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I am enjoying this pair. Does need a voltage control to the QDX or you may overdrive the amp. I have been running the amp at 25W RF out. QDX build for 12vdc. Feeding at under 7vdc.?
Joshua
KO4AWH
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Very FB, Joshua !!
What voltage controller is that ? 3D printed enclosure ?
73, Jamie
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On Jan 21, 2023, at 5:41 PM, Joshua Ellis <jjellis2010@...> wrote:
? I am enjoying this pair. Does need a voltage control to the QDX or you may overdrive the amp. I have been running the amp at 25W RF out. QDX build for 12vdc. Feeding at under 7vdc.?
Joshua
KO4AWH
<FE3AF2CC-C97B-4C32-B712-7DD92EDE873E.jpeg>
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Is that an RF-keyed amplifier? I don't see a PTT line.?
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I advise against using RF keying; it invariably places an open circuit on the driving transmitter during TX/RX switchover, AFTER the transmitter has started transmitting.? The amp does not have RF to detect until the transmitter is already on the air, then it switches the TR relays, the open circuiting occurs as the relay contacts move across.? Depending upon the relay timing (input relays are often smaller/faster than output) the amplifier could also see a momentary open while simultaneously being driven.
The QDX has keying outputs and the amp has a PTT input; it makes sense to use them.
73, Don N2VGU
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James, Yes, it's a voltage and amp controlled board, found on Aliexpress a while back. Shoot me a note if you need a link. KO4AWH@...?The Case is indeed printed. I designed it for a quick means of protection of the board on the workbench. Joshua KO4AWH
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Joshua KJ7LVZ
Yes, RF sense for TX and band selection. As Donald points out, maybe an issue? The amp does have a PTT port and even a menu for selection between either "ICOM" or "XEIGU" but not sure exactly what it will or will not do.
Joshua
KO4AHW
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Donald,
That makes great sense. Do you have any specific examples of what has actually happened to a radio in this configuration? I will have to play with the PTT port and see how it does.
Joshua
KO4AHW
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Mr. Ellis, the reason I ask is the same reason Donald made his comment.? The QDX is a bit sensitive to poor impedance matches on its output so when you transmit and the amp is figuring out what to do (milliseconds) it is likely to present a high impedance to the QDX.? Eventually (I'm surprised it hasn't happened yet), you will have a BS170 failure.? Connecting the PTT line to the amp is a good idea since it has that option.? I would not be willing to use an amplifier that uses RF keying alone.? Even for my 2m amplifier with a transverter, I really despise RF keying, it's worth it to me to key it manually and make sure everything is sequenced properly to protect both the transceiver and the amplifier.
That really is a cute amplifier though.
Joshua
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Speaking of sequencing (which makes a lot of sense), with the PTT hooked up, is there a setting in configuration to delay transmission for x time ?
(The other Joshua) HI - sure send me an Alex link !
73, Jamie
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On Jan 23, 2023, at 4:24 PM, Joshua KJ7LVZ <joshuajayg@...> wrote:
?Mr. Ellis, the reason I ask is the same reason Donald made his comment.? The QDX is a bit sensitive to poor impedance matches on its output so when you transmit and the amp is figuring out what to do (milliseconds) it is likely to present a high impedance to the QDX.? Eventually (I'm surprised it hasn't happened yet), you will have a BS170 failure.? Connecting the PTT line to the amp is a good idea since it has that option.? I would not be willing to use an amplifier that uses RF keying alone.? Even for my 2m amplifier with a transverter, I really despise RF keying, it's worth it to me to key it manually and make sure everything is sequenced properly to protect both the transceiver and the amplifier.
That really is a cute amplifier though.
Joshua
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I have used my QDX with a WA2EBY amp with a COR (carrier-operated relay) function.? So far, there has not been an issue.? Before the amp keys up, the antenna is connected to the output of the QDX.? There are a few milliseconds for the relay to switch, which could be an issue.? Switching from TX to RX, the rf power has been removed before the antenna is switched.? The only time I had a problem was when the correct antenna was not connected to the amp.? In that case, both the amp and the QDX finals got toasted.? I should note that I am running a 12-volt build at 8 volts producing 2 watts of power.? That is what the amp is designed to have as the input power.? With 2 watts in, I am getting 35 watts out with 20 volts supplied to the amp.
I plan to continue to use the COR feature of the amp.? If I run into issues, I will post the problem here.
73
Evan
AC9TU
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Well, thinking more on this, unless the PTT activation changes the band to the correct one in the amp, even delaying the RF won’t help.
I have seen little amps that you change the band manually with a knob. This wold seem to be safer.
73, Jamie
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On Jan 23, 2023, at 4:48 PM, James C. Hall, MD WB4YDL <heartdoc@...> wrote:
? Speaking of sequencing (which makes a lot of sense), with the PTT hooked up, is there a setting in configuration to delay transmission for x time ?
(The other Joshua) HI - sure send me an Alex link !
