[ARC5] Unun measurements

[Kenneth G. Gordon]

Jack:

Thank you VERY much for this information. I think it is very valuable.

One thing I might mention is that the UNun should be a 2:1, not a 4:1, if you 
are quoting the turns-ratio, and calculating from 12 ohms. 

The impedance-ratio is the SQUARE of the turns-ratio.

If you are using a 4:1 turns-ratio, you are attempting to match 16 X 12 ohms, 
or something like 192 ohms (if I am thinking correctly) and not 50 ohms.

Anyone who cares to do so may correct me if you wish. :-)

Ken W7EKB

On 25 Oct 2012 at 17:33, Jack Antonio wrote:

> I apologize if this is a resend, it appears it didn't go
> through the first time.
> 
> Ok, so I did some measurements. Not really trying
> to prove or disprove any particular point of view,
> but just thought I'd document what I see with
> my particular test bench.
> 
> Using a BC-696, with a BC-456/DM-33 as a power supply.
> 
> Frequency 3885 kc, all CW mode. In all cases, antenna
> loading coil tuned for maximum power out.
> 
> First: An 8 ohm non-inductive resistor in series with 90
> pf transmitting mica. (Assuming the radio shack resistor
> really is non-inductive like it says).
> 
> 46V P-P across the resistor which works out to 33 Watts
> BC-442 meter says 1.0, antenna coupling control at 4.
> With a small sampling loop placed around the antenna
> lead, second harmonic measured -50db.
> 
> Next: 100 pf cap in series with 50 ohm load. Measuring
> with Bird 43.
> Power out is 43 watts, antenna coupling
> control at 10. BC-442 says .25.  Second harmonic -42db.
> 
> Next:  4:1 unun to 50 ohm load, no series capacitor.
> 15 Watts out, antenna coupling at 10. Loading coil at 0.
> BC-442 meter wiggles a little.  Second harmonic only -28db.
> I would have thought the antenna coupling control would have
> been around 4 or 5, but this didn't happen.
> 
> Last:  4:1 unun, with 100 pf capacitor in series to 50 ohm load.
> 38 Watts out, antenna coupling at 5. BC-442 says 1.25. Second
> harmonic -52 db.
> 
> Sure like the way the dynamotor lugs down as the transmitter
> is brought into tune.
> 
> Jack Antonio WA7DIA/4