Home
1 KW SSPA for 1.8-54 MHz
A 1.5 KW LPF for 160-6m
1 KW 6 Meter LDMOS Amplifier
2 Meter 80W All Mode Amplifier
1 KW 2M LDMOS Amplifier
1 KW 222 MHz LDMOS Amplifier
500w 70cm Amplifier
1KW 70cm LDMOS Amplifier
A Big Power Supply for SSPAs
Low Pass Filter/Dual Directional Detector
Sampling RF Power
LED Bar Graph Meter
Amplifier Control Board
LNA Sequencing and Protection
Building UHF Antennas
VHF OCXO
MIcrowave Marker
Crystal Oven Controller
Microwave L.O.
Latching Relay Driver
12 to 28v
Relay Sequencer
High Current DC Switch
L & S Band LNA
Microwave L.O. Filters
PC Board Filters
Using Inexpensive Relays
600w 23cm LDMOS Amplifier
XRF-286 Amplifiers for 23cm
150W 23CM Turn-Key Amplifier
300w 23cm Amplifier
200w 23cm Amplifier
100w 23cm "brick"
100w 23cm Transverter
60w 23 cm Amplifier
23 CM Beacon
23cm Signal Generator
23cm Double Quad
23cm filters
13cm filter
13cm Signal Generator
13cm Transverter
120w 13 cm Amplifier
300w 33cm Amplifier
33cm filter
33 cm Crystal Source
33cm Signal Generator
9cm Transverter
Transverter Selector
12 AND 28 volts
Klitzing Amplifiers
IC-910H tweaks
Audio Files
Parts I Can Supply
Current Projects
Links

Comments? email to

120w 13 cm Amplifier

2304 is one of those bands where you can find some surplus components to build with.

This amplifier uses two 60w Spectrian amplifier boards with the usual input and output hybrid coupler and combiner.

Spectrian amplifiers and their components can be found in the usual online auctions, and occasionally offered as surplus elsewhere.

These two amplifier boards are not terribly efficient, requiring a total of 26a @ 26.5v at full output, or almost 700w in for 120w out. But they do the job.

A Dow-Key high-power transfer switch handles the changeover, and is controlled by a sequencer in the driving transverter, which is pictured below the amplifier in this photo.

As in the 60w 23cm amplifier, the rear panel connections allow for expansion. The transfer switch can be bypassed, and the internal amplifier accessed directly via the bulkhead N connectors on either side of it. These are normally jumpered to the transfer switch as shown.

The sequencer in the transverter supplies the trigger for the transfer switch, and enables the amplifier boards shortly after (the control connector is the interface link).

Here's the layout inside.

The driving transverter has decent power (25w), so I use an input attenuator to drop the drive to about 2.5w before the input splitter.

The attenuator is an 8db terminated hybrid coupler (the copper PC board at upper left). This feeds the input coupler mounted on the vertical bracket to it's right.

On the other side, the outputs are combined in the coupler shown at lower left. All couplers were made from Teflon PC board material.

The small PC board mounted atop the transfer switch is it's latching relay driver.

Well, I guess everyone discovers something else that is needed after construction is complete.

After I had the amp in use for a few minutes, I noticed I underestimated the cooling requirements - the heat sink got too hot - so I added the small fan driver you see here.

The Spectrian boards have a temperature sensor output, and this little board turns on the fan when the sensor indicates 95f.

I used a quiet (22dba) PC fan mounted atop the heat sink, and it plugs into the amp via a small DC power connector I added to the rear panel.