Saturday, August 31, 2019

Direct conversion receivers

One of the simplest type of receivers for practical amateur band listening is the direct conversion type. There's only a few stages: A local oscillator, a product detector and an audio amplifier. Better receivers have extras like RF amplification and audio filtering. 

The simple type of direct conversion receiver has only one main disadvantage compared to the superhet. Its selectivity. It responds evenly to signals both above and below where the set it tuned to. This gives it a selectivity double that of a superhet. It can mean that on a crowded band you hear more signals than are actually there because you are hearing everything twice, at two spots on the dial. 

You can overcome that either by using the direct conversion receiver as the back end of a superhet and using some RF filtering before it (eg a crystal filter) or make the direct conversion set more complex by incorporating phasing techniques to remove reception of the undesired sideband. 

Even if you don't do that the direct conversion receiver is still very useful, especially for homebrew QRP gear. A major advantage is you can use the local oscillator to form a CW transmitter. That's easy with the only thing required being to shift its frequency down by about 800 Hz on transmit and provide adequate buffering, amplification and keying for the transmit section. 

Here are some demonstrations of direct conversion receivers. 

Portable 40/20m DC receiver

A more complex direct conversion receiver - built quite a few years back

CW receiving with an unfinished DC receiver

Have you built a direct conversion receiver? If so please leave your comments below. 

PS: Heard about my new book? It's the Australian Ham Radio Handbook. It's now available both as an ebook and paperback. Find out more here!

Friday, August 30, 2019

Success with Milliwatting

QRP is normally thought of as running 5 watts or less (sometimes 10w on voice modes). If that isn't enough of a challenge there's always milliwatting. That's common for WSPR experiments but less common for modes like CW and SSB. Yet it's possible to cover hundreds if not thousands of kilometres with milliwatts of power if the conditions are right and your antenna is efficient. 

Here are some video demonstrations of milliwatt communication. 

VK5PAS reception of me running 200mW SSB on 40m

USB-powered milliwatt homebrew transmitter test

Running milliwatts during a field day contest

PS: Enjoy reading? Consider this selection of amateur radio books I have written. They are available in ebook or paperback. The most useful for milliwatting would be 'Minimum QRP'. 


Wednesday, August 28, 2019

Low frequency radio listening

Lower in frequency than the AM broadcast band is the low frequency (or long wave) band. The main use for this part of the spectrum in Australia is aircraft navigation beacons (NDBs), which transmit in the 200 to 480 kHz range. These beacons transmit their callsign (which is a two or three letter abbreviation of their location) in slow morse code, with a few transmitting voice weather information in AM. Hundreds of beacons are active; during a recent evening listening test in suburban Melbourne, some eighty were heard, some as far away as Kalgoorlie and Mt Isa, with just a small ferrite rod loopstick as an antenna. More recently some have shut down. However there are some new users of the LF and MF bands, with radio amateurs recently gaining allocations around 135 and 472 kHz.

These videos show reception of scans of NDB and amateur stations on frequencies below 500kHz. I'm using a home-made upconverter that shifts LF signals to a segment above 4 MHz. This converter contains a ferrite rod which operates as a directional receiving antenna. The videos include reception of amateurs and NDB beacons, some of which have ceased transmitting.

PS: Enjoy reading? Consider this selection of amateur radio books I have written. They are available in ebook or paperback. 


Tuesday, August 27, 2019

Testing opposite sideband rejection with a mobile phone

One of the important things when building SSB transmitters is opposite sideband rejection. You don't want to be causing interference to people on adjacent frequencies. And, if the crystal filter section is shared with the receiver, you won't want to suffer adjacent channel interference due to your receiver's poor selectivity. 

Here's a video where I use an audio spectrum analyser app to test the opposite sideband rejection of a homebrew SSB rig. 

PS: Heard about my new book? It's the Australian Ham Radio Handbook. Find out more here!

Monday, August 26, 2019

Introduction to amateur radio contesting

A major amateur radio interest is contesting. Whether your favourite activity is HF or VHF, Morse, phone or digital modes, there's sure to be a contest for you.

So what is a contest? A contest is an organised event where participants make as many contacts as possible within a given time. Apart from being an exciting and absorbing activity in its own right, contesting allows you to test the efficiency of your station together with your operating skills.

