I said traditional wattmeter. I am referring to inexpensive wattmeters that
only measure voltage.
Carl Moreschi N4PY
121 Little Bell Dr
Hays, NC 28635
www.n4py.com
----- Original Message -----
From: "Dr. Gerald N. Johnson" <geraldj@weather.net>
To: <tentec@contesting.com>
Sent: Sunday, April 25, 2010 12:35 PM
Subject: Re: [TenTec] OMNI VII vs. K3 ? Opinions invited.,
> No, a true wattmeter (Bruene design) takes the vector product of voltage
> AND current to produce DC proportional to power.
>
> 73, Jerry, K0CQ
>
> On 4/25/2010 11:32 AM, N4PY2 wrote:
>> 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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