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Author Topic: Ramsey DDF1 thought  (Read 17017 times)
KD8VQH
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Posts: 22




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« on: January 20, 2016, 08:02:56 AM »

I just got the DDF1 kit but haven't started putting it together. My thoughts are to put the antenna switching board in a a project box to keep inside the car so it is not in the elements. I plan on making my own NMO mag mount antennas. I have seen articles that say to use equal lengths of coax for each antenna. Would it be better to use RG58 or can I use RG174? I also plan on using connectors to fit what ever coax I end up using so I can disconnect the antennas from the switching board when not in use. My mag mounts will be 2 inches in diameter. I have diodes and inductors coming in the mail today to build my mounts. If these ideas will not work I will go with the plans with the kit.

Thanks in advance

73
Wes
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WB6BYU
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Posts: 17050




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« Reply #1 on: January 20, 2016, 10:34:02 AM »

If the cables are short then RG-174 is fine.  For longer cables (like reaching inside the car) then I'd use
RG-58 for lower loss.  (Doppler systems tend to be lacking in sensitivity to start with.)

You might get some ideas from K0OV's improved doppler antenna / switching system here:
http://www.homingin.com/newdopant.html

Certainly all the coax lengths have to be identical for the system to work properly.

Oh, and don't use a foam-dielectric cable such as RG-8X if you are going to be running it into
the car through the door jam - the foam is much easier to compress when slammed in the door
than the solid dielectric in RG-58.
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KD8VQH
Member

Posts: 22




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« Reply #2 on: January 20, 2016, 02:26:20 PM »

Thanks for the information. I have been to the homing in page and have done a lot of reading. I have a lot of RG58 cable with the solid dielectric to use. I will put connectors on and connectors in the box, all numbered for each antenna and numbers on the antennas. I will use the antennas with the kit if need be and set the box up so I can hold it on the roof of the car. Our club is planning some fox hunts this year. I have a "fox box" ready and working. Once I get the direction finder assembled I can use the fox box to test it out.

Thanks again for the information

73
Wes
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KO4LZ
Member

Posts: 4


WWW

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« Reply #3 on: January 24, 2016, 07:54:19 PM »

Incidentally, if you're interested in learning more about how Doppler and other DF methdologies work, you can download the slides from my workshop at VA Tech here:

https://wireless.vt.edu/2015_%20slides/document.pdf

I'm an application engineer at Rohde & Schwarz and one of my specialities is interference hunting / direction finding.  Would love to show up for a foxhunt one day with some of my "work" tools   Smiley
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KD8VQH
Member

Posts: 22




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« Reply #4 on: January 25, 2016, 07:28:30 AM »

Paul,

Thanks for the link! I will study the material. Our club is planning on doing some fox hunts this year. There is a member from another club in the area that has been helping me. I have my fox box ready to go and he has some low power foxes that we will use in a local park. We are hoping to do a demo at our April meeting.

Thanks again for the information!

73
Wes
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ESTEFAN2020

Posts: 4




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« Reply #5 on: July 03, 2016, 05:14:32 PM »

http://www.handi-finder.com/

Here is another 2 antenna df like ramsey df1 but is not bulked up price.

I like the http://www.homingin.com/newdopant.html
4 antenna style, but discouraged when the price hits $100+ for a kit.

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