Practical operation of NEScaf
Submitted by Grant McDuling on May 28, 2008 - 20:06.
G'day guys. I have just completed building my Nescaf and I must say, it's a great piece of gear for any qrp shack. Mine worked first time and I have made good use of it already in stormy weather here in the sub tropics. I would like to hear from experienced users what the best way to use the filter is. I find I am flat strapped just copying fast code without having to work out which knob to twiddle half way through a qso. What have you found works best? Where should the knobs be set to start off once the filter is switched in? Which pot is best to tune in first? Any ideas that could help would be most appreciated.
Cheers from Brisbane, Australia.
NEScaf operation
Submitted by Grant McDuling on May 29, 2008 - 19:13.
Many thanks for the comprehensive reply, Bruce. Although I have already found the filter to be most useful (and add to the enjoyment of using my SW40+) I now envisage it becoming an invaluable addition to my shack, which is entirely qrp by the way. As you described, I see it being a real necessity when using my Rockmite, Pixie 2 and DC40A rigs.
Grant VK4JAZ
NEScaf Operation
G'day Grant.
Glad you are enjoying the use of the NEScaf. Having the fully variable bandwidth and center frequency pots are powerful tools. Like all tools, having them doesn't mean you -have- to use them. It is good to have them when you need them, however.
The best practice is to properly set up the filter for the rig you are using. That is, set the trimmer pot for the 555 clock generator so that the center detent of the front panel frequency pot corresponds to the transmit offset of the radio. So if the radio you are using has a transmit sidetone (and presumably transmit offest) of 600 Hz, then that is what you would set the center detent of the frequency pot to. The kit instructions provide guidance on how to accomplish this.
Once you have done this initial step, then the filter can be used as a tuning aid. Leave the frequency pot at it's center detent. Then start at a fairly wide bandwidth setting. As you tune across the band, and find a signal of interest, you can narrow up the bandwidth. Carefully tune the radio, with the bandwidth at a fairly narrow setting. You can tell when you come right onto a station's operating frequency by the peaking of the audio level in the 'phones.
In general operation like this, you will usually leave the frequency pot at it's center position. However, If you are using a fixed frequency rig (crystal controlled, like the Rock-Mite), or if someone responds to your CQ somewhat off-frequency, you can adjust the center frequency of the filter to "focus in" on the calling station. This allows you to adjust the receiver response without changing your operating frequency. This can be a powerful tool.
In summary, the continuously variable frequency and bandwidth controls can be very helpful, and can add great flexibility to your operating enjoyment.
72/73,
Bruce N1RX