Re: Harmonics and Relay Replacement
One more........
Inquiring minds want to know............
What is the power (or "sensitivity" level) of the AXICOM 12V relay relative to the others since there are typically 3 or 4 different power level options and the coil DC resistance will vary from about 320 ohms (high current) to 960 ohms (low current), depending on the option selected.
73 Kees K5BCQ
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Re: Harmonics and Relay Replacement
Note that the addition of a 100uH choke in series with the coil improved the attenuation 10dB......but there is that self resonance peak. Don't know the effect (yet) of having a 100uH (or larger) choke on every coil lead.
73 Kees K5BCQ?
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Re: Harmonics and Relay Replacement
Those inductances all look right. Sure would like to know WHY the Axicom relays have better readings.?
It just dawned on me that when I'm measuring all these little LPFs, whether I built them up or used the parts off the uBITX......the attenuation is not going to be better than what the filter by itself shows when tested separately. I'm generally seeing -50dBm to -55dBm (Including a couple of LPFs from Hans' QRP Labs) and that's apparently as good as it's going to get. Guess I was spoiled by a larger 3" board LPF, same component values as the smaller 1.5" boards but it has an attenuation down to -70dBm and starts getting close to the noise level of the Rigol. I may be making some overall improvements but the effect is "masked" by the actual filter capability.
The task at hand is to make the SYSTEM LPF attenuation as close to the individual LPF attenuation as possible through the use of different relays, relay wiring, RF chokes, etc, etc. And, of course, if the individual LPF design on those small 1.5" boards QRP Labs uses, can be improved. As Ben, NO5K, said....those "constant K" filter designs are known for having really bad SWR outside the intended bandwidth resulting in lots of nasty reflections.....as a Smith Chart reflection vector will show. The fix may be to add some inductance between the LPFs and the PA output, but the effects are difficult to see if the LPF capabilities "mask" them . More to scratch your head about.
73 Kees K5BCQ
|
Re: Purchase of uBitx on hold until?
Hope she's ok.? Sorta suddenly stopped posting.
|
Re: Harmonics and Relay Replacement
Your values look to be in line with what I measured, Jim.? .02uH is 20 nH.? I only measured one of each brand.
--Mike--
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Re: QSX 10W HF Linear PA kit
Hans will your upcoming transceiver kit have the option to add a TCXO oscillator???
-Justin N2TOH?
|
Re: Harmonics and Relay Replacement
Thanks Jim.? That is quite promising. _._
On Wed, Oct 10, 2018 at 2:06 PM Jim Sheldon < w0eb@...> wrote:
I've just finished the tests up through 20 meters and it's only 40 that I have any issues with.
Test parameters - since the power output gets lower the higher in frequency you go, on each band I set the SA so that the carrier was on 0 dB each time I changed bands. My rf pickup is from a 50 ohm dummy load through a voltage divider to the SA to keep input below +30 dBM.
80 Meters 3.500 MHz 7.000 (2nd harmonic) - 65.7 dBC 14.000 (3rd harmonic) -76.4 dBC
40 Meters 7.000 MHz 14.000 (2nd) -58.0 dBC 21.000 (3rd) - 47.2 dBC
30 meters 10.000 MHz 20.000 (2nd) -76.9 dBC 30.000 (3rd) -75.8 dBC
20 meters 14.000 MHz 28.000 (2nd) -65.2 dBC 42.000 (3rd) -64.8 dBC
I didn't test 17, 12 and 10 meters at this time but I suspect their harmonic suppression is in the same boat as the rest.
I did do a quick test on 20 meters with 1KHz tone into the mic jack (I'm a CW op and don't keep a microphone in the shack), power out about 7 watts, SA set so carrier was 0 (top) of screen and got basically the same results - 2nd harmonic @ 28 MHz was -65.0 dBC and 3rd @ 42 MHz was -63.9 dBC, very close to the same as I got for CW.? There were a few spurs that showed up on the 20 meter test, but they were all -80 dBC or better (I do have the 2nd 45 MHz filter in place). ?
