check out the pictures. The green line across the
screen is drawn at -43 dbc, the legal limit. I adjusted the
RF attenuator so that the transmitted power stayed at
-20dbc. See how the distortion adds to the spurs in the two
21 Mhz captures.
If things look good, we will roll with this as v5
board.
73, f.

 

Farhan,

Keep the display WRT the IRF and mounting holes the same and widen the boards by a cm or 1/2 inch. That will take care
of the required acreage and ppl can upgrade too.

Raj

At 09/01/2019, you wrote:
there seems to be a light at the end of this tunnel now, i have been talking in the group and off the group with a number of you: Raj, Jerry, Allison, BIll (Meara) and this represents the consolidated output of this group. i have taken editorial liberties to leave some changes out and incorporate others in.


4. The LM386 returns. This is an unfortunate decision. I am regretting it already. The audio amplifier is now the old frenemy of hams, the LM386. We had to do this because it is the only one that is readily available to manufacture as well as to those who are going to scratch build. This is an open source project that must use easily available components and also strive for a minimum complexity. Using an op-amp with a complementary npn-pnp pair could have worked, but the complexity would have had us to use a bigger board. We wanted to keep the board size same, to allow others to upgrade as well.

Truffies
 

PLease make a upgrade kit of parts and easy to follow pictures  and instructions to purchase  I am dumb will buy.
Thank you

-----Original Message-----
From: Ashhar Farhan
Sent: Jan 9, 2019 5:32 AM
To: bitx20@groups.io
Subject: [BITX20] spurs & harmonics, whew!

there seems to be a light at the end of this tunnel now, i have been talking in the group and off the group with a number of you: Raj, Jerry, Allison, BIll (Meara) and this represents the consolidated output of this group. i have taken editorial liberties to leave some changes out and incorporate others in.

1. The spurs were cause by the harmonic distortion in the 45 MHz IF amplifier. This resulted in a 90 MHz harmonic that mixed with the local oscillator to produce a spur. the local oscillator was at 45 Mhz + tuned freq. The spur was as 90 MHz - local oscillator, that is 90 - (45 + tuned freq) = 45 - tuned frequency. Hence for 21 MHz ,we had a spur at 45-21 = 24 MHz, etc.
The cure was to increase the current in the amp by decreasing R26 from 470 ohms to 220 and introducing a low pass filter between the front-end mixer and the 45 MHz IF amplifier. This consists of L31, C205 and L32. A little snick and solder job can do this on existing boards. WIth these mods, the spurs are well under control. This hack was due to the preliminary work that Raj did followed by taking 50 odd readings of how the spurs moved and analyzing them. in the end, a two variable equation out of a 7th grade algebra book could point out this problem; but we never knew. 

2. The harmonics at below 14 MHz were due to the bad routing in the LPF relays. Allison provided a simpler and far better option. The unfortunate part is that the existing boards can't do this. The other tragedy is that the way these relays are wired . The 28 MHz filter permanantely in the tx output path and the other three LPFs switch in, in series with it. So, the Arduino code for these LPFs is going to be different too.

3. Change of 2nd IF frequency. I am moving the 2nd IF to 11.059 MHz from 12 MHz. This will avoid the frequent problem of having the the 16 mhz oscillator generating spurs inside the IF pass band. The new filter is also a little broader, it is about 2.7 KHz. The audio sounds better, at least I personally prefer it so. Hence, the crystal filters' caps are changed from 100pf to 68 pf.

4. The LM386 returns. This is an unfortunate decision. I am regretting it already. The audio amplifier is now the old frenemy of hams, the LM386. We had to do this because it is the only one that is readily available to manufacture as well as to those who are going to scratch build. This is an open source project that must use easily available components and also strive for a minimum complexity. Using an op-amp with a complementary npn-pnp pair could have worked, but the complexity would have had us to use a bigger board. We wanted to keep the board size same, to allow others to upgrade as well.

5. It is vital that the output above 14 Mhz must be kept to 5 watts. Over-driving this rig will certainly lead to the spurs. Check out the captures of 21 MHz. One is with a 5 watts output, the other has it over-driven to 10 watts.  It will stay within the legal limits wiht the supplied electret mic. 

Check out the pictures. The green line across the screen is drawn at -43 dbc, the legal limit. I adjusted the RF attenuator so that the transmitted power stayed at -20dbc. See how the distortion adds to the spurs in the two 21 Mhz captures.

If things look good, we will roll with this as v5 board.

73, f.

