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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | JUMA PA1000 Help

Reviews Summary for JUMA PA1000
JUMA PA1000 Reviews: 2 Average rating: 5.0/5 MSRP: $2200
Description: 5,5 kg + 1000W including power supply
Product is in production.
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W1CQ Rating: 5/5 Jan 17, 2019 01:48 Send this review to a friend
Ultralight 1KW SS AMP   Time owned: more than 12 months

The JUMA PA1000 defines a new category of ultralight HF amplifiers using LDMOS technology. I’ve been using it about a year - at a home station, portable, and in contests. At 5.5 kg it’s perfect for travel and fits easily in carry-on luggage! It has travelled with an Elecraft KX3 in a hard shell case.

There are a few other commercial amps using 50V LDMOS devices, as well as several homebrew projects (especially for 6m and above). What distinguishes the JUMA are its ultralight weight and very high level of engineering design and professional assembly, workmanship and finish. It covers 160 to 6m and readily produces 1 KW output power with drive input of around 10W or less. The amp is designed for SSB and CW (and is not rated for full-duty cycle operation such as AM or digital modes). A fast mechanical SMD T/R relay (quiet but not noiseless) with max operate/release of 4ms/6ms should allow for break-in CW with reasonable code speeds and relay life. The amp can be operated remotely via a RS-232. It can be ordered with a switchable 115/230 VAC option. At full power, current is about 24 amps and efficiency is very high at 70 to 80%.

The PA1000 has seen use by several recent DXpeditions, so before making the order with JUMA, I sought feedback from about half a dozen of these users. Also researched the 1K25H LDMOS device itself.* It is from NXP (formerly part of Philips) which in 2015 acquired Freescale (formerly part of Motorola, and with the legacy of Helge Granberg and Norman Dye). These LDMOS power FETs have inherent high VSWR tolerance, typically tested in pulsed, low duty-cycle industrial applications. There are used, for example, in high power lasers where the VSWR is transiently very high and then decreases rapidly. These are rugged RF power amplifier devices, but they are sensitive to overdrive. The device has a breakdown voltage, V(br)dss, of 133V. There should be adequate margin for reliable amateur radio use as rated.

JUMA has accomplished several pioneering engineering steps with the PA1000, under development since about 2011. The current product is evidence of their success in overcoming challenges of the early prototypes. First, of course, is the successful use of the MOSFET for reliable broadband HF use at the 1 KW level, with excellent heat management, SWR and overdrive protections. JUMA has utilized innovative output matching and low-pass filter capacitors that tolerate RF with low loss. There is a single PCB for simplicity, which holds the power FET and other SMD circuitry. To achieve ultralight weight, a low noise switched-mode power supply (SMPS) is used, which is just 0.8 kg. That's about 9 kg less than a typical transformer power supply! The SMPS uses LLC series resonant converter topology for high efficiency and low EMI. For output power below 700W, JUMA adds a lower voltage setting (50v rather than 56v) for added efficiency. The PA1000 has fault protections for SWR, over current and over temperature that are well-designed and function appropriately.

Thermal dissipation is a critical issue and the mounting of the ceramic package LDMOS on the heat sink is well done. There is a temperature controlled, ducted fan below the heat sink that is effective. A separate fan is used for the power supply. Fan noise is not objectionable and can be user controlled. The fans do cycle with use but can be off when the amp is not keyed. The reported experience from DXpeditions in tropical, high outdoor temperatures has been favorable. Some operators have conservatively run less than full power during extended operations.

Beyond protection from excess heat, there is the concern to avoid overdriving the MOSFET. This can happen with an inadvertent RF spike or from user error. Power transients can result from a tuner arcing or from using a roller inductor. Overdriving can occur with a severe mismatch or if a tuner is mistakenly adjusted while high power is being applied.

