Re: LF: DK7FC's VLF Active Antenna

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

I doubt that leaded components will ever go out of fashion not while we have China and Russia knocking huge amounts of parts. We can still get thermionic devices brand new so never fear the good old clunky stuff will be around all our life times (definitely my life time anyway...hee)

 

However I would recommend SMT construction it's not as bad as people would have you believe! That article in the Radcom a year or so back must have scared most amateurs off ever trying to use SMT. Talking to local stations on VHF it is something not even to be attempted which IMHO is a pitty. The only issue is creating the pads. I have found the best way without optically developed resist is to coat the board with resist and using a steel pointer like a scriber but with a finer point scribe through the resist aided with a steel rule, after first laying out the circuit with a fine pencil. Then enticing the board and removing the resist with a wire wool of solvent. (Its amazing how fine a gap you can make that way) This is fine for a few IC's but becomes progressively more difficult the more complicated the circuit, where a properly laid out board is require in my opinion. But for small circuit layouts it quite easy and dare I say quicker than poking wires through drilled  holes in the board. Also, to know doubt howls of protest, it is possible to dead bug SMT parts.

I use a big Maplin lighted magnifier and a £6-00 Maplin soldering iron solder sucker and solder wick, it all works a treat.
 

73 es GL petefmt

I support www.NotSpotTelecom.Com your community Telco / ISP.

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From: Andy Talbot <andy.g4jnt@gmail.com>
To: rsgb_lf_group@blacksheep.org
Sent: Wed, 29 December, 2010 23:52:23
Subject: Re: LF: DK7FC's VLF Active Antenna

It won't be long before leaded components become unavailable.  Certainly the useful modern ones that actually do teh job that's wanted.   I've compared availability and prices in the Farnell catalogue recently (having just got the almost cubic shaped printed version :-)   and leaded components are just more expensive and less available that SMT equivalent.    And the bulk ordering quantities available on many of them make ordering less than 100 off of some of the more popular ones just a waste of money.   

 

Constructors really will have to start getting used to using SMT devices are their first choice every time.  Start practicing now before you're forced to.

 

Andy

www.g4jnt.com

 

been using SMT components for preference for something like 15 years now.

 

 

2010/12/29 Stefan Schäfer <schaefer@iup.uni-heidelberg.de>

Hi Ken,

I have not tested other JFETs so far. Is it just because of the SMD housing? I don't use a SMD PCB but a "free air" soldering. So if this is the problem, just solder the FETs legs directly on the next part, e.g. solder the drain directly on the 390 Ohm resistor. Attached you find a picture that shows how my current used VLF grabber antenna looks inside. Don't be shocked ;-)

If you anyway want an alternative, the J310 or the (2SK170) should be possible. There are some parameters like the noise and the gain and the input capacitance which are affecting the performance but this is all not so critical on VLF.

73, Stefan/DK7FC



Am 29.12.2010 17:58, schrieb Ken:

Stefan.

Could you please recommend an equivalent to to BF862 which is not Surface Mount for use in this circuit.

73s

Ken

M0KHW

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