I constructed a K9AY initially using a Minicircuits device for the transformer.
I can state unequivocally that they are very delicate. My K9AY is 100 feet
away from a Butternut vertical. Tuning the AL-1500 up on 40m creates enough
induced power to reliably blow that transformer every time.
Al
AB2ZY
________________________________________
From: towertalk-bounces@contesting.com [towertalk-bounces@contesting.com] On
Behalf Of Gene Fuller [w2lu@rochester.rr.com]
Sent: Thursday, February 02, 2012 10:06 AM
To: Pete Smith N4ZR; towertalk@contesting.com
Subject: Re: [TowerTalk] Flag Antenna Transformer
Keep in mind that on 75/80 meters a pennant, flag, or ewe will only have a
"gain" of around -20dbi. so another db or two of loss due to miss match
will hardly be noticed and certainly isn't going to result in result in
damage due to heat or rf burns - or am I missing something ? However, if
you're running a "phased" pair with transformer "matching" you would want to
keep track of the phasing.
Gene / W2LU
----- Original Message -----
From: "Pete Smith N4ZR" <n4zr@contesting.com>
To: <towertalk@contesting.com>
Sent: Thursday, February 02, 2012 6:30 AM
Subject: Re: [TowerTalk] Flag Antenna Transformer
> Is this necessarily true? I have a couple of transformers built by
> ON4UN. They use separate windings and a binocular core, and behave
> exactly as expected.
>
> 73, Pete N4ZR
> The World Contest Station Database, updated daily at
> www.conteststations.com
> The Reverse Beacon Network at http://reversebeacon.net, blog at
> reversebeacon.blogspot.com,
> spots at telnet.reversebeacon.net, port 7000 and
> arcluster.reversebeacon.net, port 7000
>
>
> On 2/1/2012 4:58 PM, Doug Ronald wrote:
>> You are getting these results because you wound a conventional
>> transformer
>> where a Transmission Line Transformer (TLT) is required. The core is
>> fine,
>> but twist the primary with the secondary using 12 turns and 3 turns. Here
>> is
>> a reference to some theory on what you need:
>>
>> http://home.earthlink.net/~christrask/TraskTLTTutorial.pdf
>>
>> and the author (Chris Trask) has several other TLT articles on his web
>> site
>> including precise winding tips.
>>
>> Here is another helpful link to the way your finished transformer should
>> look:
>>
>> http://www.qsl.net/wa1ion/bev/bb_antenna_matching.pdf
>>
>> Hope that helps,
>>
>> -Doug, AE6SY
>>
>>
>>
>>> I have a flag antenna which has worked well for several years. I used a
>> Minicircuits T16-6 transformer to couple the ~800 ohm termination
>> resistance
>> of the antenna to 50 ohm line. Recently I decided to do some upgrades, so
>> I
>> followed the recommendations of many (here and elsewhere) and made a
>> matching transformer using an FT-140-43 core and 34:8 turns, secondary
>> and
>> primary on opposite sides of the core. I didn't have any #28 wire so I
>> used
>> #24. I tested this with a miniVNA, terminating the antenna side with an
>> 800
>> ohm noninductive resistor. The impedance does not look right at all;
>> there
>> is a lot of inductive reactance and the resistive part starts at 125 ohms
>> and climbs steeply from 1.7 MHz. No on-the-air results yet.
>>
>>
>>
>> I'm wondering if this is right or not - measurements indicate the DIY
>> transformer is much worse than the T16-6 in terms of presenting a good
>> match.
>>
>>
>>
>> This would not be the first case of theory saying it won't work but
>> practice
>> says it will - just looking for a reality check here. Seems to me like
>> the
>> core material is all wrong...
>>
>>
>>
>> -Tony, K1KP
>>
>>
>>
>> _______________________________________________
>>
>>
>>
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>>
>>
> _______________________________________________
>
>
>
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