XF-LPF-HF filter kit short wave low pass filter For Shortwave Radios
1.Item Description:
·100% brand new and high quality
·High frequency LPF
·3.5Mhz-30Mhz
·Power 100W
·Voltage: 12V
·Switch band manually: 80m, 40m, 20-17m, 15-10m
·Size: 118.6mm* 49.3mm
Type(optional):
1.kit:82g
2.Assembled Board:72g
(1) DIY Kits:
1 * Kits
(All the accessories shown in the picture below are included)
(2)Assembled Board:
1 * Assembled board
The board has been welded (already assembled)
Connections:
-J1: RF input @ 50 Ohm
-J2: RF output @ 50 Ohm
-J3: 12 V, 0 V
-J4: Jumper to Pin 5: 0 V, Pin 1: 80m, Pin 2: 40m, Pin 3: 17-20m, Pin 4: 15.10m
The activated band will be shown with a lighting LED.
Filter Transmission Loss:
The following diagrams show the Transmission Loss of the 4 Low Pass Filters. It was measure with YanaVNA-BT and visualized with program VNAJ.
The markers in the diagram are set to the following frequencies:
Marker 1: Start of SW band
Marker 2: Start of SW band * 2
Marker 3: Start of SW band * 3
Marker 4: Start of SW band * 5
If not otherwise set in the higher frequency range, because the used measurement device YanaVNA-BT does operate up to 65 MHz only.
For amateur use, FCC §97.307(d) requires that harmonics be suppressed at least 43 dB for operation below 30 MHz.
In a well designed solid-state push-pull short wave amplifier, the second harmonic is 30 to 40 dB below the fundamental (first harmonic) if the balance is good, but the third harmonic is only down by about 13 dB.
It can be seen, that the most dominant third harmonic is in all cases suppressed more than 40 dB.
The pass band loss is below 0.2 dB with the exception of the 10 m band (0.4 dB).
Standing Wave Ratio:
The Standing Wave Ratio (SWR) was measured with YanaVNA-BT and a SWR bridge. In this case I had to photograph the display.
The first two diagrams on the right show the 80 m and 40 m band.
The marker Tune shows the start of the Amateur Radio band.
The markers L and R (Left and Right vertical green lines) usually show the Amateur Radio band limits.
-Below 20 MHz the SWR is below 1:1.1, a Return Loss greater 21 dB, see ReturnLossBridge.
-Above 20 MHz the SWR is below 1:1.2, a Return Loss greater 18 dB, see ReturnLossBridge.
The next three diagrams below show the 20 m, 15 m and 10 m band.
Band fault detection:
In order to protect the Power Amplifier against Overvoltage and Overheating if a wrong short wave band was selected, or the RF output is not terminated, or the SWR of the antenna is very poor, two protection circuits can be added. In my case the SW band signals from my tranceiver are used for automatic switching.