Curt
 

Team

some usefulness in this plan for v5.  we need to remember this is a rig for all the world. 

it would be nice to provide provision on the board to patch out in front of the LM386 - to incorporate external audio filtering etc.  this is a natural location for something like a NESCAF that could be on a daughter board. 

perhaps we are staying with common relays for input and output to the filters, in order to fit the existing board outline?  yes I hear the comment from VK.  more stringent spurs for whatever reasons may require a daughter card - such as some of us are or will use with v4 -- it seems very do-able.  If HF Signals (or TBD) would provide an external board kit for use with v3 and v4 boards (hosting 3 added relays) the same board could be used with v5. 

73 Curt

ajparent1/kb1gmx
 

Farhan,

Make the vias larger and more of them for grounds.


Allison

Jerry Gaffke
 

From the last three spectrum analyzer plots that Farhan posted, 
it appears to be marginally compliant with the -50dB spec on 80m, 40m, and 20m.
Above 20m the spurs are worse, but  still marginally compliant with the -43dB spec.

Easy enough to disable those high bands, and thus meet any -50dB regs.
At the price this sells, only getting 80,40,20m is not a bad deal.

In the order posted, those screen shots are for 21 28 21(cw?) 25  28(worse) 18 14 3.6 and 7 mhz
All have the main signal at about -20dBm, so anything else above -63dBm is non-compliant 
with a -43dB spec,  above -70dBm is non-compliant with a -50dB spec.

Not totally clear why the third shot is so much better than the first since both are for 21mhz,
perhaps the third is in CW mode, not SSB?   I assume all the other shots are SSB.
The second shot shows a marginally compliant 28mhz signal, the fifth is a 28mhz signal
with a spur that is slightly over the line for the -43dB spec.

On the higher bands, the gain of the 45mhz IF amp and the linear amp for the transmitter
is less than the lower bands.
Many of us would tend to increase the audio going in to drive the transmitter harder 
on the high bands, don't do that!  As that audio gain is increased, the spurs grow faster than the
desired signal, and as the shots show the high bands are already borderline.

Farhan recommends simply using the provided electret mike, more audio than
that thing provides will overload the mixers and IF amps, resulting in increased spurs.
RV1 should be set well below the point at which compression sets in on the low bands.
If you venture into the high bands, just live with the reduction in power, don't try to 
compensate by increasing audio levels.  (And probably should not mess with RV1 either).

We may need a procedure to deal with variations in the electret mike, how loud people shout
into it, component variations, ...
Repeat:  You don't want too much audio, or the spurs get much worse.
 
Others should feel free to chime in here with corrections.
I haven't made any of my own measurements of spurs and harmonics.
Any of the above assumptions could be wrong.

Jerry, KE7ER


On Wed, Jan 9, 2019 at 03:06 AM, Cameron McKay wrote:

Ashhar,

Thanks for the update and the team's efforts on this however I have one query. Below item 5 below you state that the spurs are to be -43dBc.

In Australia (and I'm not about to push Australian requirements onto the rest of the world or this project) - our legislation requires spurious emissions to be the lessor of:

a) 43+10log(PEP)dB (which for 5W PEP would be just under 50dB below transmitted emissions) , or

b) 50dB

(refer Clause 7A of http://www.wia.org.au/licenses/assessor/documentation/documents/Radiocommunications_Licence%20Conditions_Amateur_Licence_Determination_2015.pdf). This requirement is a condition on our licences and enforceable 'in law'.

Now, this isn't actually an Australian-centric criteria. It is sourced from the ITU-R recommendations stated in Table 1 of ITU-R SM.329.7 under the Service Category 'Amateur service operating below 30MHz (including with SSB)'.

As such, targeting 50dBc would appear to be a pragmatic solution and given the nature of the ITU-R recommendations most jurisdictions would probably use this as their reference source (I recall one JA operator who has previously commented in this group and discussion about having to get his *BitX 'tested and approved' for use).

 

Best Regards,

 

Cameron McKay - VK2CKP

Ashhar Farhan
 

jerry, now that we know the fix, i can try a more aggresive 45 mhz lpf, lessee, we maybe able to hit the -50dbc after all...
- f

On Wed, 9 Jan 2019, 22:24 Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io wrote:
From the last three spectrum analyzer plots that Farhan posted, 
it appears to be marginally compliant with the -50dB spec on 80m, 40m, and 20m.
Above 20m the spurs are worse, but  still marginally compliant with the -43dB spec.

Easy enough to disable those high bands, and thus meet any -50dB regs.
At the price this sells, only getting 80,40,20m is not a bad deal.

In the order posted, those screen shots are for 21 28 21(cw?) 25  28(worse) 18 14 3.6 and 7 mhz
All have the main signal at about -20dBm, so anything else above -63dBm is non-compliant 
with a -43dB spec,  above -70dBm is non-compliant with a -50dB spec.

Not totally clear why the third shot is so much better than the first since both are for 21mhz,
perhaps the third is in CW mode, not SSB?   I assume all the other shots are SSB.
The second shot shows a marginally compliant 28mhz signal, the fifth is a 28mhz signal
with a spur that is slightly over the line for the -43dB spec.

