Originally Posted by nosratt
I got it!!!!
I switched the shortest details of
elements to the driver and swr went to
1.1 @ 27.605... so I put next longest
set on the driver and swr went to
1.1 @ 26.965.
The element order is now 1 3 2 4 and
spacing is the same...
The REFLECTOR is the longest element at one end of the beam.
Next to that, the DRIVEN element is the next longest element (this is where the Gamma match/coax is attached to). Because it DRIVES the whole beam.
Next, the 1st DIRECTOR has the 2nd to the shortest length and mounts next to the DRIVEN element.
The 2nd DIRECTOR is the shortest element - and is at the long end of the beam.
Look at the picture I previously posted above.
Notice the larger spacing between the 1st and 2nd DIRECTOR?
That proportion should be consistent with most beams.
They lengths should be in descending order of lengths from the REFLECTOR (longest) on one end, down to the 2nd DIRECTOR (shortest) at the other end.
Because the elements lengths are shorter; the antenna HAS to tune in the ~28.400mhz - or higher - range. The elements MUST be longer to tune on the CB
band. No if's, and's, or but's . . .
The "Gamma Match" is how the SWR is adjusted. If the lengths of the elements are SHORT; then they have to tune to a higher frequency. That is just the nature of antennas.
Just because the SWR look acceptable by no means that it will radiate as it should/as designed!
Looks to me that someone modified the lengths for the 10m Ham band - IMO . . . You stated that: #1 191"
#2 183" driver. With transmission line on it
But to tune PROPERLY on the CB band, they NEED to be:
#1 - 215.35"
#2 - 203.875" With transmission line on it.
#3 - 202.5"
#4 - 186.75"
If you can lengthen them to these lengths and THEN reset the Gamma match to a decent SWR, then it should be fairly RESONANT on 27.555 and below (the CB
band). In truth, to be fully resonant on the CB
band - it would need to have the REFLECTOR ~225" and the other elements "scaled" proportionally to that length.
boom 188 1/2"
distance between #1 and #2. 68. 3/4"
between #2 and center of boom 22 1/2"
between #2 and #3 55 1/2"
between #3 and #4 61 3/4" Compare your spacings to the diagram at the top of this page. Spacings change how the beam will focus and the "gain" it will have. But the LENGTHS of the elements HAVE TO BE CORRECT! The spacing between the REFLECTOR and the DRIVEN elements are critical.
Keep tryin; don't give up!
We are on your side and pulling for you!!!