Topics

Harmonics and Relay Replacement

Kees T
 

Pictures are always nice, Glenn.

Since most of these larger relays have the long armatures which run parallel to the coil and the coil is not shielded  (right ?), there would be RF coupling between the armature and the coil. It would also seem that, for a given voltage, higher current relays would imply larger wire, fewer turns, and less inductance for Port to Port coupling (right ?). 

Can't do much to reduce inner relay coupling but you could reduce relay to relay coupling by using a small RF choke (100uH) in the both existing relay coil leads. I like the WireWound ones from Bourns (CM322522-101K1). 

73 Kees K5BCQ


Arv Evans
 

Kees

Has anyone tried adding a 0.1 mfd across each of the relay coils, and additional 0.1 mfd
to ground from various places in the DC going to these relays.  Suspicion is that some of
the unwanted coupling might be via the relay coils and connecting traces.

Arv
_._


On Tue, Oct 9, 2018 at 11:20 AM Kees T <windy10605@...> wrote:
Seems like most of these larger relays have the long armatures which run parallel to the coil and the coil is not shielded  

Kees T
 




Sure is fun with good test equipment........ I deleted the last picture because it may cause confusion.

#1 The first plot is the coupling between the Armature and the coil for a small 10 pin Omron relay.
#2 The second plot is the coupling between the Armature and the coil for a larger 16 pin HFD27 relay. You can see that it is about 7dB worse than the Omron.
#3 (deleted) I tried various RF chokes (1uH to 100uH) which improves the HFD27 relay plots but not at the low end because of the self resonance of the inductor. The Bourns 100uH inductor I was using has a self resonance at about 10MHz. This requires some more study and head scratching.

73 Kees K5BCQ

MVS Sarma
 

Nice analysis.
 Could you please try with smd inductor 100uH, Please !!
regards
vu3zmv


On Wed, Oct 10, 2018 at 9:21 AM Kees T <windy10605@...> wrote:



Sure is fun with good test equipment........ I deleted the last picture because it may cause confusion.

#1 The first plot is the coupling between the Armature and the coil for a small 10 pin Omron relay.
#2 The second plot is the coupling between the Armature and the coil for a larger 16 pin HFD27 relay. You can see that it is about 7dB worse than the Omron.
#3 (deleted) I tried various RF chokes (1uH to 100uH) which improves the HFD27 relay plots but not at the low end because of the self resonance of the inductor. The Bourns 100uH inductor I was using has a self resonance at about 10MHz. This requires some more study and head scratching.

73 Kees K5BCQ

 

The contacts are below, close to the ground plane possible less coupling and short so less inductance.

Raj

Pic: from the net.

Emacs!


At 09-10-18, you wrote:

Pictures are always nice, Glenn.

Since most of these larger relays have the long armatures which run parallel to the coil and the coil is not shielded  (right ?), there would be RF coupling between the armature and the coil. It would also seem that, for a given voltage, higher current relays would imply larger wire, fewer turns, and less inductance for Port to Port coupling (right ?).

Can't do much to reduce inner relay coupling but you could reduce relay to relay coupling by using a small RF choke (100uH) in the both existing relay coil leads. I like the WireWound ones from Bourns (CM322522-101K1).

73 Kees K5BCQ

iz oos
 

If this would work it would be far cheaper than replacing the relays. I have seen on ebay and they are not very cheap.


Il 09/ott/2018 20:25, "Arv Evans" <arvid.evans@...> ha scritto:
Kees

Has anyone tried adding a 0.1 mfd across each of the relay coils, and additional 0.1 mfd
to ground from various places in the DC going to these relays.  Suspicion is that some of
the unwanted coupling might be via the relay coils and connecting traces.

Arv
_._


On Tue, Oct 9, 2018 at 11:20 AM Kees T <windy10605@...> wrote:
Seems like most of these larger relays have the long armatures which run parallel to the coil and the coil is not shielded  

Michael Maiorana
 

For those in the USA, you can order these from Arrow electronics (arrow.com). They are a little cheaper, plus you get free overnight shipping.
I ordered some and will try to replicate Mike's results.
Mike M.
KU4QO

On Mon, Oct 8, 2018 at 3:54 PM Mike Doty via Groups.Io <mikedoty=reagan.com@groups.io> wrote:
I thought I would pass this along, for whatever it is worth.  I have two Ver 3 and one Ver 4 uBiTX rigs.  I have replaced K3, KT1, KT2, and KT3 relays with Axicom relays which has knocked down the 3rd, 5th, and 7th harmonic levels from -35dB to below -50dB on all 3 rigs without any board modifications to the LPF circuits.  This may be anecdotal but with 3 rigs showing the same results it may be something to consider.  I purchased the relays from Mouser - part # 655-V23105A5403A201.  Cost was $2.89 per relay plus shipping.  I've attached photos (sorry for the blurriness) showing the before and after results on my Ver 4 rig.
--73--  Mike  --  W0MNE

Jim Sheldon
 

Thanks Mike,
Ordered 10 of them from Arrow - even cheaper than Digi-Key by a couple of bucks and certainly much cheaper on the shipping with Arrow's free overnight shipping.

