Page 38 May June 2014 TCA

Figure 6: Diplexer Circuit
Diagram

As for the design impedance, Heatherington to design air wound inductors with the Figure 8: VE4CWF working SO-50 on a cold night.
says: “Set the I/O impedance to match the correct inductance. I had to tweak the
transmission line you are using.” In my length of the coil and number of turns until With these promising preliminary results,
case that was 50 Ohm RG-58 cables. I found a design that was a close match to it was time to try the antenna on a high
the calculated values.
The last parameter to consider is the number satellite pass.
of poles. For simplicity, I chose a three- I built the diplexer on a piece of circuit On January 10, four days after the NHL
pole design as shown in the schematic. board and installed it in a box on the side lockout ended, I walked out into the feld
Heatherington says additional poles can of the antenna, making the coax next to my house and made my frst
improve the performance of the flter. connections directly to the flter, again to
reduce any insertion loss. The fnished contact via the SO-50 satellite. Figure 8
“More poles improve the stop band diplexer is shown in Figure 7. Note the two shows the QSL card I received from Frank
rejection,” he said. “Adding poles reduces 10 pf capacitors in parallel to produce the Griffn, K4FEG, a 1600 km (1000 mile)
the unwanted signals.” But there is a 20 pf needed for the circuit. QSO. Since then I have made numerous
compromise as increasing the number of other contacts, received my Satellite
components will increase the signal loss FINISHING TOUCHES Communicator’s Club award from AMSAT
through the flter. Something I didn’t want and collected nine other cards on my way
to risk when receiving weak signals from a Once the antenna was built, I mounted the to the next award.
distant satellite. diplexer box and neatly clamped the
cables to the boom. Then I reinstalled the Satellite SO-50, I’m told, can be a tricky
Once the design parameters have been blade of the hockey stick. I have no means bird to work. But with AMSAT working on
entered into Heatherington’s calculator, of checking SWR so I went straight to the two new satellites – and plans to deploy
it will output two different circuit feld test. them in the next few years (see page 20)
confgurations, complete with diagrams, HE SHOOTS, HE SCORES
and three sets of component values for – now is the time to build a satellite
Chebyshev, Butterworth and Bessel style (Testing and Operation) antenna and begin operating. It need not
flters. Heatherington says Butterworth is The VE4MAN repeater is about 70 kilometres be costly or complicated; just use what
the most popular. (45 miles) from my home QTH, and on my you have available and use some
innovative thinking and, hopefully, I will
“It has fat response in the pass-band and frst key-up I was able to hit the repeater hear you scoring goals the satellites too.
fairly good roll-off into the stop-band,” he while standing on the deck in my backyard.
said adding that all styles have Darcy Wilson, VE4DDW, who was mobile RESOURCES:
advantages and disadvantages. at the time, gave me a report of full Cheap Yagi Antenna Design:
“Chebyshev gives you steeper roll-off in quieting. With his help I was also able to http://www.wa5vjb.com
the stop-band at the expense of ripples in check the UHF portion of the antenna on
the pass-band. The least popular is the transmit and receive. Filter Design: http://www.wa4dsy.net/flter/
Bessel which has poor roll-off and flterdesign.html
stop-band rejection but has linear
phase in the pass-band.” Inductor Design: http://hamwaves.com/
antennas/inductance.html
I tweaked the flter design
parameters enough to produce Floor Hockey Sticks:
capacitor values close to values I http://www.canadiantire.ca
had available. I then used another
web-based calculator – located Christopher Friesen recently received his
online at http://hamwaves.com/ Advanced class Amateur Radio licence.
antennas/inductance.html – He writes and blogs about radio at:
http://radiofrequencyinternational.wordpress.com/
Figure 7: K4FEG QSL card.
36