[RTTY] bandpass filters

[Jeff AC0C]

To suppress harmonic content that is generated by the amps.

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: Al Kozakiewicz
Sent: Sunday, March 20, 2016 8:25 AM
To: Bill Turner ; RTTY Reflector
Subject: Re: [RTTY] bandpass filters

Since the highest power transceivers are 200 watts, why would you need 
filters rated for 1500? There is no technical reason I can think of why they 
can't go between the xcvr and amp.

Al
AB2ZY

-----Original Message-----
From: RTTY [mailto:rtty-bounces at contesting.com] On Behalf Of Bill Turner
Sent: Saturday, March 19, 2016 11:15 PM
To: RTTY Reflector
Subject: Re: [RTTY] bandpass filters

Bandpass filters at the 1500 watt level are quite expensive - around
$400 for each band. Do the math.

If you want to save some money, you can build your own.  Accompanying each 
ARRL Handbook is a CD which contains design software for high pass and low 
pass filters. By choosing the cutoff frequencies carefully and putting them 
in series, you could save a considerable amount of money.

This particular software is especially useful because it uses standard value 
components. In fact that is the name of the program: SVC Filter Designer. 
Here's a hint: Each filter segment can be looked at as a parallel resonant 
circuit, i.e. a coil paralleled by two capacitors in series. You can use a 
grid dip meter to carefully adjust the coil to resonate at the frequency 
given by the standard equations for resonance. Do each filter segment 
separately, then connect them together. You can check the final result by 
sweeping it with an SWR meter while terminated into a dummy load or a real 
antenna.

It is also available at this website:  http://tonnesoftware.com/ along with 
other filter design software and there may be others as well. It is well 
worth browsing around.

73, Bill W6WRT
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