[TenTec] Tuner

[Steve Hunt]

The problem is most acute when the length of the coax transforms the 
off-resonance feedpoint impedance to a low resistive value - for example 
around 6 Ohms for 45ft of Rg-8X; the tuner then doesn't have enough 
shunt capacitance to provide a match - about 2500pF would be needed. In 
those situations - as Rick says - extra external capacitance would help.

Steve G3TXQ




On 08/07/2013 23:14, Rick - DJ0IP / NJ0IP wrote:
> You should be able to match it by adding additional capacitance to the rear
> of the 238.
> Like Jim, I always cut mine to about 3600 and have no trouble matching it
> across the upper portion of the band with the 238B.
> I've never tried to cut it high and match it lower.
>
> If it doesn't match, add about 17 to 20 ft. of coax and then it most likely
> will.
>
> 73
> Rick, DJ0IP
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Steve Hunt
> Sent: Monday, July 08, 2013 11:56 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] Tuner
>
> At 3.5MHz, the SWR(50) of an 80m dipole cut for resonance at 3.8MHz could
> easily be 12:1 or higher. Depending on the length of the coax, that can
> present impedances at the tuner that will be well outside the matching range
> of a 238.
>
> Steve G3TXQ
>
>
>
>