"Jim" wrote in message
news:4HAXf.10092$dU3.6515@trnddc01...
I saw a construction article in the ARRL Antenna Handbook , 13th Edition,
1980 on page 247-249. I also did some google searchs and there was a
thesis paper on this very same article in the 1990's where two people
modeled the antenna described in the Antenna Handbook and said there were
errors in the article. I could not get the complete paper that would have
gone into the details.

I have built one of these antennas for the 850 mHz range using rigid coax
per the article in the ARRL Handbook (with 7 half wave elements, and two
1/4 wave elements per the article) and saw poorer performance compared to
a small 1/4 whip antenna connnected to the back of the radio. Not sure
what went wrong.

Comments??

Tnx

Jim
"K7ITM" wrote in message

Hi Jim

A properly done colinear array of 8 half wave elements will sure have a
highly directive pattern in the Elevation plane. With some luck and low
loss components you might get 8 or 9 dBi. But, the pattern will have a
pattern max thats broadside to the axis of the colinear array at only one
frequency. That pattern max will squint up and down (with respect to the
horizon) as the frequency varies from that center frequency.
I'd bet that you will be able to realize appreciable dirrectivity from an
array of 7 lengths of RG-6 with 2 quarterwave added elements. But,
developing the array to provide low VSWR and best squint angle at any chosen
frequency will demant some "field testing".
You probably already knew that. I just wasnt sure. Besides I have wasted
alot of time developing a very similar colinear array for commercial use.

Jerry KD6JDJ

"Jerry Martes" wrote
A properly done colinear array of 8 half wave elements will sure have a
highly directive pattern in the Elevation plane. With some luck and low
loss components you might get 8 or 9 dBi. But, the pattern will have a
pattern max thats broadside to the axis of the colinear array at only one
frequency. That pattern max will squint up and down (with respect to the
horizon) as the frequency varies from that center frequency.
_______________

The change with frequency in the angle of the elevation pattern maximum
field is the result of the varying relative r-f phase vs the operating
frequency that is applied to the radiating elements in this design.

This can be eliminated by using a vertically stacked array of identical
radiators fed via an n-way power divider, whose output connects to feed
cables of equal electical lengths to each element of the array. The
directivity (gain) and sidelobe distribution of this type of array will
change with operating frequency, but the elevation angle at which the peak
field is directed will remain the same, regardless of the input frequency.

This approach is used in broadcast transmit antenna designs giving good
signal coverage over large sections of the UHF TV band, or the entire FM
band.

RF