On the higher bands, the gain of the 45mhz IF amp and the linear amp for the transmitter
is less than the lower bands.
Many of us would tend to increase the audio going in to drive the transmitter harder 
on the high bands, don't do that!  As that audio gain is increased, the spurs grow faster than the
desired signal, and as the shots show the high bands are already borderline.

Farhan recommends simply using the provided electret mike, more audio than
that thing provides will overload the mixers and IF amps, resulting in increased spurs.
RV1 should be set well below the point at which compression sets in on the low bands.
If you venture into the high bands, just live with the reduction in power, don't try to 
compensate by increasing audio levels.  (And probably should not mess with RV1 either).

We may need a procedure to deal with variations in the electret mike, how loud people shout
into it, component variations, ...
Repeat:  You don't want too much audio, or the spurs get much worse.
 
Others should feel free to chime in here with corrections.
I haven't made any of my own measurements of spurs and harmonics.
Any of the above assumptions could be wrong.

Jerry, KE7ER


On Wed, Jan 9, 2019 at 03:06 AM, Cameron McKay wrote:

Ashhar,

Thanks for the update and the team's efforts on this however I have one query. Below item 5 below you state that the spurs are to be -43dBc.

In Australia (and I'm not about to push Australian requirements onto the rest of the world or this project) - our legislation requires spurious emissions to be the lessor of:

a) 43+10log(PEP)dB (which for 5W PEP would be just under 50dB below transmitted emissions) , or

b) 50dB

(refer Clause 7A of http://www.wia.org.au/licenses/assessor/documentation/documents/Radiocommunications_Licence%20Conditions_Amateur_Licence_Determination_2015.pdf). This requirement is a condition on our licences and enforceable 'in law'.

Now, this isn't actually an Australian-centric criteria. It is sourced from the ITU-R recommendations stated in Table 1 of ITU-R SM.329.7 under the Service Category 'Amateur service operating below 30MHz (including with SSB)'.

As such, targeting 50dBc would appear to be a pragmatic solution and given the nature of the ITU-R recommendations most jurisdictions would probably use this as their reference source (I recall one JA operator who has previously commented in this group and discussion about having to get his *BitX 'tested and approved' for use).

 

Best Regards,

 

Cameron McKay - VK2CKP

MVS Sarma
 

If some one wants to implement filter section mod on existing board,  they have to remove the relays to make cuts where needed..Later they have to re-jumper as per new schematic.

sarma
 vu3zmv


On Wed, Jan 9, 2019 at 11:37 PM Ashhar Farhan <farhanbox@...> wrote:
jerry, now that we know the fix, i can try a more aggresive 45 mhz lpf, lessee, we maybe able to hit the -50dbc after all...
- f

On Wed, 9 Jan 2019, 22:24 Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io wrote:
From the last three spectrum analyzer plots that Farhan posted, 
it appears to be marginally compliant with the -50dB spec on 80m, 40m, and 20m.
Above 20m the spurs are worse, but  still marginally compliant with the -43dB spec.

Easy enough to disable those high bands, and thus meet any -50dB regs.
At the price this sells, only getting 80,40,20m is not a bad deal.

In the order posted, those screen shots are for 21 28 21(cw?) 25  28(worse) 18 14 3.6 and 7 mhz
All have the main signal at about -20dBm, so anything else above -63dBm is non-compliant 
with a -43dB spec,  above -70dBm is non-compliant with a -50dB spec.

Not totally clear why the third shot is so much better than the first since both are for 21mhz,
perhaps the third is in CW mode, not SSB?   I assume all the other shots are SSB.
The second shot shows a marginally compliant 28mhz signal, the fifth is a 28mhz signal
with a spur that is slightly over the line for the -43dB spec.

On the higher bands, the gain of the 45mhz IF amp and the linear amp for the transmitter
is less than the lower bands.
Many of us would tend to increase the audio going in to drive the transmitter harder 
on the high bands, don't do that!  As that audio gain is increased, the spurs grow faster than the
desired signal, and as the shots show the high bands are already borderline.

Farhan recommends simply using the provided electret mike, more audio than
that thing provides will overload the mixers and IF amps, resulting in increased spurs.
RV1 should be set well below the point at which compression sets in on the low bands.
If you venture into the high bands, just live with the reduction in power, don't try to 
compensate by increasing audio levels.  (And probably should not mess with RV1 either).

We may need a procedure to deal with variations in the electret mike, how loud people shout
into it, component variations, ...
Repeat:  You don't want too much audio, or the spurs get much worse.
 
Others should feel free to chime in here with corrections.
I haven't made any of my own measurements of spurs and harmonics.
Any of the above assumptions could be wrong.

