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Author Topic: PJ-80  (Read 835 times)
NO9E
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Posts: 437




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« on: November 24, 2014, 01:43:52 PM »

I purchased an 80m RDF receive that looks like PJ-80:
http://www.sdr-kits.net/Webshop/products.php?94

It was assembled and came from China.
It does not show much directivity. Has anybody used anything similar?
Ignacy, NO9E
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WB6BYU
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Posts: 13482




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« Reply #1 on: November 24, 2014, 03:34:20 PM »

I have worked with the PJ-80, and there are some online articles about them that I probably could dig up.

The PJ-80 isn't very sensitive.  Directivity will depend on whether they are using the bidirectional null or the
cardoid pattern (with the sense antenna enabled).

Like any such receiver, they work best outdoors on vertically polarized ground wave signals that come
from a single point.  It's a pain trying to track electrical noise propagating along a power line, for example,
because it tends to radiate from a horizontal wire and it comes from multiple locations along the wire
rather than from a specific point.

Let me know if you have specific questions - I've built several such hand-held 80m DF receivers and
use them in competition.

                - Dale WB6BYU
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NO9E
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Posts: 437




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« Reply #2 on: November 24, 2014, 04:37:16 PM »

Dale,
Thank you for the offer.

I set my antenna analyzer with a piece of wire as a generator and could not detect much directivity, button passed or not, twisted or upright. Any suggestion welcome.
Ignacy
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WB6BYU
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Posts: 13482




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« Reply #3 on: November 24, 2014, 05:49:09 PM »

With the sense antenna OFF (button not pushed), there should be a very sharp null off
the ends of the ferrite rod.  Signals should drop at least 20dB over a very narrow range
of directions.  Turn it slowly.  (They are designed for the null to be detected by ear, but
might require adjustment of the gain control.)  If you are outside with a vertical wire and
you can hear the signal, then you should have a null unless there is a lot of metal in the
area.  That null should be bi-directional, off either end of the ferrite rod.

I'd try it also at various distances, making sure that your wire is vertical.

Or it could be that something isn't wired properly inside...


Once you get that working we can discuss adjusting the sense antenna to resolve the
bidirectional ambiguity of the loop by itself.
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