开云体育

Max Voltage for QMX 9V

Sepehr - N6IRN All Messages By This Member #142109 Hello, ? I have a QMX that is built for 9V. Now I'm making a custom LiFePO4 battery for it. My question is, what's the maximum input voltage that the QMX can handle before it breaks? Given that each LiFePO4 has around 3.55V, if I connect three of them in series, I'll get around 10.65V, is that going to damage the radio?? ? Thanks, Sepehr N6IRN
va3rr All Messages By This Member #142110 I wouldn't use FT8, but CW into a well-matched antenna might be ok... XE3/VA3RR
Daniel Conklin All Messages By This Member #142111 You could put a small buck converter or a couple of diodes in the line to drop the voltage into acceptable range. -- 73, Dan - W2DLC
W6MQI All Messages By This Member #142112 You could use 2- 7809's in parallel for added current rating or 1-78S09, which I think is good for 2 amps by itself. Your input voltage just needs to 3 or 4 volts higher then the needed output voltage. ? Dave
KK4ITX John All Messages By This Member #142113 开云体育 There doesn’t seem to be a clear consistent answer, the manual implies “a little over” is OK but does not define “little”. I admit that I don’t understand how a device that can handle 12v can’t go over 9v. I do know that I have made contacts quite well with just 2 Lion 18750’s and they last for the duration of the park operation. ?The output is <4w, not a big deal. Until we really know, just play it safe, many ways to keep the voltage under 9v. John KK4ITX ? ?Each mistake is a learning opportunity.? toggle quoted message Show quoted text On Mar 30, 2025, at 7:59 PM, Daniel Conklin via groups.io <danconklin2@...> wrote: ? You could put a small buck converter or a couple of diodes in the line to drop the voltage into acceptable range. -- 73, Dan - W2DLC
Kaufman, Matt - N3AR All Messages By This Member #142114 开云体育 The device can be built to either handle 12v or handle 9v; the person asking the question here built their radio (the transformer part, specifically) for 9v. 73 -- Matt N3AR toggle quoted message Show quoted text On Mar 30, 2025, at 5:35?PM, KK4ITX John via groups.io <jleahy00@...> wrote: There doesn’t seem to be a clear consistent answer, the manual implies “a little over” is OK but does not define “little”. I admit that I don’t understand how a device that can handle 12v can’t go over 9v. I do know that I have made contacts quite well with just 2 Lion 18750’s and they last for the duration of the park operation. ?The output is <4w, not a big deal. Until we really know, just play it safe, many ways to keep the voltage under 9v. John KK4ITX ? ?Each mistake is a learning opportunity.? On Mar 30, 2025, at 7:59 PM, Daniel Conklin via groups.io <danconklin2@...> wrote: ? You could put a small buck converter or a couple of diodes in the line to drop the voltage into acceptable range. -- 73, Dan - W2DLC
Pierre - FK8IH All Messages By This Member #142116 Sepehr, you could use this cheap converter whill will give you a steady 9V: 73 - Pierre - FK8IH
KK4ITX John All Messages By This Member #142117 开云体育 I know that he built it for 9v, same as mine. ?I know that one can choose to build it for 12v input by a small change in the winding of a toroid.? I do not know why the components after said toroid get excited if less than 12v is used if built for 9v….. I am basically a math guy. John ?Each mistake is a learning opportunity.? toggle quoted message Show quoted text On Mar 30, 2025, at 8:39 PM, Kaufman, Matt - N3AR via groups.io <matt.d.kaufman@...> wrote: ?The device can be built to either handle 12v or handle 9v; the person asking the question here built their radio (the transformer part, specifically) for 9v. 73 -- Matt N3AR On Mar 30, 2025, at 5:35?PM, KK4ITX John via groups.io <jleahy00@...> wrote: There doesn’t seem to be a clear consistent answer, the manual implies “a little over” is OK but does not define “little”. I admit that I don’t understand how a device that can handle 12v can’t go over 9v. I do know that I have made contacts quite well with just 2 Lion 18750’s and they last for the duration of the park operation. ?The output is <4w, not a big deal. Until we really know, just play it safe, many ways to keep the voltage under 9v. John KK4ITX ? ?Each mistake is a learning opportunity.? On Mar 30, 2025, at 7:59 PM, Daniel Conklin via groups.io <danconklin2@...> wrote: ? You could put a small buck converter or a couple of diodes in the line to drop the voltage into acceptable range. -- 73, Dan - W2DLC
Donald S Brant Jr All Messages By This Member #142118 On Sun, Mar 30, 2025 at 09:00 PM, KK4ITX John wrote: I do not know why the components after said toroid get excited if less than 12v is used if built for 9v….. I am basically a math guy. ? Because the toroid is connected as an RF transformer, and the "small change" result in different transformer turns ratios which in turn results in different voltages being imposed upon the output FETs when power is being reflected back from the load.?? ? ? 73, Don N2VGU ? ?
