ssd's Quad Antenna pictures


Attempted dual wire quad element
small large

small large

small large

small large

3 element quad (high gain version)
small large

small large

small large

small large

small large

small large

disassembled 2 element quad
small large

assembled 2 element quad
(horizontal polarization)
small large

driver side down
small large

dark, but at least it's in focus
small large

Quads

Pictured here are (so far):
All of these (so far) are tuned for 442 mhz, use a BNC feed connector, and are designed for a high degree of portability. Notable differences between two and three element quads: Details:
antenna predicted
impedance
predicted SWR
at 4.6 ft RG58
measured
SWR
predicted
loss
predicted
antenna gain
total gain measured gain
2 element 144 2.34 2-4 0.85 7.1 6.3 5-10 dBd
3 element 49.8 1.06 1.7 0.59 9.6 9.0 10-15 dBd
Receive gain was measured vs. a 1/4 wave dipole. Transmit gain is undoubtably worse, due to impedance mismatch. I've yet to even try to match impedance on either antenna, as they seem to work well enough without it, and my preliminary attempts to match it made things worse rather than helping.

More recently, I've made another 2 element version of this using the wire left over from the 2m loop: (0.128" dia). Of course, the big difference is the bandwidth and structural stability; the impedance and losses are about the same.
diameter predicted 2:1 SWR predicted >20db front:back
0.08" 73mhz 15.7mhz
0.128" 85mhz 18.7mhz
I've used all three of these antennas across the 70cm band, and they all work well. The biggest difference with the new antenna is that it is much less fragile with the thicker copper, and I've tuned it to 440mhz (the lowest I intend to use it) rather than 442.

Even with the mismatch, I get full quieting and <3:1 SWR. As I use these antennas on a regular basis, I will probably experiment with methods to get a good impedance match. If nothing else, this might keep my HT from overwarming my hand.

 

return to ssd's Antenna pictures
return to ssd's ham links page