With the ability to receive weak AM transmissions and world wide HF stations (including SSB for the Sangean ATS505, Eton/Grundig E5/G5, Sangean ATS909 and Sony ICFSW7600GR), you will never be without something to listen to and all in a package not much bigger then a paperback novel.


The following are also worth a mention because of their ability to tune into most of the HF band, use PLL circuitry and have generous user memory is the -
 
 *  Tevion MD81157 from Aldi, shown on the right, not too bad for the money at $50 and a better finish than the Sangean ATS505.  It covers LW 144 - 281 kHz, MW, SW 5.85 -17.9 MHz and FM with 240 station memory although in a volatile memory.

With the external aerial modification described later, this is very useful on the MW broadcast band, better reception than the radios in our car or caravan by a noticeable margin.    I also describe a 12V power input modification.
 

 And two from Jaycar,
 

*  Kason, Cat No AR1747.  (This is a Redsun RP2100 also sold elsewhere as a Kaito KA2100, shown on the left.)

It is a fully featured receiver (but minus SSB) for $100. Like the better ones from Sony and Sangean described above, this one covers 520 - 29999 kHz, 87 - 108 MHz FM, no LW (below 510 kHz) but this no great loss.   It has a 50 station memory. More importantly like the Sony and Sangean it is also has dual conversion but unfortunately misses out on direct key frequency entry. It is physically larger than all the others mentioned on this page.    Overseas technical reports are favourable.

And from Eton/Grundig range is the E5/G5 model for around $225
	AM/FM/LW  coverage 150 - 29999 kHz, FM  87.50 - 108 Mhz ( 76 - 108 Mhz User Selectable), PLL Dual Conversion AM/SW Circuitry with SSB, 700 Programmable Memory Presets, Alpha-Numeric Four Character Memory Bank Labeling, Tunes Via Auto-Scan, Manual Scan, Direct Key-in Entry and Tuning Knob
* Their flagship model E1 has the lot including sync detector, switchable bandwidths and a large dot matrix LCD but is over three time the price of the E5/G5.    For bells and whistles it also trumps the Sangean ATS909 by a good margin but at over double the Sangean's price.    (Based on overseas prices because at the time of writing this I don't believe this E1 model is available in Australia.)

 
This can be and is a very lengthy technical subject but I have tried to reduce it into just some simple practical information. 
The following is some very basic information on the three types of external aerials for your radio to improve reception at your camp site.
Aerials that we are interested in here fall into three broad categories, loop, long wire and active types.

 

A very simple yet effective do-it-yourself one I will describe here is the non-resonant broadband aerial to vastly improve the medium wave broadcast band reception of weak signals particularly suited to less sensitive radios. 
  

The essence of this is to wind 3 or 4 turns of insulated wire directly on to the ferrite aerial rod inside the radio and terminate the coil ends to a 3.5mm mono or stereo earphone socket which you will have to fit somewhere in the case of your radio.
If the radio case is metal not plastic, a stereo socket would be preferable with the coil terminating on the tip and ring only.
The aerial itself is nothing more than a length of wire forming a loop terminated in a matching 3.5mm plug.

Theoretically, the antenna loop length should ideally be as long as convenient but not exceeding 0.1 wavelength at the highest frequency, which is approximately 18 metres at 1650 kHz.
Obviously 18 metres is not practical for our traveling needs and in practice a 6 metre (2M+2M+2M) to 9 metre (3M+3M+3M) loop is good compromise.

Arrange the wire such that there is a horizontal component for best effect.  The loop, where length is less than 0.25  wavelength, is directional with maximum pickup in line (not broadside) and is referred to as a non resonant magnetic loop.
(Conversely, loops where length is greater than 0.5 wavelength have maximum pickup broadside, same as a ferrite antenna.) 

 The loop can be contained in or held in a circular of rectangular shape by any non-metallic support such as PVC conduit etc or just hung up like a small clothes line to form a "delta loop" ideally with roughly equal sides.

