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Hi Ryuji, Hans had posted how he came about using the 1n4007 as a PIN diode for the LPF switches.? You bring up one point that he found that there needs to be higher than the peak plus diode drop to

New Tx Pwr.... 80M? ?3.61W 60M? ?3.24 W 40M? ?3.61W 30M? 1.56W? ?- still lower that I'd like 20M? ?1.94W? ?- ditto

Did anyone test at what power output those “reverse biased” diodes begin to conduct? At that point I think the RF amp output is practically shorted to the ground unless operating on the lowest

Some progress! After considering the fact that 80, 60 and 40 all use the same IC402 mux selection for the BPF, I started making continuity checks on the re-installed L401. Bingo! Somehow in

Adding a series R at the BS170 gates won’t protect the BS170s. While this *might* prevent severe damage to the AC08 when one or more BS170s fail, it would degrade the overall PA performance as Ryuji

I meant to say PROTECT the BS170...

Detailed descriptions of the devices can be found on QRP-labs.com. About QMX at http://qrp-labs.com/qmx.html There are details on the forum because they refer to them. -- Gyula HA3HZ

A series R in gate is a big LPF and slew rate limiter best avoided. It is better to insert R or current limit on the chips supply line instead.

It’s best to do it on microstripline with SMD capacitors. Lumped element inductors are best avoided. If it’s just for one amateur band from direct freq synthesis rather than old fashioned freq

Hi. Quick question. Would adding some series resistance between the 74ACT08 and the BS170 gate prevent the ACT08 in the event of a PA failure or would it kill the drive level? Jim WB2LHP

Mike, when I read the forum discussions, I read the entire topic at 'QRP Labs/Topics'. I wrote to you in the previous message to read this, because I think it might help. I quote ( #109038): 'The

has anybody made one for 432Mhz. i need one for a homebrew vhf-uhf radio. ron, kc0tdj

The T/R switch, Q508, switches open during transmit, protecting the receiver circuitry. JZ

Hi Ryuji, My D109 was just "soft", having a high internal series resistance. It still began conducting at the proper voltage, it simply didn't conduct much current and allowed more than 5 volts to be

I need to clarify and apologize. Like many others, I often refer to VDD and VCC incorrectly even though I know the difference. I meant "VDD" pins on the MCU. There aren't any "VCC" pins (5 volts)

FYI zener diode very often fail in short mode especially when over voltages in small doses repeatedly or otherwise gradually.

One other thing, I tested transmit by sending a series of dits in CW - maybe 5-10 at a time. [email protected]> wrote:

From experience, I can say that it has done no damage. I'm running from an 11.5v supply, if that matters. Also TX testing was done with a dummy load. 73, Randy, KS4L [email protected]> wrote:

If someone were to transmit with T507 wired in the “U” configuration . . . would that fry the receiver? As in ruined beyond repair?

Hi, if it is QMX it is here: https://www.qrp-labs.com/images/qmx/manuals/schematics_rev1_a.pdf 73 Bojan S53DZ