Because of space limitations, am purchasing a magnetic loop antenna. Because of needing to move the antenna around, do i need a RFI choke in the feed line?
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2$\begingroup$ Hello, and welcome to the site! Can you please tell us more about this loop? You can edit your answer and include a link and/or photo of it. $\endgroup$– Mike WatersJan 6, 2019 at 20:35
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2 Answers
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From my current experience of using Cha F-Loop 2.0:
- Yes, you most definitely need an RFI choke to use a magnetic loop antenna, and a good one.
- Magnetic loops are not as good as you might think. Particularly they are very narrowband - you have to seat near it and tune the capacitor all the time. Or you need a remote tuning device.
- Despite the fact that some manufacturers may claim that their antennas work great indoor, they actually don't. For sure there is a chance to make a QSO even in this case, but this will be very tricky.
- Most magnetic loops have a power limitation 25W or so, which also reduces your chances for a successful QSO.
Simply put, I paid 400 GPB for a magnetic loop and now I can't use it. It doesn't work indoor, I can't use it outdoor because it's winter and I live in Russia.
If this is your first antenna I strongly recommend to choose some other type of antenna. I made many QSO with shortened vertical antenna, OPEK HVT-400B, installed on a balcony. There is also a similar model, OPEK-600. These antennas are very simple to use. You need to connect one cointerpose wire (or better - a few, on the balcony I use two 5m long wires for both 40m and 20m bands) with length about L/4, then you tune the length of the antenna itself to get minimum SWR, and you are ready to go. Unlike magnetic loops, these antennas 1) can handle more then 100W 2) are wideband. To get best results you still need an RFI choke, but it is optional.
This being said, if you are an experienced ham and this is not your first antenna, go for it!
73 de R2AUK
answered Jan 6, 2019 at 21:28
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2$\begingroup$ Good advice. Years ago (before switching supplies and other RFI generators were common), I used one indoors for receiving. It worked to some extent, but it coupled to the house wiring and nearby 70' tower. I finally installed it in the attic of a detached garage, where it was useful to null out a strong local signal. $\endgroup$ Jan 6, 2019 at 22:17
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Magnetic loops do not need a choke more than other kinds of antennas but I recommend you have one anyway especially if you will have coax running through your house. The reason to have a choke with a magloop is to reduce rf receive noise which can be picked up by the coax from local rf noise sources in your house. This is also valid for other types of antennas.