Contesters keep a record of the contacts they make and send it to the contest manager afterwards. The contest manager checks the logs and submits the results to be published on the organiser's website. Several months later the top scoring stations get a handsome certificate in the mail for their efforts.

Why do people enter contests?

People enter contests for various reasons. Some hams are driven by a competitive urge to be number one. They get a great buzz out of pitting their station and operating skills against others around the world. Those who wish to talk to as many countries as possible and collect QSL cards for one of the many operating awards on offer find that international contests bring out rare stations not active at other times. Others use contests to test the effectiveness of a new piece of equipment or antenna because of the large number of stations on air.

Types of contests

There are contests for all types of operators. Some are single band and single mode, while others are multi band and multi mode. The length of contests varies, from under an hour to as much as four weeks. Most major contests, however, run for 24 hours. The pace of operating ranges from relaxed to hectic.

Choosing a contest

A comprehensive list of coming contests is given in the monthly amateur magazines and on national society websites (ARRL, RSGB, RAC, WIA, NZART etc). Rules are also published there.

There are several big international contests, for instance the CQ World Wide and ARRL DX Contests. These are the real serious ones. Then there are country or state specific events. The operating pace is a bit slower and they provide a great opportunity to work many stations in a particular area. There are big and small contests to enter every few weeks if you are such inclined.

As an example here in Australia we have:

* Remembrance Day Contest (August) - Australia's biggest contest. States compete for RD Trophy. Highly recommended.
* Oceania DX Contest (October) - An opportunity for overseas stations to work Australia and New Zealand and vice versa.
* VHF/UHF Field Days (Spring, Summer and Winter) - Chances to go portable on the VHF/UHF bands. Activity is mostly SSB with a little FM.
* Ross Hull VHF/UHF Contest (December/January) - THE contest for the serious VHF/UHF DXer and microwave enthusiast. Most activity is SSB rather than FM. The contest runs for weeks and is more a marathon rather than sprints like the VHF Field Days.
* John Moyle Field Day (March) - Portable operating on all bands. Great fun!

Other groups also run contests. For example, the VK QRP Club has its QRP Hours Contest. Some clubs also have their own contests or scrambles. All these are excellent contests for beginners, as the pace of operating is fairly slow and/or the contest period is short.

DX contests that give extra points for prefixes worked are particularly good for those in less populated countries as it puts you in demand. However, participation in these events is suggested only after you have gained experience in one or more of the smaller local contests.

Making your station contest-ready

There are several aspects to consider when setting up a contest station. These include:

* Efficient equipment. Transceivers with intermittent faults have no place in the fast-paced environment of a major contest. Either fix it or use another rig. Equipment attributes such as receiver dynamic range, variable selectivity (especially on CW), punchy but clean speech processing, low levels of internally-generated receiver noise, and fast transmit-receive switching will all aid HF operating. A big linear amplifier is not a prerequisite for a successful contest operation; even homebrew QRP rigs can do quite well in contests provided that they are not the ultra-simple 'bare bones' types that omit desirable features such as VFOs, audio filtering, sidetone, easy transmit/receive switching, etc. On VHF and UHF FM set your equipment to tune in 25 kHz steps and have the most popular simplex frequencies in memory to allow quick frequency changes when required.

* Reasonable antennas. You should get some contest contacts with almost any antenna, but to win, good antenna performance is a must. Receiving performance is as important as transmitting performance - you need to hear them to work them. If noise is a problem in your area (particularly on the lower HF bands) you may need to consider a separate antenna for receiving, such as a rotatable magnetic loop. Generally speaking, however, simple dipoles and verticals are entirely adequate for the station not expecting anything more than an average score in Australian contests.

* Freedom from interference. There is nothing worse than having to shut down because of a TVI complaint in the middle of a contest. Do some operating in the week prior to the contest to assess band conditions, station performance and to establish whether TVs in the neighbourhood will be affected by your activity.

Interference to your station is just as important - ensure others are not using appliances that cause interference while you are operating. If you plan to use a computer log, do a test to ensure that the computer does not spoil reception. If there is any degradation of receive performance, use a paper log instead.

