TWT Power

Hello NTMS

I fired up my RW289 TWTA tonite and it puts out about 22 watts on 5760 with about -1 dBm of drive. Some fine tuning of the front panel beam adjust allowed some peaking of the power output. On 3456 MHz with about +10 dBm of drive it also puts out about 20 watts. With similar drive on 2304 and 10368 MHz only a few watts of power output is possible.

When using a supply voltage of -24V the peak current draw is about 8 to 9 amps with full drive. At idle with no drive the current is about 5 A.

I did not use the input and output filters and just connected directly to the TWT input and output.

To connect -24 volts to the unit, find the 25 pin connector on that long cable that connects to the front panel at P12 on the far right hand side of the TWT. I cut the cable at the point where it split in two directions so in other words I had a 25 pin connector with about 1 ft pig tails to work with.

Find the following color coded wires and connect accordingly

Ground (0VDC)
Small brown
large green white
large orange white
Negative 24 VDC (-24V to -48V)
Large green
Large orange

There appears to be two sets of small brown and white/brown wires. The small brown wire that I used ohms out to pin B on the twt power supply connector on the left side of the unit.  (Editors note:  If you have the TWT facing you with power, etc. switches and labeling in normal reading orientation, the connector referenced herein is on the top of the unit...the larger of two connectors with two thumbscrews)

PTT keying is accomplished by wiring a relay across the Standby / On switch (next to the power switch.)  Open is Standby, Closed is On.

If you happen to connect the power backwards, you will blow a 15A fuse (micro fuse) immediately behind the on/off and xmit/sby switches.  So, if unit does not come on, check that fuse!

On 10GHz, 25W seems to be a typical Pout.  Do not overdrive the tube, ease the power up out of the transverter until it maxes out and then back it off a bit (db or two).

The Yellow alarm light should not illuminate when driving the tube.  You may have to adjust the helix voltage to keep everything within tolerance.

Good luck



Additional comments by N5PYK

Main modification needed to the unit will be a means of switching the TWT in and out of standby (e.g. a PTT).  It is believed a simple relay across the ON/SBY switch will accomplish this goal quite readily.