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

[Bob McGraw - K4TAX]

The extra / external cap is used across the capacitor bank, starting at 
position #4 and #5.  Both on the Low and High Z sides.  I find the text is 
incorrect, the schematic is correct.  Yes a .01 is way too much C by a 
factor of 10x.

If you have a means to do so, what is the natural resonant frequency of the 
antenna?  I use my MFJ-259 as a grid dip meter effect to find the resonant 
frequency.  I'm not speaking of some frequency where the SWR is 1:1 or such.

I take a different approach to antennas.  I first start with a resonant 
antenna at the desired frequency, then adjust the height of the antenna to 
attain the desired feed point impedance.  I saw Jim Brown, K9YC mentioned 
this in his earlier post as he used different coax impedance lines dependant 
on the height of the antenna.  I am not one to "prune" the length of the 
antenna for some SWR value.  Now in cases I know we can't get the antenna at 
different heights specially as we get to 160M and to some extent 80M.  In 
these cases, the typical height above ground does bring the center Z to 20 
to 30 ohms.  Nothing wrong with this.  With low loss coax or a balanced 
feed, just let the tuner deal with it.  That's what it is supposed to do.  I 
find having a resonant wire is more effective and easier to effect a good 
match.

73
Bob, K4TAX





----- Original Message ----- 
From: "Mike Bryce" <prosolar at sssnet.com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Saturday, October 12, 2013 9:17 AM
Subject: Re: [TenTec] Antenna is up, but the coupler doesn't like 160 meters


> bob and the group
>
>
> I didn't have the .001 in a voltage rating that would live so I used a 
> .01, and yeah, I know that's way too much C
>
> for the instructions, it looks like the extra c is only used in position 5 
> on the low z side of the switch.
>
> Now, all that being said, NONE of the antenna couplers will find a 
> solution to the tuning of the band
>
> the best I can get is around 1.995 and it's high there about 2:1 or so
>
> of course everything is grounded.
>
> I'm going to drop the wire down and measure it from the center to the ends 
> and see what I have.
>
> I did some looking around the 'net last night and read that adding a 1/8 
> wavelength should correct the problem, however, that's 33' of open wire 
> and simply not doable. What in the world do you do with it?
>
> Mike, WB8VGE
> SunLight Energy Systems
> The Heathkit Shop
> http://www.theheathkitshop.com/
> J e e p
> o|||||||o
>
> A man with one clock knows what time it is. A man with two clocks is never 
> sure.
>
>
>
> On Oct 12, 2013, at 8:47 AM, Bob McGraw - K4TAX wrote:
>
>> Are you using any extra C connected to the rear terminals of the tuner? 
>> Likely needed if the high Z switch is in  #5 position.  The extra C is 
>> 1000 pf @ 500 V as provided by Tentec.
>>
>> I use 256 ft of wire {natural resonance measured to be 1.85 MHz}, center 
>> fed with 450 ohm window line, about 65 ft, connected direct to the center 
>> feed point of the antenna  and direct to the 1:1 W2FMY current balun at 
>> the operating position.  The balun is connected to the Tentec 238 tuner 
>> via about 1 ft of RG-213.  To get to the low end of 160M I do have to 
>> connect the extra C to the rear terminal of the tuner.
>>
>> This arrangement will work all bands, all frequencies 160M - 10M, 
>> attaining a 1.5:1 match or better.  Center of the antenna is at 50 ft 
>> configured as an inverted V with the ends about 25 ft above the ground.
>>
>>
>> 73
>> Bob, K4TAX
>>
>>
>>
>
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