Re: Another QMX Receive Issue Thread
I had the same problem and refitted the IC and installed the diode.
Despite the diode, the QM went deaf again after some FT8 transmissions. ??
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Re: QMX and FT8CN audio issue - HANS PLEASE CAN YOU NOTE??
Thanks much for the answer.
Yeah, I finally got it working earlier today myself !
IMPORTANTLY : There is at least on step for (some/a-few/at-least-my-moto-phone) androids that I cannot find any mention of in this particular group...really.
AND: I found at least one "wrinkle" within ft8cn that is NOT mentioned in their manual...hi hi.
es vy 73 OM (especially for the reply) de "baab" w9ya
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Re: RF preamp for power amp - HF and 6 mtrs. Magic silicon does all.
The main question Allison is do you agree with the splitting of the second feedback resistor as I did to do the maths.? ?
Indeed for the? AD 8009 the datasheet? recommends? about a? 50R resistor in the output drive line to? reduce chance of instability in the amplifier.?
THe datasheet is a bit coy on the conditions that lead to such instability.? Yes I refer to the? 8009.? ?IN the case in question? the OP resistors have been put in? parallel to? ensure that can dissipate? up to? 0.5? W? that is what makes me suspect that those reisistors are there not only for stability reasons but also as? a form of power dump if the? RHS transformer is left unterminated.?
Are there any? dual? Video amps of this type (two to a package )? that you know of? which? can do a similar duty at HF? to? 50 Mhz drive? I get the impression that this OPA is? pretty much unique in this regard.?
I will include a? photo of a commercial application that uses this type of? Tx chip but I have some considerable reservations about what is shown.? Specifically there appear to be be cappies in the lines from the? driver transformer to the OPA . This would mean that? ?there is no way that the signal bias can get to the op amp.. Clearly there could be components under the PCb but given there is a heat sink there , that seems unlikely.? The alternate is that the UKR Mafr has published a false photo and what is supplied does work and is subtly? different from the photo. This design has zero filtering post the? RF power amp mosfets.? ?I include it mainly because it shows how the transformers? were implemented as hand wound designs and not? commericial designs as per schematic supplied (or a completely different application).
Regards,? TEF
?
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Thanks Dean !
OK, it sounds like a linear supply is the way to go.? I have the parts to build one with the possible exception of high capacitance filter caps.? ?How large should the filter caps be for optimum performance?
Jim
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Re: QMX and FT8CN audio issue - HANS PLEASE CAN YOU NOTE??
Hi Baab,
Firmware 017 works fine for me on FT8CN 0.92.
I'm using it right now and it has transmitted just fine many times in a row.
I don't recall Hans mentioning fixing anything related to this in the release notes, though.
73, Mike KK7ER
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Thanks Dan, I will double check those things.
Doug. WX7J?
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-------- Original message -------- From: Daniel Conklin <danconklin2@...> Date: 3/4/24 1:02 PM (GMT-08:00) Subject: Re: [QRPLabs] QCX mini input noise
Doug, those pads are reserved for the TCXO board. The fact that the noise decreases when you touch them is an indication of something. Just not sure what. It could indicate a bad solder joint on a component's gound side. I have a similar issue that I traced to an antenna cable that was leaking RF, but the RF can get in in other ways, like the key, audio, or even power wires.? -- 73, Dan - W2DLC
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Re: QMX #008 Power Supply Search
how many amps should the diode be able to handle? My regulated power supply shows about 0,8A during transmit on 40m. Is a diode with 1A rating sufficient?
73 OE6HKE
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There are some good quiet switchers out there, but there are a lot of noisy ones as well.? You'll never go wrong with a linear supply.? They are inherently quiet.? You won't need to mess with any kind of isolation or noise choking with a linear supply.? But linear supplies are bigger and heavier than switchers.? If that's not a concern, go with a linear supply.? Whatever you wind up using, make sure it is regulated and that the output voltage is within the radio's input voltage limits (refer to your radio manual for the specs).?
Here's a tip from and for the frugal ham.? For powering QRP rigs, I've often used old CB-type regulated supplies.? You can buy them cheap at swap meets and garage sales.? On more than one occasion, I've also salvaged the complete regulated power supply sections out of junked solid-state base station CB radios and packaged them up in suitable chassis boxes with a fuse, suitable output connections, an LED pilot lamp, and a 3-wire power cord.? In fact, I have one sitting over on the other side of the shack right now which I salvaged from a junked Royce base station.? Cost me basically nothing and was a fun project.? Most CB power supplies are good for at least 2 amps, which is more than enough to run a typical QRP rig.?
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73/72,
Dean K5DH
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Doug, those pads are reserved for the TCXO board. The fact that the noise decreases when you touch them is an indication of something. Just not sure what. It could indicate a bad solder joint on a component's gound side. I have a similar issue that I traced to an antenna cable that was leaking RF, but the RF can get in in other ways, like the key, audio, or even power wires.?
--
73, Dan - W2DLC
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Thanks for your reply Ron. It doesn't seem to make a difference.?
