Tuesday, August 20, 2019

HF portable the simple way

HF portable the simple way

 portable operating location portable operating location

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.

Location


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. 

transmitting across water a waterside portable operating location

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.

Bands


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.

Antennas


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.

a vertical dipole a portable magnetic loop

* 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. 

a squid pole ideal as a lightweight portable wire antenna mast

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, vk3ye.com.

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.

    


Saturday, August 17, 2019

Sources of information for homebrew radio construction

Homebrewers normally have a wealth of material on which to base projects. This is obtainable from:-

* Books. There are many publications available to the amateur experimenter. As well as the conventional RSGB and ARRL handbooks, more specialised references cover practical aspects in greater detail. Titles to look out for (whether new or second-hand) include 'Experimental Methods for RF Design', 'Solid State Design for the Radio Amateur', 'QRP Notebook', 'Technical Topics Scrapbook', 'G-QRP Club Circuit Handbook', and 'Radio Projects for the Amateur', to name a few.

* Magazines. In addition to projects in the major amateur periodicals, such as QST, QEX, Practical Wireless, RadCom and Amateur Radio, there occasionally appear radio projects in general electronics magazines such as 'Silicon Chip'. Some of these designs have the advantage of a kit being available. However, be wary when considering some ultra-simple projects; for example a crystal-locked 100 milliwatt 80 metre AM transmitter is simple and cheap, and may well produce a clean signal on an oscilloscope, but is likely to disappoint when used on air under modern band conditions.

As well as being stocked by the larger newsagents, various local and overseas magazines are carried by public, TAFE and university libraries. These normally provide photocopying facilities, available on a cents per page basis.
In addition, QRP (low power) enthusiasts have their own publications. Probably the best known is 'Sprat', published by the G-QRP Club, renowned for its technical articles and circuit ideas. The US-based QRP Amateur Radio Club International issues 'QRP Quarterly', while the Australian-based VK QRP Club produces 'Lo-Key'. These magazines widely read by those interested in constructing low-powered transmitters and receivers.

* The Internet, including websites, email lists, discussion forums and YouTube. The greatest ever source of homebrew information, allowing you to tap the collective wisdom of thousands of experimenters around the world. If you have a particular question, want to know how to obtain a part, or simply want to share your experiences with a particular component or circuit design, there'll be a website, online forum or email list to assist.

Discussion takes place on the homebrew or technical sections on the eHam and QRZ forums. These have a search function and you can find material posted several years ago. As well there are homebrew amateur radio pages on Facebook. As they say, 'Google is your friend' if you want to find out about anything, and numerous YouTube videos demonstrate numerous aspects of home construction.

Picture of components in boxes


Overall I suggest a mix of information. A few of the major books (eg Experimental Methods for RF Design), subscriptions to some magazines (the QRP ones have particularly low membership fees) and liberal use of the web and email.

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, August 16, 2019

Taming the LM386 audio amplifier IC

The LM386 is possibly the most popular ever IC for audio amplification. It's readily available and requires few extra parts to make it work. But some published circuits try to push the friendship too far. The result can be an oscillating circuit that's not reproducible and causes nothing but trouble for some builders. 

If you'd like to hear about how you can tame your LM386 circuit tantrums, watch this video! 



PS: Returning to amateur radio? This book can help fill in what you've missed. Available for $US5 as an ebook with a paperback version also available, this will bring you up to speed in no time.  Available via Amazon, you can find out more here




Thursday, August 15, 2019

Review: DCT DSB/CW QRP transceiver kit from OzQRP

In the last few weeks I've been reviewing a new kit from OzQRP. It's a DSB/CW transceiver kit. It puts out 5w. You can choose between 80 and 40 m versions. In the video below I try out the 80m version on CW and DSB, including in a local contest. 


More details, including the instruction manual and ordering, can be found on the OzQRP 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. 




Wednesday, August 14, 2019

Tools and equipment needed to start radio construction

To complete most radio projects, only basic hand tools will be required. You will also need some items of electronic test equipment. The more useful items are listed below. If starting out I'd suggest obtaining most items in the Tools list and only some items in the Electronic/radio test equipment list.

* Tools
- Flat and Phillips head screwdrivers - varying sizes
- Long nose and flat pliers
- Wire cutters
- Hobby knife
- Hand drill and drill bits (from 2 to 8mm)
- Tapered reamer
- Hacksaw
- Hammer
- Mitre box
- Set square
- Metal ruler
- Tape measure
- 15 - 40w soldering iron or soldering station with suitably fine tip
- Bright work light
- Magnifying glass (may be on stand)
- 'Helping hands' circuit board holder
- Boxes or tubs for parts storage

* Electronic/radio test equipment and accessories
- Multimeter with transistor tester
- Inductance and capacitance meter (preferably accurate at low values ie uH and pF)
- Audio signal tracer (can be LM386 or similar audio amplifier)
- General coverage HF receiver (included in most HF transceivers)
- Frequency counter up to 1GHz (or you could use an SDR dongle receiver)
- RF power and SWR meter
- RF probe (can fit on to multimeter)
- RF absorption wavemeter or field strength meter (with analogue movement)
- RF milliwattmeter
- RF signal generator (can be made from DDS VFO module or use own transceiver)
- RF attenuator (can be made from resistors and switches)
- Low noise regulated power supply (12 - 14v up to 2 amps approx for most projects)
- Audio spectrum analyser (can be a cheap mobile phone app eg Frequensee for Android)
- Dip oscillator or antenna analyser
- Oscilloscope

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Tuesday, August 13, 2019

I don't have time to operate portable

Many people say they have no time to operate portable. In our busy schedules radio time often has to be put in between other activities. A station that's bulky to carry and takes too long to put up will hardly be taken or used.

