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I installed a Zenar diode to protect my (tr)uSDX against high SWR and replicated the same experiment conducted by Barb WB2CBA (the video I forwarded to this forum a while ago).
With a dummy load the (tr)uSDX shows 2.97 watt output and SWR 1.1. Without the dummy load SWR shot up to 101.5 but no smoke or visible damage.?
The third photo shows how the diode was installed in my XH2 (you remember the Poor Man¡¯s KH1?) which is made from a Hi-band (tr)uSDX kit.
So I am totally convinced that a single Zenar diode does protect your (tr)uSDX and other USDX radios.
Hiroki AH6CY
  
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Thank you Hiroki for your validation.? ?I heartedly encourage everyone who has usdx radios,? including the one from Ed Fong to do this simple mod.
|
Is there a side-by-side test documented anywhere???? Ie, showing that the radio is destroyed without the zener diode under the same conditions otherwise??? I couldn't find one.?? They're cheap -- you'd think someone would love to blow one up for the views.
I've done a little searching and all I can find as the origin for this recommendation is just one guy with a self-assembled kit who blew his radio up in an unknown way with unknown power even though he had a tuner inline and was presumably tuned up, and he doesn't know what the root cause was, and then said he'd install the zener just in case.
As for WB2CBA (Barb), he just shows that his radio still works.? He didn't do a side-by-side test.??? And it's not a TruSDX.?? Maybe he could have painted it blue or stuck a bandaid to the back of the radio instead and shown that the radio still worked after a high-swr test.?? Look!?? Painting it blue works!
DL2MAN recommends against adding the zener.?? (His recommendation is boring, just use low power for tuning.? Personally I tune by ear before any kind of tx'ing.?? Works great if you have the ear and the tuner.) ?? Also I had a friend (sadly SK now) who gave his TruSDX a hard workout for a good while and told me that it was pretty robust against mismatch.
I don't think "voltage reflected back into the radio" is exactly the problem with mismatched impedances anyway so maybe the zener works, but maybe not for its breakdown threshold; maybe it just changes the tuning.?? Or maybe it works as well as a bandaid.??? Gotta show me some measurements or a side-by-side test before I'm convinced.??
For all of these reasons, and the fact that it's a cheap radio, and any mod activity introduces unknown risk (which is why regression testing exists), I think I'll save myself the trouble for now. ? I am still open to to the idea and interested to see if any more evidence comes in, in which case it's easy enough to add the zener.???? Or if I blow up this radio in which case you can give me a good Nelson "haha!"?? (Simpsons reference)
73,
Connie? W6EFI
Connie Stillinger
650-380-2018
On Friday, June 14th, 2024 at 10:37 AM, Doug Hendricks <ki6ds1@...> wrote:
Thank you Hiroki for your validation.? ?I heartedly encourage everyone who has usdx radios,? including the one from Ed Fong to do this simple mod.
--
Connie KN2EFI
|
Connie,? when you blow your finals. (Not if, but when), I have plenty of replacement transistors,? which are not trivial to remove.? Lol.
Doug?
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|
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I'm not saying it's not possible to blow the finals. ? ?
I'm just looking for the side-by-side test or measurements compared to specs on the same radio with and without zener, and am surprised that I am not finding data.
On Fri, Jun 14, 2024 at 18:25, Doug Hendricks < ki6ds1@...> wrote: Hiroki did it twice.
--
Connie KN2EFI
|
Connie,
I agree completely. What is the effect on the spectrum, particularly on SSB, which may easily be distorted due to the diode. I think that the failure mode is due to the high voltage as the 3 FETs can dissipate the couple of watts of reflected power.
It could also be neat fix if the diode is more or less transparent under normal operating conditions. It might be interesting to run an experiment with the diode biased with the peak operating voltage on the FETs using a VNA to see what its RF characteristics are in the HF bands. I have never seen an RF amp. that uses this kind of protection.
Dave W6VYC
On Friday, June 14, 2024 at 12:39:57 PM PDT, Connie W6EFI via groups.io <stillinger@...> wrote:
Is there a side-by-side test documented anywhere???? Ie, showing that the radio is destroyed without the zener diode under the same conditions otherwise??? I couldn't find one.?? They're cheap -- you'd think someone would love to blow one up for the views.
I've done a little searching and all I can find as the origin for this recommendation is just one guy with a self-assembled kit who blew his radio up in an unknown way with unknown power even though he had a tuner inline and was presumably tuned up, and he doesn't know what the root cause was, and then said he'd install the zener just in case.