Jerry, KE7ER


On Wed, Jan 9, 2019 at 03:06 AM, Cameron McKay wrote:

Ashhar,

Thanks for the update and the team's efforts on this however I have one query. Below item 5 below you state that the spurs are to be -43dBc.

In Australia (and I'm not about to push Australian requirements onto the rest of the world or this project) - our legislation requires spurious emissions to be the lessor of:

a) 43+10log(PEP)dB (which for 5W PEP would be just under 50dB below transmitted emissions) , or

b) 50dB

(refer Clause 7A of http://www.wia.org.au/licenses/assessor/documentation/documents/Radiocommunications_Licence%20Conditions_Amateur_Licence_Determination_2015.pdf). This requirement is a condition on our licences and enforceable 'in law'.

Now, this isn't actually an Australian-centric criteria. It is sourced from the ITU-R recommendations stated in Table 1 of ITU-R SM.329.7 under the Service Category 'Amateur service operating below 30MHz (including with SSB)'.

As such, targeting 50dBc would appear to be a pragmatic solution and given the nature of the ITU-R recommendations most jurisdictions would probably use this as their reference source (I recall one JA operator who has previously commented in this group and discussion about having to get his *BitX 'tested and approved' for use).

 

Best Regards,

 

Cameron McKay - VK2CKP

Ashhar Farhan
 

it might be better to remove the coils and put them into an outboard lpf board


On Thu, 10 Jan 2019, 00:13 MVS Sarma <mvssarma@... wrote:
If some one wants to implement filter section mod on existing board,  they have to remove the relays to make cuts where needed..Later they have to re-jumper as per new schematic.

sarma
 vu3zmv

On Wed, Jan 9, 2019 at 11:37 PM Ashhar Farhan <farhanbox@...> wrote:
jerry, now that we know the fix, i can try a more aggresive 45 mhz lpf, lessee, we maybe able to hit the -50dbc after all...
- f

On Wed, 9 Jan 2019, 22:24 Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io wrote:
From the last three spectrum analyzer plots that Farhan posted, 
it appears to be marginally compliant with the -50dB spec on 80m, 40m, and 20m.
Above 20m the spurs are worse, but  still marginally compliant with the -43dB spec.

Easy enough to disable those high bands, and thus meet any -50dB regs.
At the price this sells, only getting 80,40,20m is not a bad deal.

In the order posted, those screen shots are for 21 28 21(cw?) 25  28(worse) 18 14 3.6 and 7 mhz
All have the main signal at about -20dBm, so anything else above -63dBm is non-compliant 
with a -43dB spec,  above -70dBm is non-compliant with a -50dB spec.

Not totally clear why the third shot is so much better than the first since both are for 21mhz,
perhaps the third is in CW mode, not SSB?   I assume all the other shots are SSB.
The second shot shows a marginally compliant 28mhz signal, the fifth is a 28mhz signal
with a spur that is slightly over the line for the -43dB spec.

On the higher bands, the gain of the 45mhz IF amp and the linear amp for the transmitter
is less than the lower bands.
Many of us would tend to increase the audio going in to drive the transmitter harder 
on the high bands, don't do that!  As that audio gain is increased, the spurs grow faster than the
desired signal, and as the shots show the high bands are already borderline.

Farhan recommends simply using the provided electret mike, more audio than
that thing provides will overload the mixers and IF amps, resulting in increased spurs.
RV1 should be set well below the point at which compression sets in on the low bands.
If you venture into the high bands, just live with the reduction in power, don't try to 
compensate by increasing audio levels.  (And probably should not mess with RV1 either).

We may need a procedure to deal with variations in the electret mike, how loud people shout
into it, component variations, ...
Repeat:  You don't want too much audio, or the spurs get much worse.
 
Others should feel free to chime in here with corrections.
I haven't made any of my own measurements of spurs and harmonics.
Any of the above assumptions could be wrong.

Jerry, KE7ER


On Wed, Jan 9, 2019 at 03:06 AM, Cameron McKay wrote:

Ashhar,

Thanks for the update and the team's efforts on this however I have one query. Below item 5 below you state that the spurs are to be -43dBc.

In Australia (and I'm not about to push Australian requirements onto the rest of the world or this project) - our legislation requires spurious emissions to be the lessor of:

a) 43+10log(PEP)dB (which for 5W PEP would be just under 50dB below transmitted emissions) , or

b) 50dB

(refer Clause 7A of http://www.wia.org.au/licenses/assessor/documentation/documents/Radiocommunications_Licence%20Conditions_Amateur_Licence_Determination_2015.pdf). This requirement is a condition on our licences and enforceable 'in law'.

Now, this isn't actually an Australian-centric criteria. It is sourced from the ITU-R recommendations stated in Table 1 of ITU-R SM.329.7 under the Service Category 'Amateur service operating below 30MHz (including with SSB)'.