My Digi-Key order will be here in about an hour and I'll mod the two V4 boards I have.  After the Arrow order arrives tomorrow, I'll mod the 2 V3 boards and run the Spectrum tests on them.

Jim Sheldon, W0EB

------ Original Message ------
From: "Michael Maiorana" <zfreak@...>
Sent: 10/10/2018 9:07:12 AM
Subject: Re: [BITX20] Harmonics and Relay Replacement

For those in the USA, you can order these from Arrow electronics (arrow.com). They are a little cheaper, plus you get free overnight shipping.
I ordered some and will try to replicate Mike's results.
Mike M.
KU4QO

On Mon, Oct 8, 2018 at 3:54 PM Mike Doty via Groups.Io <mikedoty=reagan.com@groups.io> wrote:
I thought I would pass this along, for whatever it is worth.  I have two Ver 3 and one Ver 4 uBiTX rigs.  I have replaced K3, KT1, KT2, and KT3 relays with Axicom relays which has knocked down the 3rd, 5th, and 7th harmonic levels from -35dB to below -50dB on all 3 rigs without any board modifications to the LPF circuits.  This may be anecdotal but with 3 rigs showing the same results it may be something to consider.  I purchased the relays from Mouser - part # 655-V23105A5403A201.  Cost was $2.89 per relay plus shipping.  I've attached photos (sorry for the blurriness) showing the before and after results on my Ver 4 rig.
--73--  Mike  --  W0MNE

Kees T
 

Thanks for dissecting an AXICOM relay and the pictures. The coil mounted over the contacts is a definite difference to the ones I dissected.

The other thing which may effect results is that most of the larger (16 pin) relays offer up to 4 different "coil sensitivity" options .....which will effect coil resistance and inductance. The resistance for a given 12V relay coil varies between about 960 ohms and about 320 ohms. That may well effect the coupling also.

I don't have enough different relays to compare but I do have some series inductors to evaluate. The thing to watch out for there is the inductor self resonance effect.

73 Kees K5BCQ

Vince Vielhaber
 

When did Arrow start the free shipping? Last time I ordered from them, a couple of molex connectors - male and female, they charged me a couple of bucks each for the connectors, plus $18 shipping. But wait! There's more! The male connectors came from one warehouse and the female ones came from another - another $18 shipping!! I hadn't looked at them since for anything. And the shipping wasn't even overnite.

Vince.

On 10/10/2018 10:07 AM, Michael Maiorana wrote:
For those in the USA, you can order these from Arrow electronics
(arrow.com <http://arrow.com>). They are a little cheaper, plus you get
free overnight shipping.
I ordered some and will try to replicate Mike's results.
Mike M.
KU4QO

On Mon, Oct 8, 2018 at 3:54 PM Mike Doty via Groups.Io
<mikedoty=reagan.com@groups.io <mailto:reagan.com@groups.io>> wrote:

I thought I would pass this along, for whatever it is worth. I have
two Ver 3 and one Ver 4 uBiTX rigs. I have replaced K3, KT1, KT2,
and KT3 relays with Axicom relays which has knocked down the 3rd,
5th, and 7th harmonic levels from -35dB to below -50dB on all 3 rigs
without any board modifications to the LPF circuits. This may be
anecdotal but with 3 rigs showing the same results it may be
something to consider. I purchased the relays from Mouser - part #
655-V23105A5403A201. Cost was $2.89 per relay plus shipping. I've
attached photos (sorry for the blurriness) showing the before and
after results on my Ver 4 rig.
--73-- Mike -- W0MNE

Arv Evans
 

Kees, and others....

Blindly changing relays may fix the problem, but are we missing something here?
What is the real problem with the original relays?  Is it capacitive coupling between
RF carrying parts and the activation conductors, or is it that the relay coils might
be acting as RF chokes and allowing RF to be coupled between relays via the
RF-isolated traces of DC relay control leads?  Has anyone measured how much
is being carried by the DC control leads?  Has anyone tried bypassing the relay
control leads for RF?

Arv
_._


On Wed, Oct 10, 2018 at 8:56 AM Kees T <windy10605@...> wrote:
Thanks for dissecting an AXICOM relay and the pictures. The coil mounted over the contacts is a definite difference to the ones I dissected.