As for WB2CBA (Barb), he just shows that his radio still works.? He didn't do a side-by-side test.??? And it's not a TruSDX.?? Maybe he could have painted it blue or stuck a bandaid to the back of the radio instead and shown that the radio still worked after a high-swr test.?? Look!?? Painting it blue works!
DL2MAN recommends against adding the zener.?? (His recommendation is boring, just use low power for tuning.? Personally I tune by ear before any kind of tx'ing.?? Works great if you have the ear and the tuner.) ?? Also I had a friend (sadly SK now) who gave his TruSDX a hard workout for a good while and told me that it was pretty robust against mismatch.
I don't think "voltage reflected back into the radio" is exactly the problem with mismatched impedances anyway so maybe the zener works, but maybe not for its breakdown threshold; maybe it just changes the tuning.?? Or maybe it works as well as a bandaid.??? Gotta show me some measurements or a side-by-side test before I'm convinced.??
For all of these reasons, and the fact that it's a cheap radio, and any mod activity introduces unknown risk (which is why regression testing exists), I think I'll save myself the trouble for now. ? I am still open to to the idea and interested to see if any more evidence comes in, in which case it's easy enough to add the zener.???? Or if I blow up this radio in which case you can give me a good Nelson "haha!"?? (Simpsons reference)
73,
Connie? W6EFI
Connie Stillinger
650-380-2018
On Friday, June 14th, 2024 at 10:37 AM, Doug Hendricks <ki6ds1@...> wrote:
Thank you Hiroki for your validation.? ?I heartedly encourage everyone who has usdx radios,? including the one from Ed Fong to do this simple mod.
--
Connie KN2EFI
|
The best way to protect? (tr)uSDX against high SWR is to use a proper antenna tuner like ZM-2 ATU that will protect the finals during the antenna tuning.73 Ned AC6YY
Connie,
I agree completely. What is the effect on the spectrum, particularly on SSB, which may easily be distorted due to the diode. I think that the failure mode is due to the high voltage as the 3 FETs can dissipate the couple of watts of reflected power.
It could also be neat fix if the diode is more or less transparent under normal operating conditions. It might be interesting to run an experiment with the diode biased with the peak operating voltage on the FETs using a VNA to see what its RF characteristics are in the HF bands. I have never seen an RF amp. that uses this kind of protection.
Dave W6VYC
On Friday, June 14, 2024 at 12:39:57 PM PDT, Connie W6EFI via <stillinger= [email protected]> wrote:
Is there a side-by-side test documented anywhere???? Ie, showing that the radio is destroyed without the zener diode under the same conditions otherwise??? I couldn't find one.?? They're cheap -- you'd think someone would love to blow one up for the views.
I've done a little searching and all I can find as the origin for this recommendation is just one guy with a self-assembled kit who blew his radio up in an unknown way with unknown power even though he had a tuner inline and was presumably tuned up, and he doesn't know what the root cause was, and then said he'd install the zener just in case.
As for WB2CBA (Barb), he just shows that his radio still works.? He didn't do a side-by-side test.??? And it's not a TruSDX.?? Maybe he could have painted it blue or stuck a bandaid to the back of the radio instead and shown that the radio still worked after a high-swr test.?? Look!?? Painting it blue works!
DL2MAN recommends against adding the zener.?? (His recommendation is boring, just use low power for tuning.? Personally I tune by ear before any kind of tx'ing.?? Works great if you have the ear and the tuner.) ?? Also I had a friend (sadly SK now) who gave his TruSDX a hard workout for a good while and told me that it was pretty robust against mismatch.
I don't think "voltage reflected back into the radio" is exactly the problem with mismatched impedances anyway so maybe the zener works, but maybe not for its breakdown threshold; maybe it just changes the tuning.?? Or maybe it works as well as a bandaid.??? Gotta show me some measurements or a side-by-side test before I'm convinced.??
For all of these reasons, and the fact that it's a cheap radio, and any mod activity introduces unknown risk (which is why regression testing exists), I think I'll save myself the trouble for now. ? I am still open to to the idea and interested to see if any more evidence comes in, in which case it's easy enough to add the zener.???? Or if I blow up this radio in which case you can give me a good Nelson "haha!"?? (Simpsons reference)
73,
Connie? W6EFI
Connie Stillinger
650-380-2018
On Friday, June 14th, 2024 at 10:37 AM, Doug Hendricks < ki6ds1@...> wrote:
Thank you Hiroki for your validation.? ?I heartedly encourage everyone who has usdx radios,? including the one from Ed Fong to do this simple mod.