As such, targeting 50dBc would appear to be a pragmatic solution and given the nature of the ITU-R recommendations most jurisdictions would probably use this as their reference source (I recall one JA operator who has previously commented in this group and discussion about having to get his *BitX 'tested and approved' for use).

 

Best Regards,

 

Cameron McKay - VK2CKP

ajparent1/kb1gmx
 

Before resorting to that with a cleaned up board I'd try putting just the coils on the
opposing side of the board and take advantage of the ground plane.  Its easy and
the vias work from either side.    Same for the relays.

Also until a new board is spun the improvement level can not be fully determined.
But a guess is it can be much improved over current.

I do know the existing filters on a separate board are far better as in they perform
nearly to modeled levels.  Its not the parts its layout.  Cheap way to test that is
layout a new board (partial the LPF area only) go to a cheap 3 board proto house
and build it and test it.  Then you have a better idea and comparison.

Allison

Lawrence Galea
 

Ashhar
there are many who have to order everything from abroad from different vendors and it would be a big help if you can make a pcb and kit of parts available to buy.
Thanks and regards
Lawrence

On Wed, Jan 9, 2019 at 7:47 PM Ashhar Farhan <farhanbox@...> wrote:
it might be better to remove the coils and put them into an outboard lpf board

On Thu, 10 Jan 2019, 00:13 MVS Sarma <mvssarma@... wrote:
If some one wants to implement filter section mod on existing board,  they have to remove the relays to make cuts where needed..Later they have to re-jumper as per new schematic.

sarma
 vu3zmv

On Wed, Jan 9, 2019 at 11:37 PM Ashhar Farhan <farhanbox@...> wrote:
jerry, now that we know the fix, i can try a more aggresive 45 mhz lpf, lessee, we maybe able to hit the -50dbc after all...
- f

On Wed, 9 Jan 2019, 22:24 Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io wrote:
From the last three spectrum analyzer plots that Farhan posted, 
it appears to be marginally compliant with the -50dB spec on 80m, 40m, and 20m.
Above 20m the spurs are worse, but  still marginally compliant with the -43dB spec.

Easy enough to disable those high bands, and thus meet any -50dB regs.
At the price this sells, only getting 80,40,20m is not a bad deal.

In the order posted, those screen shots are for 21 28 21(cw?) 25  28(worse) 18 14 3.6 and 7 mhz
All have the main signal at about -20dBm, so anything else above -63dBm is non-compliant 
with a -43dB spec,  above -70dBm is non-compliant with a -50dB spec.

Not totally clear why the third shot is so much better than the first since both are for 21mhz,
perhaps the third is in CW mode, not SSB?   I assume all the other shots are SSB.
The second shot shows a marginally compliant 28mhz signal, the fifth is a 28mhz signal
with a spur that is slightly over the line for the -43dB spec.

On the higher bands, the gain of the 45mhz IF amp and the linear amp for the transmitter
is less than the lower bands.
Many of us would tend to increase the audio going in to drive the transmitter harder 
on the high bands, don't do that!  As that audio gain is increased, the spurs grow faster than the
desired signal, and as the shots show the high bands are already borderline.

Farhan recommends simply using the provided electret mike, more audio than
that thing provides will overload the mixers and IF amps, resulting in increased spurs.
RV1 should be set well below the point at which compression sets in on the low bands.
If you venture into the high bands, just live with the reduction in power, don't try to 
compensate by increasing audio levels.  (And probably should not mess with RV1 either).

We may need a procedure to deal with variations in the electret mike, how loud people shout
into it, component variations, ...
Repeat:  You don't want too much audio, or the spurs get much worse.
 
Others should feel free to chime in here with corrections.
I haven't made any of my own measurements of spurs and harmonics.
Any of the above assumptions could be wrong.

Jerry, KE7ER


On Wed, Jan 9, 2019 at 03:06 AM, Cameron McKay wrote:

Ashhar,

Thanks for the update and the team's efforts on this however I have one query. Below item 5 below you state that the spurs are to be -43dBc.

In Australia (and I'm not about to push Australian requirements onto the rest of the world or this project) - our legislation requires spurious emissions to be the lessor of:

a) 43+10log(PEP)dB (which for 5W PEP would be just under 50dB below transmitted emissions) , or

b) 50dB

(refer Clause 7A of http://www.wia.org.au/licenses/assessor/documentation/documents/Radiocommunications_Licence%20Conditions_Amateur_Licence_Determination_2015.pdf). This requirement is a condition on our licences and enforceable 'in law'.

Now, this isn't actually an Australian-centric criteria. It is sourced from the ITU-R recommendations stated in Table 1 of ITU-R SM.329.7 under the Service Category 'Amateur service operating below 30MHz (including with SSB)'.

