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Author Topic: Does AM loopstick orientation matter? Can the phase be reversed?  (Read 2599 times)

Offline SW-J

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Someone has run an interesting experiment with a couple of receivers tied
together, and, as one radio is rotated 180 degrees to the other one, the
phase is seen to change 180 degrees.

   http://www.youtube.com/watch?v=Z9sBa_7AyNE


o Icom IC-756ProII, ProIII, Alinco DX-70, Kenwood TS-680s
o WinRadio G303e, Degen/Kaito 1103/DE1103, Stoddart NM-25
o 1/2 wave 80m Dipole used with several tuners
o Tuned loops from 2' thru 16' diam. capable of 160m thru 10m

Offline Throbbing Gristle

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Wow! Degen 1103s.

Offline SW-J

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Wow! Degen 1103s.

Yeah, fairly nice portable for the money, can be had on eBay in quantity 49.x ea (+ 24 shipping) from offshore, about 10 days I have found ...
o Icom IC-756ProII, ProIII, Alinco DX-70, Kenwood TS-680s
o WinRadio G303e, Degen/Kaito 1103/DE1103, Stoddart NM-25
o 1/2 wave 80m Dipole used with several tuners
o Tuned loops from 2' thru 16' diam. capable of 160m thru 10m

Offline Lex

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I've tried that trick of stacking two portables together to sharpen the null.  Works fairly well on the smaller portable, but does nothing for the larger Magnavox and Sony portables.  But it seems to indicate that something like the DX Tools Quantum Stick or comparable homebrewed doodad will help.
That li'l ol' DXer from Texas
Unpleasant Frequencies Crew
Al: Palstar R30C & various antennae
Snoopy: Sony ICF-2010
Roger: Magnavox D2935
(Off-air recordings.)
Email=my name at hotmail dot com

Offline SW-J

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I've tried that trick of stacking two portables together to sharpen the null.  Works fairly well on the smaller portable, but does nothing for the larger Magnavox and Sony portables.  But it seems to indicate that something like the DX Tools Quantum Stick or comparable homebrewed doodad will help.

I've placed tuned ferrite loopsticks (4" loop stick with the 'factory' coil tuned with the little plastic Japanese, now Chinese, made tuning caps) end-to-end with an AM radio to squeeze out a little more SNR (signal to noise ratio) on a weak AM broadcast signal before like I think many of the posters on the board may have done at one time or another ... the experiment in this video was to show that the RF wave does show signal 'phase' (and apparently maintains it during RF downconversion through mixers and IF stages and even down to audio bandwidth stages) with respect to an independent or external reference signal ...

From this experiment it can also be concluded that: the carrier originally sent with the modulation on an AM signal is required for proper in-phase demodulation ... not just any-old 'carrier' can be reinserted, and, it also underscores the need for some sort of 'reference' to be transmitted for proper phase of the 'demodulating' carrier in the final (last) detector (product detector for SSB or 'envelope detector' for AM), be it a full strength carrier or a reduced-amplitude carrier, which allows AMS (AM-synchronous) to be used to 'demodulate' the signal in-phase with the original modulated carrier (esp with considering ionospheric paths, phase changes st al) that exists in some form (be it the final high-level plate or collector or Drain modulated stage or further back in the transmitter in the case of low-level modulated AM or SSB or DSB/Suppressed carrier) in/at the originating transmitter. Just something I have thought about in the past ... Of course, with DRM/digital radio this phase thing (the phase relationship between the modulating program audio and the modulated carrier) 'goes away' ...

Sorry for being so long-winded on an such an esoteric subject!

o Icom IC-756ProII, ProIII, Alinco DX-70, Kenwood TS-680s
o WinRadio G303e, Degen/Kaito 1103/DE1103, Stoddart NM-25
o 1/2 wave 80m Dipole used with several tuners
o Tuned loops from 2' thru 16' diam. capable of 160m thru 10m