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Designing antennas, selecting antennas for specific applications, properties of a given antenna design.

2
votes
3answers
Numerous sources say that LW length shouldn't be a multiple of λ/2 for any frequency in interest. This will cause the antenna to have a high impedance at this frequency. Since the coax cable impedance …
3
votes
The 50 Ohm impedance doesn't eliminate the need of the balun. A balun prevents the feed line to work as a part of the antenna (eliminates common mode current). You can find more info on this topic in …
answered Jul 8 by Aleksander Alekseev - R2AUK
2
votes
The gap is neglectable in terms of λ. Let's say you are making a 20m (14 MHz) dipole and you decided to use a large gap, let's say 10cm. This is only 0.0005λ. For 2m band (144Mhz) it's 0.005λ. If you …
answered Aug 6 by Aleksander Alekseev - R2AUK
2
votes
1answer
I've build a verical for 40M band using a fishing rod as a mast, 6 radials and an RFI choke (FT240-31 ring, 8 turns of RG58, W1JR winding according to the article by Steve Hunt). When I measure SWR r …
1
vote
0answers
I wonder whether the source code of VE6YP (Tony Field) coaxtrap design program (link 1, link 2) was ever published or described. As a Mac user I'm having little difficulties using this software and I …
asked May 17 by Aleksander Alekseev - R2AUK
3
votes
3answers
I would like to use a shortened whip antenna with a coil in it's base, e.g. OPEK HVT-400B. My transceiver maximum power is 100 W (and antenna's - 120 W). To make the antenna work I need counterpoise w …
asked Nov 28 '18 by Aleksander Alekseev - R2AUK
7
votes
3answers
Recently I've build a trap dipole for 20/40/80m bands. I followed an article by John DeGood, NU3E and got following measurements: From balun to 20m trap: 485 cm From 20m trap to 40m trap: 362 cm Fro …