Paul - AI7JR All Messages By This Member #142121 I think the issue is that 12V pushes the voltage rating on the BS170's, and the increased current at 9V for the same power, ends up pushing the current rating of the parts. ? Paul -- AI7JR On Mar 30, 2025, 17:35 -0700, KK4ITX John via groups.io <jleahy00@...>, wrote: toggle quoted message Show quoted text There doesn’t seem to be a clear consistent answer, the manual implies “a little over” is OK but does not define “little”. I admit that I don’t understand how a device that can handle 12v can’t go over 9v. I do know that I have made contacts quite well with just 2 Lion 18750’s and they last for the duration of the park operation. ?The output is <4w, not a big deal. Until we really know, just play it safe, many ways to keep the voltage under 9v. John KK4ITX ? ?Each mistake is a learning opportunity.? On Mar 30, 2025, at 7:59 PM, Daniel Conklin via groups.io <danconklin2@...> wrote: ? You could put a small buck converter or a couple of diodes in the line to drop the voltage into acceptable range. -- 73, Dan - W2DLC
Evan Hand All Messages By This Member #142131 Pierre, ? I have found that using a buck/boost converter when connected to batteries is better.? That allows constant voltage to the QMX until the batteries can not supply power. ? ? or ? ? 73 Evan AC9TU
Wlado D2CR All Messages By This Member #142136 Evan: ? Will this cause additional interference due to the use of such buck/boost converter? I like this solution but I'm concerned about the additional noise and birdies when RX. I would be grateful for your/any opinion. 73 Wlado?
John AE5X All Messages By This Member #142137 Most of the noise produced by these converters is below 5 MHz. Very little at all is produced above 7 MHz. ? ? -- John AE5X ?
Evan Hand All Messages By This Member #142139 Wlado, ? I agree with John’s analysis. ?This is supported with my personal experience with the two devices I listed. ?Granted that I live in a high arm environment around Chicago. Ther may be some birdies in a quiet location. I have not tested there.? Also note that there are a number of high power shack supplies that are switchers. ?All three that I use are.? For the relatively low cost, and the fact that you can return the device to Amazon, it would be worth trying.? 73 Evan AC9TU
ajparent1/kb1gmx All Messages By This Member #142141 Sepehr ? The answer is 9V.? There is a little latitude maybe 10%. ? The issue is higher voltages run higher power with the finals and will increase current to the potential failure point. So the BS170s would likely be more prone to fail. ? The rest of the radio due to the power conversion scheme is? not impacted by voltage changes.? I just self adjusts. ? Best approach is to use a good (electrically quiet) buck converter to drop any voltage supplied to 9V. ? -- Allison ------------------ Post online only,? direct email will go to a bit bucket.
Alan G4ZFQ All Messages By This Member #142142 On 31/03/2025 12:40, John AE5X via groups.io wrote: Most of the noise produced by these converters is below 5 MHz John, Thanks, I'd often wondered about all the recommendations for these devices. I was tempted to try them but I will not be using them, LF is of interest here. 73 Alan G4ZFQ
Sepehr - N6IRN All Messages By This Member #142193 Thanks, Allision, for the definitive answer here. I've been using a buck converter to run my QMX off a 12V battery. I was hoping to come up with a ~9V LiFePO4 battery so that I can remove the buck converter from my setup but since so many people have kept suggesting it, I'm now looking into ways of integrating it into this DIY battery that I'm working on. Best, Sepehr Sahraian \| N6IRN President \| Irvine Valley College ARC \| N6IVC LICW #6377? SKCC #28841? NAQCC #11811 Sent with secure email. On Monday, March 31st, 2025 at 6:58 AM, ajparent1/kb1gmx via groups.io <kb1gmx@...> wrote: toggle quoted message Show quoted text Sepehr ? The answer is 9V.? There is a little latitude maybe 10%. ? The issue is higher voltages run higher power with the finals and will increase current to the potential failure point. So the BS170s would likely be more prone to fail. ? The rest of the radio due to the power conversion scheme is? not impacted by voltage changes.? I just self adjusts. ? Best approach is to use a good (electrically quiet) buck converter to drop any voltage supplied to 9V. ? -- Allison ------------------ Post online only,? direct email will go to a bit bucket.

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