* Station layout and operating position. All frequently used equipment should be within arm's reach of the operator. Antennas should be controllable from the shack, so that the contester doesn't have to go outside to change them. Band changing should be easy and quick. If using HF, it is desirable (but not essential) to have a second transceiver or communications receiver handy so you can monitor WWV or scan other bands for activity while operating. The operating table should have plenty of room for writing if a manual log is to be used. Comfort is important as you will be at the radio for several hours at a time, so invest in a good swivel chair and ensure that both it and the table are at a comfortable height.

Preparing for the contest

Before the contest read the rules and consider which section and category to enter. Depending on the contest, there may be a choice of phone, CW or open modes, VHF, HF or all band and various operating periods. Not all contests have as many sections as this - some have the CW and phone sections as separate contests on different weekends. Factors such as station location, equipment and bands available, likely propagation, and time available will influence the section chosen.

Decide whether to use electronic or paper logs. If electronic (most popular and now essential for club entries) download and familiarise yourself with the logging program (eg VK Contest Log ) and ensure your computer and transceiver co-operate (computers can interfere with HF reception and be affected by strong RF fields). If paper logs, make sure your pens are working and rule up (or print off) sufficient log sheets.

Have a realistic expectation of what you can achieve in a contest, taking into account factors mentioned above. As an example, a low power operator well outside the major cities may be disappointed with how few contacts they get in a VHF contest if they were hoping for a competitive score. On the other hand, someone who decided that their main aim of entering the contest was not to make a large number of contacts, but to confirm that they could be heard by city stations on a new antenna they have built could come away from the contest with their expectations satisfied. The country operator aiming for the big score might have been better off to work HF instead.

Particular contest rules can skew operating patterns and influence activity. An example some contests may reward different prefixes, countries or grid squares while others are a flat one point per contact (which is good for those in densely populated areas).

Geography makes a difference. Even if only a mediocre antenna was being used, a low power station with many amateurs 300 - 1000km away should do quite well on 80 and 40 metres. In contrast, the same station with a similar antenna in a remote area 2000km from the main centres would find things difficult. If they wish to persist with HF they may be better off on higher bands like 10, 15 or 20 metres, bearing in mind that conditions on them can be volatile.

The lesson of these examples is to consider your circumstances and how the rules and scoring system will affect your activities. Last year's results can give a guide to the relative popularity of contest sections and the scores you need to get to be competitive. If no one entered a particular section last year, try it this year - the chances are that you will be the only entrant and get a certificate.

Know the capabilities of your station. Your normal operating should provide the information needed, including the directions most and least favoured by your location and relative performance on various bands. A good opportunity to check this is to note the signal reports given when several locals are calling a distant station. If the signal reports you get are consistently weaker than for most others, your operating procedure will be different than if you are one of the louder stations.

In the hour before the contest, read the rules, look at propagation charts and check the operation of antennas and equipment. Ensure that you have sufficient pens, paper, and log sheets available.

During the contest

The big hand is approaching the twelve on the station clock, and, with microphone in hand, you're poised to make your first contact in your first contest. So how do you get contacts during contests? There are two main ways. Either scan the band looking for stations calling CQ ('search and pounce'), or put out calls yourself. The tactic chosen depends on things like band activity, propagation and the capabilities of your station.

Beginners should use the 'search and pounce' method for their first several contacts. Then later on, after you've worked all the stations calling, put out CQ calls yourself.

Making calls allows stations tuning across the band to find you and give you a number. This can significantly boost the number of contacts obtained. The reason for this is that during a contest there are all types on the band, from the die-hard contester to the station who says they're not really in the contest, but are happy to give out a few numbers. Many of these less serious participants won't put out calls themselves, but will respond to stations calling CQ.

I mentioned before that operating tactics are shaped by station capabilities. This is because people often prefer to answer CQ calls from stronger stations. A weak station on SSB with two strong stations either side may not easily be noticed by people listening. Also, strong stations can 'hold' a frequency, and ward off those who may be tempted to stray too close to it, but weaker stations may not be able to do this when the band is crowded.

If you're a weaker station it's best to use the 'search and pounce' technique most of the time, especially during the bigger DX contests when the bands are busy. Carefully scan the band for stations who are calling but haven't been worked before. Even if a calling station is weak, give them a call anyway - they may be using low power or have an antenna worse than yours. When calling, just give your own callsign - the other station already knows theirs!

