Thursday, October 31, 2019

27 MHz walkie talkie history

Here's a great article on the history of cheap 27 MHz walkie talkies in the US. 


Basically they started at 27 MHz then went up to 49 MHz to get away from interference from the then-booming 27 MHz CB radio service (though some of us would have preferred intercommunication with CBs!). Later UHF became cheaper. The USA have the Family Radio Service around 460 MHz while the Europeans have something similar around 446 MHz. 

Development was a bit different in Australia. They started on 27.240 MHz in the late 1960s. Often single channel 'handphones' with maybe 100mW output. You needed to have a licence and a genuine purpose to use them. And back then CB radio was illegal (27 MHz was then an amateur band). Pirates either used amateur gear or increasingly common mobile type transceivers (which were often crystal controlled with a few channels). 

We got a lot of imported models. They typically had a few crystal controlled channels and were licensed as CB radios. They were the size of a brick with a large antenna, a superhet receiver and squelch. 

There were also cheap ones that kids often got as presents. In the late '70s they were on a CB channel with a crystal soldered in (often 27.125 MHz or ch 14). These didn't need a licence as they were low power. They often had a hissy superregen receiver. You could directly talk to CBers but a problem was their receivers were so broad that they'd hear pretty much anyone on the band. So you wouldn't know if they were on your channel or not. But you could still talk to an AM CBer if they were on Channel 14. 

Later on, around 1980, the walkie talkies went off the CB channels. But unlike in the USA they still stayed on 27 MHz. 27.145 MHz was the most common frequency, shared with remote controlled toy cars etc. It was the worst of both worlds - their broad receivers were still susceptible to hearing 27 MHz activity but they couldn't hear you to have a conversation. Although that might have been a benefit for anxious parents worried about kids talking to truckies and others prowling the CB airwaves. 

A few walkie talkies for 29 MHz FM (just above the amateur band) were sold here. Also 55 MHz, especially by Tandy. And more recently UHF has got cheaper so that's where they've ended up. Australia was a pioneer with UHF CB (477 MHz) and once again cheap walkie talkies can communicate to CBs, reinstating the brief link that was broken after the brief 27.125 MHz years of the '70s.  

Getting back to 27 MHz, these videos are a bit more on cheap handhelds. 

The handheld below is an early '80s model sold by Dick Smith Electronics. I converted it from 27.145 MHz to 28 MHz amateur (as I had a crystal). But later, after the video was done, I converted it back. 


These are really cheap ones. Not even a crystal. You could shout further. Still if you're into bare bones electronic design they could be interesting.


Here's a comparison I did between 1970s, 80s and 90s walkie talkies. Older is better!


What were your early walkie talkie experiences? Please leave them in the comments below - I'd enjoy reading about them!

PS: Interested in 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, October 30, 2019

Receiving G4AKC from VK on 7 MHz

The warm weather is back so I've been at the beach. Didn't make any contacts but heard G4AKC working various other VK and ZL stations on 7 MHz. Here's some audio.


PS: Are you interested in portable antennas? If so this book could be just what you need. Available as an ebook or in paperback you can find out more here





Tuesday, October 29, 2019

Building electronics from schematic diagrams

Never done it? It's satisfying! Some tips in this video with a simple project to try.


PS: Ever find a term in amateur radio you don't understand? The Illustrated International Ham Radio Dictionary can help. Available as an ebook for $US 5 with paperback also available. Details in the link.

Monday, October 28, 2019

My final stage is 24 IN4148 diodes!

I've always wanted to transmit with a rig with no transistor (or valve) final amplifier stage. Yesterday I did it using a diode balanced modulator connected must before the antenna. Admittedly it was only a few milliwatts and it was WSPR but the signal was detected thousands of kilometres away. 

More in the video! 


PS: Interested in 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, October 27, 2019

VK5SFA on magnetic loops (QSO Today podcast)

Those who have seen my videos will know I've done a bit with magnetic loops. However mine have mostly been lightweight types for QRP and portable operating. If you want to build an efficient loop for home station high power operating you'll need something more solid. One of those who has built such a loop for 80 & 160m is Steve VK5SFA who won a QST magazine award for his design. 

Enjoy this QSO Today interview with Steve where, later on, he describes his experience with loops. 


PS: Are you interested in portable antennas? If so this book could be just what you need. Available as an ebook or in paperback you can find out more here


Saturday, October 26, 2019

Where can you see to?

Want to know where you can see to?

That's handy for planning operating location for VHF field days or microwave records.

Or maybe you wish to plot the path between you and another station so you can see if there are mountains in the way.