-- Connie KN2EFI
|
I have a ZM-2 that I built. If anyone wants to borrow it to try it out with your (tr)uSDX or other let me know.
toggle quoted message
Show quoted text
The best way to protect? (tr)uSDX against high SWR is to use a proper antenna tuner like ZM-2 ATU that will protect the finals during the antenna tuning.<image.png>
73 Ned AC6YY
Connie,
I agree completely. What is the effect on the spectrum, particularly on SSB, which may easily be distorted due to the diode. I think that the failure mode is due to the high voltage as the 3 FETs can dissipate the couple of watts of reflected power.
It could also be neat fix if the diode is more or less transparent under normal operating conditions. It might be interesting to run an experiment with the diode biased with the peak operating voltage on the FETs using a VNA to see what its RF characteristics are in the HF bands. I have never seen an RF amp. that uses this kind of protection.
Dave W6VYC
On Friday, June 14, 2024 at 12:39:57 PM PDT, Connie W6EFI via <stillinger= [email protected]> wrote:
Is there a side-by-side test documented anywhere???? Ie, showing that the radio is destroyed without the zener diode under the same conditions otherwise??? I couldn't find one.?? They're cheap -- you'd think someone would love to blow one up for the views.
I've done a little searching and all I can find as the origin for this recommendation is just one guy with a self-assembled kit who blew his radio up in an unknown way with unknown power even though he had a tuner inline and was presumably tuned up, and he doesn't know what the root cause was, and then said he'd install the zener just in case.
As for WB2CBA (Barb), he just shows that his radio still works.? He didn't do a side-by-side test.??? And it's not a TruSDX.?? Maybe he could have painted it blue or stuck a bandaid to the back of the radio instead and shown that the radio still worked after a high-swr test.?? Look!?? Painting it blue works!
DL2MAN recommends against adding the zener.?? (His recommendation is boring, just use low power for tuning.? Personally I tune by ear before any kind of tx'ing.?? Works great if you have the ear and the tuner.) ?? Also I had a friend (sadly SK now) who gave his TruSDX a hard workout for a good while and told me that it was pretty robust against mismatch.
I don't think "voltage reflected back into the radio" is exactly the problem with mismatched impedances anyway so maybe the zener works, but maybe not for its breakdown threshold; maybe it just changes the tuning.?? Or maybe it works as well as a bandaid.??? Gotta show me some measurements or a side-by-side test before I'm convinced.??
For all of these reasons, and the fact that it's a cheap radio, and any mod activity introduces unknown risk (which is why regression testing exists), I think I'll save myself the trouble for now. ? I am still open to to the idea and interested to see if any more evidence comes in, in which case it's easy enough to add the zener.???? Or if I blow up this radio in which case you can give me a good Nelson "haha!"?? (Simpsons reference)
73,
Connie? W6EFI
Connie Stillinger
650-380-2018
On Friday, June 14th, 2024 at 10:37 AM, Doug Hendricks < ki6ds1@...> wrote:
Thank you Hiroki for your validation.? ?I heartedly encourage everyone who has usdx radios,? including the one from Ed Fong to do this simple mod.
-- Connie KN2EFI
|
Why is that better than the diode. What if you hook things up wrong and the antenna tuner is not connected?? Dave, there were no bad effects shown on the spectrum analyser.? Dave all of Steve Weber designs use the diode.? I guess you guys don't? believe in empirical evidence.? ?Hiroki had 2 sets of finals blow before he installed the diode.? Qrpguys have never had one complaint about a blown final, and we have sold thousands.? ?Hiroki even transmitted into an open load with the diode protection and no problems at all.? I have yet to see any evidence from anyone that the addition of the diode is harmful yet I have seen where it helps.? Respectfully submitted.? Doug, KI6DS?
