Antennas 101?

rljames · Apr 24, 2015

I'm interested in "simple" shortwave listening. That is to say, I'd like a smaller battery operated radio offering good overall performance via built-in whip antenna but also have the ability to add an external antenna when needed. Basically a portable "system" I can take out on the porch at night and easily poke around various frequencies with some success.

I can probably sort out finding a decent radio but I'm confused on antennas. Discussions on; "Impedance and Balancing", "Grounding" and more all seem to suggest that using an external antenna is at least complicated and at most useless if not done right.

As a complete radio and electronics novice, Where can I learn more about the basics of selecting/using antennas for my purposes?

Thanks,
Bob

nanZor · Apr 29, 2015

Both the ARRL and the RSGB have some great books for the shelf, but it might be easy to get overwhelmed with the standard antenna references. You don't have to be a ham to benefit from them for swl duty.

Two that come to mind from the ARRL you might be interested in are:

Simple and Fun Antennas for Hams
Small Antenna for Small Spaces

Both can be found at places like Universal Radio, HRO etc..

Just understand that some of the antennas they describe, even if simple, may just be too much for your standard portable and require heavy attenuation.

I don't know your budget, but one modern small portable radio that WILL handle real antennas is the CommRadio CR1a.

SCPD · Apr 30, 2015

Bob, this is a pretty cool PDF. It may look overly technical but remember the US Navy has to teach this stuff to young men and women coming out of high school, so it can't be that technical. :wink:

http://jacquesricher.com/NEETS/14182.pdf

Here's the link to the complete course outline which covers basic electronics:

NEETS - Navy Electricity and Electronics Training Series

I also agree that the ARRL handbook is a good read but IMHO that is far more technical than NEETS.

Another guide book I've used is the US Marines version of the above but its focus is more on "field antennas." It's a bit more simplified with more practical drawings:

http://www.zerobeat.net/r3403c.pdf

Found another book that is very similar to the above PDFs:

http://www.apparentlyapparel.com/up...ical_antenna_handbook_fourth_edition_carr.pdf

rljames · May 1, 2015

Nick, Thanks for the references. I'll be sure to give them a look. (And simple is GREAT for me so I'll start with the Marine document!)

Boombox · May 2, 2015

If you're talking a digital portable SW radio -- I.e. a portable radio designed to work well off of the whip antenna -- balanced antennas and the like will do you little good. They'll just overload the radio's RF amp circuits.

However, if you get one of those radios, often clipping 20-30 ft of wire to the whip, or plugging in a 20-30 ft wire to the external antenna jack will help (if the radio you get has an external antenna jack).

Most digital portables are designed to work off the whip on Shortwave. Which usually means that unless you live in a low signal area, the radio's front end, RF amp circuit can get 'swamped' if you use a large antenna.

The RF transistors on most digital portables are designed to amplify the signals off of a short piece of metal (the whip) and a large antenna will deliver more signal than the RF transistors can handle without putting fake 'images' of signals on various places in the SW spectrum.

But if you get a radio capable of handling high-signal antennas, the ARRL antenna book and similar resources will help. Plus, there is a LOT of information on antennas on the internet.

If you can find one of the old William Orr books on antennas ("Simple Wire Antennas", etc.) on the internet they are very good -- easy to read, easy to understand.

ridgescan · May 2, 2015

Boombox said:
If you're talking a digital portable SW radio -- I.e. a portable radio designed to work well off of the whip antenna -- balanced antennas and the like will do you little good. They'll just overload the radio's RF amp circuits.

However, if you get one of those radios, often clipping 20-30 ft of wire to the whip, or plugging in a 20-30 ft wire to the external antenna jack will help (if the radio you get has an external antenna jack).

Most digital portables are designed to work off the whip on Shortwave. Which usually means that unless you live in a low signal area, the radio's front end, RF amp circuit can get 'swamped' if you use a large antenna.

The RF transistors on most digital portables are designed to amplify the signals off of a short piece of metal (the whip) and a large antenna will deliver more signal than the RF transistors can handle without putting fake 'images' of signals on various places in the SW spectrum.

But if you get a radio capable of handling high-signal antennas, the ARRL antenna book and similar resources will help. Plus, there is a LOT of information on antennas on the internet.

If you can find one of the old William Orr books on antennas ("Simple Wire Antennas", etc.) on the internet they are very good -- easy to read, easy to understand.

This is probably the best explanation of why a portable behaves the way it does just off the whip that I have seen other than when Majoco said as much in another thread.
My two cents; do you own a metal tape measure? if you do, you already have an external SWL antenna to use now. Attach an alligator clip to its end, connect that to the collapsed whip, reel it out across the room, and see what you get.
This is the original "reel" antenna.

Antennas 101?

rljames

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nanZor

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SCPD

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rljames

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Boombox

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ridgescan

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