Re: LF: Re: Basic LF understanding

[M0FMT <m0fmt@yahoo.co.uk>]

Hi all

 

I would not rate The LF Experimenters Handbook publications that highly for a beginner.

 

1/ Some of the schematics have errors and omissions.

 

2/ The TX schematics call out "Unobtainium". Such as ferrites that probably only available to "professionals" and some of the IC devices that were only available to 1000up buyers.

 

3/ A lack of clear circuit description in some cases. No clear description of Class D and E etc, operation and in one case I think a positively misleading description of power FET feeding requirements for best efficiency.

 

Also the deficiencies of the first issue were carried over into the second edition. Having bought both I felt a little disappointed in that the missing information in the PA0 136TX design in the driver stage was not put right in the second edition......... I am not the only person to have been disappointed by this.

 

To some extent these publications are produced with an assumption of a certain amount of pre-knowledge.

 

To the expert in the field these criticisms are minor but to a constructor and not a designer 

the missing information and unobtainable components become a show stopper.

 

Not only that, there is reference to the design of the Decca navigation legacy equipment which there could only be a hand full available in the country and was irrelevant to the new starter on these LF bands who could not obtain these pieces of kit or construct them.

 

One of the best and helpful additions to the MF/LF canon (not in the LF handbook) was the series of TX designs by Rog GW3UEP who saw the need to avoid "Unobtainium". His designs are clear, use components obtainable at Maplin and not a "Magical" ferrite core in sight. Not only that he illustrates his construction article with typical Oscillographs of the circuit under test so the constructor can be sure he has got the circuit operating in the correct mode by reproducing them.

 

I know that if anybody cares to read this it will provoke a backlash. It is not intended to belittle the efforts of the original authors to who I am grateful to for enthusing me. However after several fruitless attempts to recreate some of the circuits in those publications I had to go elsewhere to get a better understanding of what I was trying to make.

 

Buyer beware.

 

73 es GL Pete M0FMT IO91UX

From: Alan Melia <alan.melia@btinternet.com>
To: rsgb_lf_group@blacksheep.org
Sent: Tuesday, 1 May 2012, 23:29
Subject: LF: Re: Basic LF understanding

Hi Stephan to be afir anyone starting needs to read Riks pages and if they
dont understand just ask. I am not in favour of "nursury" guides as you
finish up wasting a lot of time saying well that not really how to do it.
The other sources are pre internet and are the early LF sourcebook and the
LF exprimenters guide (by Peter Dodd)

The thing is every one if different, has different starting knowledge,
different locations, with different local conditions and QRM. Starting is a
matter of conquoring those or at least recognising them. A read of the
waterfall dispay pages (I cant remember what Rik calls them is an essential
starter) The DSP waterfall is so usefull for identifying problems it should
not be avoided in the early satges and even if the QRM is bad and the
receiver deaf it will probably aid you to hear something. One of the most
difficult part is finding a receiver that has any performance down there out
of the standard Amateur range. A lot that advertise they go from DC to
1300MHz are very deaf below 500kHz or even 2MHz.

If a newcommer wants something less daunting than the occasional maths in
Rik's pages them  Dave Picks pages at http://wireless.org.uk/geton136.htm
are to be recommended. Dave being one of the true pioneers of LF in the UK.

Alan G3NYK


----- Original Message -----
From: "Stefan Schäfer" <Stefan.Schaefer@iup.uni-heidelberg.de>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, May 01, 2012 9:53 PM
Subject: LF: Basic LF understanding


> LF!
>
> Has someone a very good link to basic understanding about LF? I mean the
> LF amateur radio stuff, all which one has to learn when starting rx-wise
> in our hobby! Maybe some ideas and examples, a good compliation. Not to
> complex and focusing on 137 kHz amateur radio?
> For newcomers in the "LF-transmit-world" i recommend ON7YD's page
> http://www.strobbe.org/on7yd/136ant/
> Is there maybe something for receive newcomers?
>
> A collection of some links may help as well...
>
> Thanks in advance.
>
> 73, Stefan/DK7FC
>