[TenTec] Antenna is up, but the coupler doesn't like 160 meters

[Marsh Stewart]

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 at 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 at 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 at 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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