The solution is to do all you can to make your station so light and quick to set up that it will be used even if you have an hour or less to spare.

Light to carry

Don't take stuff you don't need. Economise the station to save on separate items. Fewer things means less left at home or behind.

Use end-feds not dipoles to save feedline bulk. Build an L-match inside the transceiver to save taking a seperate antenna coupler for the same length of wire. Ditch the SWR meter if you're can tune up on receiver noise. Use antenna insulators, wire and support rope. Lightweight keys, microphones, headphones likewise save room.

A simple QRP rig on a popular band like 40 metres can keep you talking for most of the time. 4 amp hours of battery capacity is enough for several hours on air, especially with low-drain homebrew rigs. I use nickel metal hydride battery packs but others do well with lithium ion or lithium polymer (note charging and safety due to high maximum currents).

Then there's the non-radio stuff. Some people seem to clutch bottled water or a can of carbonated sugar even on the shortest of errands. Similarly, ask yourself if you really need food, drink and extra clothing if the location's near home and you're not out long? Neither is it a crime to leave the mobile phone behind occasionally. After all it's not an Antarctic expedition! Though bear in mind the Ten Essentials if going bush.

a minimum QRP portable station that takes just minutes to set up

I'm attracted to taking as little as possible; the photo above is a typical summer beach outing near home. There is refinement in the sense that nothing taken will be unused. One less thing taken is one step towards perfection provided good contacts are made. I'm holding a 'Beach 40' 7 MHz DSB transceiver capable of contacts up to 1000km or more (details elsewhere on this site). The 9 metre squid pole typically supports an end-fed half wavelength of wire. The only other items include a 12 volt battery pack, antenna coupler and a small zippered case holding the earphone, microphone, velcro straps for the pole, pen and paper.

Setting up

Most set up time is in the antenna. Antennas that require hammered stakes or lots of radials can take an hour or more to set up and adjust which is too long. Antennas should not need nuts and bolts to erect. Especially if they are easily dropped (which will happen) or need screwdrivers or pliers to tighten (which will be forgotten). For speed you can't go past a half wave end-fed wire supported on a squid pole.

The big reward

The big reward when operating portable is the lack of noise and clarity of received signals. Here's some examples. Compare the signals here with what you might experience at home. This is what makes it worth the effort!

 





The weather

There are times when you might almost be motivated to go portable but the weather's looking a bit iffy. You might be in front of the computer and, seeing it's only 10 or 15 degrees outside, give up on the idea of going portable. However temperature isn't the only factor that affects operator comfort. Wind and rain are equally if not more important. If it's windless and sunny then portable operating can still be enjoyable, even if temperature readings imply otherwise. Of course weather can change and it pays to be aware of approaching electrical storms before you feel the tingle (or worse) on your antenna lead. Get to know nearby sheltered public locations in case a sudden change forces you to close at short notice.

Light passing drizzle isn't so objectionable if it's reasonably warm and not windy. Equipment protection though is desirable. Plastic bags aren't always good because they lack openings for leads coming out of the transceiver. However you may be able to make your own, fitted to suit the equipment in use, from thick clear plastic (eg clothing or blanket storage bags) and adhesive velcro straps. Both are available from discount variety stores. If worried about damaging accessories, construct ruggedised microphones, keys, headphones and antenna couplers for use in inclement weather.
There are few things more pleasant than being in cold sodden clothes in driving wind. Wear natural fibres in the heat and synthetic clothing in the cold and wet. A wetsuit may also be a good choice, especially if pedestrian mobile near (or in!) water. Wetsuits can be expensive new but are sometimes cheaply available from charity shops.
If the worst comes to the worst and the weather is so bad that you can't operate, little time is lost if the station is quick to set up. And you'll be particularly grateful if its dismantle time is even less, especially if a storm is coming.

Conclusion

Taking as little as possible, or 'minimum QRP' is challenging, satisfying and practical. There is a sense of achievement through simplifying a station yet maintaining sufficient performance to reliably get contacts. And you'll probably use it more as it's not so much trouble to carry and set up. So I'd encourage you to look carefully over what you need and don't need in a quest to save both kilograms and time.



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.

    

Monday, August 12, 2019

Roll up coaxial cable magnetic loop

Efficient magnetic loops can be made fairly small but due to their rigidity can still be heavy and bulky to carry in packed luggage. If high performance and power handling capability are not required one work-around is to make the loop from coaxial cable braid. This approach is used in the popular Alexloop used by pedestrian mobile operators. I've worked a couple of stations on 40 metres using such antennas and as expected signals have been weak.

Results can be improved if you use a longer conductor length. Here I use about 7 metres of coaxial cable connected to a variable capacitor. A toroid is threaded over the cable with a few turns of wire providing coupling from the transceiver. Below is a description and demonstration of an experimental loop set up in an open area.



Inspiration for my loop came from G4FON's website. The above loop is nearest to the version 2 described.

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. 



Sunday, August 11, 2019

Inside an Australian AWA VHF carphone

A while ago I picked up this 1970s transceiver from a local hamfest.  I didn't know at the time but it was already converted to 2m with a few useful frequencies included. This video tells you a bit more about it:



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

    


HF portable the simple way

HF portable the simple way   One of the most enjoyable facets of amateur radio is operating portable. You may live in an are...