My understanding is that the auto tuner in the exciter should be OFF when
driving the Amp. The input impedance changes with drive, so I've been told.
Therefore, I allow the auto tuner to tune the antennas in bypass mode then ture
off the auto tuner when driving the Amp.I may be all wet, but it works for
me.Andy,,,W3LI
> Date: Wed, 17 Apr 2013 15:52:20 -0400
> From: jrichards@k8jhr.com
> To: tentec@contesting.com
> Subject: [TenTec] Tuning Amp on 17 meters
>
> Greetings TT Mavens.
>
> Background -
>
> I rarely work 17 meters SSB with my Omni VII. Today, I reworked my 10
> meter vertical ground plane antenna into a 17 meter ground plane which
> measures about 1.3:1 SWR at around 42-45 ohms both in the back yard and
> inside the shack using a RigExpert AA-230 analyzer.
>
> I also have a TenTec Centurion and a TenTec 238C and/or a Palstar
> AT-auto matchbox in line, which I alternate using at my whim on other
> antennas. I generally put them in bypass mode when working a resonant
> dipole or vertical.
>
> For 17 meters, I set the Centurion to the 15m Band, and set the LOAD and
> TUNE controls according to the chart in the user manual, and then fine
> tune for most power out with the TUNE knob.
>
> Sidebar: This seems to be a very forgiving amp...
> I can set the LOAD wide to either side of the
> recommended LOAD setting and it has no apparent
> effect, while the TUNE control is quite response
> and it is easy to tune to highest power out with
> very little movement. The Plate Meter almost
> never changes no matter what I do. I have never
> heard it arc or make any odd noises... he said
> knocking on wood...
>
> When I briefly transmit a CW tone barefoot on 17 m, the rig meter says
> it sees 1.2 SWR, but when I put the amp in line, and run exciter power
> (maybe only 2-30w) I get 2.1:1 SWR. I have not tried it on higher
> power. I am sorry I don't recall what it did into my dummy load, and I
> cannot test that again right now because a humongous thunder storm is
> rolling in off Lake Michigan and ...well... you understand my reticence
> to be operating while that is brewing in the neighborhood.
>
> The Inevitable Questions -
>
> * So... why does this happen?
> * Is this a normal occurrence?
> * Does this have anything to do with working 17m
> opposed to another band? The radio usually
> reports SWR close to the antenna's inherent
> measurements on the other main bands like 40m
> 20m, 15m, and 10m. I have not tested for this
> on 12m or 30m.)
> * Using the auto tuner does not change this dichotomy
> of SWR reports. I did not think it would, but
> I tried it anyway.
>
> So... any thoughts?
>
> ---------------------- K8JHR -------------------------
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