Notwithstanding the above paragraph, weaker stations should not give up calling CQ altogether. If conditions seem reasonable but there are few stations around (common during less popular times eg early morning or late at night), you will work no one if you just listen. Put out calls yourself - if your signal is readable, people tuning across will call. As was mentioned before, calling CQ attracts many of the types tuning across the band who you'll never work if you only answer other people's calls.

Contest contacts are much shorter than other amateur radio contacts. All you need to exchange with the other station is a five or six digit number, consisting (usually) of a signal report followed by a serial number starting at 001. This serial number increases by one for every contact you make, thus you might send 57003 to the third station you work in a contest. Repeat this if your signal is likely to be weak at the other end. An example of a typical contest exchange is given below. The pace of operating varies between contests. When it's fast and frantic, just give the signal report and number. When it's slow, some people will tell you their name and location as well. Conciseness is particularly important when signals are weak or if using CW - 5wpm is excruciatingly slow for most CW operators, and you'll win the thanks of many if you just send the bare minimum of information the contest rules require.

While operating, fill in a log sheet. This should show date, time (UTC), band, mode, callsign, number given, number received and points. Try to keep it legible - the Contest Manager may need it when he is checking logs.

A typical contest exchange

The following is a typical example of a phone contest exchange between VK3AA and VK6AA.

{VK3AA seeking a contest contact}

(VK6AA): VK6AA {VK6AA responds}

{VK6AA's signal is 5/7, VK6AA is VK3AA's eleventh contact in the contest}

{VK3AA's signal is 5/8, this contact is VK6AA's first in the contest}

. {Contest contact ended successfully and both stations enter the contact in their logs. VK3AA continues calling CQ, while VK6AA looks for other stations calling CQ}

On CW, the procedure is similar, except there is a heavy use of abbreviations to save time. Very often, nines are sent as 'N', and zeroes as 'T'. Thus, the first station you work might receive a '5NNTT1' number from you, which is the equivalent of a 59001 report on phone.

Contest videos

Watch these to hear contesting in action.

PS: Do you sometimes come across terms that you're unfamiliar with? The Illustrated International Ham Radio Dictionary can help. Available in both ebook and paperback it's great value. Find out more here

Sunday, August 25, 2019

The joys of AM transmitting

Voice transmission techniques have expanded to include FM, SSB and various digital voice modes. However a band of amateurs still enjoys using the very first - AM phone.

Unlike SSB, which has best cut-through when signals are weak or fading, AM transmissions are most known for their body, warmth and fidelity. AM achieves this by laying down a welcome rug called a carrier. A strong carrier quietens the receiver by smothering noise and signals below it.

After a brief period of suspense, similar to a curtain raising at the theatre, some evidence of audio may appear. Possibly an unfolding of paper or a suppressed cough.

Then, on the rug a voice may dance. Freed of a crystal filter's cutting, its bandwidth may enable audio more associated with broadcast music transmissions to be faithfully transmitted.

Or maybe not.

The voice may instead be that from a carbon or crystal microphone. Lows attenuated, slightly peaky, compressed. 'Communications quality'.

There is then some fading. Sometimes it sounds like the carrier drifts away from under the signal, with a hint of duck talk. But it soon returns, restoring a clarity that allows truly easy listening without strain.

This is AM. While not the choice for multi-hop DX in a crowded band, the decision to use AM plugs you in to a broader bigger and unified story of radio.

An era where early broadcasting, hamdom and crystal sets were intertwined. Before radio's Big Bang, which sent its practitioners hurtling along narrow specialties.

AM is not push and play. Its devotees invariably have at least one project to build or restore. Even on the air there are numerous settings to adjust and things to measure. Audio. Modulation. RF. Antenna current.

AM is the antithesis of the automised digital modes or multi-multi contest station. Contacts are not 59 then 73. It's both a personal mode and a mode of personalities, which adds to its appeal.

AM can be generated with restored broadcast equipment, modified marine transceivers, the latest high efficiency transformerless FET homebrew designs or commercial gear with it offered as a mode. Whatever approach makes your signal open to reception on a simple crystal or regenerative receiver and a part of the bigger radio story.

