A CW filter is on the market that is hard to resist if you need help in the selectivity department, MFJ has a setectabie, 80, 110, 180 Hz bandwidth audio filter that utilizes four op amps (2-duaf 741's) in a modern design performance package. It will work with any voltage from 6 to 30V and does not require an internal connection to your receiver.
Packaged with the unit was a very complete set of instructions that makes sure you know exactly what you have just purchased, how it works and a number of ways to wire it mto your receiver. Although it is noted that excellent results can be had by just plugging the filter into the phone jack, the test unit was wired into an SBE-34 sideband rig.
Since 40m is the only CW band that is covered by the SBE, things were tuned up there. The mechanical filter in the unit affords around 2 kHz selectivity, which is fine for general use but not on the novice band on a Sunday afternoon! Everyone was, naturally, clobbering everyone else. With the filter switched in there was a marked change. Signals that were very close were now individually readable. Even at the sharpest position there seemed to be no ringing as the signals popped through the QRM. A damned good filter! The peak frequency is 750 Hz and is comfortable to copy.
if you are a novice with an inexpen* sive receiver, or are a higher class licensee that needs optimum CW selectivity, the CWF 2 filter is probably the best buy on the market today. It out performs filters costing twice its price. It sells for the amazingly low price of
The New DELUXE DIGITAL SYNTHESIZER from
. TRANSMIT and RECEIVE OPERATION — SIMPLEX
(transceivc) and REPEATER MODES
• ACCURATE FREQUENCY CONTROL — .0005% accuracy
• STABLE LOW DRIFT OUTPUT — 20 Ha par degree C typical
• 10 KHr CHANNEL SPACING
• FAST ACTING CIRCUIT — 0.15 ftacond typical sattling time
• LOW IMPEDANCE OUTPUTS — 50 ohm output Impedance both transmit and receive
« LOW SPURIOUS OUTPUT LEVEL — similar to crystal output
COMPLETE STATIONS (WITH SYNTHESIZER)
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