[ARC5] TCS 50-Ohm Matching Configurations.

[Dennis Monticelli]

The unun transformer is a fine solution.  It can be built broadband style
with integer ratios as suggested or inasmuch as our sets are single band,
just via the old-fashioned auto-transformer technique.  A torroid insures
good coupling in both casees.

Dennis AE6C



On Fri, May 11, 2018 at 8:43 AM, J Mcvey via ARC5 <arc5 at mailman.qth.net>
wrote:

> Why is everyone loathe to use a 4:1 or 9:1 unun autotransformer to match
> these radios?
> If your antenna is in the 30 to 90 ohm area, it's a home run every time.
> These radios were desined for very short antennas and have resistance
> range of 5 to 12 ohms and can tune against a reactance  of zero up to 800
> ohms or so.
>
> The series cap method depends a lot  on the cable length and what
> impedance is being presented due to that length.
> The shunt  variable cap on the output will ( hopefully) produce an L
> section with the internal inductor that will tune the appropriate range.
> Of coarse, the other variable with any of this stuff is characteristics of
> your local antenna...
>
> On Friday, May 11, 2018, 10:59:19 AM EDT, DSP3 <jeepp at comcast.net> wrote:
>
>
> Dave,
>
> Very good info.  I tried them out bhut the one that falls into place for
> me is using Tap 5.  I can't get power out using Tap 4 or 6?  The R-24 Q-5er
> crapped out yesterday but found a bad cap buried in the rear area, the
> audio primary bypass was bad.  That's a new one?  Back on the air.  I run
> about 600v and tuned indicating 165ma for 38 watts output.  Scope looks
> quite good.  I will archive your data in my ARC-2 manual.  Who knows who
> will need it in 30 years????
>
> Jeep - K3HVG
>
> On 5/11/2018 7:50 AM, David Stinson wrote:
>
> 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.
>
> ARC-2 Primary 27V. Dynamotor B+
> All tests at 3890 KC, tuned for max out.
>
> 100 pFd capacitor in series to load.
> 40 W out.
> 130 mA PA current.
> ARC-2 Ant Tuning 472
>
> 1000 pFd ANT to ground.
> 40 W out.
> 145 mA PA current.
> ARC-2 Ant Tuning 652
>
> Capacitive Divider (TCS tuning box)
> 270 pFd ANT to Load,
> 1370 pFd, Load to Ground.
> 44 W out.
> 190 mA PA Current.
> ARC-2 Ant Tuning 576
>
> "Each to their own," of course.
> My preference is to trade 10% of power out
> for a 30% reduction in PA current, which is
> not only easier on the PA, but makes fully
> modulating the rig that much easier as well.
>
> GL OM ES 73 DE Dave AB5S
>
>
>
>
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