Such a story, enriched by listening to the transmissions of persons long gone, may have made you determined to follow. And perhaps to add a page of your own. Parts of your station may have been handed down generations, come from a notable old-timer or have played an important role in your nation's wireless history.

AM can be as simple or complex as you like. It can potentially be generated with a carbon microphone in the cathode or emitter connection of a single oscillator tube or transistor. It's crude and won't be heard far but transmitters like this gave many their start.

Later on you can boost your range with higher power. Or make what you have more effective with improved audio. There may be the search for components like modulation transformers, high voltage capacitors, coils and more. The quest for more power and a bigger signal and wider coverage represents another retreading of the path that early AM broadcast stations took.

Interested in joining the 'AM club'? Watch the videos below to see various facets of AM amateur radio operating. Most involve portable operating of low power equipment on 160 and 40 metres. They demonstrate the success possible even with low power with an allegedly inefficient mode.

160m AM

40m AM

PS: Enjoy reading? Consider this selection of amateur radio books I have written. They are available in ebook or paperback. 


Saturday, August 24, 2019

NEW! Introducing the Australian Ham Radio Handbook

I've got a new book out! It's the Australian Ham Radio Handbook. It will help you become a radio amateur, set up a station and make contacts on air.

Written for Australian conditions it covers practical topics that existing licence study and theory books miss. For beginning and experienced hams alike, it's an ideal read for anyone interested in taking up, continuing in or returning to amateur radio. A bit more about it is in this video. 

Click here if you'd like further information. It's currently available as an ebook but there'll also be a paperback version soon. 

What if you're overseas? I won't stop you buying it but be prepared for a lot of Australia-specific content. Stuff like band plans, frequencies, licence levels, activity and suppliers probably won't be useful. For material on operating you're probably better off with Minimum QRP. Or for the various facets of amateur radio, such as what a beginner might wish to know about, then 99 things you can do with Amateur Radio would be more suitable. 

Friday, August 23, 2019

Quick introduction to amateur satellites

At one time an amateur satellite station required expensive or specialised equipment such as VHF and UHF SSB equipment and elaborate steerable antennas. You also needed to manually calculate satellite pass times or use a computer program that required continual entry of data to remain accurate.

Now it's simpler. A new breed of satellites are effectively orbiting FM repeaters. A few watts from an FM handheld transceiver can be enough to work the easier satellites. Pass times are now available online so there is no need to calculate them. And suitable antennas are easy to build and cheap to buy. You may even be able to do it with just the antenna that comes with your handheld transceiver.

The simplest satellites to get on to are all low earth orbiters. Because they pass close to earth signals from them are strong and are audible with simple antennas. The low earth orbits mean that passes are short. This in conjunction with the satellite being a single channel repeater means that most satellite contacts are brief unless you operate at a time when most are asleep. A current list of satellites available for communications is on the AMSAT website.

PS: Enjoy these well-reviewed books on various amateur radio topics. They're available for under $US 5 each in electronic form. Or you can get them in paperback. Visit VK3YE Radio Books to find out more. 

Thursday, August 22, 2019

Transmitting on 160 metres (1.8 MHz)

160 metres can be a challenging band to operate on, especially if you have limited space. Nevertheless results can still be good provided attention is paid to sound antenna practice. Compared to other amateur bands it features more AM activity and a slower pace of operating.

For a quick guide on 160 metres, see the article on my website

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. 

Wednesday, August 21, 2019

Pedestrian mobile DX

It's still summer in the northern hemisphere and the weather is getting better down here. So what better than preparing for some HF pedestrian mobile? Here's some videos from various hams to inspire.

UK to NZ pedestrian mobile contact (from 2015)

Contest pedestrian mobile

Pedestrian mobile from the south coast of England

Using ex-military gear

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.


Tuesday, August 20, 2019

HF portable the simple way

One of the most enjoyable facets of amateur radio is operating portable. You may live in an area plagued with electrical interference, antenna space restrictions or dwell in an 'RF hole'. In such cases, portable operation gets you contacts not possible from home.

While not a substitute for proper RFDS or Marine equipment, amateur radio can add to the enjoyment of the trip on holidays and excursions. And the portable communications capability may be useful in emergencies.

Philosophy and Objectives

A weighty heading. But it's worth thinking about before you set off. Why are you going? What do you want to get out of it? And will the results be worth the chance of getting cold, wet, sunburnt or bogged?

