![]() OE1CGS found these values for the missing R6 over the input transformer for a low input swr. at 5 Wattt input (-: The output has dropped to 50 Watts, more than enough on a good antenna. This is more than enough for fieldwork.īetter input swr update by OE1CGS : Link I had a 18 Ohm 3 Watt resistor in stock, the swr is near perfect on 20m. swr at 2.5 Watt input 1:1.8 with more than 50 Watt output. For best results reduce the drive power to 2.5 Watt. Visit the blog of John DK9JC for a nice test : LinkĬonclusion : This is a nice kit with acceptable results for a low price. Unfortionally the seller often forgets to add the documentation, the picture shows a copy of the original pdf file.Ī You Tube impression by KC2IRV : Overall impression of the amplifier Better use a power attenuator : Power att. Don't reduce the drive by reducing the Bias voltage for this results in a distorted modulation in SSB mode. It's better to reduce the drive power to 2 Watt when working 12V FM/AM. The 150 Ohm resistors over the FETs heat up strongly at full power FM. Click the pictures below to see details and specifications for all amps from our current production to our earliest offering. Our tradition of using the best components, providing superior headroom, power, clarity, and durability continues today. but the modulation was as expected distorded in ssb mode at the recommended 2.7V bias voltage.Īt 3.7V ( gate ) bias the modulation is acceptable but far from perfect. Linear Power has been proudly producing some of the finest car audio amplifiers on the market since 1975. At 3 Watt input the output was about 50 Watt at 20m. The test was in the original configuration at 13.8V and 5Watt FM input from my FT-817. Best results with this PA are obtained on CW and FM. I replaced the FETs by a pair of IOR IRF530N resulting in more stabillety en less input SWR however the input swr is highly effected by the drive power. Turn the potentiometer anti clockwise and slowly adjust the bias to aprox. Start soldering the small parts and end with the transformers. It's better to replace it to avoid shortcuts. The provided wire for the power chocke ( 2 turns ) has a weak coating. I used the low pass data from W3NQN for a 7 element Chebyshev with standard value silver mica capacitors and T68-6 toroids. Construction is easy but a lowpass filter for each band is mandatory. While linear power supplies may not be as efficient as switch mode power supplies, they offer the best performance and are therefore used in many applications where noise is of great importance. Supports for the transformers need to be cut out of the pcb. The 0.5 turns windings are on the PCB by means of the tubes inside the toroids. ![]() Capacitors are 10nF instead of 100nF as shown in the schematic but that's not a problem. My first impression : High quality PCB ( 100 x 50mm ), all parts in the kit including 2 power FETs type IRF530N. As recommended by John, PD7MAA a drive of 2,5W seems to be ideal for me too.It's time for a new project. I will now mount a bigger heatsink, 2 fans and a case and then I will do some more measurements. While in the QSO I pushed 5W from the 817 into the amp and with 3 SWR-bars on the dispay and 74W output I killed another pair of IRF530N mosfets. Numbers indicates the output and the numbers in brackets are "SWR-bars" on the FT-817 display: InputĪfter the "measurements" I was able to work S57DX on 20m with 60W output (2,5W drive from the FT-817) and I also worked my friend Peter, DC2ZO. I did some power output and SWR measurements then. ![]() After the QRL I soldered them in, and I drilled the holes into two pieces of an old heatsink harvested from an old PC power supply. I ordered a pack of five new IOR IRF530N mosfets on Ebay which arrived today. ![]() It took not more than five seconds to kill both FETs while sending an AM carrier (1,5W drive). When I had everything assembled I tested it without a heatsink on the two IRF530N mosfets from IOR. Building the kit was not too hard, but the surface-mount (SMD) parts are very tiny and you need a calm hand and good eyes. He does not only have the schematic available, he also shows how nice such DIY-projects can look like.Įspecially the filter is worth a look. While waiting for the kit I found an interesing article from John, PD7MAA on his website. But even if it does not work, the parts alone are worth the money. The kit took only 2,5 weeks to arrive and came in a simple plastic bag without any protection and it also came without a manual or instructions. Some weeks ago I bought a chinese amplifier kit on Ebay which came for 16 Euro / Dollar shipped. ![]()
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