As such, targeting 50dBc would appear to be a pragmatic solution and given the nature of the ITU-R recommendations most jurisdictions would probably use this as their reference source (I recall one JA operator who has previously commented in this group and discussion about having to get his *BitX 'tested and approved' for use).

 

Best Regards,

 

Cameron McKay - VK2CKP

Richard Spohn
 

Asshar, all is great and I look forward to the availability of Version
5 uBitx. Regarding the return of the LM386, I do not consider this a
bad thing, the LM386 and I have never been enemies. However...how
much extra would it cost to put the LM386 chip into a socket for
version-5? That way anyone who does not like the LM386 can simply
remove the chip and insert a replacement of their choosing. There are
a number of audio-amp ICs which are pin-for-pin compatible with the
LM386. And -- THANK YOU FOR ALL YOUR GREAT RADIOS! 73 and Happy New
Year, Rich WB2GXM

Nick VK4PP
 

Hi Farhan, et al.
Some comments from me if I may:
1: Nice simple addition. Would there still be merit to using a 45mhz crystal filter in place of R27 as an alternative fix? (I have a bunch of them + boards and mini transformers...)
2: I am working on a replacement LPF board, I have just completed and tested one using original LPF components. However, it does require 8 Omron g5 relays, a code change and some wiring, But all easy I think.
3: I will start testing my box of 100 11.052 crystals to find a few matched groups. I have 3 radios to convert. I assume its easy to change the IF in code...
4: Long live the LM386. nuff said.
5: Are these spurs still from the 45mhz IF amp? Caused at higher frequencies due to the 2n3904? Would the BFR106 not "cure" this in the IF AMP?
6: Thanks again for such an enjoyable/hackable radio. I continue to learn due to your efforts within the ham community.

73 Nick VK4PP

Nick VK4PP
 

Also quick note, IMHO, M1 and M2 dont need to go through the RX/TX antenna relay anymore either due to the Q74 muting circuit.
here is my LPF board layout: using diodes to switch in and out the highest LPF automagically:


Coming soon, if there is a demand for them...
73 VK4PP

Bob Lunsford <nocrud222@...>
 

Why not leave the radio as is and put an external
LPF at the antenna connection? Would this be
enough to put the radio in spec? A tight filter with
a 30MHz cutoff is what I had in mind. Would it be
enough?

I hate to think of hacking away at such a nice board.
I'm not that kind of hacker.

Bob — KK5R

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

On Wed, 1/9/19, Ashhar Farhan <farhanbox@...> wrote:

Subject: Re: [BITX20] spurs & harmonics, whew!
To: BITX20@groups.io
Date: Wednesday, January 9, 2019, 1:47 PM

it might be better
to remove the coils and put them into an outboard lpf
board
On Thu, 10
Jan 2019, 00:13 MVS Sarma <mvssarma@...
wrote:
If some one wants to implement filter section
mod on existing board,  they have to remove the relays to
make cuts where needed..Later they have to re-jumper as per
new schematic.
sarma vu3zmv

On Wed, Jan
9, 2019 at 11:37 PM Ashhar Farhan <farhanbox@...>
wrote:
jerry, now that we
know the fix, i can try a more aggresive 45 mhz lpf, lessee,
we maybe able to hit the -50dbc after all...-
f
On Wed, 9
Jan 2019, 22:24 Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io
wrote:
From the last three
spectrum analyzer plots that Farhan posted, 
it appears to be marginally compliant with the
-50dB spec on 80m, 40m, and 20m.
Above 20m
the spurs are worse, but  still marginally compliant with
the -43dB spec.

Easy enough
to disable those high bands, and thus meet any -50dB
regs.
At the price this sells, only getting
80,40,20m is not a bad deal.

In the order posted, those screen shots are for
21 28 21(cw?) 25  28(worse) 18 14 3.6 and 7 mhz
All have the main signal at about -20dBm, so
anything else above -63dBm is non-compliant 
with a -43dB spec,  above -70dBm is
non-compliant with a -50dB spec.

Not totally clear why the third shot is so much
better than the first since both are for 21mhz,
perhaps the third is in CW mode, not SSB?   I
assume all the other shots are SSB.
The
second shot shows a marginally compliant 28mhz signal, the
fifth is a 28mhz signal
with a spur that is
slightly over the line for the -43dB spec.

On the higher bands, the gain
of the 45mhz IF amp and the linear amp for the transmitter

is less than the lower bands.
Many of us would tend to increase the audio
going in to drive the transmitter harder 
on the high bands, don't do that!  As that
audio gain is increased, the spurs grow faster than the
desired signal, and as the shots show the high
bands are already borderline.