I once did Field Day with a club where, despite the large number of helpers, it took hours to set up and dismantle the truly impressive portable station. Others spend months (and thousands of dollars) kitting out vehicles specially for portable use. There is no denying the effectiveness of such stations in earning high contest scores or setting microwave records.

Another approach to portable operating emphasises low cost, low power and quick setup. It won't win contests but there are other benefits. 'Minimum QRP', as I sometimes call it has a 'grab and go' spontanaety with little preparation or setup time required. And there's a certain beauty and satisfaction in getting good results from simplicity.

I also prefer HF portable over VHF and UHF. For several reasons. VHF and UHF are generally quieter and yield fewer contacts. And, especially on SSB, few progress much beyond a signal report. HF, particuarly the lower bands, is more congenial. My home location also plays a role; being a short walk to water but some distance from hills further adds to HF's appeal.

You may be different. If you're more technical, more elevated but less conversational, then VHF / UHF / microwaves may hold more interest. Long-distance VHF, UHF and particularly microwave contacts can make up in quality what they lack in quantity. This is especially if made on home-made equipment; something more common in the gigahertz range.

For this article I'll guess that you want to go portable, get on air and talk to a range of people. Right now it doesn't matter much where they are, but you do want to be heard and for there to be people around when you set up. HF is best for these purposes and is concentrated on here.


If escaping interference or antenna size restrictions at home, any open area such as a park or beach will be worthwhile. However some sites are better than others for various reasons.Things to think about when choosing a site include:

* Availability of tall trees with branches in the clear (for supporting HF wire antennas)* Availability of fences or metal railings (for earthing and tying telescopic antenna masts to)* Sloping ground and/or water in favoured transmitting directions* Sufficient room to erect masts and wires without getting in the way of other users* Distance from power lines and other potential man made interference sources* General site amenity. Eg shade, shelter from wind and rain, decks/tables/seating, lighting, etc* Ease and availability of access. If driving, how near can you get to the favoured operating position? And if it's a park, do the gates shut at night?* Proximity to home

The relative importance of these factors will vary according to the bands used, and the type and distance of contacts desired. If you're into DXing you may be willing to go for a further or less comfortable site if it means lower noise, better ground slope or water in the chosen direction. More on this later.


You can often get by with just one band, though another one or two improves operating flexibility and range of contacts. Forty metres is a good all-round band where there's many hams within 300 to 1000km, allowing contacts at most times. Add 20 metres if you're operating mostly during the day. 40 metres provides easy contacts up to about 1000km, increasing to 3000km around dusk. 20 metres isn't so good for closer in but comes good over distances of 1000 - 3000km and worldwide for multi-hop. Antennas for both bands are easy to build and not too large.

At certain times and places other band come into their own. Examples include 80 metres (evenings), 160 metres AM (ground wave during the day), 10 metres (Summer sporadic E or DX openings) and 17 metres (when there's a major contest on 20 metres). If you're up for a challenge, consider dawn or dusk greyline DX on the lower HF bands. More on the properties of various bands in the Foundation guide to frequencies and at QRP activity by band.


A half wavelength of wire (20 metres on 40 metres or 10 metres on 20 metres) is the basic building block for HF portable antennas. Don't believe me? Jam a quarter wavelength of wire into your antenna socket and try to make contacts. You'll get some but adding another quarter wave to the transceiver's ground should improve results.

The main differences are how you support it, how you orient it and how you feed it. The method chosen depends on what's most convenient and the types of contacts desired. Below I describe the variants most useful for portable operating.

* Centre fed half wave horizontal dipole. Take your half wavelength of wire, fold it and cut into two equal lengths. Attach any length of feedline to the centre. String the antenna ends between two trees and have the feedline hanging down. If the feeder is coaxial cable you'll have an antenna efficient for one band and won't need an antenna coupling unit. Whereas with open wire the antenna will operate efficiently on multiple bands but will need an antenna coupling unit. The basic half wave dipole will perform well up to medium distances, with height an advantage for longer distance contacts.

* Inverted vee dipole. Everthing's the same as the dipole above. The difference is that instead of hoping there's two trees spaced just the right distance apart, you support it at its centre. The ends are tied off to lower trees or fence posts. Again good for reliable HF contacts up to a few thousand kilometres, with longer distance DX very possible.

