[OZAPRS] Newb HF questions ;)

[Ray Wells]

This is probably close enough to on-topic. Certainly as close as 
knitting needles :-)

The most interesting antenna I ever played with is a  DDRR. A  WHAT, you 
say? The DDRR (Directional Discontinuity Ring Radiator) was brought to 
our attention in 1963 in the US magazine, Electronics. An article in QST 
in 1972 provided a mathematical analysis. It is essentially a grounded 
quarter wave vertical that, at a particular distance above the earth 
plane, is bent at right angles so that the bent section is parallel to 
the earth plane. That bent-over section is then formed into a circle and 
the far end of it is attached to a tuning capacitor. The feedline is 
tapped up from the earthed end. The original QST article had dimensions 
for antennas from 160m to 2m. I again came across the antenna in the 
1983 ARRL Antenna Handbook.

The DDRR was touted as an efficient and effective small antenna for the 
HF bands. I worked with a guy who had a 27MHz version made from one inch 
diameter soft aluminium rod mounted on the roof rack of his car, with a 
bit of a ground plane. The antenna was about three feet in diameter, and 
worked exceptionally well.

When an amateur friend was hospitalised (Multiple Sclerosis), I built a 
2m version that attached to the curtain rail around his hospital bed. 
The "ground plane" was an aluminium disc about 8 inches in diameter and 
the radiating ring was about 6" diameter. The antenna, BTW, produces 
vertical polarisation. The one I made for Jim enabled him to access the 
local 2m repeater. Of course, this was in the early 1980's before people 
worried about being killed by anything they don't understand. Both the 
27MHz and 2m version exhibited very high Q that restricted their 
operating bandwidth.

For anyone with a caravan who is looking for an effective 30m aprs 
antenna, this might be the (ugly) way to end up with divorce.

Ray vk2tv

Shaun Pitcher wrote:
> And then I read the rest of the comments about knitting needles.  Load 
> them for 2m APRS I say  :-))
>
> Regards, 
> Shaun Pitcher 
> ozaprs-bounces at aprs.net.au wrote on 24/05/2009 12:42:22 PM:
>
>   
>> The only way I will be picking up knitting needles is to make a dipole 
>>     
> out 
>   
>> of them!
>>
>> Regards, 
>> Shaun Pitcher 
>> ozaprs-bounces at aprs.net.au wrote on 23/05/2009 05:12:43 PM:
>>
>>     
>>> There I go, living in the past again. It's such a nice place.
>>>
>>> Ray vk2tv
>>>
>>> Ben Lindner-VK5JFK wrote:
>>>       
>>>> "Have you thought about trading in your radios for knitting needles 
>>>>         
>> :-) "
>>     
>>>> Ray,  I believe that Scrap Booking and Quilting have taken over from 
>>>>         
>
>   
>>>> knitting now. :-)
>>>>
>>>> Ben
>>>> VK5JFK
>>>>         
>
>
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