Posts Tagged ‘Loop’
|10m band loop|
A magnetic loop can be a very effective HF antenna, especially when the very sharp tuning is not an issue. They can be very efficient but there is a trade between bandwidth and efficiency. They are ideal for modes that do not need frequent retuning such as PSK31, JT65 or WSPR. Ideally the inductor should be made of copper pipe or thick coax and the capacitors need to be low loss and high voltage types. Tuning is usually very sharp. Having said all this. quite decent results have been obtained with loops made of quite thin wire.
Magnetic loop antennas can be very effective, small, antennas. They work well and are ideal for modes like WSPR, JT65, JT9-1 and PSK31 where frequencies don’t have to be moved much. Their main disadvantage is they are narrow-band so require retuning if moving very far in frequency and they are directional.
As ever, Steve G1KQH has been tracking down bargains – in this case motors that could be used to either tune or rotate loops.
Rather than go QRT because of the approaching storms, I decided to try my Wonder Wand Tunable Compact Loop antenna indoors on 20m WSPR. The loop is about 0.5m diameter. In my case, more for convenience, it goes to the rig via my Z817 ATU. SWR is perfect 1:1 on the tuned frequency. No TX spots seen yet at 2W, but no shortage of RX spots across Europe so far. The loop is just above the rigs in a far from ideal, indoors location.
|WSPR spots so far today on 20m with the indoor Wonder Wand Compact Loop|
UPDATE 0916z: My first TX spot on the indoor Wander Wand Compact Loop came from DJ6LB at -28dB S/N.
UPDATE 0944z: Second TX spot was by DJ7KA at -26dB S/N.
UPDATE 1010z: I QSYed to 15m and am getting lots of spots on TX at just 2W. Best DX report on 15m is from SM6WZI (1007km) at -6dB/-9dB S/N (i.e. strong) – it is amazing this tiny indoor antenna works so nicely. So far 6 TX spots of my 2W in just 8 minutes on 15m. Incredible. Sorry about the poor photo of the loop, but you get an idea of the set-up. It will work even better on 10m and 6m as the loop is larger electrically. Set-up is totally un-optimised: the loop just happens to be where it is.
UPDATE 1230z: Now QSYed to 10m and the best DX on the Wonder Wand Compact Loop indoors is now LB9YE (1489km) at -25dB S/N with 2W.
|10m WSPR spots with 2W today with indoor loop|
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- HF Antennas, Horizontal vs. Vertical
- Tonight, our hosts discuss the pros and cons of horizontally and vertically polarized HF antennas.
- One thought is that once the RF radiation hits the various layers in the ionosphere, the polarization doesn’t really matter much as it gets reflected to and fro.
- Richard offers the practical reason for preferring horizontal antennas for HF: it’s easier to build and erect the long antennas necessary for these frequencies. However, for chasing DX, those long-distance contacts, many hams prefer vertical antennas as they tend to have lower angles of radiation.
- Also mentioned: GAP antennas and the G5RV antenna.
- Wire horizontal dipoles are inexpensive and easy to construct. Verticals are a good choice when space is limited and can have a lower take-off angle, providing a good ground radial system is installed beneath them.
- Horizontal antennas can be more directional. A dipole wire running north and south will have a better propagation east and west. A vertical is omnidirectional, radiating equally in all directions. To complicate matters, a horizontal antenna lower to the ground will radiate at higher angles than the same antenna that is higher. This can be useful for communicating with stations that are close to you.
- A new section of the podcast: Russ’ Rant!
- Russ has a Yaesu FT-7900R, a dual-band UHV/VHF mobile radio. It has a removable front panel, allowing the main part of the radio to be hidden and the display can be easily mounted on the dash. However, the speaker is on the body of the radio, so you can’t hear it if it’s hidden under the seat or in the trunk! Russ thinks the head unit should also contain a speaker, perhaps a very small one like in an mp3 player. Or put the speaker in the microphone.
- Returning to antennas, Richard recommends that KD8SZG (in the chat room), should try building his own wire antennas for HF. Any of the antenna books written by Doug DeMaw, W1FB, are good resources. His Antenna Notebook is one. (I also like the various ARRL antenna books, like the Simple and Fun Antennas for Hams. -Ed.)
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