It appears that the Axicom relays DO provide a significant harmonic reduction over the originals used. ( Except for 40 meters on MY uBITX board.? I suspect there is something else in play there that I need to track down).? I still need to swap relays on the 2nd board and check it but as I said earlier that will be most likely tomorrow.
Jim Sheldon, W0EB
------ Original Message ------
Sent: 10/10/2018 2:37:30 PM
Subject: Re: [BITX20] Harmonics and Relay Replacement
Thanks,? Jim for doing those tests!!
Sorry to hear the 3rd wasn't reduced any further.? ? In my tests of the external daughterboard idea, the 3rd harmonic on that particular band?was reduced by 1.5 S units, and calibrations with inline attenuators suggested 1 S unit = 12 dB in that region.?
?Due to the granularity of the S-unit display on the ICOM 718 it might have really only been just over 1 S Unit...but still it appears the daughterboard (which deals more with the wiring) achieved a higher degree of harmonic reduction.
It is great there is such a huge group of people working on various solutions!!!
Gordon..
Ref:? ??
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 ------
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
|
Re: Harmonics and Relay Replacement
How did you measure the inductance of the armature? ?I tried with my AADE LC meter and I get .02 to .028 microhenry on all 5 new relays. ?Not sure I'm using the right method to measure that particular inductance.
Jim - W0EB
------ Original Message ------
Sent: 10/10/2018 5:58:17 PM
Subject: Re: [BITX20] Harmonics and Relay Replacement
Kees,
In measuring a Virtual relay and an Axicom relay that I have here, both show approximately 20nH.
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Re: Harmonics and Relay Replacement
Kees,
In measuring a Virtual relay and an Axicom relay that I have here, both show approximately 20nH.
|
Re: Harmonics and Relay Replacement
Since we have AXICOM relays in the group now, can someone please measure the inductance from the N/C contact to the Armature on one of those relays. To see if it differs any from the 6 other relays I tested from 12nH to 19nH.?
73 Kees K5BCQ
|
Re: Harmonics and Relay Replacement
Jim, I stand corrected on my CW comment since the uBITX is not QSK. Someone asked what adding a 100uH inductor in series with the coil does. This is the plot of the larger 16 pin HFD27 relay with the 100uH inductor added.? The "hump" is the inductor self resonance point of about 7MHz??.....making the inductor larger (1mH) lowers the self resonance point to about 2MHz.? Compare this to the 2nd plot I listed earlier. 73 Kees K5BCQ 
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Re: Harmonics and Relay Replacement
Kees, and others.
After much testing, re-designing, analysis, re-testing, etc. we seem to be slowly zeroing in on
several ways to improve the situation regarding spurs, harmonics, etc.? When this is all done
the uBITX may become the most regulation compliant rig in hamdom!?
Arv _._
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
|
Re: Purchase of uBitx on hold until?
Are you saying that the second 45mhz mod can be removed from the TX with this mod? How much power loss is lost with the 45mhz is in place?
Nice work by the way. I¡¯d like to try this for sure.
Joe
PS wheres Allison been? She must be on vacation.?
toggle quoted message
Show quoted text
On Oct 10, 2018, at 3:22 AM, Raj vu2zap < rajendrakumargg@...> wrote:
Mike, see my SIMPLER spur fix without loss of Po!
Tested on two boards here..
Raj
At 10-10-18, you wrote:
Iz
Spurs news item:? ??
Just 3 parts and you will have that one licked.? ?? However, it may
just be an expensive way of introducing -6dB of gain!
Mike
On 10/10/18 7:56 PM, iz oos wrote:
Mike, what are the three parts to resolve spurs? I might have missed
something.
Il 10/ott/2018 08:38, "Mike Woods"
<mhwoods@...> ha
scritto:
- Eliott
- The latest version of the uBITx is the v4, which doesn't have an
audio chip at all (it has discrete transistors).??
- The v4 board MAY have audio issues ... a small proportion of owners
have experienced audio distortion.?? There is a known fix for this
issue and the fix is documented on
.?? The audio also has a bit
lower output than the v3 board.
