Month: January 2015

About the Elecraft K3 vs Kenwood TS-590 debate

I was just reading earlier Simone IW5EDI’s article about a short overview on the K3 and the TS-590. This is an interesting debate as they are some of the popular high-performance transceivers on the market today, and I would like to share my views. Simone’s article is indeed an interesting read, comparing some of the points that make or break a transceiver. I think the fame of superior IMD characteristics for the H-mode mixer itself is owed to the bus switches, wich generally have much sharper turn-on/turn-off characteristics than simple FET transistors. It is proven by multiple reasearches (PA3AKE, RZ4HK, I7SWX etc) that designs (be it H-mode, ring, etc) wich incorporate bus switches are superior to diode/FET based ones, constantly reaching IIP3 in excess of 40dBm; also, N7ZWY’s article about the KISS mixer shows identical performance between diode-based ring and H-mode mixers. So I would say that K3’s mixer is actually superior to the one used in TS-590, thanks to the bus switches. The use of SA612 as the second mixer in the K3 is indeed kind of weird, but remember that if you keep the input level below a certain point it makes for a pretty good mixer. I am guessing the AGC is supposed to keep the SA612 from overloading. In turn, SA612 has the advantage (unlike passive mixers) of not requiring very good impedance matching. About...

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HF-P1 portable antenna review

The HF-P1 is a lightweight antenna with HF to UHF coverage, designed for portable operations where size and weight are important. Thoughtful design and the use of quality materials make it look like a reliable choice for outdoors aficionados, but is it so ? Read further to find out. Looking for the HF-P1 name, not many results popped up – it’s not a very widespread brand name. The HF-P1 is sourced in Germany and you can find it in amateur radio shops there, plus probably a few other countries in the EU. It’s not clear who is the manufacturer as the german websites don’t list one and the product comes in a whitebox, but it seems identical to the Superantennas MP1B (US made). The small leaflet inside just says “HF-P1 portable HF antenna”, so that doesnt help much. The leaflet also claims that this antenna can cover 3.5MHz to 440MHz, a bold claim that got easier to understand once I saw what it’s all about. The design is optimised for small size, reduced weight and versatility, being able to form a resonant antenna system on almost any frequency between 3.5 and 440MHz by the use of various fixed or adjustable elements and coils. HF-P1’s leaflet contains the minimal information needed to get you going The package is comprised out of a small black handbag, a whitebox that contains all...

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Testing the Ultimate 3 WSPR beacon

Some time ago Aurel YO3IBZ borrowed me his Ultimate3 to try and replace the AD9850 DDS with AD9851 so we could make it into a useful 6m WSPR beacon. Unfortunately I only managed to make it work at low frequencies (below 10Mhz or so), and even though Hans (who created the Ultimate3) was very supportive with firmware and such, I came to the conclusion the easiest way was to just force the AD9850 to work at 50Mhz. This is not really an issue, it’s just that above ~25MHz the AD9850 output level starts decreasing and spurs start to appear. Output level is not really an issue because there is some amplification after the DDS, and the spurs above 50MHz should be largely stopped by the DDS onboard low-pass elliptic filter (cutoff around 72MHz) plus the other low-pass filter I’ve attached to the output (cutoff around 55MHz). So I just strapped the new filters I made (not only for 6m, but also for 10m and 15m) into the sockets of the Ultimate3 and found a nice metal casing for it: It needed some adjusting in order to make the internal clock and frequency generation spot-on: the 20MHz AVR clock is actually 19.997.285 and the AD9850 125MHz reference is 125.000.350. It might not seem like much but WSPR relies on perfect timing and frequency accuracy, and the 350 Hz error on...

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