Sony AN-LP1 Active Loop Antenna: What about putting it outside?

In the previous part, I was looking at improving the performance of the Sony AN-LP1. With the modifications not really achieving the desired effect, I decided to do what most sensible people might do – put the antenna outside, so it can be further away from the interference and noise.

The manual strictly states that the antenna is to be used indoors. This is likely because there is no internal protection against lightning strikes (due to not having a ground connection) and potential vulnerability to static build-up and maybe even UV damage of the materials used in the construction. It is also not waterproof. Deciding to “let everything loose” on a string of good-weather days, I threw the cable out of my window and hung the loop outside, on the feedline to the Wellbrook loop I regularly use.

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At first, I hung it like this, as you would expect with the printing, hanging hook, etc. But then I figured that the loop is rotationally symmetrical. There is no reason why the wire can’t lead upwards … so I moved it and rotated it …

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… and with the help of a clothes peg, managed to get it a little further away from my room.

Another improvement I made was to ditch the long-wire adapter. I decided that additional magnetics weren’t going to help a weak signal if it didn’t show any improvement on the spectrum analyzer, and instead would be a source of distortion and losses. In fact, it seems my reasoning as to the output impedance may have been backwards – the output stage of the antenna module has a FET driving one side of an RF transformer, with the other side as the output. Because of the 3.5mm connection, and the use of the FET, it’s reasonable to assume it can actually drive decent currents and it might be closer to 75 ohm impedance match (as RCA audio/video is often that impedance and commonly adapted to 3.5mm).

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Instead, I grabbed an old coax lead-in with BNC plug on the end, and soldered it to a 3.5mm mono jack. This was hooked up to the same Icom IC-R75 which has served me well over the past few years, just to see how it fared.

In the end, the result was slightly better (as expected) but not by much. Interference still seems to show up in the signals, and although the SNR has improved somewhat, it’s not as good as with even the 15m longwire.

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Typical reception of a local BOM VMC weatherfax shows readable signals, but grey backgrounds and “wavy” patterns from interference. Strong fade lines can be seen during periods of ionospheric disturbance – this is more severe than with the long-wire possibly because of the small receiving aperture.

At least the faxes are much more readable as opposed to unreadable. On a good day of propagation, it was also possible to copy JJC (Kyodo News Japan) on 12745.5khz, which was quite unexpected (as it is normally fairly difficult to receive).

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That being said, the local VMC weatherfax can come in very well on the longwire – about two weeks earlier, it was received at its clearest (shown below).

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And here’s an equivalent graph to that received with the AN-LP1, received just a few days afterwards.

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The scary thing is that the Wellbrook loop still beats the longwire, which still beats the AN-LP1 sitting outside. I suppose it is still “physics” in the end – a smaller antenna won’t magically be able to beat a larger one, and the quality of the engineering design used in the active circuitry can really make a mile of difference. I suppose it’s still rather good to know the AN-LP1 can pull in JJC if it is placed outside – so it’s a good idea to put the AN-LP1 outside when travelling, if the weather is good.

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One Response to Sony AN-LP1 Active Loop Antenna: What about putting it outside?

  1. William Conlan says:

    Its not a feasable proposition at the price it comes in at. I would not try it outside the shack as Irish WX is 90% rain.
    Still good review.

    Cheers from S/E Ireland.

    William

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