magnetic loop and pre-amp?

Useful information regarding antennas for SDR products.
ToryGlenn
Posts: 5
Joined: Mon Mar 19, 2018 3:47 am

magnetic loop and pre-amp?

Postby ToryGlenn » Wed Jul 04, 2018 4:26 pm

If I"m using a magnetic loop antenna with my RSP1A, do I need to connect a pre-amp between the antenna and the radio?

I've put together a magnetic loop antenna, but all I seem to get is tons of noise. Even when I turn the antenna in a given direction
and turn the knob on the capacitor, it's just constant noise but no signals.

I was told that I might need a pre-amp with a magnetic loop antenna. Can someone please verify this?

Thanks.
Last edited by ToryGlenn on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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mark.
Posts: 38
Joined: Tue Oct 03, 2017 9:14 pm

Re: magnetic loop and pre-amp?

Postby mark. » Thu Jul 05, 2018 2:00 am

RSPs have a sensitive front end. A preamp should not be needed for casual listening. Are you saying you pick up no signals at all? Even in the AM and FM broadcast bands? If the antenna is indoors maybe it is close to a strong source of rf noise that is wiping out reception.

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DanubeBCL
Posts: 195
Joined: Sat Jul 02, 2016 12:39 pm

Re: magnetic loop and pre-amp?

Postby DanubeBCL » Thu Jul 05, 2018 7:35 am

Tuned loops have a high resonant circuit impedance. How is your loop matched to the RSP input? Are you using a high impedance FET source follower or some other matching network?
73, Heinrich

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DaveB
Posts: 137
Joined: Sun Feb 01, 2015 6:04 pm

Re: magnetic loop and pre-amp?

Postby DaveB » Thu Jul 05, 2018 2:37 pm

Hi Tory,
See my post in this forum regarding my shielded magnetic loop. Here's a link to the original construction article by PA0FRI: article.https://pa0fri.home.xs4all.nl/Ant/Activ ... %20eng.htm

It is untuned - and feeds an original SDRPlay RSP (not a 1 or 1A). I was more than pleasedwith it. It wasmounted about 6 ft agl and was 25 ft from the house.

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harley040
Posts: 2
Joined: Fri Jul 06, 2018 2:32 pm

Re: magnetic loop and pre-amp?

Postby harley040 » Fri Jul 06, 2018 2:37 pm

I was wondering about the MFJ-1886 receive only antenna. I have heard good things about it for its sensitivity that rivals long wire antennas.
Last edited by harley040 on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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NK7Z
Posts: 34
Joined: Fri Sep 02, 2016 1:14 pm
Contact:

Re: magnetic loop and pre-amp?

Postby NK7Z » Fri Jul 06, 2018 4:10 pm

I have been using my three diameter loop with my SDRPlay RSP-1 without a preamp for a few weeks now... I see all sorts of signals. If you are seeing nothing, check your loop construction. You should hear a pronounced increase in background noise as you tune through resonance. Make sure you are listening on the design frequency of the loop. If you designed it for say-- 7-14 MHz., and you are listening on the Broadcast band, you will NOT hear the pronounced increase in noise. There is an advantage to testing in your home, lots of noise sources to hear...

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