Farhan recommends simply using the provided
electret mike, more audio than
that thing
provides will overload the mixers and IF amps, resulting in
increased spurs.
RV1 should be set well
below the point at which compression sets in on the low
bands.
If you venture into the high bands,
just live with the reduction in power, don't try to 
compensate by increasing audio levels.  (And
probably should not mess with RV1 either).

We may need a procedure to
deal with variations in the electret mike, how loud people
shout
into it, component variations, ...
Repeat:  You don't want too much audio, or
the spurs get much worse.
 
Others should feel free to chime in here with
corrections.
I haven't made any of my
own measurements of spurs and harmonics.
Any
of the above assumptions could be wrong.

Jerry, KE7ER


On Wed, Jan 9, 2019 at 03:06
AM, Cameron McKay wrote:


Ashhar,
Thanks for the update and the team's efforts on this
however I have one query. Below item 5 below you state that
the spurs are to be -43dBc.
In Australia (and I'm not about to push Australian
requirements onto the rest of the world or this project) -
our legislation requires spurious emissions to be the lessor
of:
a) 43+10log(PEP)dB (which for 5W PEP would be just under
50dB below transmitted emissions) , or
b) 50dB
(refer Clause 7A of http://www.wia.org.au/licenses/assessor/documentation/documents/Radiocommunications_Licence%20Conditions_Amateur_Licence_Determination_2015.pdf).
This requirement is a condition on our licences and
enforceable 'in law'.
Now, this isn't actually an Australian-centric
criteria. It is sourced from the ITU-R recommendations
stated in Table 1 of ITU-R SM.329.7 under the Service
Category 'Amateur service operating below 30MHz
(including with SSB)'.
As such, targeting 50dBc would appear to be a pragmatic
solution and given the nature of the ITU-R recommendations
most jurisdictions would probably use this as their
reference source (I recall one JA operator who has
previously commented in this group and discussion about
having to get his *BitX 'tested and approved' for
use).
 
Best Regards,
 
Cameron McKay - VK2CKP

Ashhar Farhan
 

allison,

these captures are from a newly laid out board. i got this board from pcbway. i have tried keeping all components on the same side for now. 
let me try your suggestions of flipping the coils to the other side. same with relays too. probably the 'add on' board can go to the other side.


On Thu, 10 Jan 2019, 07:04 Bob Lunsford via Groups.Io <nocrud222=yahoo.com@groups.io wrote:
Why not leave the radio as is and put an external
LPF at the antenna connection? Would this be
enough to put the radio in spec? A tight filter with
a 30MHz cutoff is what I had in mind. Would it be
enough?

I hate to think of hacking away at such a nice board.
I'm not that kind of hacker.

Bob — KK5R

--------------------------------------------
On Wed, 1/9/19, Ashhar Farhan <farhanbox@...> wrote:

 Subject: Re: [BITX20] spurs & harmonics, whew!
 To: BITX20@groups.io
 Date: Wednesday, January 9, 2019, 1:47 PM

 it might be better
 to remove the coils and put them into an outboard lpf
 board
 On Thu, 10
 Jan 2019, 00:13 MVS Sarma <mvssarma@...
 wrote:
 If some one wants to implement filter section
 mod on existing board,  they have to remove the relays to
 make cuts where needed..Later they have to re-jumper as per
 new schematic.
 sarma vu3zmv

 On Wed, Jan
 9, 2019 at 11:37 PM Ashhar Farhan <farhanbox@...>
 wrote:
 jerry, now that we
 know the fix, i can try a more aggresive 45 mhz lpf, lessee,
 we maybe able to hit the -50dbc after all...-
 f
 On Wed, 9
 Jan 2019, 22:24 Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io
 wrote:
 From the last three
 spectrum analyzer plots that Farhan posted, 
 it appears to be marginally compliant with the
 -50dB spec on 80m, 40m, and 20m.
 Above 20m
 the spurs are worse, but  still marginally compliant with
 the -43dB spec.

 Easy enough
 to disable those high bands, and thus meet any -50dB
 regs.
 At the price this sells, only getting
 80,40,20m is not a bad deal.

 In the order posted, those screen shots are for
 21 28 21(cw?) 25  28(worse) 18 14 3.6 and 7 mhz
 All have the main signal at about -20dBm, so
 anything else above -63dBm is non-compliant 
 with a -43dB spec,  above -70dBm is
 non-compliant with a -50dB spec.

 Not totally clear why the third shot is so much
 better than the first since both are for 21mhz,
 perhaps the third is in CW mode, not SSB?   I
 assume all the other shots are SSB.
 The
 second shot shows a marginally compliant 28mhz signal, the
 fifth is a 28mhz signal
 with a spur that is
 slightly over the line for the -43dB spec.