The other thing which may effect results is that most of the larger (16 pin) relays offer up to 4 different "coil sensitivity" options .....which will effect coil resistance and inductance. The resistance for a given 12V relay coil varies between about 960 ohms and about 320 ohms. That may well effect the coupling also.

I don't have enough different relays to compare but I do have some series inductors to evaluate. The thing to watch out for there is the inductor self resonance effect.

73 Kees K5BCQ

Jim Sheldon
 

Arv and others,
#1 I really believe it's capacitive coupling within the relay itself and between the contacts, as well as from contacts to coil.  The original relays in the uBITX are inexpensive (read CHEAP) Chinese power relays that are not (I have their spec sheet) rated for RF and there are no RF parameters in their data sheet such as capacitance between contacts, from coil to armature and coil to contacts at all.  I had already bypassed the coil terminals to ground with .1uF SMD capacitors and didn't notice an appreciable difference.

#2, After this came to light, I don't consider myself "blindly" changing relays.  I'm investigating the cause and effect of changing these relays.  My two version 4 uBITX boards DO barely meet spec with the strongest harmonic(s) being -49 dB below the carrier level on MY (calibrated last year) spectrum analyzer.  Others' results will surely vary depending on the precision and how well and when calibrated their spectrum analyzers are.  I do not have the test equipment to measure inter contact/coil, etc. capacitance so I have no choice but change the relays as part of my experimentation.  It's an expense I am willing to undertake to attempt to improve MY uBITX rigs and if it helps others, so be it.  If others chose to ignore the results (good or bad) then the consequences are on them, not me as I am only sharing the information out there with the caveat "For What It's Worth!"  

Looking at the construction of the original relays after dissecting one, I can certainly see the wire to the far end of the coil runs parallel to the contacts along that same side of the relay and not very far away either.  Even though it's smaller than 30 gauge wire, the internal capacitance between the coil and at least one set of contacts is going to be a factor in these relays not to mention there is no shielding of the coil so inductance and capacitance could also be playing a part in the "blow-by".  

The new ones are too expensive to disect one as far as I'm concerned, but at least TE Products (Axicom) saw fit to publish the RF parameters (isolation by frequency) and inter contact/coil capacitance.  

Jim Sheldon, W0EB 





------ Original Message ------
From: "Arv Evans" <arvid.evans@...>
Sent: 10/10/2018 11:16:53 AM
Subject: Re: [BITX20] Harmonics and Relay Replacement

Kees, and others....

Blindly changing relays may fix the problem, but are we missing something here?
What is the real problem with the original relays?  Is it capacitive coupling between
RF carrying parts and the activation conductors, or is it that the relay coils might
be acting as RF chokes and allowing RF to be coupled between relays via the
RF-isolated traces of DC relay control leads?  Has anyone measured how much
is being carried by the DC control leads?  Has anyone tried bypassing the relay
control leads for RF?

Arv
_._


On Wed, Oct 10, 2018 at 8:56 AM Kees T <windy10605@...> wrote:
Thanks for dissecting an AXICOM relay and the pictures. The coil mounted over the contacts is a definite difference to the ones I dissected.

The other thing which may effect results is that most of the larger (16 pin) relays offer up to 4 different "coil sensitivity" options .....which will effect coil resistance and inductance. The resistance for a given 12V relay coil varies between about 960 ohms and about 320 ohms. That may well effect the coupling also.

I don't have enough different relays to compare but I do have some series inductors to evaluate. The thing to watch out for there is the inductor self resonance effect.

73 Kees K5BCQ

Arv Evans
 

Jim

Sorry for the "blindly changing relays" comment.  That was not intended to be derogatorily in
any way.  Thinking when I said that was about those who follow what we say, assuming that
we have performed all the necessary testing and evaluation.  Some have measured the
capacitance between relay armatures and between relay contacts, but I have seen little
said about capacitance between RF carrying parts of these relays and the windings.  My
point was about the possibility of relay windings acting as RF chokes, thus allowing the DC
traces between relays to be coupling agents with respect to RF. 

Arv
_._


On Wed, Oct 10, 2018 at 11:02 AM Jim Sheldon <w0eb@...> wrote:
Arv and others,
#1 I really believe it's capacitive coupling within the relay itself and between the contacts, as well as from contacts to coil.  The original relays in the uBITX are inexpensive (read CHEAP) Chinese power relays that are not (I have their spec sheet) rated for RF and there are no RF parameters in their data sheet such as capacitance between contacts, from coil to armature and coil to contacts at all.  I had already bypassed the coil terminals to ground with .1uF SMD capacitors and didn't notice an appreciable difference.