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Upon rereading Dave's post I think I? misunderstood what he said.? I think he said that he had never seen a final that was biased as he said not that he had never seen a final with a 1n4756a protection diode.? ?My apologies,? Dave.? Doug
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I have more data.? I measured the power out on the Trusdx with and without the diode protection.? ?Here is the data:
Band. W/diode. WO/diode. % lost
80.? ? ? ?5.96.? ? ? ? 6.35.? ? ? ? ? ?6.1
60.? ? ? ?5.00.? ? ? ? 5.19.? ? ? ? ? ?3.7
40.? ? ? ?5.27.? ? ? ? 5.59.? ? ? ? ? ?5.7
30.? ? ? ?5.38.? ? ? ? 5.60.? ? ? ? ? ?3.9
20.? ? ? ?5.35.? ? ? ? 5.52.? ? ? ? ? ?3.1
Voltage = 12.59V
The power lost ranged from .22W on 80m to .17W on 20m.? I will gladly trade that power loss for the protection and peace of mind.?
72, Doug?
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6% is about 0.5 dB.? The difference won't be heard.??
Good to have protection for the times when something wasn't connected or the tuner wasn't or ...
On Wednesday, June 26, 2024 at 12:16:13 PM PDT, Doug Hendricks <ki6ds1@...> wrote:
I have more data.? I measured the power out on the Trusdx with and without the diode protection.? ?Here is the data:
Band. W/diode. WO/diode. % lost
80.? ? ? ?5.96.? ? ? ? 6.35.? ? ? ? ? ?6.1
60.? ? ? ?5.00.? ? ? ? 5.19.? ? ? ? ? ?3.7
40.? ? ? ?5.27.? ? ? ? 5.59.? ? ? ? ? ?5.7
30.? ? ? ?5.38.? ? ? ? 5.60.? ? ? ? ? ?3.9
20.? ? ? ?5.35.? ? ? ? 5.52.? ? ? ? ? ?3.1
Voltage = 12.59V
The power lost ranged from .22W on 80m to .17W on 20m.? I will gladly trade that power loss for the protection and peace of mind.?
72, Doug?
|
It¡¯s possible that manufacturer(s) could retune the output circuit(s) to get that power back. We should tell them to add this zener.?
On Wed, Jun 26, 2024 at 12:16 PM Doug Hendricks via <ki6ds1= [email protected]> wrote: I have more data.? I measured the power out on the Trusdx with and without the diode protection.? ?Here is the data:
Band. W/diode. WO/diode. % lost
80.? ? ? ?5.96.? ? ? ? 6.35.? ? ? ? ? ?6.1
60.? ? ? ?5.00.? ? ? ? 5.19.? ? ? ? ? ?3.7
40.? ? ? ?5.27.? ? ? ? 5.59.? ? ? ? ? ?5.7
30.? ? ? ?5.38.? ? ? ? 5.60.? ? ? ? ? ?3.9
20.? ? ? ?5.35.? ? ? ? 5.52.? ? ? ? ? ?3.1
Voltage = 12.59V
The power lost ranged from .22W on 80m to .17W on 20m.? I will gladly trade that power loss for the protection and peace of mind.?
72, Doug?
|
I would gladly trade a little power lost for protection, but I am not yet convinced that the diode actually provides protection.?
Show me a side-by-side test demonstrating that the radio is destroyed without the diode, but ?remains intact with the diode installed under otherwise identical conditions.
Testimonials and strongly asserted opinions don't have the same standing as experimental data.
Any mod activity introduces some risk ?not to mention time, effort, and materials, and now we have measurements showing that there is power loss associated with the mod. Show me data demonstrating the theoretical benefit is real it or I am going to put my efforts toward higher priority issues.
I will close with a reminder that I am NOT asserting that I will not blow up my trusdx at some point. I AM saying that no one is producing actual data, one way or the other. ? just theories along with some data showing that there is a downside. Show me the data and I will consider the mod.
On Wed, Jun 26, 2024 at 12:16, Doug Hendricks < ki6ds1@...> wrote: I have more data.? I measured the power out on the Trusdx with and without the diode protection.? ?Here is the data:
Band. W/diode. WO/diode. % lost
80.? ? ? ?5.96.? ? ? ? 6.35.? ? ? ? ? ?6.1
60.? ? ? ?5.00.? ? ? ? 5.19.? ? ? ? ? ?3.7
40.? ? ? ?5.27.? ? ? ? 5.59.? ? ? ? ? ?5.7
30.? ? ? ?5.38.? ? ? ? 5.60.? ? ? ? ? ?3.9
20.? ? ? ?5.35.? ? ? ? 5.52.? ? ? ? ? ?3.1
Voltage = 12.59V
The power lost ranged from .22W on 80m to .17W on 20m.? I will gladly trade that power loss for the protection and peace of mind.?
