[ARC5] TCS 50-Ohm Matching Configurations.

[Bob kb8tq]

Hi

Like most tube radios, the TCS matches the output tube to an antenna load. It only has
an “output impedance” in a vague sort of way. You don’t want to “match” the load and 
burn up half the power in the transmitter’s 50 ohm source. You want to deliver as much
power to the load ( and burn up as little in the transmitter) as possible. 

The only real way to work out what the matching circuit will do is to take a look at what
it was designed for. They ran them into electrically short wire antennas. Whatever a short
wire (whip or horizontal) presents as a load, that was the target. You can match them with
a capacitor because that is what the “intended” load looked like ….

Bob

> On May 11, 2018, at 9:08 AM, Brian Clarke <brianclarke01 at optusnet.com.au> wrote:
> 
> Hello Dave,
> 
> If the output impedance of the TCS is non-reactive and less than 50 Ohm,
> there is just no way to match to a 50 Ohm load using capacitors. I used to
> teach this stuff. Presently, I'm preparing a presentation on the design of
> antenna coupling units for my local amateur radio club.
> If you tell me, even  approximately, the output impedance of the TCS, or the
> ARC-2, I can produce for you designs that will work properly. If you want to
> use the TCS over several frequencies, tell me those, too.
> 
> 73 de Brian, VK2GCE
> 
> Brian Clarke
> BE, MBA, PhD,BOCP, CPEng, Fellow Eng Aust
> 
> On Friday, 11 May 2018 9:51 PM, Dave said:
> 
> Yesterday, I took a few minutes to test three of 
> the suggested capacitive matching methods which 
> adapt a 50-Ohm non-reactive load to the output 
> of TCS and similar transmitters.  The ARC-2 is 
> on the bench and it has an output circuit similar
> to the TCS, so used that for the test.  
> Can get some time to do this on the TCS 
> if anyone is interested.  This wattmeter has not
> been calibrated in some time, so take these 
> Power readings as relative.
> 
> <snip>
> 
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