#2, After this came to light, I don't consider myself "blindly" changing relays.  I'm investigating the cause and effect of changing these relays.  My two version 4 uBITX boards DO barely meet spec with the strongest harmonic(s) being -49 dB below the carrier level on MY (calibrated last year) spectrum analyzer.  Others' results will surely vary depending on the precision and how well and when calibrated their spectrum analyzers are.  I do not have the test equipment to measure inter contact/coil, etc. capacitance so I have no choice but change the relays as part of my experimentation.  It's an expense I am willing to undertake to attempt to improve MY uBITX rigs and if it helps others, so be it.  If others chose to ignore the results (good or bad) then the consequences are on them, not me as I am only sharing the information out there with the caveat "For What It's Worth!"  

Looking at the construction of the original relays after dissecting one, I can certainly see the wire to the far end of the coil runs parallel to the contacts along that same side of the relay and not very far away either.  Even though it's smaller than 30 gauge wire, the internal capacitance between the coil and at least one set of contacts is going to be a factor in these relays not to mention there is no shielding of the coil so inductance and capacitance could also be playing a part in the "blow-by".  

The new ones are too expensive to disect one as far as I'm concerned, but at least TE Products (Axicom) saw fit to publish the RF parameters (isolation by frequency) and inter contact/coil capacitance.  

Jim Sheldon, W0EB 





------ Original Message ------
From: "Arv Evans" <arvid.evans@...>
Sent: 10/10/2018 11:16:53 AM
Subject: Re: [BITX20] Harmonics and Relay Replacement

Kees, and others....

Blindly changing relays may fix the problem, but are we missing something here?
What is the real problem with the original relays?  Is it capacitive coupling between
RF carrying parts and the activation conductors, or is it that the relay coils might
be acting as RF chokes and allowing RF to be coupled between relays via the
RF-isolated traces of DC relay control leads?  Has anyone measured how much
is being carried by the DC control leads?  Has anyone tried bypassing the relay
control leads for RF?

Arv
_._


On Wed, Oct 10, 2018 at 8:56 AM Kees T <windy10605@...> wrote:
Thanks for dissecting an AXICOM relay and the pictures. The coil mounted over the contacts is a definite difference to the ones I dissected.

The other thing which may effect results is that most of the larger (16 pin) relays offer up to 4 different "coil sensitivity" options .....which will effect coil resistance and inductance. The resistance for a given 12V relay coil varies between about 960 ohms and about 320 ohms. That may well effect the coupling also.

I don't have enough different relays to compare but I do have some series inductors to evaluate. The thing to watch out for there is the inductor self resonance effect.

73 Kees K5BCQ

Jim Sheldon
 

Yup, and after opening up one of the original relays that I removed from a V4 board in prep for putting new ones on (they should be here within the hour) it was extremely obvious that those relays were not designed with RF in mind.  There is no shielding of the relay coil at all and all the contacts are on movable arms that run parallel to each other and the full length of the relay as well as close to the relay coil itself.  The armature is mostly made of plastic so doesn't provide much (if any) shielding between the coil and the movable contact arms.  The movable arms are each made up of 2 parallel, approximately 2mm wide strips of metal that are separated in the middle of the top of the relay by about 1 mm.  (Pictures not possible as the relays were pretty much destroyed in the dissection.)  I believe the parallel arm construction was for current carrying capability (not needed in small signal RF relays) as the contacts are rated to 125V @ 60 watts (their designation) in the data sheet.  The width & placement of these contact arms would allow a whole lot of coupling between both sets of contacts and I really believe it's one of the culprits though not necessarily the entire problem.  

Changing the relays to an RF rated set with proper isolation certainly can't hurt and may just wind up being the simplest fix for the problem.

The Postman just delivered the new relays from Digi-Key so off to install them and run some tests to see if I can prove or disprove Mike Doty's data.  

I do believe my results will corroborate his after chopping up one of the old relays to see what was in it.

Jim Sheldon


------ Original Message ------
From: "Arv Evans" <arvid.evans@...>
Sent: 10/10/2018 12:20:51 PM
Subject: Re: [BITX20] Harmonics and Relay Replacement

Jim

Sorry for the "blindly changing relays" comment.  That was not intended to be derogatorily in
any way.  Thinking when I said that was about those who follow what we say, assuming that
we have performed all the necessary testing and evaluation.  Some have measured the
capacitance between relay armatures and between relay contacts, but I have seen little
said about capacitance between RF carrying parts of these relays and the windings.  My
point was about the possibility of relay windings acting as RF chokes, thus allowing the DC
traces between relays to be coupling agents with respect to RF. 