73, Jamie WB4YDL On Jan 23, 2023, at 4:24 PM, Joshua KJ7LVZ <joshuajayg@...> wrote:
?Mr. Ellis, the reason I ask is the same reason Donald made his comment.? The QDX is a bit sensitive to poor impedance matches on its output so when you transmit and the amp is figuring out what to do (milliseconds) it is likely to present a high impedance to the QDX.? Eventually (I'm surprised it hasn't happened yet), you will have a BS170 failure.? Connecting the PTT line to the amp is a good idea since it has that option.? I would not be willing to use an amplifier that uses RF keying alone.? Even for my 2m amplifier with a transverter, I really despise RF keying, it's worth it to me to key it manually and make sure everything is sequenced properly to protect both the transceiver and the amplifier.
That really is a cute amplifier though.
Joshua
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James,
Here is the link:?
You can manually change the band prior to key up if needed. Push the button 3 times successively.
A manual knob for band selections is what my MX-P50M has.
I did a quick check with a 3.5mm TRS cable with the IC705 and am finding strange behavior of the amp. I will need to do a bit more testing.
Joshua KJ7LVZ,
I will give the PTT cable a try with the QDX as well, hopefully today. As mentioned above, I am seeing strange behavior that I want to sort out.
Joshua
KO4AWH
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Many thanks Joshua ! ? 73, Jamie WB4YDL ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Joshua Ellis
Sent: Tuesday, January 24, 2023 10:02 AM
To: [email protected]
Subject: Re: [QRPLabs] QDX pairs nicely with the Micro PA50 ? James,
Here is the link:?
You can manually change the band prior to key up if needed. Push the button 3 times successively.
A manual knob for band selections is what my MX-P50M has.
I did a quick check with a 3.5mm TRS cable with the IC705 and am finding strange behavior of the amp. I will need to do a bit more testing.
Joshua KJ7LVZ,
I will give the PTT cable a try with the QDX as well, hopefully today. As mentioned above, I am seeing strange behavior that I want to sort out.
Joshua
KO4AWH
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Joshua:
You can shorten the URL considerably by just using the ID number (3256804580861697). (See below.) The same idea works on Amazon and eBay, too.
Jack, W8TEE
On Tuesday, January 24, 2023 at 11:32:06 AM EST, James C. Hall, MD WB4YDL <heartdoc@...> wrote:
Many thanks Joshua ! ? 73, Jamie WB4YDL ?
From: [email protected] [mailto:[email protected]] On Behalf Of Joshua Ellis
Sent: Tuesday, January 24, 2023 10:02 AM
To: [email protected]
Subject: Re: [QRPLabs] QDX pairs nicely with the Micro PA50 ? James,
Here is the link:?
You can manually change the band prior to key up if needed. Push the button 3 times successively.
A manual knob for band selections is what my MX-P50M has.
I did a quick check with a 3.5mm TRS cable with the IC705 and am finding strange behavior of the amp. I will need to do a bit more testing.
Joshua KJ7LVZ,
I will give the PTT cable a try with the QDX as well, hopefully today. As mentioned above, I am seeing strange behavior that I want to sort out.
Joshua
KO4AWH
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This would make a great amp but unfortunately it does not cover the whole 10m band. Not a good idea to stop at 28,5 MHz. ? Robert, OE7OER ? ? ? James,
Here is the link:?
You can manually change the band prior to key up if needed. Push the button 3 times successively.
A manual knob for band selections is what my MX-P50M has.
I did a quick check with a 3.5mm TRS cable with the IC705 and am finding strange behavior of the amp. I will need to do a bit more testing.
Joshua KJ7LVZ,
I will give the PTT cable a try with the QDX as well, hopefully today. As mentioned above, I am seeing strange behavior that I want to sort out.
Joshua
KO4AWH
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All,
I had a chance to look at PTT on this AMP and the QDX as a pair. It works as intended! Here is some info if any are curious.
From the Micro PA50 Listing:
From the QDX Manual:
My updated QDX settings (I only intend to operate this on 40/20m at the moment:
Joshua
KO4AWH
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Great, I am glad you got that sorted.? You are more likely to have a long-lasting QDX at this point.
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Awesome Joshua!
I have a couple of the original QDX's.? Does anyone know if you can add a PTT out on those??
Or maybe buy just the back panel?? If it fits the original case?? Or maybe the whole new case if it fits the original board?
Thanks!
W4MRP
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On 03/05/2023 19:55, W4MRP via groups.io wrote: add a PTT out on those? The TX+ line goes to 3.3 volts on TX, current firmware . I forget exactly what I did but find a suitable point to extract it. It can turn on a BS170 for a relay. The via in the picture could be used. 73 Alan G4ZFQ
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Thanks!
--- Mike R. Prevost, W4MRP
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------- Original Message ------- On Wednesday, May 3rd, 2023 at 3:39 PM, Alan G4ZFQ <alan4alan@...> wrote: On 03/05/2023 19:55, W4MRP via groups.io wrote:
add a PTT out on those?
The TX+ line goes to 3.3 volts on TX, current firmware .
I forget exactly what I did but find a suitable point to extract it. It
can turn on a BS170 for a relay.
The via in the picture could be used.
73 Alan G4ZFQ
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Joshua KJ7LVZ
Donald S Brant Jr
jjpurdum
W4MRP