JUMA Amateur Radio Forum

Hi dear hobby colleagues,

my name is Andrei Avirvarei -YO6TJJ and i represent roWaves Technologies. We are based in Sibiu, Romania and we are a team of 3 HAMs & electronic engineers (Sabin S.- YO6SRS, Cristian Capra - YO8SJP, Andrei Dragan and myself - YO6TJJ). Some time ago (oct. 2020) we started to have exciting discussions with JUMA® team Matti & Juha, in order to try to continue the production of their great work they done over the years with Juma radio products. It was during my university studies back in 2009 when i first have seen these products and have started to think that i would like to build or buy one of these.. But i was young and could not afford to buy one at that time...Neither have the knowledge to build one back then, if i think better now Anyway, time have passed and...

Since oct. 2020 we started to hardly work (after we got the legal written permission from JUMA team to manufacture & sell some of their products) day by day and we successfully built and sold more than 38 units of JUMA RX-1 80/40m DDS receiver in Romania and EU and latest, the PA100D amplifier (we sold 4 units so far). The PA100D 100W was a challenge, after we successfully tested the HuaGao 2SC2879 transistors that we bought directly from Chinese manufacturer HuaGao Semiconductor Co., Ltd. We tested 6 pcs. of 2SC2879 transistors from the 16D0 lot (as assured by North, from HuaGao). We lately ordered 30 pcs. for 15 more complete PA100D units. We can build 15 more units in the next months. So here is a glimpse from what we were able to accomplish so far:

- 17.3 dB gain in first 3 lower HF bands and aprox. 16dB gain on the rest 6 bands
- 16Adc current consumption @ 13.8Vdc
- the 3 units we completely built so far can deliver up to 100W on 80m, with just 1W input

Next week we hope to start the IMD3 measurements on the spectrum analyzer and test the thermal protection / SWR/ overcurrent protections. We have managed to build the back panels in a laser shop based here in Sibiu, RO and front panels in China. The enclosures and all semiconductors (except 2SC2879 transistors) are from EU & USA suppliers (TME, Farnell, Mouser etc.). We have learned and have to learn more on this great piece of equipment. Also, we are still getting along with the product, performance and its specs etc. The high power capability (RF in 2W+) has been tested with mcHF SDR QRP radio as PA driver and the low power capability (RF in 100mW) has been tested with Agilent 33120A signal generator. We did not test YET the freq. sense mode with FT-817 Trx as companion / PA driver, due to the lack of FT817 in our lab.












You can see our complete work on our facebook page https://www.facebook.com/rowaves and on Instagram https://www.instagram.com/rowaves_technologies/ (we pulblish there the latest updates on the products we work on) and of course, on our website, https://rowaves.com/

I hope i did not violate the rules of the forum, and if yes, my appologies i will change the post. Thanks a lot Matti & Juha for your continuous support you offered us during this period. If anyone has questions, do not hesitate to contact us at suppor@rowaves.com. I would be glad to answer your questions.
Thank you!
73's, Andrei @ roWaves

Hello Andrei,
I have a bitter experience with the use of the Chinese 2SC2879,HuaGao Semiconductor, (from the same manufacturer you are talking about), with which I bought my JUMA 100 (maybe the last issue). They lasted several months. JUMA 100D, I use as a driver of ACOM 1000, with no more than 55 -60 watts and exactly SWR. I had to buy from e-bay parts old TS-450 to get the transistors-2SC2879. Let the old people rest, these legendary transistors lived out their time.
If you want to use bipolar transistors, use those that are built into the TS-480 and ELECTRAFT K3 - 2SC2782 , if not, then RD-70, RD-100 is a good choice.
If you decide to stay on the Chinese 2SC2879, then God help you!
73 de Slav - LZ1ZJ