Arv
_._


On Wed, Oct 10, 2018 at 11:02 AM Jim Sheldon <w0eb@...> wrote:
Arv and others,
#1 I really believe it's capacitive coupling within the relay itself and between the contacts, as well as from contacts to coil.  The original relays in the uBITX are inexpensive (read CHEAP) Chinese power relays that are not (I have their spec sheet) rated for RF and there are no RF parameters in their data sheet such as capacitance between contacts, from coil to armature and coil to contacts at all.  I had already bypassed the coil terminals to ground with .1uF SMD capacitors and didn't notice an appreciable difference.

#2, After this came to light, I don't consider myself "blindly" changing relays.  I'm investigating the cause and effect of changing these relays.  My two version 4 uBITX boards DO barely meet spec with the strongest harmonic(s) being -49 dB below the carrier level on MY (calibrated last year) spectrum analyzer.  Others' results will surely vary depending on the precision and how well and when calibrated their spectrum analyzers are.  I do not have the test equipment to measure inter contact/coil, etc. capacitance so I have no choice but change the relays as part of my experimentation.  It's an expense I am willing to undertake to attempt to improve MY uBITX rigs and if it helps others, so be it.  If others chose to ignore the results (good or bad) then the consequences are on them, not me as I am only sharing the information out there with the caveat "For What It's Worth!"  

Looking at the construction of the original relays after dissecting one, I can certainly see the wire to the far end of the coil runs parallel to the contacts along that same side of the relay and not very far away either.  Even though it's smaller than 30 gauge wire, the internal capacitance between the coil and at least one set of contacts is going to be a factor in these relays not to mention there is no shielding of the coil so inductance and capacitance could also be playing a part in the "blow-by".  

The new ones are too expensive to disect one as far as I'm concerned, but at least TE Products (Axicom) saw fit to publish the RF parameters (isolation by frequency) and inter contact/coil capacitance.  

Jim Sheldon, W0EB 





------ Original Message ------
From: "Arv Evans" <arvid.evans@...>
Sent: 10/10/2018 11:16:53 AM
Subject: Re: [BITX20] Harmonics and Relay Replacement

Kees, and others....

Blindly changing relays may fix the problem, but are we missing something here?
What is the real problem with the original relays?  Is it capacitive coupling between
RF carrying parts and the activation conductors, or is it that the relay coils might
be acting as RF chokes and allowing RF to be coupled between relays via the
RF-isolated traces of DC relay control leads?  Has anyone measured how much
is being carried by the DC control leads?  Has anyone tried bypassing the relay
control leads for RF?

Arv
_._


On Wed, Oct 10, 2018 at 8:56 AM Kees T <windy10605@...> wrote:
Thanks for dissecting an AXICOM relay and the pictures. The coil mounted over the contacts is a definite difference to the ones I dissected.

The other thing which may effect results is that most of the larger (16 pin) relays offer up to 4 different "coil sensitivity" options .....which will effect coil resistance and inductance. The resistance for a given 12V relay coil varies between about 960 ohms and about 320 ohms. That may well effect the coupling also.

I don't have enough different relays to compare but I do have some series inductors to evaluate. The thing to watch out for there is the inductor self resonance effect.

73 Kees K5BCQ

Ashhar Farhan
 

Guys,
If someone else too can confirm this fix. We will start ordering axion relays from now on. - f

On Wed, 10 Oct 2018, 23:15 Jim Sheldon, <w0eb@...> wrote:
Yup, and after opening up one of the original relays that I removed from a V4 board in prep for putting new ones on (they should be here within the hour) it was extremely obvious that those relays were not designed with RF in mind.  There is no shielding of the relay coil at all and all the contacts are on movable arms that run parallel to each other and the full length of the relay as well as close to the relay coil itself.  The armature is mostly made of plastic so doesn't provide much (if any) shielding between the coil and the movable contact arms.  The movable arms are each made up of 2 parallel, approximately 2mm wide strips of metal that are separated in the middle of the top of the relay by about 1 mm.  (Pictures not possible as the relays were pretty much destroyed in the dissection.)  I believe the parallel arm construction was for current carrying capability (not needed in small signal RF relays) as the contacts are rated to 125V @ 60 watts (their designation) in the data sheet.  The width & placement of these contact arms would allow a whole lot of coupling between both sets of contacts and I really believe it's one of the culprits though not necessarily the entire problem.  

Changing the relays to an RF rated set with proper isolation certainly can't hurt and may just wind up being the simplest fix for the problem.

The Postman just delivered the new relays from Digi-Key so off to install them and run some tests to see if I can prove or disprove Mike Doty's data.  

I do believe my results will corroborate his after chopping up one of the old relays to see what was in it.