- You discuss the IMD issue, but this doesn't appear to affect most
users in practice.? ?? It may result in some splatter if you are
over-driving the audio, but really can't be considered a major impediment
to a purchaser.??
- There are several other issues (see
for a summary
of pros and cons).
- If you don't want to modify the board to fix issues that really
matter (harmonics - the most substantial mod that is required), spurs
(requires 3 parts), and to add an AGC (multiple parts) then I suggest you
don't bother buying the kit.? ?? You may have to wait a while to see
a further upgrade from HF Signals though (if ever)! If you don't mind
spending a bit of time having fun making these changes, then go for
it!?? Lots of us out there are having fun.
- 73
- Mike ZL1AXG
- ??
- On 9/10/18 6:26 AM, Eliot Ricciardelli via Groups.Io wrote:
- I am specifically referring to the current rev of the uBitx.
Specifically - the audio chip issue and the IMD issue. You stated all of
yours are in spec and didn't mention any component issues so I assume you
have none. That is helpful, thank you.
- --
- Mike Woods
- mhwoods@...
--
Mike Woods
mhwoods@...
|
The through-hole 2n3904 uses a silicon die that is identical to the surfacemount MMBT3904.
The through hole package can dissipate more power,
but I believe the failure mode is excessive voltage punching through a junction.
So yes, still need diode protection.
toggle quoted message
Show quoted text
On Wed, Oct 10, 2018 at 01:32 PM, <craigmclean@...> wrote:
If I have replaced Q13 with a larger through hole version of the transistor, is the diode protection mod still required to protect that transistor?
|
One other question.
If I have replaced Q13 with a larger through hole version of the transistor, is the diode protection mod still required to protect that transistor?
|
Re: Harmonics and Relay Replacement
That¡¯s very good news! ??
That will probably suffice for the vast majority of people. ?
On Oct 10, 2018, at 16:07, Jim Sheldon < w0eb@...> wrote:
toggle quoted message
Show quoted text
I've just finished the tests up through 20 meters and it's only 40 that I have any issues with.
Test parameters - since the power output gets lower the higher in frequency you go, on each band I set the SA so that the carrier was on 0 dB each time I changed bands. My rf pickup is from a 50 ohm dummy load through a voltage divider to the SA to keep
input below +30 dBM.
80 Meters 3.500 MHz
7.000 (2nd harmonic) - 65.7 dBC
14.000 (3rd harmonic) -76.4 dBC
40 Meters 7.000 MHz
14.000 (2nd) -58.0 dBC
21.000 (3rd) - 47.2 dBC
30 meters 10.000 MHz
20.000 (2nd) -76.9 dBC
30.000 (3rd) -75.8 dBC
20 meters 14.000 MHz
28.000 (2nd) -65.2 dBC
42.000 (3rd) -64.8 dBC
I didn't test 17, 12 and 10 meters at this time but I suspect their harmonic suppression is in the same boat as the rest.
I did do a quick test on 20 meters with 1KHz tone into the mic jack (I'm a CW op and don't keep a microphone in the shack), power out about 7 watts, SA set so carrier was 0 (top) of screen and got basically the same results - 2nd harmonic @ 28 MHz was
-65.0 dBC and 3rd @ 42 MHz was -63.9 dBC, very close to the same as I got for CW. ?There were a few spurs that showed up on the 20 meter test, but they were all -80 dBC or better (I do have the 2nd 45 MHz filter in place). ?
It appears that the Axicom relays DO provide a significant harmonic reduction over the originals used. ( Except for 40 meters on MY uBITX board. ?I suspect there is something else in play there that I need to track down). ?I still need to swap relays on
the 2nd board and check it but as I said earlier that will be most likely tomorrow.
Jim Sheldon, W0EB
------ Original Message ------
Sent: 10/10/2018 2:37:30 PM
Subject: Re: [BITX20] Harmonics and Relay Replacement
Thanks,? Jim for doing those tests!!
Sorry to hear the 3rd wasn't reduced any further.? ? In my tests of the external daughterboard idea, the 3rd harmonic on that particular band?was reduced by 1.5 S units, and calibrations with inline attenuators suggested 1 S unit = 12 dB in that region.?
