RF FAQ

Why do I get a screen over load on my FM-T or FMi-T TX with less than 100 Volts of screen Voltage?
Most likely issue is that one of the neutralization capacitors (C7, C8, C17, or C18) are shorting under low screen voltage.    Remove the neutralization s...
Tue, 8 Oct, 2019 at 1:08 PM
Why do I not have any digital carrier output of my FMi series transmitter?
It is possible that the LVDS (Cat 5) cable is not connected/defective, the transmitter is in FM Only mode, or the HDC from the XPi to FXi has dropped out.
Tue, 8 Oct, 2019 at 1:10 PM
Why do the F1 fuses on either the PA modulator or the PA boards of my AM transmitter routinely open?
ther than a hard failure of a device or component drawing excessive current, the most likely cause is that the fuse clips for the fuse have overheated and/o...
Tue, 8 Oct, 2019 at 10:20 AM
Why do the GPIO inputs on the back of my CPE equipped unit seem to be intermittent?
The CPE board may be set for isolated ground.  Verify the isolated/non-isolated ground jumper on the CPE board J9 is in the 1-2 position.  This connects the...
Tue, 8 Oct, 2019 at 1:13 PM
Why does the FM 250C exciter F1 15A fuse routinely open?
Other than a hard failure of a device or component drawing excessive current, the most likely cause is that the fuse holder for the fuse has overheated and/...
Tue, 8 Oct, 2019 at 1:14 PM
Why does the FX 50 exciter F1 12A fuse routinely open?
Other than a hard failure of a device or component drawing excessive current, the most likely cause is that the fuse holder for the fuse has overheated and/...
Tue, 8 Oct, 2019 at 1:15 PM
Why does the TPO on my FMi C Series transmitter seem to drift and not stay at 100%?
If the power on your FMi C Series transmitter seems to drift up or down in output power over time or whenever my air handling system turns on, the problem m...
Tue, 8 Oct, 2019 at 1:18 PM
Why doesn't my FM-T or FMi-T TX have RF output? The readings appear ok, except for 0 PA current.
Remove tube and check the filament rings to ground; normally the Ohm meter will indicate zero Ohms. If the filament rings indicate an infinite resistance, c...
Tue, 8 Oct, 2019 at 1:23 PM
Why doesn't my FM-T or FMi-T TX have RF output? The syptoms: high screen Voltage and high IPA VSWR.
Most likely issue is that R4 (10 watt 1.5 Ohm resistor) in the grid circuit is open. A temporary fix is to create a coil of 10 turns of #24 wire around a pe...
Tue, 8 Oct, 2019 at 1:21 PM
Why don't the buttons on the front panel of the FM 100C Exciter stay selected?
If the button does not stay selected unless it is held, the problem is most likely associated with the C53 and C55 capacitors in the power supply section of...
Tue, 8 Oct, 2019 at 2:04 PM