72, Doug?
--
Connie KN2EFI
|
Connie.? Hiroki had 2 sets of finals burn out because he was operating into a high swr.? When he put the diode in the same radio, he was able to transmit for several minutes with no antenna attached and infinite swr.? There is your proof.? Without the diode and high swr, the radio? blew the finals.? Not once, but twice.? ?With the diode, the radio was protected when operating into even worse conditions.? ?What more do you need?????
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I would like to do an infrared survey of the board and zener running into an infinite mismatch. If the power is going into the 1 Watt zener, it might be overheating. If some power is being dissipated elsewhere, I¡¯m curious about where else it might go.?
On Wed, Jun 26, 2024 at 12:56 PM Doug Hendricks via <ki6ds1= [email protected]> wrote: Connie.? Hiroki had 2 sets of finals burn out because he was operating into a high swr.? When he put the diode in the same radio, he was able to transmit for several minutes with no antenna attached and infinite swr.? There is your proof.? Without the diode and high swr, the radio? blew the finals.? Not once, but twice.? ?With the diode, the radio was protected when operating into even worse conditions.? ?What more do you need?????
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I also have a Q-Match manual tuner that has a tune mode with a resistive bridge that keeps the SWR below 2:1 under all load conditions. I agree, this type of tuner will protect these simple FET QRP finals.
Dave W6VYC
On Tuesday, June 25, 2024 at 06:15:17 PM PDT, HOWARD POMERANTZ <howpom@...> wrote:
I have a ZM-2 that I built. If anyone wants to borrow it to try it out with your (tr)uSDX or other let me know.
The best way to protect? (tr)uSDX against high SWR is to use a proper antenna tuner like ZM-2 ATU that will protect the finals during the antenna tuning.<image.png>
73 Ned AC6YY
Connie,
I agree completely. What is the effect on the spectrum, particularly on SSB, which may easily be distorted due to the diode. I think that the failure mode is due to the high voltage as the 3 FETs can dissipate the couple of watts of reflected power.
It could also be neat fix if the diode is more or less transparent under normal operating conditions. It might be interesting to run an experiment with the diode biased with the peak operating voltage on the FETs using a VNA to see what its RF characteristics are in the HF bands. I have never seen an RF amp. that uses this kind of protection.
Dave W6VYC
On Friday, June 14, 2024 at 12:39:57 PM PDT, Connie W6EFI via <stillinger= [email protected]> wrote:
Is there a side-by-side test documented anywhere???? Ie, showing that the radio is destroyed without the zener diode under the same conditions otherwise??? I couldn't find one.?? They're cheap -- you'd think someone would love to blow one up for the views.
I've done a little searching and all I can find as the origin for this recommendation is just one guy with a self-assembled kit who blew his radio up in an unknown way with unknown power even though he had a tuner inline and was presumably tuned up, and he doesn't know what the root cause was, and then said he'd install the zener just in case.
As for WB2CBA (Barb), he just shows that his radio still works.? He didn't do a side-by-side test.??? And it's not a TruSDX.?? Maybe he could have painted it blue or stuck a bandaid to the back of the radio instead and shown that the radio still worked after a high-swr test.?? Look!?? Painting it blue works!
DL2MAN recommends against adding the zener.?? (His recommendation is boring, just use low power for tuning.? Personally I tune by ear before any kind of tx'ing.?? Works great if you have the ear and the tuner.) ?? Also I had a friend (sadly SK now) who gave his TruSDX a hard workout for a good while and told me that it was pretty robust against mismatch.
I don't think "voltage reflected back into the radio" is exactly the problem with mismatched impedances anyway so maybe the zener works, but maybe not for its breakdown threshold; maybe it just changes the tuning.?? Or maybe it works as well as a bandaid.??? Gotta show me some measurements or a side-by-side test before I'm convinced.??
For all of these reasons, and the fact that it's a cheap radio, and any mod activity introduces unknown risk (which is why regression testing exists), I think I'll save myself the trouble for now. ? I am still open to to the idea and interested to see if any more evidence comes in, in which case it's easy enough to add the zener.???? Or if I blow up this radio in which case you can give me a good Nelson "haha!"?? (Simpsons reference)
73,
Connie? W6EFI
Connie Stillinger
650-380-2018
On Friday, June 14th, 2024 at 10:37 AM, Doug Hendricks < ki6ds1@...> wrote:
Thank you Hiroki for your validation.? ?I heartedly encourage everyone who has usdx radios,? including the one from Ed Fong to do this simple mod.