That's all possible with the Hey What's That website: http://heywhatsthat.com/

You'll be hooked!

PS: Want to do more with amateur radio? 99 things you can do with Amateur Radio is full of ideas. Available as a low-cost ebook or in paperback, you can find out more here



Friday, October 25, 2019

Fun with circuit bending

An off-beat diversion from radio when the bands are crook is to get a bit of consumer electronics and see if you can make some odd sounds from it. 

One can make an amplifier into an oscillator by adding some positive feedback. Even a pair of sweaty hands can do it. Of course for safety's sake one should only do this with battery powered gear. 

Another thing you can do is get an electronic toy and connect resistors and capacitors across various parts of the circuit. You'll get some interesting sound effects. Especially if you add variable resistors, light dependent resistors and more. 

Anyway here's a few videos on circuit bending I've done. 







PS: Are you interested in portable antennas? If so this book could be just what you need. Available as an ebook or in paperback you can find out more here

Thursday, October 24, 2019

Comparing various simple antennas for 144 MHz reception

I've been trying some simple antennas on 2m lately. There's not a lot of difference between them in the performance stakes. But I though it was worth testing reception of a CW beacon about 400km distance during a band opening. 

The antennas featured are a dipole, a 2 element yagi, an oblong loop (1 wavelength perimeter) and an hourglass (2 wavelength perimeter with two loops). 




PS: I've now written six books on various aspects of amateur radio. Whether you experiment with antennas, enjoy QRP or are starting out in radio there's a book for you. Find out more here.

Wednesday, October 23, 2019

OWA Yagis

When I was younger I noticed that most yagis had approximately equal spacing between the elements. 

More recently I've noted very different spacing patterns. For example the outer directors were very widely spaced while the first director was not far from the driven element. 

And when I was experimenting with a 4 element beam for 2m directly fed with 50 ohm coax I found I could get a match with wide bandwidth with this narrow driven element/first director spacing. On 144 MHz this spacing is about 10cm or 0.05 wavelength. 

Only recently did I find that these types of yagis had their own name - Optimised Wideband Array or OWA for short. 

They are easy to feed and have a good bandwidth. The main compromise is you lose a small amount of forward gain. 

Anyway here's some OWA links you might find handy for your next antenna project. 




PS: Are you interested in more portable antennas? If so this book could be just what you need. Available as an ebook or in paperback you can find out more here

Tuesday, October 22, 2019

Introduction to Amateur Radio (video)

Know someone who has expressed interest in amateur radio?

Refer them to this video.

Professionally produced, it tells people a little about what we do.



PS: Want to do more with amateur radio? 99 things you can do with Amateur Radio is full of ideas. Available as a low-cost ebook or in paperback, you can find out more here





Monday, October 21, 2019

Hourglass Loop Antenna for 144 MHz SSB and WSPR

Described nearly a year ago in QST I finally got around to building one. With some great results.

Ideal if you want a horizontally polarised antenna in a tight space with a little gain.


PS: Want to do more with amateur radio? 99 things you can do with Amateur Radio is full of ideas. Available as a low-cost ebook or in paperback, you can find out more here




Sunday, October 20, 2019

Retro review: Handbook for Radiotelephone Ship Station Operators

It's amazing what you can find in a charity shop for 50 cents.

A book on ships radio operating procedure. How could I not buy it? Anyway here's my review with some distress traffic interspersed.



PS: I've now written six books on various aspects of amateur radio. Whether you experiment with antennas, enjoy QRP or are starting out in radio there's a book for you. Find out more here.


Saturday, October 19, 2019

Not all BNC connectors are equal

I think I've featured this before but here's a reminder for almost everyone who experiments with RF!



PS: Heard about my new book? It's Australia's own amateur radio handbook. Available in both electronic and paperback form, you can find out more here

Friday, October 18, 2019

Simple two metre to VHF airband receiving converter

Some receivers cover VHF airband but not 2m FM.

This simple and crude one transistor converter works surprisingly well. More in the video.


PS: Want to do more with amateur radio? 99 things you can do with Amateur Radio is full of ideas. Available as a low-cost ebook or in paperback, you can find out more here








Thursday, October 17, 2019

Yahoo Groups Closing - save needed files!

Not a regular blog post but something still worth knowing for those who read and save technical information, circuits, construction accounts, pictures and sound files.

Way before Facebook people used Yahoo Groups to exchange ideas. These groups had file sections where people put circuits, notes and recordings of their projects. Anyway Yahoo is closing their groups down and will shortly be deleting files, with data gone forever.

