[ARC5] Unun measurements

[Geoff]

Baluns, etc can also be wound as a true transformer when isolation between a 
receiver and antenna is desired to reduce common mode coupling of the 
neighborhood digital and switching PS noises. Use earth grounds seperated by 
20-30' for the antenna side coax and the shack end.

Noise reduction is an art unto itself these days usually requiring a non 
trivial cash outlay for 31 Mix ferrites.

I'll go into details if there is interest.



----- Original Message ----- 
From: <brianclarke01 at optusnet.com.au>
To: <kgordon2006 at frontier.com>
Cc: "Jack Antonio" <scr287 at att.net>; <arc5 at mailman.qth.net>
Sent: Thursday, October 25, 2012 8:08 PM
Subject: Re: [ARC5] Unun measurements


> Hello Ken,
>
> I had the same discussion with Dennis (signing mac) a few posts back.
>
> Many people on this list don't seem to realise that Baluns, Ununs and 
> Unbals are all specified by their turns ratios. The only exception is when 
> a specific frequency is involved, and then you might say 'a Channel 5 TV 
> balun for 75 : 300 Ohm'. Jerry Sevick wrote the definitive tome in this 
> area, after Guanella.
>
> 73 de Brian, VK2GCE.
>
>
>
>> Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:
>>
>> 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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