Allmode RF Power Amplifier
for the HF 15 and 17 meterband (21Mc/18Mc)
RE-PA10HF17 and RE-PA10HF17

revision 1.3
By Guy, de ON6MU

About the 15- and 17-meterband HF amplifiers

This project and your efforts will provide you with a 0.55...2 watt input to easily 8 watt output. The two linear amplifiers are ment for use with QRP SSB/CW/FM/AM transmitters on the amateur bands 15 and 17 meters can be powered from a 12 volt DC supply. The design is a good balance between output power, physical size. The completed amplifier will reward the builder with a clean, more powerful output signal for a QRP rig when radio conditions become marginal. It has a RF-sensing circuit (Q2) wich allows the amplifier to switch on automatically when transmitting. This project uses a "classic" RF transistor. MOSFET power amplifiers are discussed and build in the near future on this website.

Bias
Power amplifiers used in base stations require biasing for proper RF performance. BIAS has be applied to Q1 to have clean proper and correct SSB modulation using this amplifier. Set P1 so +/- 35 mA current flows through Q1. Depending on the type of transistor this can vary somewhat, although you should never exceed 60mA! You don't need SSB? Read next part.

CW/AM/FM only
If you only want to amplify AM/FM/CW/FSK type of modulation (NOT SSB) then you can leave out the BIAS section for Q1 (between b1 and b2 in the schematic). You simply connect connection b2 to the ground, hence leaving out the somewhat critical setting of the correct BIAS for operating clean SSB.

Modulation modes
If using the schematic as displayed below and so also using Q1 BIAS, you can amplify any type of RF generated modulation waves.

Filter
RF purity and harmonic suppression is done here. Also allowing the transistor to be coupled to the antenna system through antenna impedance matching circuitry (C14). Care is taken at this stage so that no harmonic frequency is generated which will cause interference in adjacent band (splatter) on other bands. This 4-element L-type narrow bandpass filter circuit and a 3 element low-pass PII filter for the desired frequency cleans out any remaining harmonic signals very efficiently.

Housing/shielding
The whole circuit needs to be mounted in an all-metal/aluminum case. If you're unable to obtain an all-metal case, then use a roll of self-sticking aluminum tape (available from your hardware store) or PVC box painted with graphite paint. Just make sure that all individual pieces of aluminum-tape (or the graphite paint) are conducting with each other. Works fine.

RF-sensing
The basic principle of RF-sensing using a relay is clearly drawn in the schematic and pretty much self explaining. Q2 (BC338, 2N2222) will conduct when RF energy is applied at the input of the amp (and so also via C18, D3, D5 biasing the base of Q2) hence powering up a RF capable relay. This relay switches between RX and TX with amp. When no Vcc is applied to our amplifier (and so Q2 too) no amplification is done. The input is simply re-directed directly to the output (as if your transceiver is connected without an amp). The RF sensing circuit is sensitive enough to react on .5 watt easily.
To allow the amplifier in SSB-modulation some extended PTT time-on the RF-sensing unit (Q2->relay) has to be increased. This is done by closing S1 (SSB/FM) and so C20 adds the needed "breathing" time. In FM/CW/AM/FSK modes a carrier is present and extended PTT time-on of the amplifier isn't needed, hence can be short.
Important: timing can vary on the type of relay used (Ohms resistance value of the relay coil), so often experimentation of C19 & C20 is needed.

An error in the schematic previous to rev. 1.3 connected the input of the rf-sensing circuit wrongly to C10, instead of the input PL259 connector IN.

Important: Everything will be within specs if you use RY5W relay, but timing (the "breathing time") can vary on the type of relay used (Ohms resistance value of the relay coil), hence experimentation of C31 is needed.

Note:
Although this example of RF-sensing isn't the Worlds most best sollution, it is pretty easy for beginners though. Better would be to drive t2 from your transceiver (amp drive) as this will switch at the very moment of PTT.

RE-PA10HF17: 17-meterband Amplifier settings

First set C12 and C14 to the middle and centre pin of P1 to the ground. After carefully mounting all parts and using as short as possible connections between the parts, gently add voltage to the amplifier while checking the current. The only current you should see is a the liddle idle current of Q1 (and LED D6 if connected). Increase the voltage to 12 volts. Check current again. It should (at this stage) be lower then +/- 20mA.

Now gently turn P1 till you get approx. 35 mA. Do not forget to mount Q1 on a heat sink isolated electrically from the transistor.

So far so good? Now we check if the (Q2) RF-sensing circuit is working properly. Connect a proper dummy load and a power meter to the output of the amp. Remove any connectors from your power supply and temporary disconnect the collector from the VCC. Connect your transceiver to the input. Be sure you set your tranceiver's power to minimum (never more then 3 watts) and you set your transceiver to 18.100Mc in CW/FM. Key your transceiver and if all goes well the Relay should power up and you should see the current rise and your power meter should already show an amplification of the RF input power.

Still all working as planned? Excellent! Now carefully turn C12 till you get maximum output power (whilest checking the input SWR on your transceiver or SWR meter). And finally tune C14 to maximum power. If needed re-tune C12 and C14 till you reached the maximum. Current should be around 1.2 Amp +/- (depending on the voltage and input power).

