CAKE Cookery Lessons, Feb.25, 2017
The a highly energized group meeting today were Richard W1WUH, John N6QX, Peter K6UNO
John N5HPB, Tom KW6S, Warren NR0V and Ron W6WO We learned the very good news that our dear friend Frank K6BDK is now living at a 3rd floor level and the property manager has provided a 130 ft antenna. Hey Frank a few more of us are likely to be joining you HI HI
At a previous meeting Ron had expressed doubts about the Buckmaster “magic” Multi band Off Center Fed antenna. The OCF concept was originated by Lauren Windom ( he described it as an “Etherial Adornment” before coax became popular. It benefits from the harmonic relationship of our HF bands and in Ron’s mind would not work well on 12 or 17m.. However Don K6GHA has just erected one and provided graphs of the SWR for all the bands from 160 to 10m, including 17 and 12 . “Well shiver me timbers” both these bands looked well matched. Anyone care to comment please do.
Tom showed some Kits and Parts items he has been working wih, one project being a transformer with 3 ports, call them 1,2 3) . It is designed to have a low attenuation between 1-2 and 1-3 and high attenuation between 2.3) They couple a 2-wire circuit to a 4-wire circuit and were invariably found in landline telephones to connect the mic and earpiece on on side to the line the other They have many similar applications and may be called Splitters or Hybrid Transformers.Tom’s RF version had the normal 6dB through loss and excellent 40 dB isolation between ports 2 and 3 .
There was an interesting discussion on signal generators that span many decades. It began with Ron describing the tiny synthesizer kit used in the QRP Labs U3S digital mode transmitter. This can be configured as an accurate VFO. The cost of this tiny board and all components was $12 shipped from China. In contrastTom mentioned WWII military URM25 and the venerable HP 8640 also goes back several decades. Richard showed a brochure describing a Chinese VHF/UHF hand held radio being advertised for $10 sounds incredible (and rather troubling ?) but let’s wait and see.
We discussed attenuators and Warren mentioned an IC component used in Anan radios -software controlled attenuation of course. Warren went on to describe the Anan 8000 under developed by Apache Labs. Their hardware and software is quite exceptional so this is something to look for. One feature of the Anan 100 and 200 D radios is their clever use of the enclosure as the heat sink.
Warren was asked what he thought of the Icom 8300, he responded by saying that unlike the Anan HPSDR radios it uses an analog stage for direct conversion which, in effect, makes it a hybrid analog/software defined radio. A great radio for the price, however some might describe it as a toy !
John (HPB) mentioned his interest in a XTAL CW filter for his FT 857. This type of filter are becoming scarce because DSP filters have taken over the market for them. We briefly discussed the changes taking place in high power linear amplifiers. The availability and price for MOS components is within our pockets and these can be driven with only a few Watts. (now if only they were as robust as our traditional tubes. In the digital domain it is now possible to drive legal limit amplifiers with just a few milliwatts. Tom reminded us of W6TQL’s web site for more on the subject.
Tom disagreed with a prior comment by Ron that scramble-wound coils are as satisfactory as those with neat windings. Ron agrees that there are pros and cons but neatness can limit the number of turns in which case untidy multiple layers provide the answer. John HPB is our authority on 3D printing so we expect to be learning a lot from him.
Ron mentioned his use of the free analog circuit simulation program 5SPICE which is easy to use, quite powerful but lacks the sophistication and challenge of LTSPICE. Why use a breadboard with plug-in components to build and test circuits ?
During CAKE sessions half- baked ideas are always welcome. Ron asked if it might be possible to combine the functions of low pass filters and antenna tuners as these typically act in tandem.
John QX politely reminded us to pay dues / join the SCCARC which can be done via the Club site.Mia Culpa.
73 Ron W6WO
BCNU March 11