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Re: #qmx high band harmonics
#qmx
Be sure to also buy attenuator(s), since the SA can be catastrophically damage? if connected directly to even a QRP rig.
I use a combination of a 10W dummy load with a built in 30dB attenuator followed by a 30dB SMA attenuator. |
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Re: QMX Feature Request - field “tune” mode
The schematic of the N7VE bridge is readily available from many sources. I used the one from wb3gck.com as shown on his Z-Match tuner; just implement the bridge portion if you want. There are several minor variations that others have made. Contact me off list if you’re interested in building one, I’m good on qrz.
Steve W6WU? |
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Re: QMX Feature Request - field “tune” mode
Too easy
""...(mini SWR indicator)...Or better yet make one, they’re very simple and low cost. Light weight, it won’t add any significant burden on your ?field operations.""...w6wu es have not popped a final since Note ...number of primary turns sets sensitivity... 72 73 John N3AAZ |
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Re: QMX Feature Request - field “tune” mode
Would it be possible to turn the power down automatically as the SWR rises to protect the PA?? Maybe start at a SWR of 2 and reduce to the specified limit by 3. Restore the power, ideally slowly, after the SWR improves.
Then a user could transmit and the PA would be kept safe automagically.? This is rather like the way my IC-7300 behaves, the power is reduced automatically at high SWRs, then as I tune the antenna the SWR reduces and the power increases. There would be no need for any user control, it's normal operation. Transmit and watch the SWR and power. Minimise one and the other will be maximised. . Chris, G5CTH |
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looking for non-US keyer chip
I just read Frank DL2GRF's post and noted that we have a common
issue, small component orders are eclipsed by shipping and handling costs. After spending some time looking for the once common basic keyer chip, or a chip that I could program to be a keyer (I'd need to find online the program) I was about to place an order from a US supplier. The cost of getting across the border and to me was uneconomical. In the past I've done much better ordering from the UK or EU with affordable mail costs. These chips are hard to find now, any suggestions as to where to look outside of the US? Ron VE8Rt VE8TEA -- Ron VE8RT <ve8rt@...> |
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Re: QMX Feature Request - field “tune” mode
“?Often my antenna is a rather high Q base loaded vertical in which small adjustment to the coil position can result in big swings in feed point impedance.” If you’re concerned about protecting the finals while finding the right tap on the coil you might consider a different solution. An ?N7VE LED SWR bridge between the QMX and your antenna, in ?the tune position, would keep the radio from never seeing an SWR over 2:1. ? QRPguys and qrpkits (mini SWR indicator) has them. Or better yet make one, they’re very simple and low cost. Light weight, it won’t add any significant burden on your ?field operations. |
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Re: #qmx high band harmonics
#qmx
Consider the TinySA Ultra instead:??
It is quite advanced in features and functions compared to the previous TinySA model; I felt that it was well worth the cost increment. 73, Don N2VGU |
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Re: Faulty Progrock2 - no response to ticket
#progrock2
Thanks, but the problem is almost certainly caused by the STM32 which no longer communicates with the computer. All I have left is the recovery of the si5351 and the TCXO
73 iw2ggb FCIl mer 28 feb 2024, 23:12 Muhsin TA1MHS <muhsin.dogrular@...> ha scritto:
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Re: QMX Feature Request - field “tune” mode
Hi Ronan ? Could one of the front panel long-presses be made configurable? That way it could default to the present way of working but could be made to jump straight to a menu of choice if desired.... Yes, also on my list - is to make ALL the controls configurable... If people diverged from the default then of course the laser etched printing on the front panel wouldn't match the function but the flexibility will?be there for those that want it.? 73 Hans G0UPL |
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New Chat: QMX replacement parts
#chat-notice
Group Notification
A new chat has been created: Hi folks,
I have the problem with Rev.2 board (shipped before 2024) where the modification with the 1N4148 diode is required to prevent IC402 from dying. This is exactly what happened to me. I then ordered 2 IC's and 1x the transistor as a spare part. Value of goods $5. Here in Germany I paid 13,35� incl. shipping. I also had to pay 2.14� customs duty and 6� DHL handling fee for customs clearance. So the design error, which was not my fault, cost me 21.49�. Why is this not declared as a gift? It really annoys me.
73 de Frank DL2GRF
By: DL2GRF Frank <dl2grf@...> Do not reply to this message to post to the chat. You can participate in chats only through the group's website. |
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Hello Tisha The MOSFET gates are particularly ESD sensitive. It's the Drain which is connected to the external jack (via a resistor).? 73 Hans G0UPL On Wed, Feb 28, 2024 at 5:29?PM Tisha Hayes, AA4HA <Tisha.Hayes@...> wrote: Would Q204 be as sensitive to ESD? Being connected to an external jack (PTT) isn't it sort of hanging out there like an antenna? |
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Re: list of acceptable digital modes?
