HFU HF Underground
Technical Topics => The RF Workbench => Topic started by: JimIO on December 02, 2018, 0434 UTC
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What if you took the classic diode ring modulator
https://en.wikipedia.org/wiki/Ring_modulation
and replaced the center taped audio transformer with
https://en.wikipedia.org/wiki/Bridged_and_paralleled_amplifiers#Bridged_amplifier
The BTL amp could be a China TF card MP3 unit and the diodes 1n5817 or simalar.
If it would work you can't get more simple.
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It might work at a few hundred kilohertz, but not much more. The larger the diodes get, so do their stray capacitances, which limit the switching speed. I have done the same thing in the past with low level mixers, then amplify it up to 100W pep. During the peak of the solar cycle, it did quite well.
+-RH
p.s. All mixers exhibit something called conversion loss. In low level mixers its usually about 7dB...so for 100W pep, you would have to drive the carrier port with about 500 watts....kinda lossy.
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http://www.flashwebhost.com/circuit/dsb_transmitter_for_hams.php
Is about as simple as it gets.
Str.
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for 100W pep, you would have to drive the carrier port with about 500 watts....kinda lossy.
old microwave transmitters often had a 20 or 50 watt VHF transmitter going to a passive diode multiplier and filter for a watt or 2 of rf output. not efficient, but at a time when microwave devices were not very good, more reliable.
I think this might be a really good technique for a very low power high reliability transmitter, like a QRSS beacon. but that negates the need for dsb modulation.
I bet the DSB modulation could be REALLY linear though, with careful design
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Older US build varactor multiplied STL transmitters usually had a 470 MHz PA driving the multiplier with 15 watts to get 10 out at 950 MHz.
+-RH