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From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
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Date: Mon, 30 Sep 2013 00:06:59 +0100
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Subject: Re: LF: Re: HF SWR meters on MF?
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Status: O

"SWAR GREASE"  echoshield    use that  on radars  and  its  sodding 
expensive  !

--------------------------------------------------
From: "pat" <g4gvw@aol.com>
Sent: Sunday, September 29, 2013 11:29 PM
To: <rsgb_lf_group@blacksheep.org>
Subject: Re: LF: Re: HF SWR meters on MF?

> And some of the demos when done at CB clubs in the early days of UK 27Mhz 
> licensing used to frighten the audience when they saw just what 
> "sacrileges" would be committed with "expensive" chicken boxes and "bits 
> of wire"!
>
> Of course, they were always advised "Don't try this at home - unless under 
> the supervision of a responsible adult!"
>
> My favourite will always remain the manufacturers agent who came into our 
> store and attempted to get us to stock "SWAR GREASE" - apparently you 
> could ignore "SWAR" meters, the grease would guarantee a perfect match!
>
> 73
>
>
>
> On 29/09/13 21:36, Alan Melia wrote:
>> No it does not.....BUT I did not imply that, with knowledge, it can not 
>> yield useful information....Too many think 1:1 swr means resonance. A 
>> friend of mine used to do a demo at clubs where he had a closed box with 
>> coax going into it and a reading 1:1 on a meter. He asked what was in the 
>> box and the guess was usually a dummy load. He then in true stage 
>> magician style got someone to come and open the box and display what he 
>> found. To their amazement there was only several metres more coax left 
>> open at the end !! Of course the frequency setting of the exciter was 
>> vital :-))
>>
>> Having detuned your antenna you could bring the non-resonant result to 
>> 1:1 by then changing the tranformer ratio....But that would not indicate 
>> resonance.:-))
>>
>> When I got into radio 60 yeas ag the Club sages of the time stressed 
>> first resonate, then match. That was before many SWR meters were around 
>> though the "Monimatch" had been described in QST few understood how it 
>> worked, or how to use it. Most resonated with a GDO and matched for max 
>> antenna current
>>
>> Actually for your purpose I would suggest you look at the tuning aid 
>> described by Jim Moritz M0BMU in a number of the books (LF Today)  and 
>> probably on several web sites. It was original designed in the 136kHz 
>> days but should be just as useful at 470k. This aids the tuning and 
>> matching process.
>>
>> A lot of topband meters should work try them with a load, then two loads 
>> "teed" together, also use different length of coax between the load and 
>> meter.....it should give sensible results.
>>
>> Alan
>>
>> ----- Original Message ----- From: "Stefan Schäfer" 
>> <Stefan.Schaefer@iup.uni-heidelberg.de>
>> To: <rsgb_lf_group@blacksheep.org>
>> Sent: Sunday, September 29, 2013 7:26 PM
>> Subject: Re: LF: Re: HF SWR meters on MF?
>>
>>
>> Does it not?
>> I suggest to do a test:   Use a MF antenna (on 160m, for this test),
>> resonate it to the TX frequency by using a variometer. Then use a
>> ferrite transformer to match the impedance to 50 Ohm.
>>
>> Insert the SWR meter (i'm using this one for HF:
>> http://www.astrosurf.com/luxorion/Radio/swr-meter.jpg   (you can find
>> 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
>> (i.e. add a significant reactive component to the feed point impedance)
>> so that the resonance is lost. I bet that the reflected power will rise
>> dramatically. Then i interprete that the SWR meter tells me that i have
>> lost the resonance, since the ratio of the transformer didn't change.
>> Sure, there could be a change of the earth losses which cause a change
>> of the resistive component of the impedance. This will result in a
>> change of the SWR as well. But these changes are small compared to the
>> 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 Schäfer" 
>>> <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 
>>>> 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 (no 
>>>> oscilloscope...)...
>>>>
>>>>
>>>> 73, Stefan/DK7FC
>>>>
>>>
>>>
>>
>>
>
>
> -- 
> 73 de pat g4gvw
> es gd dx
> qth nr Felixstowe
> East Coast UK
>
>