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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | JUMA PA100-D HF Amplifier Help

Reviews Summary for JUMA PA100-D HF Amplifier
JUMA PA100-D HF Amplifier Reviews: 3 Average rating: 5.0/5 MSRP: $460 Euro
Description: JUMA PA100 is a small size true 100 W linear amplifier for all amateur HF bands. The amplifier is available as a component kit. There are two models available, the PA100 with analog user interface and the PA100-D with digital user interface.

The JUMA PA100 amplifier can be used with any low power transceiver or transmitter with an output power range of 3 watts to 10 watts.

The size of the JUMA PA100 is compact and it is equipped with a fan in the heatsink. The fan is typically OFF during normal QSOs and it starts only when needed. The fan is very quiet.
Product is in production.
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KI6PU Rating: 5/5 Feb 8, 2013 10:16 Send this review to a friend
Great Amplifier for QRP Rigs  Time owned: 0 to 3 months
This review is for the JUMA PA100 (Analog version).

After acquiring the kit I realized the kit was beyond my kit bulding expertise. Through the "JUMA Community" I found KH2BR, Robert, who was willing to build JUMA kits. Robert agreed to construct the JUMA PA100 amplifier and returned the completed kit in about ten days.

I am really satisfied with the quality of the amplifier and its operation. The amplifier is used every day on SSB and CW. I like the analog version because it enables me to swithch quickly through the METER functions to determine its status or if there are any problems. The GAIN contol allows the output to be vaired from about 35 watts to 100 watts using the FlexRadio 1500 (5 watts). Once, the cooling fan turned on due to excessive heat from high SWR. The fan is very quiet and cooled the final tranistors quickly. If the SWR is adjusted to 1:1, the fan has never operated during transmissions.

Overall, I am very satisfied with teh JUMA PA100 amplifier and its builder, Robert, KH2BR. I would recommend this ampliier to those hams who want a QUALITY amplifier to give their QRP rigs a little more output.
5B4AIY Rating: 5/5 Jul 1, 2012 03:19 Send this review to a friend
Really nice little afterburner!  Time owned: more than 12 months
I purchased the kit version of this amplifier to complement its matching transceiver, the Juma TRX-2. This review covers the digital model, the PA-100D.

This kit is of the same high quality and the TRX-2, with silk-screened gold-plated fibreglass printed circuit boards, and high quality components. As a previous reviewer has mentioned, the components are packed in separate packs with each pack containing an itemised listing of its contents, with the component designators marked.

Although there is no 'Heathkit style' assembly manual, there are numerous photographs, layout drawings, and schematics available from the website. It uses virtually all surface mounted components, mostly of the 1206 size, except for the digital control board which uses the smaller 0805 size.

You would be well advised to purchase the accessory Starter Kit which contains the necessary tweezer, flux, and solder to help assemble this kit. You will be required to wind your own toroidal inductors for the low-pass filters, but there is plenty of wire supplied.

When used with the Juma TRX-2, fully automatic bandswitching is achieved by coupling the RS-232 ports of the transceiver and the linear, and setting their respective serial port protocols to the JUMA-TRX2 mode of operation.

The transmit-receive switching is accomplished by means of a switched DC voltage provided by the TRX-2 on its RF connection.

To operate with other transceivers there are a number of connection possibilities.

The bandswitching can be accomplished automatically by setting the sensing of the linear to the Frequency Sense mode. In this mode the RF input signal's frequency is measured, and the appropriate output filter selected.

If you are using a Yaesu transceiver, then the amplifier can also automatically select the band by using the band select voltage from this transceiver. You will have to make the necessary cable to couple the transceiver's CAT/Linear socket to the linear.

It is also possible to select the desired band manually from the front panel buttons.

Transmit/Receive switching is handled by means of an accessory input socket on the real panel that accepts a closure to ground to place the amplifier in the transmit mode.

