Re: [Paddlewise] Ch 16 and DSC

Michael Daly wrote:
> Mike Jackson wrote:
>
>> Can you tell us more about the roll up j pole idea?
>
> You can determine the dimensions you need from an online calculator like:
> <http://www.hamuniverse.com/jpole.html>
>
> Just plug in the frequency you're interested in - I'd use something 
> intermediate to ch 16 and 22.
>
> This will give you about 3 dB gain over the rubber ducky, IIRC.
Which, if I recall correctly is equivalent to doubling the wattage 
produced by the radio.

A long, long time ago I used to build CB radio antennas, one of which 
was a four element "quad" (basically four square loops of wire on 
spreaders and appropriate distance apart), which allegedly was suppose 
to produce a 16dB gain.
>
> While the instructions might call for copper tubing, you can use a 
> single strand of insulated wire bent into a J and held into shape by 
> laying it onto some duct tape and covering it over with more duct 
> tape.  Another alternative is to make a twinlead version - google 
> searches will find instruction.  You'll also need a bit of coax to 
> make a coil of about five turns to reduce interference and a coax 
> connector that fits your VHF rubber ducky's connector.  For tools you 
> just need a wire cutter and soldering pencil.  Altogether quite cheap 
> - the coax connector is likely the most expensive part.
>
> The antenna can be rolled up for storage and stretched out for use.  
> You'll have to hold up the end with a paddle or something.  You can 
> attach a loop of line or punch a hole in the duct tape for a line.
>
> I haven't made one for VHF, but I did make one for my stereo receiver 
> for local FM stations and I no longer have reception problems compared 
> to the cheapo twinlead antenna.

It's worth noting that the length of the antenna and coil "balun" are 
not as critical if you're only going to be receiving singles.  If, 
however, you're going to be transmitting VHF, it can be very important 
and an SWR meter used to measure how well the antenna matches the 
radio.  A ratio of over 3:1 can cause damage to the radio.
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