Thank you again Cliff,
I should keep the list handy, Thor is of interest at the moment. 73 rRon VE8RT On Thu, 29 Feb 2024 00:24:30 -0600 "Cliff" <ae5zaham@...> wrote: Yes, Ron. I was over zealous in what I said. Indeed PSK, Throb and a couple others won't for the reason you said. Only single tone modes like Thor, Olivia, Contestia, DominoEX, FSQ, MFSK, Hell, RTTY, CW work. -- Ron VE8RT <ve8rt@...> |
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Re: list of acceptable digital modes?
开云体育Yes, Ron. I was over zealous in what I said. Indeed PSK, Throb and a couple others won't for the reason you said. Only single tone modes like Thor, Olivia, Contestia, DominoEX, FSQ, MFSK, Hell, RTTY, CW work.73, Cliff, AE5ZA
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Re: QMX Band Pass Filter (and Band pass filters in general) question
Hi Jonathan The analysis is too simplistic. The filters can be designed approximately using some theory (such as your calculation) but then in the real world the results differ considerably. There are interactions between the LPF and the BPF, and other components such as the load on the filter, termination impedances, and a lot of parasitic circuit elements such the capacitances of the BPF MUX switch pins, and of the PCB traces etc. Generally since these parasitic elements are ADDING to the desired circuit values, the resonant frequency?realized in practice is normally lower than the value given?by a simple calculation.? In the QMX 80-20m version the lowest filter is used for 40/60/80, the mid filter for 30 and the highest filter is used for 20m. The use of few filters, and wide (single series resonant circuit) is a design compromise for the targeted small size and cost. The fact that the QSD intrinsically has such high performance mitigates the liberties taken with the BPF so the overall performance is still excellent. Other choices of receiver?architecture would differ. For example if using a much weaker mixer such as a <shudder>SA602</shudder> then you would probably like to use a much narrower and sharper filter to better protect the weak mixer.? > I eventually want to have a 5 band circuit made of SMD? > components so I can shrink my design into a portable package? > so I am avoiding the QRP labs Band pass filters since they? > use transformers. That's also a compromise, size vs performance. Trade-offs, trade-offs. Physically smaller inductors have lower Q and lower saturation levels.?We assume that in a receive application, flux density is not important as we aren't passing watts through the toroids however in reality flux isn't something that is zero until a certain level then suddenly kicks in. Smaller inductors can easily become the limiting factor to performance of the whole radio. That depends on the rest of the radio architecture. But it is worth bearing in mind if you are aiming for a high performance front end.? Martein PA3AKE's pages? are an excellent read, and specifically in this instance, his discussion on IMD in toroids:? But in the end it's all trade-offs, if very small size is critical then some sacrifice has to be made.? 73 Hans G0UPL On Thu, Feb 29, 2024 at 9:07?AM Jonathan Kayne, KM4CFT <jzkmath@...> wrote: Hi, |
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QMX Band Pass Filter (and Band pass filters in general) question
Hi,
I am currently in the process of designing a band pass filter for a homebrew CW radio I want to build. I was looking at the bandpass filter design for the QMX and was confused because the passband of the filter doesn't seem to match up with anything on the appropriate bands. If I am reading the schematics properly, there are 15 and 23 turns on a T50-2 Toroid, which would have inductances of 1.1uH and 2.59uH respectively. Connecting them to the listed caps we have the following combinations:
What confuses is me is the first combination which is clearly not in the 80-20 meter bands. I am pretty sure I am missing something but not sure what. I am not even sure if a single resonant band pass filter is the best option for my use. Honestly I have been at my wits end trying to design a functional band pass filter, because when I simulate a filter in Elsie or RF tools, the passband on the built filter is off by a few MHz. Whenever I try to use recommended values from Experimental Methods in RF Design or Solid State Design plugging it into LTspice or Elsie yields a completely different passband. I eventually want to have a 5 band circuit made of SMD components so I can shrink my design into a portable package so I am avoiding the QRP labs Band pass filters since they use transformers. Can anyone point out to me what is probably a blatent mistake I have made? Thanks, -Jonathan KM4CFT |
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Re: QMX Feature Request - field “tune” mode
Hi all I do think?W6CSN's request is fulfilled by the SWR feature in the hardware menu. However, it does need operational convenience improvements as Garrett KC3UNP says. It was already requested and on my list that the frequency and band should default?to the current operating parameters; then the left knob should adjust band and the right knob, frequency.? Regarding a graphical sweep display: it is my eventual plan (but after other higher priority items) that all the graphical tools in the terminal screens (Image sweep, BPF, LPF, SWR sweep) should also be available in miniature form on the LCD; remember?we only have 8 characters to use for custom graphics but it is nonetheless possible to make a quite usable display from this. Some readers may recall, dare I say it, this QSX video? that demonstrates some code I wrote for that. It just needs to be adapted?and incorporated into QMX.? 73 Hans G0UPL On Thu, Feb 29, 2024 at 8:53?AM Garrett kc3unp <kc3unp@...> wrote:
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Donald S Brant Jr
Jonathan Kayne, KM4CFT
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