Sunday, June 30, 2019

Radio circuit modules explained (with food containers)

I'm broadening The Daily Antenna to cover other facets of radio and electronics.

I hope you'll still find it of interest.

Here's two videos I did a while back explaining what the various stages in radio transmitters and receivers do.




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Saturday, June 29, 2019

My first pedestrian mobile magnetic loop

The link below is my first magnetic loop antenna for HF pedestrian mobile operation. Subsequent antennas I built have been more efficient. But this one, unlike the others, is made from flexible wire that can be folded up into a small package. 

Want more information? Read the description on my website.

Or watch the videos below (four parts):





Operating (to be fair this was when HF conditions were better)






PS: Into low power amateur radio? Minimum QRP is the top-selling manual on the equipment, antennas, operating and strategy of successful QRP operating. It's available for under $US 5 each in electronic form. Or you can get a paperback version. Visit VK3YE Radio Books to find out more. 

Friday, June 28, 2019

Fun with Neon bulbs

Neon bulbs have a particular allure. Only tiny amounts of current are required to light them. They were used to detect RF in high impedance circuits or parts of antennas. 

If you have a few lying around here's some experiments you can do with them. 



PS: Like something else to read? Books by Peter Parker VK3YE are read worldwide and have been favourably reviewed.  Available in both electronic and paperback.

Thursday, June 27, 2019

Ferrite rods for transmitting

We normally associate ferrite rods as receiving antennas in AM radios. However they can be used for transmitting as well. They're not the most efficient antenna but they're still worth playing around with. Especially since amateurs got access to bands below 500 kHz and the rise of efficient digital modes like WSPR. 

Here's some accounts of other peoples experiences with ferrite rod antennas for transmitting: 

* G3XBM's experiments

* US Dept of Interior report on ferrite rods for VLF mine communication antennas Also see this

* Vintage Radio discussion forum thread

* UA6CA & UA6ACA Antentop article

PS: Want to get more from low power amateur radio? Minimum QRP is what you need. This top-selling manual covers the equipment, antennas, operating and strategy needed to be successful with low power amateur radio. Available for under $US 5 as an ebook. Or in paperback form (some countries). Click here to find our more and to see reader reviews.



Wednesday, June 26, 2019

Loop receiving antennas for medium frequencies

Unlike for transmitting, you don't need very big antennas for receiving medium frequency stations. This is because most receivers (apart from crystal sets) are sufficiently sensitive. It's more important to minimise noise and interference from stations on the same or nearby frequencies than to maximise the number of microvolts being delivered to the receiver. 

Loop antennas are a popular choice. They comprise several turns of wire wound on an insulated frame. A variable capacitor resonates the loop on the desired frequency of reception. Maximum response is off the edge of the loop, with nulls broadside (like a magnetic loop but unlike a much larger quad loop element). 

A loop can turn even a mediocre transistor radio into an excellent receiver due to the additional signal, selectivity and directivity enabled. You don't even need a direct wired connection if the radio is placed inside the loop's field. 

Here are some MF receiving loop ideas: 

* Dave's home made loop antennas

* Bruce C's loop antenna page

WA1ZMS Loop for 500 kHz

VE7SL's new LF MF loop Also see Wellbrook Loop

My video demonstrating a loop made from a wooden coathanger

PS: Enjoy the Daily Antenna and my videos? Wish to support them? If so please store this link to Amazon Shopping as a bookmark or favourite. Then when you buy something I receive a small commission (at no extra cost to you). Or browse my books page to see if any titles appeal. 

Tuesday, June 25, 2019

Equipment and antennas for cave communications

The normal radio frequencies that we mostly use (MF, HF, VHF, UHF) are not very good for communicating with submarines in salt water or cave explorers underground. 


Instead much lower frequencies are used. These are around a few kilohertz. Antennas of a practical sized can't be very efficient due to the long wavelength. But they are still effective for their job which doesn't always require very long distances to be spanned (especially in caves). The latter may use induction loops or earth current systems. 

Here are some interesting articles on techniques and antennas for these frequencies: 






PS: Like something to read? Books by Peter Parker VK3YE are 
read worldwide and have been favourably reviewed.  Available in both electronic and paperback.

Monday, June 24, 2019

Slinky antennas

Many of us had or saw those metal toy Slinky springs as children.

Then when we got our ham licence we noticed the spring-like loading coils on antennas. Especially on mobile and portable antennas, the loading allowed antennas to be made smaller.

What if you could marry the two and operate the Slinky as part of a continuously loaded dipole or vertical antenna?

Performance is going to be a substantial compromise, but some hams have done just that. Read about their experiences here:

* Constructional article by F Dorenberg

* KB6NU's experiences

* Eham user reviews

* Video by W5CYF on building one

* Video by W1GV on how they work

To summarise they seem to be a curiosity rather than a serious antenna. But, especially for receiving they still have something to offer. If you've tried a Slinky antenna please leave comments below on your experiences.

PS: Want to read more about antennas? Consider this selection of antenna books. They are affiliate links meaning that I receive a small commission (at no extra cost to you) if you decide to purchase.
    

