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Date: Sun, 29 Sep 2013 20:26:51 +0200
From: =?ISO-8859-15?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: Re: HF SWR meters on MF?
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Status: O

Does it not?
I suggest to do a test:   Use a MF antenna (on 160m, for this test),=20
resonate it to the TX frequency by using a variometer. Then use a=20
ferrite transformer to match the impedance to 50 Ohm.

Insert the SWR meter (i'm using this one for HF:=20
http://www.astrosurf.com/luxorion/Radio/swr-meter.jpg   (you can find=20
the words "SWR" and "meter" on the instrument) into the signal path.

I bet it will show something close to 1:1. The detune the variometer=20
(i.e. add a significant reactive component to the feed point impedance)=20
so that the resonance is lost. I bet that the reflected power will rise=20
dramatically. Then i interprete that the SWR meter tells me that i have=20
lost the resonance, since the ratio of the transformer didn't change.=20
Sure, there could be a change of the earth losses which cause a change=20
of the resistive component of the impedance. This will result in a=20
change of the SWR as well. But these changes are small compared to the=20
possible change of the reactive part, especially on MF and LF...

73, Stefan


Am 29.09.2013 20:02, schrieb Alan Melia:
> er ......an SWR "meter" will tell you nothing about resonance :-))
> Alan
> G3NYK
>
> ----- Original Message ----- From: "Stefan Sch=E4fer"=20
> <Stefan.Schaefer@iup.uni-heidelberg.de>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: Sunday, September 29, 2013 6:34 PM
> Subject: LF: HF SWR meters on MF?
>
>
>> Hi MF,
>>
>> Did someone try to use a normal HF SWR meter on 630m? They are=20
>> specificated down to 1800 kHz of course but what about 472 kHz?
>>
>> At least it would be good to get some indication that:
>>
>> -There is some output power (e.g. when using an IC706)
>> -One is coming closer to resonance
>> -Impedance is/comes close to 50 Ohm
>>
>> I'm supporting a new potential MF RX station with limited equipment=20
>> (no oscilloscope...)...
>>
>>
>> 73, Stefan/DK7FC
>>
>
>