Bob and the group,
If Mike would extend his feed line to 241 feet (as you have been
saying), he would have an SWR at the end of the line of about 2.5-3.0. This
is a SWR that can be easily matched by the 238 or most any other tuner. His
loss will be about 22-25% due mainly to the high SWR on the long feed line.
Still 75% radiation isn't all that bad. I have had a lot worse.... ;-)
Jerry W5JH
"building something without experimenting is just solder practice"
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Bob McGraw
- K4TAX
Sent: Tuesday, October 15, 2013 5:58 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Antenna is up, but the coupler doesn't like 160 meters
Very good analysis.
73
Bob, K4TAX
----- Original Message -----
From: "Marsh Stewart" <marsh@ka5m.net>
To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Sent: Tuesday, October 15, 2013 9:33 AM
Subject: Re: [TenTec] Antenna is up, but the coupler doesn't like 160 meters
> Mike,
>
> Modeling your doublet with EZNEC+ ver 5.0.59 and making 3 assumptions:
> 1. The antenna is in a straight line
> 2. Each end slopes down from 50 ft to 10 ft above the ground
> 3. Freq 1.830 MHz
> EZNEC calculates the feedpoint impedance to be 15.44 +j44.89
>
> Using TLW with a load of 15.44 +j44.89 on the antenna end and 170 feet of
> 600-ohm open-wire ladder line, the impedance at the station end would be
> about 45.31 -j764.71 or about 766 ohms at -87 degrees.
>
> Your actual measured impedances will vary from the calculated values due
> to
> unknown variables such as nearby objects, house wiring, etc.
>
> With a 1:1 balun (common mode choke) a high-pass L "antenna tuner" would
> need about 32.75 uH of inductance and about 118.1 pF of capacitance. The
> voltage across the inductor would be 5703 volts, and the voltage across
> the
> capacitor would be 5716 volts.
>
> My Ten-Tec 238C "antenna tuner" has an 18uH inductor and the variable
> capacitor has a voltage rating of 3500 volts. It is advertised to match at
> least an SWR of 10:1 any phase angle. You are asking your "antenna tuner"
> to
> match about a 34:1 SWR at a phase angle of -87 degrees.
>
> Of course your antenna / transmission system CAN be matched to 50 ohms at
> 1.830 MHz, but a commercial "standard antenna tuner" might not do it.
>
> There are others with considerable technical knowledge and years of
> real-world experience that regularly read and respond to posts on this
> reflector. Perhaps they will offer more insight on this interesting
> real-world application.
>
> 73,
> Marsh, KA5M
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Mike
> Bryce
> Sent: Monday, October 14, 2013 5:57 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] Antenna is up, but the coupler doesn't like 160
> meters
>
> 131 on each side
>
> Mike Bryce, WB8VGE
>
>
>
> On Oct 14, 2013, at 6:54 PM, Marsh Stewart wrote:
>
>> Mike,
>>
>> About how long is each side of the doublet? (You may have already given
> this
>> info in a previous post but I do not have it.)
>>
>> Marsh, KA5M
>>
>> -----Original Message-----
>> From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Mike
> Bryce
>> Sent: Monday, October 14, 2013 4:53 PM
>> To: Discussion of Ten-Tec Equipment
>> Subject: Re: [TenTec] Antenna is up, but the coupler doesn't like 160
> meters
>>
>> Jim,
>>
>>
>> The antenna is a doublet up 50 feet inverted vee style.
>>
>> It is feed with about 170 ish feet of 600 ohm open line.
>>
>> None of the couplers can find a tuning solution
>>
>>
>> All other bands work fine
>>
>>
>> Sent from my iPad at Aultman hospital.
>>
>> Mike wb8vge
>>
>>> On Oct 14, 2013, at 11:09 AM, Jim GM <jim.gmforum@gmail.com> wrote:
>>>
>>> Hi Mike, WB8VGE
>>>
>>> Hope your surgery goes well for you.
>>>
>>> I have gone and still going thru issues with my inverted L on 160M like
>>>
>>> your having.
>>>
>>>
>>> How long is your antenna? Is it a dipole or Folded dipole? I did not
>>> see on your post the answers to these questions.
>>>
>>>
>>> How high do you have it?
>>>
>>>
>>> Your going to find or have found that the tuner you have and other
>>> tuners will not work on 160M. They just cannot handle a near 50 ohm
>>> match or less no matter what they claim. All they want is your money.
>>>
>>> So you need to add additional matching out side the shack with coils
>>> and homemade capacitors made from coax cable, thats if you have a
>>> limited junk box like I do.
>>>
>>> Any ways the external matching will aid your tuner in the shack to take
>>> care of the rest.
>>>
>>> It will take some time and it is not a quick fix.
>>>
>>>
>>> --
>>> Jim K9TF
>>> _______________________________________________
>>>
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