Meter 8. 0W All Mode Amplifier. Published in QST. May 2. 01. 3) - there are several corrections and. There. are lots of different 2 meter low- power rigs in use out there, ranging from. FM, older multi- mode transceivers, and even the newer all- purpose. FT- 8. 17 or the Elecraft 2. M transverters. QRP.

Good news.. if you have a couple of afternoons to spend on a project, you can. Easy because it uses one of. S- AV3. 6 Toshiba modules, 5. I wanted to keep it. After absorbing the specs in the data sheet, it was clear this module could. A configurable input attenuator capable of.

FCC. regulations for harmonic and spurious suppression. Low- loss antenna relay. RF- sensing t/r switch for remote operation, as. T/R sequencing to protect the S- AV3. Indicator LED's and control switches. Reverse polarity protection. The. devil is in the details for the designer, though, and it did take a little.

PC board and just a few interconnecting. Add a heat sink, connectors, switches, a couple of sheet metal parts. The Photo to the left is the first prototype, using a board made with common. Since the input. power required to drive it is only about 5. S- AV3. 6. The chart shown on the right lists the resistor values for 5.

About the Kits Component Quality. The amplifier modules are built on high quality 2-layer FR-4 PC Boards. Critical signal path capacitors have high linearity NPO or.

There are some strange values there, but these. For example, a 2. L5 is not really necessary, it's purpose. R7 at 2 meters (a 3. The input SWR was acceptable without it, but it does make the input. Not good enough for the FCC, so we need an output filter that will put us in. For that 2. 5db second harmonic.

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The filter shown is a standard pi- type Chebyshev, 7 poles, and provides the. The last analyzer display shows the sampled harmonic content of the amplifier. Good filter. Less than $5 in cost, the contacts are rated at 8 amps. At 2. meters, a bit of reactance is introduced by this part, but compensated for by a. C1. 5) in series with it's input. The best way to tell the amplifier to switch on is to use a control line back.

PTT). If this is unavailable or inconvenient, the amplifier. RF- sensing circuit that samples a bit of drive from the input connector to. Another little twist; switching from receive to transmit should be sequenced. S- AV3. 6 is tough, but no self- respecting amplifier. For this reason, the module has to be kept off while the. The other reason is to protect the relay contacts. Showing the full schematic now, C4, D1, and D2 sample the input, and C5, C6.

R1 and R2 provide filtering and some timing, depending on the position of S1. In SSB mode, the. RCV mode. In FM mode, the switch back to receive is much quicker, as the.

FM operation. The circuit is sensitive, and will. Q1 is the switch that operates the relay. Default Microsoft Exchange Services Stopped 2003 Ford.

When the relay is turned on by Q1. Q2 (the bias switch) after a short delay. This delay is. provided by C9 and R4, and is about 5. When switching back to RCV, the bias to the module is cut off before the.

This fast cutoff is timed by C9 and R5, and is only about. Another noteworthy component is D6, the reverse- polarity protection diode. L2 and L3 are 7 turns #1. ID and 1. 0mm long. For parts supplied by. Mouser, you can order all of these by ordering the project list from their web site at. The access I. D. At the time of publication of the QST.

Mouser was temporarily out of stock on the 5. R7). A. 2. 0w resistor can be substituted there, part # PWR2. S- 2. 0- 5. 6R0. J. If you use the. 2.

L5, part # imc. 12. RFPARTS (www. rfparts. Toshiba module and coax connectors; artwork for the PC. Drawings for making the chassis parts are here.

For heat sink material, a heat sink with a base thickness of . The size of the one I used was 8. You can also position the Toshiba module and mark. Drill and tap the module mounting holes for 6- 3. PCB holes for 4- 4. Fill the plated- through holes. Lawrence Of Arabia Restored Edition here.

R7 with solder; this will help to draw heat away. R7. Install all the PC board components except for the. The relay should be installed last, and because the pins will protrude. Make the two aluminum spacers as as shown in this.

The two aluminum spacers must be positioned under the board on. These spacers elevate the board to a convenient height for the. Some minor tuning of the low pass filter coils. Connect a dummy load to the output of the board. SWR meter to the trace at the input of the filter where the module.

Apply 1. 2v across the relay coil to close the relay, and spread. SWR reading. If this is inconvenient to do. It's best to do it now, though. Using heat sink compound, mount the Toshiba. Module with 6- 3. Note that the mounting bar of the module is. Do not attempt to sand this footing.

I'm just guessing, but I believe the. Solder the module wires to the.

PC board (cut off the excess wire length if. Mount the connectors, switches and LED's, and. The LED's have their 1.

K resistors soldered. Use. solder lugs under the mounting screws for the connectors on the rear panel. DC chassis ground, and bypass. Make the power cord with #1.

If you will be hard- keying your amplifier from your radio. The radio's PTT relay contacts or other switch. Testing the amplifier. Once everything is wired and in place, you can. Connect the output to a suitable wattmeter and.

Connect the power cord to a power supply. Place the Amplify/Bypass switch in bypass. Transmit, and verify that bypass mode works (most of the driver's. Figure xx shows the. Turn off the driving radio and put the. Jumper PTT to. ground, and the Xmit LED should also illuminate. Adjust the IDQ trimmer.

VR1) for 8 amps. Place the amplifier back in bypass mode and remove the PTT. Turn the radio back on, place the amplifier in. Performance should be similar to the data shown. I experimented some with various IDQ settings, and. Toshiba must have designed the module to operate close to class. A; setting IDQ lower tended to introduce lower overall gain and crossover. SSB, and setting it higher resulted in higher gain and saturated.

At 1. 0 amps IDQ, for example, the amplifier could be driven to over. IDQ. This does exceed. I resisted the temptation to leave it that way. Knowing how bias levels work could be useful in. FM, CW); you could set the bias level to control output. VR1 for this. purpose. For all- mode versatility, leaving IDQ set at 8 amps is best.

One. last note; at 1. I noticed R7 (the 3.

PC board I made for. Most of us making our own prototype boards at home don't have the. If you purchased the commercial board, you won't need the. R7 with solder to help with heat sinking. Corrections to the May 2. QST. article: The value of C1.

PC. boards offered here)The positions of R1 and R2 were. R1 (5. 11k) should be the resistor that is bypassed (or not) by S1. C6, C8, C9 and C1.

Here is a photo of the populated. Clicking on the photo above will.