开云体育

QMX High Band - No RF

Jim Bennett / K7TXA All Messages By This Member #116482 Starting a new thread on this one, as it appears that the slight damage to the corner of the PS board causes no problems. So, my high band QMX, Rev 2, built for 12v powers up just fine. Using Putty, all controls are fully functional. But, I get no RF output and the SWR protection kicks in immediately. Using a verified, short cable of RG-8x to a 50 ohm dummy load.? ?Using Putty I did an SWR sweep and on 20 meters it isn't looking very pretty: ?-- ?Other bands show similar, nasty results. Back in Putty, the "P" button in the transmitter diagnostic portion gives me 30.6 ma current draw. When I press "T", I get red for RF output and 0.0 watts. Voltage goes from resting at 0.6 v up to 9.8 volts. Where would be some good starting points to check? I've made sure there are no shorts anywhere, and I didn't see any missed or cold solder connections. Jim / K7TXA Eagle, ID SKCC 10447C BUG 301
Thomas Fritzsche All Messages By This Member #116491 Hi Jim, I had same problem that you describe. Here solution was just turning off the Practice Mode. Hope it's as easy solution for you too. BEST 73 DE DJ1TF - Thomas Am Do., 11. Jan. 2024 um 19:18?Uhr schrieb Jim Bennett / K7TXA via <w6jhb=[email protected]>: toggle quoted message Show quoted text Starting a new thread on this one, as it appears that the slight damage to the corner of the PS board causes no problems. So, my high band QMX, Rev 2, built for 12v powers up just fine. Using Putty, all controls are fully functional. But, I get no RF output and the SWR protection kicks in immediately. Using a verified, short cable of RG-8x to a 50 ohm dummy load.? ?Using Putty I did an SWR sweep and on 20 meters it isn't looking very pretty: ?-- ?Other bands show similar, nasty results. Back in Putty, the "P" button in the transmitter diagnostic portion gives me 30.6 ma current draw. When I press "T", I get red for RF output and 0.0 watts. Voltage goes from resting at 0.6 v up to 9.8 volts. Where would be some good starting points to check? I've made sure there are no shorts anywhere, and I didn't see any missed or cold solder connections. Jim / K7TXA Eagle, ID SKCC 10447C BUG 301
Jim Bennett / K7TXA All Messages By This Member #116520 Thomas - thanks for the hint, but practice mode is off. Something is funky with what it sees for SWR, and it is tripping the SWR protection. My SWR scans are not good for some reason even though I'm connected to a known good dummy load. Another poster in a different thread mentioned that I might have problems in the vicinity of the "SWR Transformer". Unfortunately I don't know what part that is on the board - I'm unable to find a circuit description that explains stuff like that. :-( -- Jim / K7TXA Eagle, ID SKCC 10447C BUG 301
Evan Hand All Messages By This Member #116521 Hello Jim, Here is the section of the schematic that measures the power and SWR: Since you are getting a SWR trip on a known good 50 Ohm load, I suspect the circuit's forward voltage part has an issue.?? To calculate the SWR, first calculate the reflection coefficient: $\text{[math]}$ (the voltages should include a relative phase factor). Then, calculate the SWR: $\text{[math]}$ (Vfwp+Vrev)/(Vfwd-Vrev).? ?If Vrev = 0, then you get 1.? As Vfwd approaches zero, you get an undefined, huge number for the SWR.? Hans has never published the formula he uses in the QMX software.? Here is a link that explains this type of circuit operation (It has many names, one being a Stockton Bridge): And a Wiki Link that explains the math: . There is a good YouTube video that explains how it works: If you are sure about the connections and dummy load, you can turn off the SWR protection.? If you do so, I suggest you use a lower voltage to feed the radio to limit the power output (Hans has suggested 7 volts). 73 Evan AC9TU ?
Cliff All Messages By This Member #116533 开云体育 Jim, T507 73, Cliff, AE5ZA toggle quoted message Show quoted text On Jan 11, 2024, at 23:08, Jim Bennett / K7TXA via <w6jhb@...> wrote: Thomas - thanks for the hint, but practice mode is off. Something is funky with what it sees for SWR, and it is tripping the SWR protection. My SWR scans are not good for some reason even though I'm connected to a known good dummy load. Another poster in a different thread mentioned that I might have problems in the vicinity of the "SWR Transformer". Unfortunately I don't know what part that is on the board - I'm unable to find a circuit description that explains stuff like that. :-( -- Jim / K7TXA Eagle, ID SKCC 10447C BUG 301
Bruce KG8IW All Messages By This Member #116536 Jim, the likely problem area is around T507. It's construction is on page 44 of the manual.? There are four connection points on each side of this transformer, and with the heavy wire used, and connection to the internal ground plane it can be difficult to make these good solder joints.? Problems here can cause the symptoms you are seeing, the bad traces and swr protection kicking in.? Good luck,, 73 Bruce KG8IW ?

Previous Topic Next Topic