Extending the range of a Discone antenna down to 3.6 MHz

Useful information regarding antennas for SDR products.
ON5HB
Posts: 140
Joined: Sat Dec 29, 2018 1:07 pm

Re: Extending the range of a Discone antenna down to 3.6 MHz

Post by ON5HB » Wed Feb 20, 2019 4:36 pm

The only thing an antenna-analyser tells you is the impedance at a given freq.

It does not tell you anything about it's performance.

Very sorry, but because an impedance is high doesn't mean anything.

Reception antenna's often have terrible bad SWR, doesn't mean anything.
For transmitters it's a different story as amplifiers or cables could burn when not being 50 Ohm and/or matched.

For example, I use the G5RV, often regarded as a poor antenna because the SWR can be very high, so some folks with analysers started to "improve" it.
Result, ZS6BKW, sure it has a better SWR but the performance is far worse, they only focussed on SWR alone.

I personally do not care about SWR, I have tuner to solve that for TX....for RX it matters little.

Google for: "Reflections" By M. Walter Maxwell

Not only a very good read (very funny too) but also proven reality about antenna's and transmission-lines as also described in: ARRL Handbook and the Antenna Book.

SWR isn't as bad as most people think :D

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SDRnerd
Posts: 53
Joined: Sun Jan 07, 2018 6:29 pm

Re: Extending the range of a Discone antenna down to 3.6 MHz

Post by SDRnerd » Thu Feb 21, 2019 4:07 pm

Bas, I mostly check a balun with a VNA and after this is acceptable I fire up the W&G SPM30 and see what the attenuation is on various frequencies. When a balun has a good Return Loss figure the next thing is the resistance and SWR value. :)

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ON5HB
Posts: 140
Joined: Sat Dec 29, 2018 1:07 pm

Re: Extending the range of a Discone antenna down to 3.6 MHz

Post by ON5HB » Thu Feb 21, 2019 4:47 pm

I never use baluns as I find them debatable if they really matter compared to a good tuner and a good transmission-line, like modern coax.

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