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-------- Original message -------- From: Ronald Taylor <wa7gil@...> Date: 3/4/24 11:54 AM (GMT-08:00) Subject: Re: [QRPLabs] QCX mini input noise
Doug, I see you installed the AGC option. If that is turned on, try turning it off and see if it makes any difference... Ron On Mon, Mar 4, 2024 at 12:44?PM Doug Boyer WX7J < dougbo@...> wrote: Dan, I only notice it decreases when i touch the empty pads next to the 27mhz crystal.? Did i not install something i should have??
Doug
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-------- Original message -------- Date: 3/4/24 11:19 AM (GMT-08:00) Subject: Re: [QRPLabs] QCX mini input noise
Doug, do you notice any increase in volume of the noise when you touch the case or other object, like the key, that's attached to the QCX?? -- 73, Dan - W2DLC
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Doug, I see you installed the AGC option. If that is turned on, try turning it off and see if it makes any difference... Ron
On Mon, Mar 4, 2024 at 12:44?PM Doug Boyer WX7J < dougbo@...> wrote: Dan, I only notice it decreases when i touch the empty pads next to the 27mhz crystal.? Did i not install something i should have??
Doug
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-------- Original message -------- Date: 3/4/24 11:19 AM (GMT-08:00) Subject: Re: [QRPLabs] QCX mini input noise
Doug, do you notice any increase in volume of the noise when you touch the case or other object, like the key, that's attached to the QCX?? -- 73, Dan - W2DLC
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Dan, I only notice it decreases when i touch the empty pads next to the 27mhz crystal.? Did i not install something i should have??
Doug
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-------- Original message -------- From: Daniel Conklin <danconklin2@...> Date: 3/4/24 11:19 AM (GMT-08:00) Subject: Re: [QRPLabs] QCX mini input noise
Doug, do you notice any increase in volume of the noise when you touch the case or other object, like the key, that's attached to the QCX?? -- 73, Dan - W2DLC
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Re: Faulty Progrock2 - no response to ticket
#progrock2
Hi Steve - it was just powered from the PC via the USB port.
Peter
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Doug, do you notice any increase in volume of the noise when you touch the case or other object, like the key, that's attached to the QCX??
--
73, Dan - W2DLC
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Burt: I had the same problem as yourself. Check the tab soldering on the large MOSFET Q507. That is a pre-installed unit and on my board the tab was sitting above the circuit board by about 1/2mm and had not been properly soldered at the factory. When I soldered that on properly it solved my no power out on Tx.
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Re: QMX Rev 3 build instructions
Hi Todd, Dave
I will clarify on the web page. The assembly instructions?for Rev 3 are the same as for Rev 2. It incorporates the changes made manually on Rev 2 PCB's and?a couple of other changes to SMD parts and additions; there is NO change to the assembly of through-hole parts.?
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Re: QMX Rev 3 build instructions
Hey Dave,
I just received my 2x QMX this AM, and had the same question. ?I assume we would use Rev 2 instructions but I’m waiting to see if someone answers here.
Todd K4MSW
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Not on a QMX, rather a QDX, I found a small bit of machining swarf (the "metal sawdust" from machining) jammed in the female slot where the top an bottom case join, preventing a fit.? The bit was actually powder coated black... A dental pick removed it, and the two half's fit fine.?
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Good evening everyone, I have the same problem as Burt, but I bought the high band QMX already built, I did a few CW QSOs with friends nearby and everything was fine, then I transmitted for 10 hours in WSPR on the 10 m and it stopped delivering RF, now it absorbs 90 mA in reception and 190 mA in transmission, previously it was from 5 W to 6 W on all bands, the antennas are all single band with SWR less than 1, I don't know what it is happened, I also replaced the bs170, but the absorption remained the same, I hope some of you can help me.? thank you very much 73
Giuseppe iu8eun
Burt, I'll check out you screen shots later. Thanks for posting them.
Burt, That current draw in TX is quite low. Check continuity through L502.
In TX the four PA transistors will have an RF square wave signal at the gates . The magnitude of that signal is 5 volts and an oscilloscope will show that. As the duty cycle is 50% a multimeter will read 2.5 volts.
The primary side of T501 should have a DC potential in the range of 9-12 volts on each of 3 pins but during transmit the drain terminals will also have an RF signal riding on that voltage of approximately 45V p-p. At the secondary side? in TX you should see? 15-25 volts p-p RF voltage with no DC bias. These are all from memory and are approximate.?
Hope that helps and GL? 73 JZ KJ4A?
On Mon, Mar 4, 2024, 9:24?AM Burt Wizeman < burt@...> wrote: Hey John, thanks for the reply:
All bands no power out.
Verified that no input exists to the antenna tuner.
12 Volts for power.
97 milliamps on receive.
60 meters - 141 Milliamps xmit
40 meters - 154 Milliamps xmit
30 Meters - 177 Milliamps xmit
20 Meters - 207 Milliamps xmit
80 Meter - XMIT Disabled -?
I did a jeweler's loop inspection and checked continuity for the Transformers.? Was wondering what the voltage readings should be at the pads for T501 and T507.? Also, do you know the expected Bias on Transmit for QW503-Q506?? Will check C526 specifically.??
Burt
K4SRQ
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Might be a winding issue. I will perform the precious suggestions and if necessary , rewind the transformer and see what happens. ? Those transformers. What a blast!
Thanks John,
Burt
K4SRQ?
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Timothy Fidler
Daniel Conklin
Ronald Taylor
Ray D Congdon
Burt Wizeman