Jim Sheldon


------ Original Message ------
From: "Arv Evans" <arvid.evans@...>
Sent: 10/10/2018 12:20:51 PM
Subject: Re: [BITX20] Harmonics and Relay Replacement

Jim

Sorry for the "blindly changing relays" comment.  That was not intended to be derogatorily in
any way.  Thinking when I said that was about those who follow what we say, assuming that
we have performed all the necessary testing and evaluation.  Some have measured the
capacitance between relay armatures and between relay contacts, but I have seen little
said about capacitance between RF carrying parts of these relays and the windings.  My
point was about the possibility of relay windings acting as RF chokes, thus allowing the DC
traces between relays to be coupling agents with respect to RF. 

Arv
_._


On Wed, Oct 10, 2018 at 11:02 AM Jim Sheldon <w0eb@...> wrote:
Arv and others,
#1 I really believe it's capacitive coupling within the relay itself and between the contacts, as well as from contacts to coil.  The original relays in the uBITX are inexpensive (read CHEAP) Chinese power relays that are not (I have their spec sheet) rated for RF and there are no RF parameters in their data sheet such as capacitance between contacts, from coil to armature and coil to contacts at all.  I had already bypassed the coil terminals to ground with .1uF SMD capacitors and didn't notice an appreciable difference.

#2, After this came to light, I don't consider myself "blindly" changing relays.  I'm investigating the cause and effect of changing these relays.  My two version 4 uBITX boards DO barely meet spec with the strongest harmonic(s) being -49 dB below the carrier level on MY (calibrated last year) spectrum analyzer.  Others' results will surely vary depending on the precision and how well and when calibrated their spectrum analyzers are.  I do not have the test equipment to measure inter contact/coil, etc. capacitance so I have no choice but change the relays as part of my experimentation.  It's an expense I am willing to undertake to attempt to improve MY uBITX rigs and if it helps others, so be it.  If others chose to ignore the results (good or bad) then the consequences are on them, not me as I am only sharing the information out there with the caveat "For What It's Worth!"  

Looking at the construction of the original relays after dissecting one, I can certainly see the wire to the far end of the coil runs parallel to the contacts along that same side of the relay and not very far away either.  Even though it's smaller than 30 gauge wire, the internal capacitance between the coil and at least one set of contacts is going to be a factor in these relays not to mention there is no shielding of the coil so inductance and capacitance could also be playing a part in the "blow-by".  

The new ones are too expensive to disect one as far as I'm concerned, but at least TE Products (Axicom) saw fit to publish the RF parameters (isolation by frequency) and inter contact/coil capacitance.  

Jim Sheldon, W0EB 





------ Original Message ------
From: "Arv Evans" <arvid.evans@...>
Sent: 10/10/2018 11:16:53 AM
Subject: Re: [BITX20] Harmonics and Relay Replacement

Kees, and others....

Blindly changing relays may fix the problem, but are we missing something here?
What is the real problem with the original relays?  Is it capacitive coupling between
RF carrying parts and the activation conductors, or is it that the relay coils might
be acting as RF chokes and allowing RF to be coupled between relays via the
RF-isolated traces of DC relay control leads?  Has anyone measured how much
is being carried by the DC control leads?  Has anyone tried bypassing the relay
control leads for RF?

Arv
_._


On Wed, Oct 10, 2018 at 8:56 AM Kees T <windy10605@...> wrote:
Thanks for dissecting an AXICOM relay and the pictures. The coil mounted over the contacts is a definite difference to the ones I dissected.

The other thing which may effect results is that most of the larger (16 pin) relays offer up to 4 different "coil sensitivity" options .....which will effect coil resistance and inductance. The resistance for a given 12V relay coil varies between about 960 ohms and about 320 ohms. That may well effect the coupling also.

I don't have enough different relays to compare but I do have some series inductors to evaluate. The thing to watch out for there is the inductor self resonance effect.

73 Kees K5BCQ

MVS Sarma
 

Farhan jee, I suppose it is "Axicom" and not axion.
regards
sarma vu3zmv


On Wednesday, October 10, 2018, Ashhar Farhan <farhanbox@...> wrote:
Guys,
If someone else too can confirm this fix. We will start ordering axion relays from now on. - f

On Wed, 10 Oct 2018, 23:15 Jim Sheldon, <w0eb@...> wrote:
Yup, and after opening up one of the original relays that I removed from a V4 board in prep for putting new ones on (they should be here within the hour) it was extremely obvious that those relays were not designed with RF in mind.  There is no shielding of the relay coil at all and all the contacts are on movable arms that run parallel to each other and the full length of the relay as well as close to the relay coil itself.  The armature is mostly made of plastic so doesn't provide much (if any) shielding between the coil and the movable contact arms.  The movable arms are each made up of 2 parallel, approximately 2mm wide strips of metal that are separated in the middle of the top of the relay by about 1 mm.  (Pictures not possible as the relays were pretty much destroyed in the dissection.)  I believe the parallel arm construction was for current carrying capability (not needed in small signal RF relays) as the contacts are rated to 125V @ 60 watts (their designation) in the data sheet.  The width & placement of these contact arms would allow a whole lot of coupling between both sets of contacts and I really believe it's one of the culprits though not necessarily the entire problem.  

