[ARC5] Unun measurements

[Geoff]

That resistor is likely only non inductive at audio frequencies as are most 
consumer grade components marked "Noninductive".


----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: "Jack Antonio" <scr287 at att.net>; <arc5 at mailman.qth.net>
Sent: Thursday, October 25, 2012 7:38 PM
Subject: Re: [ARC5] Unun measurements


> 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
>
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