Sunday, June 23, 2019

KE4ERO's Hourglass loop antenna for VHF/UHF

Every month the ARRL's QST magazine makes one article free to read for non-members.

Sometimes it's an antenna article.

Designed by KE4ERO, this is a novel antenna for VHF and UHF bands.

It's very tall and skinny.

So it doesn't stick out as much as a beam might.

However it's horizontally polarised and exhibits some gain.

That's makes it suitable for VHF/UHF SSB operators, especially those in areas where most stations are in one line, eg up and down a coast or valley.


Read the Hourglass Loop Antenna article here (pdf).


PS: Like something else to read? Books by Peter Parker VK3YE are read worldwide and have been favourably reviewed.  Available in both electronic and paperback.

Saturday, June 22, 2019

A series and parallel antenna coupler with light bulb tuning indicator

This was one of the first antenna coupler projects I built. It was described by W9SCH in Sprat (and the G QRP Club Circuit Handbook). It's very simple, needing only one variable capacitor. It also covers a wide range, from 160 to 10 metres.

I built is nearly 30 years ago. Recently I fired it up to see if it still worked. It did! Not only that but it operated on more bands than I envisaged when I built it. It matched an end-fed 20m wire perfectly on all bands with only a slight difficulty on 40m (where the wire's impedance would have been very high). You could make it slightly shorter or longer to resolve that. 

This is my video describing and demonstrating it.




PS: Want to read more about antennas? Consider this selection of antenna books. They are affiliate links meaning that I receive a small commission (at no extra cost to you) if you decide to purchase.

    

Friday, June 21, 2019

Weird and wonderful indoor TV antennas from around the world

Some countries have television mostly delivered through cable systems. Or satellites. Here in Australia we still make heavy use of free-to-air television received via antennas on our homes. Or, if you're in a strong signal area, an indoor antenna may also work. 

The most common type are the rabbits ears that used to be supplied with many portable TVs. You can still buy them in the shops. Also common (in Australia) was a spiral type. This was basically a VHF dipole connected to 300 ohm ribbon. The spiral was springy metal that went around the dipole. I don't know if it did anything but it might have stopped children poking their eyes out with the ends of the dipole element.

We haven't seen those for about 20 years. But there have been other indoor antennas. The dearer ones sometimes had RF amplifiers to boost reception. Especially for non-radio types, how indoor antennas look is more important than how they perform. Something about fitting in with the household décor and not looking too out of place.

In that spirit, presented below are some weird and (not necessarily) wonderful indoor TV antennas to look at. 








Have you tried indoor TV antennas recently? What worked for you? And what didn't? Please leave any comments below. 

PS: Want to get more from amateur radio? This book can help. Available in electronic and paperback form, exploring the facets suggested will keep you entertained for hours. Find out more at vk3ye . com or search the title on Amazon. 

Thursday, June 20, 2019

Amp hour interview with Pete Bevelacqua (antenna designer)


Just one link today. An Amp Hour video with antenna designer Pete Bevelacqua. Listen to it here.

Pete's website is http://antenna-theory.com/ which is worth perusing.

PS: Want to read more about antennas? Consider this selection of antenna books. They are affiliate links meaning that I receive a small commission (at no extra cost to you) if you decide to purchase.




    



Wednesday, June 19, 2019

Antennas etched from printed circuit board material

While unfamiliar to most amateurs, one way of constructing antennas is to etch them on printed circuit board material. This approach is particularly good at UHF and microwave frequencies where antennas are a practical size. Although you could potentially use compact etched antennas at VHF frequencies if they were miniature types like magnetic loops or loaded dipoles.

Circuit board antennas have many applications for short range communication devices.  They are particularly suitable for compact low power radio equipment where users want the antenna concealed, small or both. 

You might not build any of these, but if you want some background on etched printed circuit board antennas, some reading is here: 


* Louis Frenzel article on PCB antennas

* Compact patch antennas on circuit boards in space (pdf by Min, Howland & Potts)

* Choosing circuit board for low PIM Antennas by John Coonrod

PS:Want to read more about antennas? Consider this selection of antenna books. They are affiliate links meaning that I receive a small commission (at no extra cost to you) if you decide to purchase.

    

Tuesday, June 18, 2019

Robust antennas for beacon and repeater sites

Yesterday we talked about antennas in snowy environments.

A common example is at hilltop beacon and repeater sites.

Antennas at such places need to be super robust and super reliable.

That's not just because of the extreme weather high sites experience. 

Reliable operation is essential for a beacon and (particularly) a repeater that may be used for emergency communication. 

Sites may be a long drive away for those who maintain them. 

They may be inaccessible in winter. 

If they are owned by other users, sites may be difficult to gain access to.

And commercial users will probably insist on commercial standard equipment and antenna installations. 

These considerations are paramount. They probably outweigh matters like antenna lightness, gain and low cost that are top of mind for those planning what to put up for casual operating from home.