10 watt RF HF power amplifier for 18 and 21 Mc

Parts list 17-meterband power amplifier

Ls

Note:
Always use a dummy load for testing and adjusting the amplifier!!!

Specifications RE-PA10HF17

 

DL6NL design of the 18MHz amp
How Peter DL6NL made it!
Click image to enlarge

RF Power transistors:

2SC1969/ERF-2030
Features:

Application:

Absolute Maximum Ratings: (TC = +25°C unless otherwise specified)

Collector-Emitter Voltage (RBE = Infinity), VCEO 25V
Collector-Base Voltage, VCBO 60V
Emitter-Base Voltage, VEBO 5V
Collector Current, IC 6A
Collector Power Dissipation (TA = +25°C), PD 1.7W
Collector Power Dissipation (TC = +50°C), PD 20W
Operating Junction Temperature, TJ +150°C
Storage Temperature Range, Tstg -55° to +150°C
Thermal Resistance, Junction-to-Case, RthJC 6.25°C/W
Thermal Resistance, Junction-to-Ambient, RthJA 73.5°C/W

Electrical Characteristics: (TC = +25°C unless otherwise specified)

Parameter Symbol Test Conditions Min Typ Max Unit
Collector-Base Breakdown Voltage V(BR)CBO IC = 1mA, IE = 0 60 - - V
Collector-Emitter Breakdown Voltage V(BR)CEO IC = 10mA, RBE = Infinity 25 - - V
Emitter-Base Breakdown Voltage V(BR)EBO IE = 5mA, IC = 0 5 - - V
Collector Cutoff Current ICBO VCB = 30V IE = 0 - - 100 µA
Emitter Cutoff Current IEBO VEB = 4V, IC = 0 - - 100 µA
DC Forward Current Gain hFE VCE = 12V, IC = 10mA, Note 1 10 50 180  
Power Output PO VCC = 12V, Pin = 1W, f = 27MHz 16 18 - W
Collector Efficiency   60 70 - %

Note 1. Pulse test: Pulse Width = 150µs, Duty Cycle = 5%.

 

ERF-2030 Features...
1/ The ERF-2030 is a 25 watt* transistor - therefore, it is not just a replacement part, but also an UPGRADE to the old Mitsubishi part.

2/ The ERF-2030 is NOT an "electrical drop in replacement" for the 2SC2166, 2SC1969 and 2SC2312. However, circuit modifications on most radio's are minimal and documentation is readily available for FREE.

3/The ERF-2030 is a "mechanical drop in replacement" for the 2SC2166, 2SC1969 and 2SC2312. This means that the The ERF-2030 features a TO-220 package with the SAME pinout configuration as the 2SC2166, 2SC1969 and 2SC2312. Therefore NO mechanical modifications to the ERF-2030 are necessary for most installations

Allmode RF Power Amplifier for the 15 meterband (21Mc)
RE-PA10HF15

By Guy, de ON6MU

 

About the 15-meter band HF amplifier RE-PA10HF15

All is already explained above (17-meter band amplifier): Read it here

15-meterband Amplifier settings

First set C12 and C14 to the middle and centre pin of P1 to the ground. After carefully mounting all parts and using as short as possible connections between the parts, gently add voltage to the amplifier while checking the current. The only current you should see is a the liddle idle current of Q1 (and LED D6 if connected). Increase the voltage to 12 volts. Check current again. It should (at this stage) be lower then +/- 20mA.

Now gently turn P1 till you get approx. 35 mA. Do not forget to mount Q1 on a heat sink isolated but electrically from the transistor.

So far so good? Now we check if the RF-sensing circuit is working properly. Connect a proper dummy load and a power meter to the output of the amp. Remove any connectors from your power supply and temporary disconnect the collector from the VCC. Connect your transceiver to the input. Be sure you set your tranceiver's power to minimum (never more then 3 watts) and you set your transceiver to 21.200Mc in CW/FM. Key your transceiver and if all goes well the Relay should power up and you should see the current rise and your power meter should already show an amplification of the RF input power.

Still all working as planned? Excellent! Now carefully turn C12 till you get maximum output power (whilest checking the input SWR on your transceiver or SWR meter). And finally tune C14 to maximum power. If needed re-tune C12 and C14 till you reached the maximum. Current should be around 1.2 Amp +/- (depending on the voltage and input power).

 

Parts list 15-meterband power amplifier RE-PA10HF15

Ls

Note:
Always use a dummy load for testing and adjusting the amplifier!!!

Specifications

Antenna's

It's important to use a correct designed antenna according to band you would like to operate, or at least use a good antenna tuner to match the antenna (protecting your transmitter and proventing harmonics/interference...). Several examples can be found on my website and all across the Web. A dipole is always a good alternative (total length = 150/freq - 5%).
The performance (distance relative to you RF power) of your antenna is as importent (if not more) as the RF power you transmit! A dummy load gives also a perfect 1:1 SWR, but you wont get any farther then the street you live in HI. Finally, athmospheric conditions (D-,E-,F-layers depending on the frequency you're using) is equally important to be able to make DX QSO's.

Related

Remember that transmitting and/or using an power levels higher then your local license permit is illegal without a valid radioamateur license!

Another related project:1watt 10 meterband transmitter project


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