-- Connie KN2EFI
|
Doug and All,
I took a look at Steve's ATS-4 and Doug is correct there is a 47V zener diode across the FETS in the PA, so this has been used on simple CW amp. designs for some time. I still think that the uSDX+ design, using SSB, is a little more complicated than a straight CW amp.
Dave W6VYC
On Tuesday, June 25, 2024 at 05:41:14 PM PDT, David W Crocker via groups.io <dwcae@...> wrote:
Connie,
I agree completely. What is the effect on the spectrum, particularly on SSB, which may easily be distorted due to the diode. I think that the failure mode is due to the high voltage as the 3 FETs can dissipate the couple of watts of reflected power.
It could also be neat fix if the diode is more or less transparent under normal operating conditions. It might be interesting to run an experiment with the diode biased with the peak operating voltage on the FETs using a VNA to see what its RF characteristics are in the HF bands. I have never seen an RF amp. that uses this kind of protection.
Dave W6VYC
On Friday, June 14, 2024 at 12:39:57 PM PDT, Connie W6EFI via groups.io <stillinger@...> wrote:
Is there a side-by-side test documented anywhere???? Ie, showing that the radio is destroyed without the zener diode under the same conditions otherwise??? I couldn't find one.?? They're cheap -- you'd think someone would love to blow one up for the views.
I've done a little searching and all I can find as the origin for this recommendation is just one guy with a self-assembled kit who blew his radio up in an unknown way with unknown power even though he had a tuner inline and was presumably tuned up, and he doesn't know what the root cause was, and then said he'd install the zener just in case.
As for WB2CBA (Barb), he just shows that his radio still works.? He didn't do a side-by-side test.??? And it's not a TruSDX.?? Maybe he could have painted it blue or stuck a bandaid to the back of the radio instead and shown that the radio still worked after a high-swr test.?? Look!?? Painting it blue works!
DL2MAN recommends against adding the zener.?? (His recommendation is boring, just use low power for tuning.? Personally I tune by ear before any kind of tx'ing.?? Works great if you have the ear and the tuner.) ?? Also I had a friend (sadly SK now) who gave his TruSDX a hard workout for a good while and told me that it was pretty robust against mismatch.
I don't think "voltage reflected back into the radio" is exactly the problem with mismatched impedances anyway so maybe the zener works, but maybe not for its breakdown threshold; maybe it just changes the tuning.?? Or maybe it works as well as a bandaid.??? Gotta show me some measurements or a side-by-side test before I'm convinced.??
For all of these reasons, and the fact that it's a cheap radio, and any mod activity introduces unknown risk (which is why regression testing exists), I think I'll save myself the trouble for now. ? I am still open to to the idea and interested to see if any more evidence comes in, in which case it's easy enough to add the zener.???? Or if I blow up this radio in which case you can give me a good Nelson "haha!"?? (Simpsons reference)
73,
Connie? W6EFI
Connie Stillinger
650-380-2018
On Friday, June 14th, 2024 at 10:37 AM, Doug Hendricks <ki6ds1@...> wrote:
Thank you Hiroki for your validation.? ?I heartedly encourage everyone who has usdx radios,? including the one from Ed Fong to do this simple mod.
|
Hiroki-
The zener? protection diode is a common design practice and is
favored by Wes Hayward, W7ZOI. In his ARRL publication
"Experimental Methods..." he explains the design on 1.19, fig.
#1.35. subsequent design examples feature this design component.
Your experiments confirm the usefulness and utility of his
recommendation. Great job.
Phil
On 6/14/2024 8:42 AM, Hiroki Kato
wrote:
toggle quoted message
Show quoted text
I installed a Zenar diode to protect my (tr)uSDX
against high SWR and replicated the same experiment conducted by
Barb WB2CBA (the video I forwarded to this forum a while ago).
With a dummy load the (tr)uSDX shows 2.97 watt
output and SWR 1.1. Without the dummy load SWR shot up to 101.5
but no smoke or visible damage.?
The third photo shows how the diode was installed in
my XH2 (you remember the Poor Man¡¯s KH1?) which is made from a
Hi-band (tr)uSDX kit.
So I am totally convinced that a single Zenar diode
does protect your (tr)uSDX and other USDX radios.
Hiroki AH6CY
  
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David W Crocker
Jeff Reagan