* Vertical dipole Again the centre fed dipole is used unchanged. But this time you support one end from a high support so that the radiating element is vertical. The feedline must be brought off to the side, as near as 90 degrees as possible from the centre of the antenna. A vertical dipole is difficult to arrange on 40 metres as a 20 metre high support is needed. However they're much easier on 20 metres as only a 10 metre support (such as a lightweight squid pole) will suffice.Especially if used over a conductive ground, such as salt water, a vertical dipole will outperform a horizontal dipole for long distance contacts because of its lower angle of radiation. Because I normally operate near salt water, I've become a big fan of vertical dipoles for 20 metre QRP DXing. I should warn you that they can be noisy on receive, but this might be a signal that it's time to try a quieter location.

* End fed inverted vee. Here's where we ditch the bulky coax feedline and substitute a small L-match antenna coupler and short counterpoise. As its not supporting anything, the antenna wire can be the lightest grade of insulated hook-up wire. This lightness allows it to be supported on a telescopic squid pole - a huge advantage near the beach without trees.

An end-fed wire of approximately 20 - 22 metres long and a 9 metre pole provides good local and medium distance results on 7 MHz. Because of the coupler it provides multiband capability. It will tune on 14 MHz as a 1 wavelength end-fed but doesn't seem to be as good as a vertical dipole for DX. 
Alternatives include forming it into a full wavelength loop on 14 MHz, or using the same loop split at the top as a bi square on 28 MHz. The end-fed inverted vee is highly recommended for local and medium distance portable work on 7 MHz and usable on other frequencies as well.

Generally the antenna should be mounted as high as possible. In most areas, it should be possible to find a suitable tree to support an antenna, though there are cases when it would be wise to bring a collapsible mast, for instance in the mulga or at the beach where there's few tall trees. Telescopic squid poles have been particularly successful up to heights of 9 or more metres. They will work with end-fed wire antennas if the thinnest type of plastic insulated wire is used to minimise pole bending. 

A 9 metre pole can easily support a span of 20 metres; adequate for 7 MHz and up. Light duty squid poles won't normally support even RG58 coax feedline unless it's run down the pole and taped to it every metre or two for support. Squid poles are too flimsy to support a VHF beam but they'll work with a lightweight antenna such as the 'hanging dipole' elsewhere on this site provided the feedline is taped to the pole. These poles have revolutionised amateur portable operation due to their low cost (under $50) and light weight. A suggested supplier in Australia is Haverford who ship nation-wide.

There are other antennas suitable for portable usage (such as the loop pictured above) but those described are the simplest and most foolproof. More elaborate antennas are not needed unless space is extremely limited or gain is needed for DXing.

This article originally appeared on my website,

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. 

Monday, August 19, 2019

Some radio history

Today we'll delve into the past. 

I'm not sure how many people visit it, but my website has a historical section

What will you find there? 

Firstly there are some old Dick Smith catalogues, going from the 1970s into the 2000s. Dick Smith Electronics was an Australian electronic reseller who sold just about all the bits that electronic enthusiasts used to build their stuff. They were also the Yaesu dealer for amateur radio equipment in Australia for the better part of 25 years. They tried to grow too big and branched into lower margin but higher volume consumer electronics. Some bad decisions resulted in them shutting shop (after some changes of ownership) a few years back. 

Secondly I look in old magazines to find ads for old Melbourne electronic shops. I go to those addresses to see what's there now. Some of the buildings are still standing. There's some videos on all that. 

Finally there's some links to an archive of old Amateur Radio magazines. And old articles I've written that are now obsolete. 

Happy reading and watching! 

PS: Want to support The Daily AntennaPlease start your Amazon shopping hereYou won't be charged extra and I'll get a small cut from any purchases you make (affiliate link). You can buy lots of stuff there, including electronic parts and my books. And for those in it, today is Amazon Prime Day, where members may get special offers. 

Sunday, August 18, 2019

A look at the Midland 70 340 VHF transceiver

My look at the AWA VHF carphone was popular so here's another video.

It's a newer set made in Japan. It's synthesised so it has a lot more frequencies.

But there were some challenges to getting it on air. Find out what they were in this 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.


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