[TenTec] Tuning Amp on 17 meters

[Lee WA3FIY]

Ooooops.....   I missed the point that you are not using the tuner with this antenn because the 
match is so good.   I think that is the case.  The balance of what I said still applies though.  
With the amp in line you are seeing it's input Z, not the antenna.

-Lee-




On 17 Apr 2013 at 15:52, Richards wrote:

> 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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