JUMA appropriately recommends using well-matched antennas with good SWR, and strongly cautions against use of a tuner, especially an autotuner. There is also another consideration relating to autotuners when driving an amplifier with 10W or less. Many high power autotuners achieve a best match when the input power is around 20W. With 10W or less input, the autotuner may need to first have the memory pre-populated (for each band and at multiple frequencies) using a 15-20W setting, so that an appropriate nearby match is then found when the power is reduced to 10W or less. In short, for me, a tuner option meant extra weight and added complexity. It seemed best to focus on selecting well-matched antennas anyway, and to avoid the inevitable loss from an antenna that needed tuning. I typically run the amp at around 800 watts or so and it has handled SWR up to 1.8 or 2.0 without trouble. An ideal match is, of course, best.

The PA1000 interfaces band data very well with popular transceivers. JUMA recommends that automatic, rather than manual, band data selection be used. I found the use of the JUMA COM HUB, to connect the PA1000, KX3 and laptop computer with logging software, to be reliable and seamless. (Use a ferrite choke on the USB cable to keep the computer connection active and free of stray RF). There’s also a convenient BCD output that can be used to control antennas or other equipment.

To prevent inadvertent overdrive, the PA1000 uses adjustable (and band-specific) RF input attenuation (gain levels G1 to G8). Some transceivers may transiently overshoot to their full 100W even when set to a lower power output of, say, 10W. Such high power pulses may be from sluggish ALC and can be hard on amplifiers. The PA1000 does not use ALC. The built-in input attenuation is an important protection from user error and overdrive. At Max Exciter Pwr of 100W, only the G1 to G4 gain levels are available. As the Max Exciter Pwr is adjusted to 50, 25, 10 or 5W, the higher gain levels become usable. With the KX3 at about 10W or less there was typically 1 KW output even at the middle gain settings, so there was no need to adjust higher or change the Max Exciter Pwr setting.

JUMA has measured IMD3 on 14 MHz at 420W to be -42.8dBc and at 1000W to be -34.8dBc. On 50MHz at 600W it is -34.4dBc. I find these as expected and consider them acceptable, especially with a monoband or tuned antenna. On 6m, I'd consider adding a low-pass filter.

Among the many DXpeditions, which certainly subjected the PA1000 to rigorous use, I noted only two instances of problems. In one, operator error (overdrive from excessive input) was clearly the cause. In the other (2016) DXpedition, a LDMOS gate shorted, which could have resulted from component failure or from overdrive. JUMA responded with a helpful modification - adding transient-voltage-suppression (TVS) diodes, which can suppress an overvoltage. This should even further enhance high reliability. Firmware updates have also refined protection features and added other improvements.

The combination of the PA1000 and KX3 brings a new level to ultralight portability and suitcase DXpedition. These fit together nicely in a carry-on case. It may be argued that an amplifier failure in such a situation would leave just a 10-15W radio. However the reliability of the 50V LDMOS technology is certainly sufficient, with prudent precautions taken against overdriving. If a DXpedition trip warranted an added layer of certainty, rather than a heavier amplifier, I'd prefer a buddy with another carry-on PA1000 plus KX3.

To sum up, the PA1000 is a reasonably priced ultralight KW SS amplifier that travels extremely well and is also quite suitable at the home station. It defines a new ultralight weight category. From pre-order questions, to set up and follow through, the experience with JUMA has been first rate.

* Update - According to JUMA, the PA1000 now uses the BLF188XR LDMOS. The performance characteristics are quite comparable to the 1K25H, with a slight improvement in thermal resistance. The BLF188XR was released in 2013 by NXP in their XR "eXtremely Rugged” line. In 2015, after NXP acquired Freescale, the RF power division was spun-off as Ampleon.

OH1VR Rating: 5/5 Oct 16, 2015 22:47 Send this review to a friend
5,5 kg + 1 KW  Time owned: 3 to 6 months
JUMA PA1000 is an excellent answer for a handbag DXpeditioner = 5,5 kg including power supply in a small box. With my KX3 xcvr I have now 1 KW station less than 7 kg of weight. Since late May 2015 I have worked with it several thousands of q's mainly on CW. My motives to buy it were 6m and DXpeditions but of course it is also designed for a use at home shack. It runs well more than a kilowatt of power if the SWR of the antenna is good or if you have a antenna tuner. Juma PA1000 is for cw and ssb operations. The SN of my amplifier is 0010.

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