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I finished assembling my QMX+ (including a battery mod) and finally got the chance to test it.? In the diagnostics everything appears to check out, until I press P.? At that point the SMPS bias current for every band is ~4.6mA (where the PIN forward bias is 30mA).? If I press T (while connected to a dummy load), the RF output and the Transmitter Voltage turn RED, with the Voltage reporting ~9.5-10.0V.? Power is consistently listed as 0.0W, and the SWR (into the 50 Ohm dummy load) is all over the map.

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Any ideas what I did wrong?? I've looked at all of my soldering connections multiple times and don't see any bad joints or bridges.? I've checked everywhere I can think of for continuity, and everything has checked out so far.

Did you remember the loop between the bnc and the output from the swr bridge ?

I did, but on another readthrough of the directions, I missed that it said to put it in from the underside of the board.? Let me try changing that.

No good. :( I redid the loop connecting the SWR bridge to the BNC connector and the results are still the same.

I just discovered a slight change.? On 6m, the Bias SMPS current is about double at ~8.2mA.

I just finished my build sounds similar to your issue?

0 watts

9.xx volts?

swr jumping a little mostly around 1.2-1.5

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I am going to start form the bnc and work my way back through the circuit unless I find any other advise?

let me know if you discover anything!!

On Apr 6, 2025, 15:43 -0700, mitchellrlawrence via groups.io <mitchellrlawrence@...>, wrote:

On Sun, Apr 6, 2025 at 06:43 PM, <mitchellrlawrence@...> wrote:

I am going to start form the bnc and work my way back through the circuit unless I find any other advise?

Be aware that the VSWR transformer winding puts a DC (not RF) short across the output BNC connector.

73, Don N2VGU

On Sun, Apr 6, 2025 at 04:02 PM, Paul - AI7JR wrote:

Hard to understand measuring SWR if you truely have 0 watts out... :-)

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Paul -- AI7JR

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That's why I mentioned it in my original post.? The SWR is reported in the Diagnostics page on the terminal when I hit T for Transmit.? For me, it's all over the map, sometimes reporting in the 6-7 range, sometimes so high it just reports ####, and other times dropping down to the 1-2 range.? All of that while it claims 0W output (and a wattmeter on the dummy load shows no power).

SWR is calculated by measuring the forward and reverse voltages obtained from T507 and calculating the SWR from those.? It there's no power out then those values can still be measured, they will both be close to zero, with noise.? A 'SWR' value can be calculated but it's just done from two noise measurements which is why the value varies widely.? The power is derived from the forward value only.

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Chris. G5CTH