Changing the relays to an RF rated set with proper isolation certainly can't hurt and may just wind up being the simplest fix for the problem.

The Postman just delivered the new relays from Digi-Key so off to install them and run some tests to see if I can prove or disprove Mike Doty's data.  

I do believe my results will corroborate his after chopping up one of the old relays to see what was in it.

Jim Sheldon


------ Original Message ------
From: "Arv Evans" <arvid.evans@...>
Sent: 10/10/2018 12:20:51 PM
Subject: Re: [BITX20] Harmonics and Relay Replacement

Jim

Sorry for the "blindly changing relays" comment.  That was not intended to be derogatorily in
any way.  Thinking when I said that was about those who follow what we say, assuming that
we have performed all the necessary testing and evaluation.  Some have measured the
capacitance between relay armatures and between relay contacts, but I have seen little
said about capacitance between RF carrying parts of these relays and the windings.  My
point was about the possibility of relay windings acting as RF chokes, thus allowing the DC
traces between relays to be coupling agents with respect to RF. 

Arv
_._


On Wed, Oct 10, 2018 at 11:02 AM Jim Sheldon <w0eb@...> wrote:
Arv and others,
#1 I really believe it's capacitive coupling within the relay itself and between the contacts, as well as from contacts to coil.  The original relays in the uBITX are inexpensive (read CHEAP) Chinese power relays that are not (I have their spec sheet) rated for RF and there are no RF parameters in their data sheet such as capacitance between contacts, from coil to armature and coil to contacts at all.  I had already bypassed the coil terminals to ground with .1uF SMD capacitors and didn't notice an appreciable difference.

#2, After this came to light, I don't consider myself "blindly" changing relays.  I'm investigating the cause and effect of changing these relays.  My two version 4 uBITX boards DO barely meet spec with the strongest harmonic(s) being -49 dB below the carrier level on MY (calibrated last year) spectrum analyzer.  Others' results will surely vary depending on the precision and how well and when calibrated their spectrum analyzers are.  I do not have the test equipment to measure inter contact/coil, etc. capacitance so I have no choice but change the relays as part of my experimentation.  It's an expense I am willing to undertake to attempt to improve MY uBITX rigs and if it helps others, so be it.  If others chose to ignore the results (good or bad) then the consequences are on them, not me as I am only sharing the information out there with the caveat "For What It's Worth!"  

Looking at the construction of the original relays after dissecting one, I can certainly see the wire to the far end of the coil runs parallel to the contacts along that same side of the relay and not very far away either.  Even though it's smaller than 30 gauge wire, the internal capacitance between the coil and at least one set of contacts is going to be a factor in these relays not to mention there is no shielding of the coil so inductance and capacitance could also be playing a part in the "blow-by".  

The new ones are too expensive to disect one as far as I'm concerned, but at least TE Products (Axicom) saw fit to publish the RF parameters (isolation by frequency) and inter contact/coil capacitance.  

Jim Sheldon, W0EB 





------ Original Message ------
From: "Arv Evans" <arvid.evans@...>
Sent: 10/10/2018 11:16:53 AM
Subject: Re: [BITX20] Harmonics and Relay Replacement

Kees, and others....

Blindly changing relays may fix the problem, but are we missing something here?
What is the real problem with the original relays?  Is it capacitive coupling between
RF carrying parts and the activation conductors, or is it that the relay coils might
be acting as RF chokes and allowing RF to be coupled between relays via the
RF-isolated traces of DC relay control leads?  Has anyone measured how much
is being carried by the DC control leads?  Has anyone tried bypassing the relay
control leads for RF?

Arv
_._


On Wed, Oct 10, 2018 at 8:56 AM Kees T <windy10605@...> wrote:
Thanks for dissecting an AXICOM relay and the pictures. The coil mounted over the contacts is a definite difference to the ones I dissected.

The other thing which may effect results is that most of the larger (16 pin) relays offer up to 4 different "coil sensitivity" options .....which will effect coil resistance and inductance. The resistance for a given 12V relay coil varies between about 960 ohms and about 320 ohms. That may well effect the coupling also.

I don't have enough different relays to compare but I do have some series inductors to evaluate. The thing to watch out for there is the inductor self resonance effect.