There is an adjustable input attenuator providing for 0dB, -1dB, -2dB, and -3dB attenuation. In the 0dB position my amplifier exhibited 15dB power gain. In other words, for the full 100W output you would need 3W of input.

The amplifier uses a matched pair of Toshiba 2SC2879 transistors rated at 45V, 25A, and 250W collector dissipation. The amplifier can easily provide 150W of output, and when operated at the 100W level provides plenty of 'headroom' for speech peaks, and is free from clipping leading to a clean sounding signal.

The fan is very quiet in operation, and if you use my modified firmware you can choose how the fan operates. There are a number of other upgrades and new features with my latest firmware that enhance the operation of this really nice little 'afterburner'.

Having now used it extensively both for fixed-station and portable operation, it has proven to be rugged, reliable, and reasonably efficient. Its small size and light weight (1.2kg) make it ideal for portable/field day operations.

I am well pleased with this amplifier, and can thoroughly recommend it.

If you would like my updated firmware for this or the TRX-2, then this can be downloaded from the Juma website of by sending me an email:
N1JR Rating: 5/5 Dec 29, 2010 14:28 Send this review to a friend
High quality Amplifier  Time owned: 3 to 6 months
Over the past few months, I have built and used a JUMA PA100-D Digitally controlled 100 watt linear amplifier for HF bands ( and wanted to share my experience with the group. This amplifier (and the manual non-digital version) is one of the kits designed and produced by JUMA kits ( ) a company owned by Finnish hams Juha OH2NLT and Matti OH7SV. Their kit products are offered through the “SRAL Oy” ham store run by The Finnish Amateur Radio League. In the background, there is a Finnish “kitting” company which puts the parts kits together for sale.

The JUMA site has extensive and excellent photographs to support assembly of the various kits. There are also good write-ups for details which may not be clear from the photos. The PC boards are of the highest quality and have printed parts names printed on them. The parts come in small plastic bags with lists of the included parts to check the contents. The parts themselves are of first quality by recognized manufacturers and the chassis and metal work is also of high quality in fit and finish. (Any missing items are quickly supplied by the kitting company after an email to them.)

I built the small ( 4.9” x 7.1” x 2.4”) robust PA100-D amplifier for use with my Icom IC-703+. The amplifier makes use of two matched 2SC2879MP transistors capable of up to 150 watts output. The input of the amplifier has 4 levels of attenuation available so that rigs with power levels from 2 through 10 watts can be readily used. The rear heat sink also makes use of a quiet fan. The amp has four ways to change frequency including manual, RF sensing, DC control and JUMA TRX2 serial protocol. The amp is protected from high SWR conditions, over current and over temperature and will alert the operator both visually and through a built-in beeper. Various properties of the amplifier, including power out, heat sink temperature, input voltage, final transistor current draw among others, can be seen from the blue digital screen (or meter on the manual amp). The amp also has a “Service Mode” which allows the operator to calibrate and/or adjust items such as the beep length, forward power calibration, RF amp current, etc.

JUMA provides technical support for its products via email and, if this was not enough, some of the Finnish Amateur Radio Club members will actually repair or fix the malfunctioning (or non-functioning) assembled kit generally without charge for the price of shipping back and forth to Finland. They won’t let you fail. I received help on my amplifier when I couldn’t seem to find my error in assembly of a surface mount part. All of the kits make use of surface mount parts and this will require learning some new skills. (There are some very good articles on the internet in manual surface mount part work and it is not at all as hard as it might seem if one uses a suitably small soldering iron and a magnifier lens.)

So, how does it work? I can leave the amplifier in line but turned off until I want to abandon my QRP power level and break into a pileup. It’s simple and virtually foolproof. While the JUMA kits are not inexpensive, they offer a great value when their design and build quality, electronic sophistication and functionality are considered. I enjoyed the building of the kit, learned a lot and have a visually pleasing and beautifully functioning piece of gear of which I’m proud. This amplifier kit easily deserves a 5/5 from eHam.


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