I am going to have to say something here.
If there is a need to match two different impedances the
network is no longer simply a low pass or high pass filter but
becomes resonant with some Q which introduces a peak at the
resonant frequency.
If the impedances are simply resistive this is still true but the
Q of the L network is lower than that of the T or PI since it the
square root of the ratio of the resistances to be matched. This is
great when having to match very high resistance ratios.
Also, with the L network having a lower Q the currents in the inductor
and voltages across the capacitor are lower as well.
Now, saying that, I assume your amplifier or transmitter has low
harmonic output in the first place. So, why worry so much about
the "HI Pass" or "Low Pass" characteristics in the first place.
73
bill wa4lav
At 10:43 PM 5/4/2012 -0400, you wrote:
>I guess you are only familiar with leading Ts and not lagging networks.
>
>On 5/4/12 9:52 PM, Carl wrote:
> > True. they can be no pass and the coil becomes the dummy load. Very easy to
> > do if not familiar with a T tuner.
> >
> >
> > ----- Original Message -----
> > From: "W2XJ"<w2xj@nyc.rr.com>
> > To:<amps@contesting.com>
> > Sent: Friday, May 04, 2012 5:22 PM
> > Subject: Re: [Amps] Antenna tuner loss
> >
> >
> > Ts are not necessarily High pass nor are Ls for that matter.
> >
> > On 5/4/12 4:59 PM, Rob Atkinson wrote:
> >> I wouldn't touch a T network. High pass = no pass here
> >>
> >> 73
> >>
> >> Rob
> >> K5UJ
> >>
> >> On Fri, May 4, 2012 at 8:37 AM, Tom
> Thompson<tlthompson@qwest.net> wrote:
> >>> Kevin Schmidt, W9CF, has a nice Java app where you can study the losses
> >>> in a T-network tuner at http://fermi.la.asu.edu/w9cf/tuner/tuner.html
> >>>
> >>> Tom W0VJ
> >>>
> >>> On 5/4/2012 7:22 AM, Carl wrote:
> >>>> The first series of tests even had the MFJ coils catching on fire in the
> >>>> ARRL lab at well under power ratings on 160.
> >>>>
> >>>> Tuners with 250pf max on 160 will always be inefficient, a High C tuner
> >>>> with
> >>>> 500pf will be very efficient and require proportionally less L. The
> >>>> higher Q
> >>>> results in less bandwidth so there is no free lunch.
> >>>>
> >>>> Its so much easier to modify an amp to be able to do the matching and
> >>>> toss
> >>>> the tuner in the dumpster.
> >>>>
> >>>> Those with autotune amps are left swinging in the wind and need autotune
> >>>> tuners (-;
> >>>>
> >>>> Carl
> >>>> KM1H
> >>>>
> >>>>
> >>>>
> >>>> Carl
> >>>> KM1H
> >>>> ----- Original Message -----
> >>>> From: "Roger (K8RI)"<k8ri@rogerhalstead.com>
> >>>> To:<amps@contesting.com>
> >>>> Sent: Friday, May 04, 2012 3:32 AM
> >>>> Subject: Re: [Amps] Antenna tuner loss
> >>>>
> >>>>
> >>>> On 5/3/2012 12:32 PM, Dan Hearn wrote:
> >>>>> ARRL tested some popular commercial antenna tuners and reported the
> >>>>> results in QST as follows. They covered 160-10 and various loads. All
> >>>>> were
> >>>>> quite lossy on the low bands with low Z loads.
> >>>> And there are people out there that didn't expect this? They are
> >>>> running into low impedance loads which means high currents and high
> >>>> losses. I believe the Palstar manual even mentions this. Also the
> >>>> power handling capability drops off substantially with low Z loads
> >>>>
> >>>> 73
> >>>>
> >>>> Roger (K8RI)
> >>>>> February, 2003
> >>>>> Product Reviews
> >>>>> High Power Antenna Tuners:
> >>>>> ? AMERITRON ATR-30
> >>>>> ? MFJ-986
> >>>>> ? PALSTAR AT1500CV
> >>>>> ? TEN-TEC 238A
> >>>>> ? VECTRONICS HFT-1500
> >>>>>
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