ARDF transmitter hunting

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ARDF transmitter hunting

Postby VA2KEY » Tue Jul 19, 2011 5:39 pm

The UMS guys were in the West-Island last Sunday to run an ARDF transmitter hunt in Terra Cotta park. http://en.wikipedia.org/wiki/Amateur_ra ... on_finding . It was a lot of fun.

The "new project idea" is in multiple parts:

1- Building a small, handheld, directional antenna: http://pages.videotron.com/ve2jmk/tape_bm.htm
2- Building an attenuator: http://pages.videotron.com/ve2jmk/ofst_att_proj.htm
3- Borrowing the UMS transmitters and stagging a fox hunt in Terra Cotta (or maybe Morgan's arboretum)
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Re: ARDF transmitter hunting

Postby ve2rfi » Sun May 13, 2012 2:12 pm

Hello all, I am going to go ahead and build a offset attenuator with optional selectable passive attenuation. The plans can be found in the March-April 2012 TCA.

Eamond I have about 40 1n4148 diodes, I will donate up to 30 for this project. I found plans to build a 40mW transmitter that I will also build if I can find all the parts.

Charles
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Re: ARDF transmitter hunting

Postby ve2rfi » Mon May 14, 2012 8:55 pm

OK, after looking at several desings of attenuators I decided on WB2HOL's.

Eamond, I would need a 1Mhz cristal and a N channel depletion JFET MPF102 (NTE 451). I found some cristals on ebay, they are 26$ plus 14$ for shipping for a lot of 10, Digikey sells them for 16$ each. Let me know if you have a better source.

Charles
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Re: ARDF transmitter hunting

Postby VE2EVN » Thu May 17, 2012 8:37 am

ve2rfi wrote:I found some cristals on ebay, they are 26$ plus 14$ for shipping for a lot of 10, Digikey sells them for 16$ each. Let me know if you have a better source.

Woah! I know it's not as common a value but, thats real expensive for just a xtal. It should be around $1-2 at most. The J-fet should be under $1.
Have you had a look at Addisons/Maddisons/Abbra?

M-A
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Re: ARDF transmitter hunting

Postby ve2rfi » Thu May 17, 2012 11:14 am

I picked up the missing parts yesterday at Abra, I should be ready for testing and debugging @ Saturday's SolderSpot.
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Re: ARDF transmitter hunting

Postby Eamon » Sun May 20, 2012 4:14 pm

I have the whole attenuator priced out at about $10 including metal box, connectors and potentiometer.

Here is a link to the schematic Charles built:

http://theleggios.net/wb2hol/projects/rdf/a_attn_s.gif
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Re: ARDF transmitter hunting

Postby Eamon » Sun May 20, 2012 4:40 pm

I am also interested in a time of arrival scheme.

Since I already have a 555 in my attenuator, I could change its frequency to 500Hz and try this instead.

http://theleggios.net/wb2hol/projects/rdf/tdoa2.htm


- Eamon
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