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Building and Operating a Transmitter from the Roaring 20s

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Radio was booming in the 1920s: transmitters had started using the pure tone of 'continuous wave' signals, replacing signals sent with sparks, and increasingly selective and sensitive receiver circuits offered greater range seemingly by the month. Amateurs, not yet able to tame their simple transmitters with crystal-controlled oscillators, constructed them on simple wooden boards with heavy wiring and large inductor coils in order to keep heating from causing their signals to drift. These homebrew transmitters were ongoing experiments in electronics and engineering. The position of a coil might increase output power but cause the signal to sound like a buzzsaw. If you could find a higher voltage power supply, that too would raise its power, but the increased currents in the rig would add more drift: if the other guy can't find your signal wandering up and down the band, what use is that extra 3 watts? The 1929 QSO Party Every year the Antique Wireless Association holds a tw...
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Trans-Canada Trail Bicycle Mobile POTA Activation

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A fine Thursday night, only somewhat spoiled by a record-breaking mosquito population, and another "park" activated by bicycle mobile QRP. The photo above shows what I'm using to carry the equipment: a seat-stem backpacking pack, with the fiberglass mast strapped to the top. I thought I'd solved the problem of it falling off when on the way in the dollar-store velcro elastic straps seemed to do the job, but more on that later. I'd wondered if this park, being perhaps the most activated in Canada (spanning the whole country) would prove less popular with hunters than the last two, neither of which have been activated more than 5 times. 33 QSOs over about an hour suggests that's not the case, though I was beginning to doubt the endeavour after the first 5 minutes of calling CQ with no takers. Eventually they streamed in, and Europeans, too, including a QSO with YU9CF in Serbia. I've long dreamt of a Balkans bike camping trip; a Balkans bike camping and POTA...
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La Coupe Dry Dock National Historic Site: Bicycle Mobile POTA Activation

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  The POTA hunters sure know how to make someone feel like an old pro very fast. This second activation had a lovely familiarity to it: the easy rolling gravel roads of the Tantramar Marsh, the assembly of the antenna and station, and the continual flow of QSOs on 20m CW. Here, though, the mosquitos were more ever-present despite the grass being cut for hay.  The Tintramarre Wildlife Site of two weeks ago is a product of 1970's conservation with friendly support from Ducks Unlimited. (It seems Hunters from south of the border are looking for what comes from the marsh, either on the airwaves or in the air!)  In contrast, the La Coupe Dry Dock site purports to be a 17th century set of dykes and control gates that furnished a place for boats to be stored in the winter and to be worked on in dry conditions. At least that was the view of Webster, who studied the site in 1933. Barka's survey published in 1970 is far less certain: he's pretty sure we can't know either when t...
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Bike Mobile POTA Activation VE-0100

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  Earlier this year, I discovered 5 POTA parks and one SOTA summit lie on the routes that I like to cycle in the Tantramar region between SE New Brunswick and Nova Scotia, Canada. So for the past few months, I've been building up a bike-mobile kit for QRP POTA work, especially on CW. And on Tuesday, it all came together with the activation of park VE-0100 the Tintamarre National Wildlife Area . While there are patches of this area only about 12km away from my home, I chose to go to the site of area's official sign, down an additional few km of dirt road. The whole route, including a stop for a beer with a friend back in my home town, is on the cycling social media site, Strava . My backpacking seat bag (pictured above) carried everything I needed, including a comfortable camp chair and my near-new IC-705, housed in a bode bottle bag whose front pouch holds both the radio's mic and an N6ARA  TinyPaddle .  The antenna is a simple 20m 1/4 wave vertical with counterpoise of t...
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Defining a 49:1 EFHW Transformer's Losses

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 End-fed halfwave antennas are so convenient, especially in rapidly deployed setups, and they're easy to build . But how much energy is lost in the 49:1 transformer that makes it possible? Because I operate mainly QRP, and I'm using a rather large core for 5w, I'm not concerned with losses that appear once the transformer's core reaches the Curie temperature. So I can use a nanoVNA, performing a S21 logmag trace on two cores back-to-back, to see how much power my transformer is eating up on the way to the antenna. I used the Fair-Rite 2643625002 core, inspired by excellent results MM0OPX reports in a generously shared spreadsheet of results. Could I get around 0.5 dB loss from 80m all the way to 10m if I used that core in 21:3 turns ratio?  My experience with more donut-shaped ones suggested that such broad-banded performance was a tough order: a 14:2 turns ratio works well on one end of the HF band; 21:3 works well on the other. In the end, Colin's accompanying vi...
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