So you may wish to visit groups of interest and save what you can. Here's a few groups I've enjoyed:



At least some groups have already moved to another provider (groups.io is very popular). 

PS: I've now written six books on various aspects of amateur radio. Whether you experiment with antennas, enjoy QRP or are starting out in radio there's a book for you. Find out more here.




Wednesday, October 16, 2019

K1YPP magnetic loop does three bands

Nothing from me today but I know many readers like magnetic loops.

Here's a nifty design for a home station loop from K1YPP.

It does three bands and, unlike many designs, is good for a decent amount of RF power.

I think you'll like the way the capacitor is done.


PS: Are you interested in more portable antennas? If so this book could be just what you need. Available as an ebook or in paperback you can find out more here




Tuesday, October 15, 2019

Electronics on an OBike

A year or two ago Melbourne had a dockless bike share scheme. A foreign company dumped hundreds of bikes on our streets and tried to charge people to use them through their app. It didn't work; anyone who seriously wants to cycle has their own bike, we have mandatory helmet laws and, as far as traffic and cycling conditions go, we're no Amsterdam. 

The company went bust and the bikes had no owner. Those that didn't end up in the river ended up in private hands. This is how I came to acquire mine. 

The only problem was hacking off the electronic locking system so the bike could be ridden. That wasn't too hard.  Anyway if you enjoy electronic tinkering you might enjoy what I found on my OBike in these videos.  






PS: Heard about my new book? It's Australia's own amateur radio handbook. Available in both electronic and paperback form, you can find out more here

Monday, October 14, 2019

CW vs SSB: How do they compare?

We know that CW gets through better than SSB under noisy or weak signal conditions but how much better is it? 

Here's a test where I used a web SDR to compare by signal while switching between modes and power levels. The SDR was about 700km away. I did the test on 7 MHz under poor band conditions during the middle of the day. 




PS: I've now written six books on various aspects of amateur radio. Whether you experiment with antennas, enjoy QRP or are starting out in radio there's a book for you. Find out more here.

Sunday, October 13, 2019

Kitchen foil hula hoop loop

Another magnetic loop! Covers 21 - 30 MHz.



PS: Are you interested in more portable antennas? If so this book could be just what you need. Available as an ebook or in paperback you can find out more here

Saturday, October 12, 2019

Kit suppliers and ideas

Many of us like to build stuff. And there's a great thrill from getting results you've put together yourself. However not everyone wants to design or build something from scratch. And the cost isn't necessarily cheaper than buying a kit where you've also got the benefit of better documentation and a proven design. 

Here's some tips on kits you could build. It's one of my pages about QRP equipment options. But scroll down and you'll find links to kit suppliers that could be worth browsing. 

http://home.alphalink.com.au/~parkerp/qrp/equipment.htm

PS: Want to know more about QRP? You need Minimum QRP. It's a top selling manual on success with low power amateur radio. Available in ebook or paperback formats you can find out more here

Friday, October 11, 2019

How to write an article for a magazine

Once completing a project it's good to share your experience with others. Because at any one time there will be others wanting to try it or something similar. Options for sharing including making a video, writing a forum post, saying something on Facebook, or, if you want something more enduring, writing a magazine article.

This popular (but highly disliked) video, tells you how one might approach this.


PS: Are you interested in more portable antennas? If so this book could be just what you need. Available as an ebook or in paperback you can find out more here



Thursday, October 10, 2019

Closure of an electronics shop - Truscotts of Melbourne

The rise of software over hardware, increasing shop rents and online ordering from China has made the independent electronics shop a threatened species. Here in Melbourne we're luckier than most cities. We still have outlets from the Jaycar and Altronics chains, and there is still Rockby

But until a month ago there was also Truscotts Electronic World in Croydon in Melbourne's east. As well has stocking the usual parts there were also hard to get items like RF ICs and variable capacitors. Along with various surplus stuff. Enjoy these pictures as I go for a walk through back in July. 


PS: Heard about my new book? It's Australia's own amateur radio handbook. Available in both electronic and paperback form, you can find out more here

Wednesday, October 9, 2019

Fun with ring modulators for inverted SSB and crazy audio

Have a receiver that only receives upper sideband signals but wish to receive lower sideband transmissions (eg from hams) on it? Here's something that can  help. It's a sideband inverter. Because it operates at audio there's no internal modification to your equipment needed. And if you wish to transmit on the opposite sideband you could use it in reverse as well. 

