In fact it is driviing the load with 36 watts in your example.
When the wattmeter shows forward power of 100 watts and reflected power of
40 watts into a high swr, because the load is not 50 ohms, the wattmeter
readings are false. Traditional wattmeters are calibrated for 50 ohms. The
wattmeters really only measure voltage and assume the load is 50 ohms. The
100 watt reading in this case for forward power is not correct because the
load is not 50 ohms. But it happens to work out that the true power is the
forward power reading minus the reflected power reading. All the true power
is delivered to the load minus transmission line loss. Transmission line
loss goes up with SWR.
Carl Moreschi N4PY
121 Little Bell Dr
Hays, NC 28635
www.n4py.com
----- Original Message -----
From: "Rick - NJ0IP / DJ0IP" <Rick@DJ0IP.de>
To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Sent: Sunday, April 25, 2010 12:20 PM
Subject: Re: [TenTec] OMNI VII vs. K3 ? Opinions invited.,
> As always Sinisa, you are correct.
> Nice to hear from you again!
>
> The one place I have seen a difference is when trying to tune a linear.
> While varying the power on any Ten-Tec, and tuning the amp, it simply
> varies
> the output power of the amp.
> I've had JA makes that seemed to jump around, like they would suddenly
> reduce power.
> Then I wasn't sure if the input power had dropped or if it was the
> settings
> of the amp causing the change.
>
> In any case I preferred the way the Ten-Tec tuned.
>
> Now something to think about.
> If I run 100w on the Ten-Tec and 40 watts are reflected, then as you say,
> the amp or antenna receive 60w.
> If my non TT rig reduces the power to 60w, due to high SWR, it is putting
> out 60W but it is only driving the load with about 40w.
> Or is my thinking wrong?
>
> 73
> Rick
>
> -----Original Message-----
> From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
> On Behalf Of shristov
> Sent: Sunday, April 25, 2010 9:56 AM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] OMNI VII vs. K3 ? Opinions invited.,
>
>
> Rick - NJ0IP / DJ0IP <Rick@DJ0IP.de> wrote:
>
>> ... this full power into 3:1 SWR
>
>
> Hi Rick,
>
>
> "full power into 3:1 SWR" is just a myth.
> Did you ever read such a claim made by TenTec?
>
> There is nothing inside TenTec transceivers to make them to DELIVER full
> power into a mismatched load.
>
> TenTec transceiver do not DELIVER full power into a mismatched load.
> They just fail to reduce the drive with high SWR because they mis such a
> circuitry.
> Consequently, the FORWARD power stays the same, at 100 W.
>
> But we must remeber that:
>
> DELIVERED power = FORWARD power - REFLECTED power.
>
> Power meters inside Orion, Omni VII, and virtually all the other rigs
> display FORWARD, not DELIVERED power.
>
> With SWR = 3, we have:
> FORWARD power = 100 W
> REFLECTED power = 25 W
> DELIVERED power = 75 W
>
> Similarly, with SWR = 10, we would have:
> FORWARD power = 100 W
> REFLECTED power = 67 W
> DELIVERED power = 33 W
>
> The only thing that can make PA deliver full power into a mismatched load
> is, of couse, a tuner.
> TenTec transceivers are no exception.
>
>
> 73,
>
> Sinisa YT1NT, VE3EA
>
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
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