Getting a simple 1 transistor CW transmitter to talk. Modification adds an LM386 audio amplifier as a modulator to transmit AM voice.
If you haven't done so please watch Part 1 first: https://www.youtube.com/watch?v=rVlBkbnxRMc
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https://www.youtube.com/watch?v=775eAs02wds
How a filter-type HF SSB transceiver works.
The PCM Hawk transceiver pictured here was built in the 1980s and has 10 fixed crystal-controlled channels between 2 and 8 MHz. I haven't measured the RF output power but my estimate is somewhere between 50 and 100 watts.
The intermediate frequency is 1.650 MHz. Crystals are be 1.65 MHz above the desired transmit and receive frequency. The SSB signal generated is lower sideband, but because it is subtracted it becomes upper sideband, which is the general standard.
Widely used in outback Australia (4 wheel drive, school of the air, flying doctor etc) these transceivers were simple, rugged and designed for use (and abuse) by non-radio people. Until satellite phones, radios like these were the only connection with the outside world.
Though most radio amateurs prefer frequency agile equipment so they can operate across the whole band, converting a set like this is still a great project. Luckily the set fitted has channels for 2, 4 and 6.9 MHz so very little work is needed for use on 1.8, 3.5 and 7 MHz.
The main problem is the upper sideband which is not generally used on these amateur bands - lower sideband is preferred. To fix this you can change the mixing scheme (so you add the 1.650 MHz IF so don't invert the sideband) but this requires some tuned circuit changes. Or you can leave the mixing as is and change the 1.650 MHz carrier crystal so it's below, not above the filter's passband. It requires a lot of effort to swing a 1.650 MHz crystal down to 1.647 MHz, but it can be done by (i) adding an extra crystal in parallel, (ii) adding a lot of series indductance and (iii) fiddling with capacitor value(s) in the oscillator.
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https://www.youtube.com/watch?v=9saTnTsAe4U
Portable operating from local pier. Mostly 40 metre SSB contacts. Two stations worked were using small antennas or were in apartments.
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https://www.youtube.com/watch?v=bN-9LVQTYWs
Testing a $2 charity shop solar helicopter. What do I end up doing with (or to) it?
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https://www.youtube.com/watch?v=cxFUVLhvnj8
Station IDs and short snatches from various AM broadcast stations heard from suburban Melbourne.
A loop antenna is used to provide some directivity and null out interference. This is connected to a car radio, which generally perform better than domestic receivers.
(warning - don't listen with tall outdoor antennas during storms; the one here was a small tabletop unit)
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https://www.youtube.com/watch?v=s-zQrYLr6Dk
In which I go to a local park and transmit as my first POTA activation.
Contents
0:00 Introduction to POTA
1:56 Selecting operating site
2:14 Setting up and antenna
3:36 On air and making contacts
7:12 Summary of contacts and packing up
8:16 Books
PS: If you liked this video please consider supporting Amateur Radio VK3YE by:
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https://www.youtube.com/watch?v=PqT2p4oE0nk
A demonstration of the improvement that a tuned loop can make for AM broadcast and 160 metre amateur reception.
The station on 558 kHz was 7BU, Burnie (Tasmania). The test was done during the day from an RF-noisy ground floor apartment in Melbourne.
This loop is nothing special and there are plenty of plans on the web. Or see the novel crystal set article here: http://home.alphalink.com.au/~parkerp
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https://www.youtube.com/watch?v=dZ4GBvTlNUY
Testing of a newly-built 160 metre AM transceiver at Chelsea on Port Phillip Bay near Melbourne.
The receiver featured in a previous video. The transmitter is similar to the one presented here: http://www.angelfire.com/de/RadioAnarchy/ It is crystal controlled on 1843 kHz. A centre-tapped 15 volt 1A power transformer is used for modulation.
Efficiency is quite high - total Tx power consumption is 1A for approx 7 watts out on peaks. The IRF510 final stage does however need to be presented with an acceptable antenna impedance otherwise distortion can appear on the output, as happened here (the switched inductor in series with the antenna has since been replaced).
The transmitter's circuit is described in 'Lo Key' September 2011 - published by the CW Operators QRP Club.
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https://www.youtube.com/watch?v=17IdJz1iGVQ
Portable QRP using the VK QRP Club's VK5WAT callsign from beaches around Melbourne, Australia. The activity also coincided with the G-QRP Club's Winter Sports, held between Boxing Day and New Years Day.
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https://www.youtube.com/watch?v=_eyLKZmd5tw