The unit uses a diode ring modulator made with two transformers. And an audio oscillator at 3 kHz. Find out more in this detailed video here: 



PS: I've now written six books on various aspects of amateur radio. Whether you experiment with antennas, enjoy QRP or are starting out in radio there's a book for you. Find out more here.


Tuesday, October 8, 2019

Two ground tuning units for portable antennas

A ground tuning unit is sometimes useful for vertical antennas. 

Especially those over or near salt water. 

The first one was when I was trying pedestrian mobile antennas for walking along the beach. It worked but changing ground conditions meant its settings varied when I walked over different patches. I eventually reconfigured it to an L-match antenna coupler that became the basis for the Wadetenna I've used for hundreds of pedestrian mobile contacts. 


This is a beefier version that could handle more power. It's a much more recent project. It's just the thing if you want to set up antennas for operating from piers.


PS: I've now written six books on various aspects of amateur radio. Whether you experiment with antennas, enjoy QRP or are starting out in radio there's a book for you. Find out more here.

Monday, October 7, 2019

Street finds 2019 - more pickings from the kerb

Some more finds from the street. Not as much as before but there was a 27 MHz CB walkie talkie. I give it an overhaul and do a range test. How far does it transmit? Find out in this video.




PS: Are you returning to amateur radio after a spell away? If so this book might be just the ticket. It fills you in on what you missed and brings you up to speed with activities modern hams enjoy. Available in electronic or paperback form you can find out more here

Sunday, October 6, 2019

Street finds 2019 - pickings from the kerb

Join me as I prowl the streets for thrown out electronic bits and pieces. Do I find anything useful? Does anything work? Are items fixable? Watch and find out!


PS: These books are so rare you'll never find these on the street. And their owners will never wish to part with them. I've now written six books on various aspects of amateur radio. Whether you experiment with antennas, enjoy QRP or are starting out in radio there's a book for you. Find out more here.


Saturday, October 5, 2019

Using salt and vinegar to clean corroded connections

I've probably mentioned this before but it's still a technique you rarely see being written about.

Salt and vinegar is more useful than just putting on chips.

And the video is really popular with about 40 000 views.

So here it is!


PS: Want to do more with amateur radio? 99 things you can do with Amateur Radio is full of ideas. Available as a low-cost ebook or in paperback, you can find out more here


Friday, October 4, 2019

Loop tuner loads up 2 metres of coax cable as an antenna

Everyone loves magnetic loops and magnetic loop videos. At least that's what the stats and comments tell me. Anyway here's another. I'm using the magnetic loop tuner described before but with a short length of coax. Only 2m. That allows resonance on 7, 10 and 14 MHz.

But just because you can get resonance doesn't mean that results will be good as you'll see here.



PS: Heard about my new book? It's Australia's own amateur radio handbook. Available in both electronic and paperback form, you can find out more here


Thursday, October 3, 2019

Australian pirate radio examples

Pirate radio broadcasting is rare in Australia. I've only ever heard one. Older people may have heard several. Reasons for its rarity could be our sparse population density and long-standing tradition of commercial broadcasting; something less common in more highly regulated European countries. 

Anyway enjoy these accounts of local pirate activity.

1970s: Radio FU2 transmitted on 27 MHz (before CB was legalised). This is Part 1. It's continued in Parts 2, 3 & 4. Coarse language and controversial themes.



2007: Tim Wong See. Led to a career in commercial and ABC radio. 
2017: Broadcast after the shut down of Radio Australia on shortwave


Have you ever heard pirate broadcast transmissions? If so please leave your comments below.

PS: I've now written six books on various aspects of amateur radio. Whether you experiment with antennas, enjoy QRP or are starting out in radio there's a book for you. Find out more here.


Wednesday, October 2, 2019

Uses for a two dollar MP3 player in amateur radio

Incredibly cheap and incredibly useful. I'm talking about very low cost MP3 players. Watch the video for some ideas on how you can put them to use around the ham shack. 




PS: Want to do more with amateur radio? 99 things you can do with Amateur Radio is full of ideas. Available as a low-cost ebook or in paperback, you can find out more here

Tuesday, October 1, 2019

Nocturnal transmitting with the 80 & 160m coaxial magnetic loop

Yesterday we featured a magnetic loop, made from 15m of coaxial cable, that worked on 80 and 160 metres. I was using it during the day which limited transmitting range. Last night I went out to see what distances I could get when it was dark. Here are my results. 


PS: Are you interested in more portable antennas? If so this book could be just what you need. Available as an ebook or in paperback you can find out more here


[Article] Batteries for QRP gear

The March 2020 issue of QST has an article on batteries for QRP rigs that some of you might find interesting.  Even better is it's...