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Reviews For: CALF KC9ON

Category: Filters, RF: bandpass, duplexer, lowpass, highpass, RFI/EMI

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Review Summary For : CALF KC9ON
Reviews: 3MSRP: 55.00 plus shipping
Description:
Audio filter for CW work. Comes as a kit.
Product is in production
More Info: http://
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
0035
K5MH Rating: 2020-07-04
Sharp and Flexible Time Owned: 3 to 6 months.
For a long time, I have been looking for an audio filter to optimize my CW experience with an ICOM 718. I think I have found it—the CALF from 3rd Planet Solar/KC9ON. Having owned three other audio filters, I am especially impressed by the CALF, a reasonably priced analog filter with an ideal combination of selectivity and flexibility. (I did not take advantage of the option to make it even more flexible by varying the types of active filters and the order in which the filter stages are arranged.)
The CALF offers five levels of bandpass filtering. For my “standard” CALF, the narrowest bandwidth is about 200 Hz at the -20 dB points. When connected to my ICOM 718, the maximum audio selectivity approximates that of my Ten-Tec Eagle. A sixth position of the switch on the CALF attenuates noise bursts such as the static crashes that are common in the summer. Separate gain controls are provided for audio input and for output to the speaker or headphones, and LEDs on the front panel facilitate adjustment of both controls. I have experienced no interference from my transmitted signal, even at the 800-watt level, and the keying sidetone is conducted through the CALF without distortion. The unit delivers a smooth, pleasant note that I have not always found with digital filters. When turned off, the CALF passes audio from the transceiver as if the CALF were not there. Finally, customer service from John, the CALF’s designer, has been exceptional.
K0FTC Rating: 2017-03-31
Excellent AF Filter Time Owned: 0 to 3 months.
I got this filter to use with a KD1JV transceiver being built for me by someone skilled at surface mount and will follow up with a review when I get that radio. However in the meantime I've played with this filter with my KX2 (it uses the same size power connector as the KX2- so easy to power with a splitter from the same power source for the KX2) and TS-590, both radios having great DSP filtering. This filter extends your options to manipulate what you are hearing by the AF filtering of the CALF and while using the IF DSP filters/shift capabilities of the transceiver. I think it really helps to clarify the signal and helps with QRN and static crashes caused by this stormy spring weather. I personally think the signal is less harsh listening with the CALF than the narrow filtering of the transceiver alone. The CALF also has its own input and output volume controls and that has helped with my poor hearing, especially with the KX2, which is pretty low volume for my ears. It also allows an extension of headphones further away from the radio and putting the volume control closer to my operating position. I bought the built model, and John (KC9ON) sent me a graph of the filtering that each of six filter choices provides. (There are a wide variety of options from un-built kit with no case, to a fully assemble with case choice.) John also included cabling and adapters from my stereo outputs to match up with the mono ports on this device. My built model has been done exceptionally well. KC9ON, is very responsive to questions via email, and shipped this unit quickly with documentation. I missed not having more filtering with my KD1JV MTRs on occasion and I am really looking forward to using it with the KD1JV SODA when I get it.
W2OSR Rating: 2017-03-23
Good filter for CW Time Owned: 0 to 3 months.
Works very well with my LNR Mountain Topper to reduce the background hiss. The kit is not for a first time kit builder. Excellent instructions for assembly. Some of the screws supplied could be a bit longer. No noticeable ringing at the narrowest filter position.