SSA400 swr question

[HA3KGX]

Welcome everyone!

I have a question, I have a video attached, it has a ssa400 connected to a 50ohm dummy load. A power / swr meter is also connected, the amplifier shows that there is reflected power, the above power meter does not indicate anything.

Did I understand the description correctly?

VIDEO






If I read it well SSA400 is sensitive enough to swr and very quickly regains output power, the video is also about 180w only.


If you have any idea about the phenomenon, I would be happy. It would also be good because it would need to set the performance on the UD1 module with a 50ohm dummy load lock, but if it behaves this way it will be difficult.

 

[HA3KGX]

Hi!

Unfortunately the translator doesn't understand this, "max 5 skd" in the picture is the A or B notation?

 

[SM0AOM]

The full scale reading in POWER/F (=forward) is 100 skd (=divisions), and the permitted reading in the POWER/B (=reflected) meter position is less than 5 skd when terminated in a 50 ohm load.

The adjustment procedures for the level-setting trimpots on UD1 are somewhat different between the TD90 and the CTD500.

You should first verify that the level control output voltages which are proportional to forward power and reflected power actually are present at the TD90 PA interface connector X35 pins 13 and 23. If not, the SWR detector module may have damaged diodes.

The adjustment procedures are somewhat involved, and are best made using a known mismatch (SWR 2:1). The pots R3 and R5 in the SWR module set the power and protection levels.

The general idea is to adjust the level control pots so when changing frequency or pressing the "TUNE" button the power level detector in the SWR module should limit the power ramp-up at 400 W into a dummy load. If the level from UD1 is too low, the TD90 output power will reach maximum before 400 W output has been reached.

If you have 50 divisions of forward power and 20 divisions of reflected power, the SWR reading is so high that the SWR protection circuit will limit the power to about 150 W.

Should this happen when driving a dummy load, there is something wrong with the SWR module.

 

[HA3KGX]

The full scale reading in POWER/F (=forward) is 100 skd (=divisions), and the permitted reading in the POWER/B (=reflected) meter position is less than 5 skd when terminated in a 50 ohm load.

The adjustment procedures for the level-setting trimpots on UD1 are somewhat different between the TD90 and the CTD500.

You should first verify that the level control output voltages which are proportional to forward power and reflected power actually are present at the TD90 PA interface connector X35 pins 13 and 23. If not, the SWR detector module may have damaged diodes.

The adjustment procedures are somewhat involved, and are best made using a known mismatch (SWR 2:1). The pots R3 and R5 in the SWR module set the power and protection levels.

The general idea is to adjust the level control pots so when changing frequency or pressing the "TUNE" button the power level detector in the SWR module should limit the power ramp-up at 400 W into a dummy load. If the level from UD1 is too low, the TD90 output power will reach maximum before 400 W output has been reached.

If you have 50 divisions of forward power and 20 divisions of reflected power, the SWR reading is so high that the SWR protection circuit will limit the power to about 150 W.

Should this happen when driving a dummy load, there is something wrong with the SWR module.

Thanks for the answer!

Don’t get mad at the language difficulties, a question I want to understand.
If I measure the reflected power with the letter B, what do the numbers on the scale correspond to? Pl 1: 2 swr = 20? 1: 3 = 30? And so on?

I connected it to an antenna tuner, its swr meter is much more sensitive, the dummy load is between 1: 1 and 1: 2.
The video below is set to 7 megahertz, output power is 400w, Power F is 75-80, the other measuring ranges are all within the limits described.

VIDEO2

 

[SM0AOM]

Please keep the camera still when filming, I get motion sickness by watching...

The indications in both forward and reflected are proportional to voltage, so
100 divisions are full scale = 400 or 500 W
50 divisions are 1/4 power or 100-150 W
10 divisions are about 1/100 power or 5 W

This is the same both in forward and reflected.

A way to adjust the power settings on UD1 is to turn all pots fully counter-clockwise and
then tune the transmitter in mode F1 on the lowest frequency range. Adjust the first pot until
the power reaches 400 W but does not increase over than 450 W or so, and the over-current trip does not activate when the TUNE button is pressed. Repeat for all frequency ranges.

 

[HA3KGX]

Please keep the camera still when filming, I get motion sickness by watching...

The indications in both forward and reflected are proportional to voltage, so
100 divisions are full scale = 400 or 500 W
50 divisions are 1/4 power or 100-150 W
10 divisions are about 1/100 power or 5 W

This is the same both in forward and reflected.

A way to adjust the power settings on UD1 is to turn all pots fully counter-clockwise and
then tune the transmitter in mode F1 on the lowest frequency range. Adjust the first pot until
the power reaches 400 W but does not increase over than 450 W or so, and the over-current trip does not activate when the TUNE button is pressed. Repeat for all frequency ranges.

Sorry for the video, I made it in a hurry.

Something is not right,
If 100 = 500 watts
then 50 = 250 watts
and 10 = 50 watts

If the division of 100 is 100% then shouldn't it be proportionally?

This is how I set the UD1 in A1 mode, selected the frequency with the TUNE button, CW press, and slowly turned the trimmer clockwise until it reached the desired power. However, if I pressed the TUNE button again after that, about 400 watts dropped to 250. After that I rode the trimmer again, 2-3 times and even after pressing TUNE, the power I wanted to set remained. If I only do it once on each frequency, I have little power .....

I'm sorry if not everything is clear at first, but I don't speak English well and not Swedish at all. I’m sure if we spoke one language, the matter would have been resolved in two letters.

(I last sent you a private message)

 

[SM0AOM]

If 100 = 500 watts
then 50 = 250 watts
and 10 = 50 watts

If the division of 100 is 100% then shouldn't it be proportionally?

No, power is proportional to voltage squared, so half voltage = 25 % power.

You should press the TUNE button several times and adjust the pots on UD1 so the
power level in each band reaches 400 W and then some.

This ensures that the level control circuit will keep the power as high as possible, but not
overdriving the amplifier.

 

[HA3KGX]

No, power is proportional to voltage squared, so half voltage = 25 % power.

You should press the TUNE button several times and adjust the pots on UD1 so the
power level in each band reaches 400 W and then some.

This ensures that the level control circuit will keep the power as high as possible, but not
overdriving the amplifier.

I see, thank you!

The value between 10-15 is the maximum (not skd) which is my reflected power, so counting the surprisingly few watts, it's a pretty good value, I'm glad of that!

I also pay attention to the antenna tuner, but I believe better in the instrument built into the amplifier.