?Due to the granularity of the S-unit display on the ICOM 718 it might have really only been just over 1 S Unit...but still it appears the daughterboard (which deals more with the wiring) achieved a higher degree of harmonic reduction.
It is great there is such a huge group of people working on various solutions!!!
Gordon..
Ref:? ??
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 ------
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
|
Re: Harmonics and Relay Replacement
Why would it bother the CW ops? ?The uBITX is NOT full QSK anyway and the relays do not follow keying. ?They remain energized for a short time after key-up before returning to RX.
Jim - W0EB
------ Original Message ------
Sent: 10/10/2018 1:48:27 PM
Subject: Re: [BITX20] Harmonics and Relay Replacement
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
|
Re: Harmonics and Relay Replacement
I've just finished the tests up through 20 meters and it's only 40 that I have any issues with.
Test parameters - since the power output gets lower the higher in frequency you go, on each band I set the SA so that the carrier was on 0 dB each time I changed bands. My rf pickup is from a 50 ohm dummy load through a voltage divider to the SA to keep input below +30 dBM.
80 Meters 3.500 MHz 7.000 (2nd harmonic) - 65.7 dBC 14.000 (3rd harmonic) -76.4 dBC
40 Meters 7.000 MHz 14.000 (2nd) -58.0 dBC 21.000 (3rd) - 47.2 dBC
30 meters 10.000 MHz 20.000 (2nd) -76.9 dBC 30.000 (3rd) -75.8 dBC
20 meters 14.000 MHz 28.000 (2nd) -65.2 dBC 42.000 (3rd) -64.8 dBC
I didn't test 17, 12 and 10 meters at this time but I suspect their harmonic suppression is in the same boat as the rest.
I did do a quick test on 20 meters with 1KHz tone into the mic jack (I'm a CW op and don't keep a microphone in the shack), power out about 7 watts, SA set so carrier was 0 (top) of screen and got basically the same results - 2nd harmonic @ 28 MHz was -65.0 dBC and 3rd @ 42 MHz was -63.9 dBC, very close to the same as I got for CW. ?There were a few spurs that showed up on the 20 meter test, but they were all -80 dBC or better (I do have the 2nd 45 MHz filter in place). ?
It appears that the Axicom relays DO provide a significant harmonic reduction over the originals used. ( Except for 40 meters on MY uBITX board. ?I suspect there is something else in play there that I need to track down). ?I still need to swap relays on the 2nd board and check it but as I said earlier that will be most likely tomorrow.
Jim Sheldon, W0EB
------ Original Message ------
Sent: 10/10/2018 2:37:30 PM
Subject: Re: [BITX20] Harmonics and Relay Replacement
Thanks,? Jim for doing those tests!!
Sorry to hear the 3rd wasn't reduced any further.? ? In my tests of the external daughterboard idea, the 3rd harmonic on that particular band?was reduced by 1.5 S units, and calibrations with inline attenuators suggested 1 S unit = 12 dB in that region.?
?Due to the granularity of the S-unit display on the ICOM 718 it might have really only been just over 1 S Unit...but still it appears the daughterboard (which deals more with the wiring) achieved a higher degree of harmonic reduction.
It is great there is such a huge group of people working on various solutions!!!
Gordon..
Ref:? ??
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 ------
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
|
Re: Harmonics and Relay Replacement
Thanks,? Jim for doing those tests!!
Sorry to hear the 3rd wasn't reduced any further.? ? In my tests of the external daughterboard idea, the 3rd harmonic on that particular band?was reduced by 1.5 S units, and calibrations with inline attenuators suggested 1 S unit = 12 dB in that region.?
?Due to the granularity of the S-unit display on the ICOM 718 it might have really only been just over 1 S Unit...but still it appears the daughterboard (which deals more with the wiring) achieved a higher degree of harmonic reduction.
It is great there is such a huge group of people working on various solutions!!!
Gordon..
Ref:? ??
toggle quoted message
Show quoted text
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 ------
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
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Re: Harmonics and Relay Replacement
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 ------
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
|
Jim Sheldon