There don't seem to be a lot of resources online for repeater and beacon antennas. But the one source I found, WA6ILQ repeater builders' antenna information, proved a goldmine. Alternatively you can get some inspiration from commercial manufacturers who make ruggedised antennas for use in or near the amateur bands.


PS: Enjoy the Daily Antenna and my videos? Wish to support them? If so please store this link to Amazon Shopping as a bookmark or favourite. Then when you buy something I receive a small commission (at no extra cost to you). Or browse my books page to see if any titles appeal. 

Monday, June 17, 2019

Ham antennas in the snow and ice

It very rarely snows in the towns and cities where most Australians live. But it does regularly in the high country. Which affects amateurs who live in such pockets (possibly to exploit the altitude) or who build and maintain repeaters and beacons in such locations. And snow is widespread in parts of North America, Europe and Japan where many readers live. 

Some antennas are better than others when it comes to endurance under snowy conditions. Then there's ice. The weight of that can easily weigh down and break antenna elements. 

Here's some experiences and tips from people who have had to encounter snow and ice in their antenna installations or operating: 


* W1GV video on snow and ice on antenna feed lines

* Question and answers on ice affecting a dipole's VSWR indication

* Stopping snow static by Joseph Kopeczy

* Operating in cold weather by KB9VBR

PS: Enjoy reading? Here's some books that might appeal. Enjoyed all over the world you can find out more from my website VK3YE Radio Books

Sunday, June 16, 2019

Bamboo's uses in antennas

It really made me envious. I was holidaying in a subtropical city walking through a park. I came across some stands of bamboo. Really tall.

I wanted to break off a few pieces and carry them  home. The only problem is I'd have to carry them over 1000km. The airline would have something to say if I tried to take them as oversized luggage. That would only be the start of it as no car, taxi, train or bus home could accommodate them. 

So if you live in an area where bamboo is common count your lucky stars. It can be super versatile for antennas. Sure, it might not be the longest lasting material or have the best RF properties but it's light and cheap. Many an island DXpedition has succeeded because its operators lashed together a bamboo and wire beam that, together with the excellent location, can provide world-beating signals. 

So what might you use bamboo for? The most obvious is some sort of antenna mast. You're not going to support a heavy metal beam and rotator with one or even a few lengths. But it would be fine for wire antennas, such as fixed direction wire yagis or quads. Or if you wanted to make the latter rotatable it could form quad spreaders. 

Verticals and ground planes is another use, with the bamboo forming a guide for the wire. Although for the latter it's probably better to not have too much of the wire running right along the bamboo, especially at high voltage points. Using the bamboo as a former for some sort of helical element or loading coil also sounds a bit chancy for me. 

Here's some ideas and articles where people have succeeded in using bamboo or related materials in antenna construction:

* 5 band ground plane vertical antenna by HC/W4BWS




Have you tried bamboo supported antennas? Or ones where wire elements were held in place with bamboo? Please share your experiences below. 

PS: Want to read more about antennas? Consider this selection of antenna books. They are affiliate links meaning that I receive a small commission (at no extra cost to you) if you decide to purchase.

    

Saturday, June 15, 2019

Homebrew radio astronomy antennas and equipment

An intriguing branch of radio spectrum exploring is radio astronomy. 

It's cheaper than it used to be and it doesn't require a lot of equipment. 

These items that could be helpful if you wish to get into it: 

* WA8SME QST article on building a radio telescope (pdf)

* Marcus Leech Radio Astronomy with an RTL SDR

* Amateur Radio Astronomy by F5VLB

* Joachim Koppen's Fundamentals of Radio Astronomy

* Build your own Radio Telescope by Bogusław Malański & Szymon Malański

* Mike Brown's radio telescope


PS: Like something to read? Books by Peter Parker VK3YE are read worldwide and have been favourably reviewed.  Available in both electronic and paperback.

Friday, June 14, 2019

Antennas and transmitters used for animal tracking

Amateurs have to be innovative with antennas because we normally have less budget than commercial radio spectrum users. And our communication needs are different, with a general preference for DX communication at low to medium transmit powers. Available space may be limited and we might want one antenna to work on several  bands.  

It's interesting to read about other radio users. They have a whole different set of requirements for antennas. Some are tougher than what we hams have to design for. 

One example is antennas used for animal tracking. These would normally be attached to a VHF or UHF transmitter. The antennas need to be inconspicuous and not harm the animal's life or movement. 

Here are some items on antennas (and transmitters) for animal tracking you might find interesting:

* Wikipedia item on wildlife radio telemetry

* Telonics . com product range of tracking devices

* ATS Systems Australia animal tracking

* Perdix radio tracking tags

* Biotrack radio telemetry

* Use of UHF modules for animal tracking (pdf)

Have you used any of these? Or even built some? Please let me know your experiences below.

PS: Want to read more about antennas? Consider this selection of antenna books. They are affiliate links meaning that I receive a small commission (at no extra cost to you) if you decide to purchase.

    

One hour in the 2020 Summer VHF/UHF Field Day

This is about the most basic setup you could have. Five watts of 144 MHz SSB only with a 2 element yagi at not much higher than sea level. ...