swr9.9 What's going on

[bh3wbq]

新pcb显示swr9.9。老pcb显示正常，不知怎么回事，fwd也不正常，已确定RF正常

[LILO]

http://forum.dl2man.de/viewtopic.php?t=132

[SP9TKW]

Most likely your LPF filter for 80m band has a bad solder joint. Usually its one of the coils where enamels wasn't removed totally.

GL Marek

[bh3wbq]

Most likely your LPF filter for 80m band has a bad solder joint. Usually its one of the coils where enamels wasn't removed totally.

GL Marek

Thank you for your reply. The signal-to-noise ratio of all frequency bands is abnormal, showing 9.9. Other motherboards tested this rf normally
BH3WBQ 73

[s57l]

There is probably something wrong around swr bridge, t1 and t2. Maybe bad soldering, wrong wiring, enamel not removed and no contact… check for bad solder joints and compare it with a working board.

[BD3OOX]

The RF board is connected to the old motherboard normally, but when connected to the new motherboard, the standing wave is infinite. Is there a fault with the motherboard

[DL2MAN]

Well there´s not much involved in SWR Measurement, that´s not on RF Board....
So when your RF Board is working (confirmed), then there´s only 2 things left:
1. Inter PCB Connector has bad or no connection
2. Main Processor bad

73 Manuel; DL2MAN

[KD4BJW]

I just built a kit, purchased from Amazon in the USA. I am also getting 9.99 on SWR. I have checked with a dummy load attached to the SMA connector using an Oscilloscope that the voltage at the SMA connector showing that all bands have roughly 40V p-p with little variations with 12V input so about 4W. No reflected power to measure. The display shows between 3.5 and 3.8W Forward power, but still 9.99 for the SWR. I do have the T2 mod with 3:21 turns.

I have started looking at voltages in the sample circuit and am seeing about 6V for FWD and almost nothing for RVS. I will attempt to trace the signal through the main board or perhaps inject known signals into the main board pins to determine if the main board is reading correctly or has some type of broken trace, any other ideas for determining if the board or processor have a problem?

73, KD4BJW