73 Kees K5BCQ

Gary Anderson
 

It would be cool if someone with a S.A. could prove / disprove the coupling theory, by testing the 400mA, 200mA, 150mA versions of the AXICOM P2 Relay Series :)
They are all the same maximum coupling spec.  There is no reason to use more power if there is no benefit (shock/vibration argument aside), especially if it is to be chosen in the factory BOM.

Very happy to see there is merit in relay choice at HF frequencies. https://groups.io/g/BITX20/message/55897

Rgds,
Gary
AG5TX

Kees T
 

Arv,

A good friend of mine, Ben Bibb, NO5K, said his analysis shows it is a difference in the INDUCTANCE of the relay contacts because these are really "Constant K" filters and they are notorious for bad reflections due to high SWR at the non passband frequencies and therefore affect the ability to reduce harmonics, etc. He gave me the data plots to prove it and showed how a small inductor 3nH to 6nH in series with the filter input and output greatly improve the situation. It has to be able to handle the RF current, of course. I am trying to duplicate his data.

In the meantime, I checked the N/C to Armature Inductance on 6 different relays (none are AXICOM) and they are all 12nH to 16nH.

Can someone check an AXICOM relay ? 

I still think coupling to the coil is a factor, Ben says "maybe a factor".

73 Kees K5BCQ

Kees T
 

Gary,

I would think that the various coil "sensitivity" options (power) would affect power consumption (at 12V, about 13mA to 38mA per relay)  and operating speed ? which may be something to consider for the CW guys. 

73 Kees K5BCQ

Jim Sheldon
 

OK peeps,
I measured the harmonics with my spectrum analyzer.  I can only show the fundamental, 2nd and 3rd harmonic so it's  not a complete test, but the results though positive, are not all that encouraging.

First, with the original relays, Carrier @ 7.000 MHz set to 0 on the vertical scale.  2nd harmonic was -58 dB from the carrier and the third was only -45 dB from the carrier.  I didn't measure the 4th & 5th though they were farther down than the 3rd.

Changed out the relays and measured again without changing any settings.

7.000 MHz carrier @ 0 (top) of the vertical scale.  2nd harmonic was -67.6 dB down and 3rd was -47 dB down.  That was a 2 dB improvement on the 3rd harmonic but not enough to call it a reliable harmonic fix with the Axicom relays.  It did help and it IS in spec, but there are other things that most likely need to be addressed to make it better.  It IS a step in the right direction and did NOT require complete re-design of the filters.  At least for 40 meters.

I will run the tests on the other bands and see how they come out, but I'm not holding out for much if any improvement over the 40 meter spec.

Ashhar Farhan, the Axicom relays DID help some in my V4 board, but not sure the added expense is justified for production.  I think the filter redesign on the production boards would be a far better long term solution IMO.

I am going to change out the relays on my other V4 board and test it as well but that will be later this evening or tomorrow.  If I don't report on that one, it will mean I didn't find any significant difference between the two boards.

The Axicom part # for the relays I used is V23105A5403A201.

Jim Sheldon, W0EB


------ Original Message ------
From: "Ashhar Farhan" <farhanbox@...>
Sent: 10/10/2018 12:58:56 PM
Subject: Re: [BITX20] Harmonics and Relay Replacement

Guys,
If someone else too can confirm this fix. We will start ordering axion relays from now on. - f

On Wed, 10 Oct 2018, 23:15 Jim Sheldon, <w0eb@...> wrote:
Yup, and after opening up one of the original relays that I removed from a V4 board in prep for putting new ones on (they should be here within the hour) it was extremely obvious that those relays were not designed with RF in mind.  There is no shielding of the relay coil at all and all the contacts are on movable arms that run parallel to each other and the full length of the relay as well as close to the relay coil itself.  The armature is mostly made of plastic so doesn't provide much (if any) shielding between the coil and the movable contact arms.  The movable arms are each made up of 2 parallel, approximately 2mm wide strips of metal that are separated in the middle of the top of the relay by about 1 mm.  (Pictures not possible as the relays were pretty much destroyed in the dissection.)  I believe the parallel arm construction was for current carrying capability (not needed in small signal RF relays) as the contacts are rated to 125V @ 60 watts (their designation) in the data sheet.  The width & placement of these contact arms would allow a whole lot of coupling between both sets of contacts and I really believe it's one of the culprits though not necessarily the entire problem.  

Changing the relays to an RF rated set with proper isolation certainly can't hurt and may just wind up being the simplest fix for the problem.

The Postman just delivered the new relays from Digi-Key so off to install them and run some tests to see if I can prove or disprove Mike Doty's data.  

I do believe my results will corroborate his after chopping up one of the old relays to see what was in it.

Jim Sheldon