Alternatively, the loop can be arranged in a diamond configuration with a non-metallic spreader (a length of 25mm electrical conduit is ideal) and can be more convenient to erect.   A 1.5M spreader will give you a 4M loop and a 2M spreader will give a 5.5 - 6M loop

This is a very simple basic aerial but nevertheless works very well, is simple to implement, does not require constant retuning, is highly portable, easy to set up and not too critical on direction - a good compromise.    Also, loop aerials in general are less susceptible to inference than a long wire aerial. 

Whilst it's possible that selectivity may be slightly degraded due to the unmatched loading effect, this is of little concern since, generally speaking, we are out in the bush trying to pick up whatever we can.  (Trying to receive a weak distant signal adjacent to a strong local one is not a priority in this instance.)
And our antenna needs to be simple and easy to throw up at our camp site.
Having said that, I haven't noticed any degradation in selectivity during field testing.
 
With this modification to a couple of cheap portable radios and using just 4 metres of aerial wire, stations were picked up clearly that are totally absent without.    The performance of these radios from the aspect of receiving a weak medium wave broadcast band AM signal now is as good as if not better my Sony IFCSW7600GR with just this 4 metre loop.

Unfortunately this is difficult to implement on the IFCSW7600GR, the ferrite rod is difficult to access and the radio is so jam packed full that fitting another socket is virtually impossible, however........the dramatic improvement seen on the cheaper radios is not seen with the Sony unless using at least a 8-10M loop.
The same goes for inductively coupled loops, good results on cheaper radios, nowhere near us useful with radios the caliber of the 7600.

I have performed this mod on a Tevion MD81157 which has a readily accessible ferrite rod and plenty of room for an antenna socket, with excellent results.     It now pulls in weaker signals than either my car or caravan radios with just a 4 metre loop.
(Why did I buy the Tevion ?   It caught my eye for $19-95 (usually $49-95) in an Aldi sale that I attended out of curiosity.)

Caution - some radios, such as the Sony IFCSW7600GR, that have an external aerial socket, have a superimposed DC voltage to power an active aerial.   In this case you can not connect a DC loop to the aerial socket directly, you have to make sure a capacitor is in series with the loop.

Before you go defacing your radio, wind the turns on the ferrite aerial rod and just lead them outside the case and connect it to  4 - 6 M of wire and arrange in a delta fashion as described with the wire 2 M or more above ground.   If you like the results, you can make the modification permanent.    It will however be the end of any warranty you may have.


Small loops

I am describing these just as a matter of interest, I don't believe they are quite as suitable for our wandering needs, my "cloths line delta loop" above takes a lot of beating in this situation.

This is another type of loop aerial consisting of the aerial wire, several turns of it, contained in a plastic loop (picture a hulla hoop) ranging in diameter from 300mm to 450mm.   Generally narrow bandwidth, they are tuned with a variable capacitor to suit the received frequency.  They tend to be reasonably directional.

The radio needs to be placed in close proximity, usually inside the loop since, generally speaking, there is no physical connection needed, they are inductively coupled to the radio.
They are commercially available and are reasonably effective and the cheaper the radio, the greater the improvement in reception.
There are passive and active (amplified) types.

Picture on the right is an example of a small amplified loop for the HF band connected to the radio's external input socket.

Then there are small loops (600 - 1200mm) with inductive or physical connection to the receiver that you can build yourself, both passive and active.
 
.

Although out in the bush a length of wire 10 M or more long strung up a few metres above the ground with one end tied to a tree and the other attached to the radio's telescopic antenna can be quite effective on the HF and FM bands, once again, I'd suggest you be very cautious, especially if there is even a hint of a thunder activity or if you are picking up random crackles.

Normally only suitable for the HF and FM bands and will have no effect whatsoever on LW and MW which use the internal ferrite rod for these bands.
It does however work for a car radio on the MW and FM bands.

