Radio W4KAZ

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Notes On SSB RFI In Homebrew SO2R Box

Chasing down the RFI caused by inserting all of the home-brewed SO2R components into the station set up was a useful hands-on experiment. Annoying, but certainly educational. I verged on ordering the ARRL RFI tome, but now the thing is fixed, owning the reference seems less urgent. Might be worth reading though…..probably quicker than re-inventing each technique personally.

To start, the shack layout resulted in a few less than ideal situations. Both radios are side-by-side, separated by about 300mm. The computer that logs and controls both radios is on a rolling cart normally kept close to the station desk. The computer was also being introduced into the audio chain as the DVK, and I was also working towards routing the mic audio through the sound card full time. The cramped space on the desk is further reduced by the antenna switching controls and an antenna tuner. One set of bandpass filters is built into a relatively large computer case, and that occupies much of the top shelf.

No RF problems were noticed on CW, but on SSB the audio was terrible, and I got many reports to that effect. Apologies to those who were exposed to it.

The unshielded plastic enclosures used may have contributed to the problem, but so far most of the trouble has been corrected by applying the normal RFI kludge, clamp on ferrites. Shielded enclosures probably can’t make the problem any WORSE though.

The audio stream for the Yaesu FT-920 was relatively easy to clear up. […]

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The K9AY

A recent conversation with N1LN caused me to dig out the schematic for my slightly customized K9AY, built back in pre-blog 2006. In general it has been a great antenna, and it has earned its permanent place in the antenna farm.

In its current location, it is not as good as it was in its original ‘test of concept’ location. Practicality won out over performance. The antenna now occupies a space in the rear corner of the yard. That permanent location places it in close proximity to a chain link fence on two sides, and a storage shed is nestled into its NW quadrant. Significantly less than ideal location.

This location reduces the effectiveness of the F/B ratio, but the lower noise level makes the antenna a better choice for RX on both 160 and 80 in most cases. When conditions on 160 and 80 are QRN free, the transmit antennas are sometimes better on RX. Sometimes.

On the days where noise is an issue, the K9AY is almost always a better choice, especially if there is also QRM which can be nulled off the rear of the K9AY. I built the antenna as described by K9AY, with the additional mod to provide control voltages on a cable separate from the coax. I was also forced to use the SPDT relays I had on hand at the time of construction. The transformer used was constructed on an FT-125-K core, with 8 turns on the low [coax] side and 27 turns […]

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Home Brew SO2R Box

This home brew SO2R controller project follows the “old-n-busted” theory, and is based on the design by N6BV in the ARRL Handbook, as well as some input from K4QPL. In summary, it is built around the use of an LPT port for computer control of the CW, PTT, Radio A/B, and band data. As previously outlined, the LPT port is less expensive and easier to accommodate – even if obsolete. Hence “old-n-busted”. I expect to be able to bridge the gap to USB at some point by adding a K1EL WinKeyer, and the Piexx SO2Rxlat dongle.

The rig control is still accomplished via a serial port for each radio. The LPT parallel port is used for PTT, CW, transmit focus, and band data for one radio. The K2 band data is a separate option not installed in my K2[another void the Piexx SO2Rxlat dongle will solve].

As it stands now the only parts missing for a conversion to USB device control are the WinKeyer and SO2Rxlat devices. Everything else in the SO2R control chain is home brew.

There are several resources available that block diagram the components needed inside the shack for SO2R[e.g.,see DL1IAO, for the W5XD SO2r Box]. For ease of use and construction, the heart of the SO2R box breaks down into four logical units which were built into three separate boxes.

Band Decoder: One of the peripheral boxes will provide automated band switching driven by the logging program[or directly from a radio] by acting as the band […]

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