 On the higher bands, the gain
 of the 45mhz IF amp and the linear amp for the transmitter

 is less than the lower bands.
 Many of us would tend to increase the audio
 going in to drive the transmitter harder 
 on the high bands, don't do that!  As that
 audio gain is increased, the spurs grow faster than the
 desired signal, and as the shots show the high
 bands are already borderline.

 Farhan recommends simply using the provided
 electret mike, more audio than
 that thing
 provides will overload the mixers and IF amps, resulting in
 increased spurs.
 RV1 should be set well
 below the point at which compression sets in on the low
 bands.
 If you venture into the high bands,
 just live with the reduction in power, don't try to 
 compensate by increasing audio levels.  (And
 probably should not mess with RV1 either).

 We may need a procedure to
 deal with variations in the electret mike, how loud people
 shout
 into it, component variations, ...
 Repeat:  You don't want too much audio, or
 the spurs get much worse.
  
 Others should feel free to chime in here with
 corrections.
 I haven't made any of my
 own measurements of spurs and harmonics.
 Any
 of the above assumptions could be wrong.

 Jerry, KE7ER


 On Wed, Jan 9, 2019 at 03:06
 AM, Cameron McKay wrote:


 Ashhar,
 Thanks for the update and the team's efforts on this
 however I have one query. Below item 5 below you state that
 the spurs are to be -43dBc.
 In Australia (and I'm not about to push Australian
 requirements onto the rest of the world or this project) -
 our legislation requires spurious emissions to be the lessor
 of:
 a) 43+10log(PEP)dB (which for 5W PEP would be just under
 50dB below transmitted emissions) , or
 b) 50dB
 (refer Clause 7A of http://www.wia.org.au/licenses/assessor/documentation/documents/Radiocommunications_Licence%20Conditions_Amateur_Licence_Determination_2015.pdf).
 This requirement is a condition on our licences and
 enforceable 'in law'.
 Now, this isn't actually an Australian-centric
 criteria. It is sourced from the ITU-R recommendations
 stated in Table 1 of ITU-R SM.329.7 under the Service
 Category 'Amateur service operating below 30MHz
 (including with SSB)'.
 As such, targeting 50dBc would appear to be a pragmatic
 solution and given the nature of the ITU-R recommendations
 most jurisdictions would probably use this as their
 reference source (I recall one JA operator who has
 previously commented in this group and discussion about
 having to get his *BitX 'tested and approved' for
 use).
  
 Best Regards,
  
 Cameron McKay - VK2CKP



















Ashhar Farhan
 

nick,

can do. lemme see what all i can get done this weekend.

- f

On Thu, 10 Jan 2019, 05:30 Nick VK4PP <nickpullen@... wrote:

Hi Farhan, et al.
Some comments from me if I may:
1: Nice simple addition. Would there still be merit to using a 45mhz crystal filter in place of R27 as an alternative fix? (I have a bunch of them + boards and mini transformers...)
2: I am working on a replacement LPF board, I have just completed and tested one using original LPF components. However, it does require 8 Omron g5 relays, a code change and some wiring, But all easy I think.
3: I will start testing my box of 100 11.052 crystals to find a few matched groups. I have 3 radios to convert. I assume its easy to change the IF in code...
4: Long live the LM386. nuff said.
5: Are these spurs still from the 45mhz IF amp? Caused at higher frequencies due to the 2n3904? Would the BFR106 not "cure" this in the IF AMP?
6: Thanks again for such an enjoyable/hackable radio. I continue to learn due to your efforts within the ham community.

73 Nick VK4PP

Christopher Miller
 

I said an external filter would work, but the problem is you need to switch filters per band. This would change filter per band automatically. Im really excited I can buy a ubitx soon!

Chris 

On Wed, Jan 9, 2019, 6:42 PM Ashhar Farhan <farhanbox@... wrote:
nick,

can do. lemme see what all i can get done this weekend.

- f

On Thu, 10 Jan 2019, 05:30 Nick VK4PP <nickpullen@... wrote:

Hi Farhan, et al.
Some comments from me if I may:
1: Nice simple addition. Would there still be merit to using a 45mhz crystal filter in place of R27 as an alternative fix? (I have a bunch of them + boards and mini transformers...)
2: I am working on a replacement LPF board, I have just completed and tested one using original LPF components. However, it does require 8 Omron g5 relays, a code change and some wiring, But all easy I think.
3: I will start testing my box of 100 11.052 crystals to find a few matched groups. I have 3 radios to convert. I assume its easy to change the IF in code...
4: Long live the LM386. nuff said.
5: Are these spurs still from the 45mhz IF amp? Caused at higher frequencies due to the 2n3904? Would the BFR106 not "cure" this in the IF AMP?
6: Thanks again for such an enjoyable/hackable radio. I continue to learn due to your efforts within the ham community.

73 Nick VK4PP