However, with the above modification to the radio, a short whip or length of wire connected to one side of the coil and the other earthed can give good results for LW and MW but in a camp site situation, an effective earth may be difficult to establish.
This works very well on a boat where connection to any underwater metallic object forms an excellent "earth".
 
 
This is probably beyond the scope of an introductory article like this but later, I may also describe a simple ATU (aerial tuning unit) and also a tunable active RF preselector (tuned amplifier) circuit for the MW broadcast band, either of which you could build yourself, for the more adventurous.

 These are a commercially available non directional (in the horizontal plane) vertical whips with an amplifier.
The radio would need an aerial input socket, not likely to be found on cheaper portable radios.

Some have small inductive loops which you place near your receiver for the LW and MW bands for radios without a suitable input connector for those bands.
 
 
Shown on the right is simple yet effective wideband active aerial you can build for under $10 using a 1M vertical whip for ease of use in a caravan.
 
 

This radio lends itself to very simple "improvements" due to the liberal amount of free space inside such as the aerial  modification described above and a 9 to 30VDC input, much more convenient than the original 6VDC one for several reasons.

The radio received the above aerial modification and in addition, one side of the winding is connected to the telescopic aerial so that the new external aerial works well on all bands, LW & AM as well as HF & FM.
 
Also, the 8 - 24VDC input modification means the radio can now be used with the external power simultaneously with the batteries so that you don't lose your preset stations if the external power is interrupted.
It can also be made to trickle charge internal Ni-Mh batteries (don't do this if you are using non-rechargeable batteries). 
Note - This mod is suitable only if the radio is to be used mostly with external power - reason, the combination of using lower voltage rechargeable batteries and loss across an isolating diode means the radio is only seeing about 4.5V instead of 6V, therefore onset of low voltage shutdown will occur after fewer hours use.
Also, depending on the quality/complexity of the radio circuitry, lower operating voltage can result in impaired reception performance.   Not applicable to high end radios like the Sony ICFSW7600GR that maintain internal operating voltages  irrespective of battery voltage, up to their shut down point, with internal DC-DC converter circuits.
  
Just a small handful of components costing less than $10 is all that is needed and the two mods improve the performance and usefulness by a huge amount.

The accompanying photo show the new aerial input socket and the DC power socket below the original 6V input socket.

Of course, these simple mods can work with other radios too. 

The Sony like many others is operated from 6VDC and that's what the radio's external power socket wants to see.   And in Sony's case they don't see fit to supply an AC power pack.

Problem............. 
- while good 12VDC AC plug packs are very common, good regulated  6VDC ones are not, also
- it would be very useful to be able to operate the radio from the caravan and/or vehicle 12V battery.

A simple solution to both is to make a 12VDC to 6VDC reducer.   This is easily done with $5 worth of parts from Dick Smith, Tandy, Jaycar etc. 
All you need is the appropriate plug for the radio and a socket to suit your power supply, a 7806 regulator, tantalum capacitor and a small enclosure (mine is an old lipstick type dispenser - see photo).

This makes for a compact in-line connection between radio and power source.

Fortunately, the Sony uses a smallish (uncommon) size plug so that it can't be accidentally confused with the larger diameter more common sizes found on most 12VDC plug packs.

Now, using this reducer, any voltage between 9 and 30VDC can be used with the radio.   The output is maintained at a constant 6VDC.
The current capability of the regulator (which is rated at 1A max,15W dissipation) will depend on input voltage and size of heatsink used.    In my case with a nominal 12VDC input and <250mA output, just a small one is needed which is obviously contained within the lipstick dispenser.
 
 

My original from long long ago It was a Nordmende from West Germany, a better than average portable radio in its day (early ' 60s). A three band 9 transistor radio covering,     LW -    160 - 280 kHz    MW -   510 -1650 kHz    SW - 1500 - 3500 kHz Case was vinyl covered plywood