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Posted by swlem3 on December 30, 2023 at 16:38:49.
In Reply to: Re: managing utility noise posted by Ed Holland on December 30, 2023 at 14:00:39.
Hi Ed,
Yes, that's the circuit I'm using. I didn't buy the completed unit though. I found a seller offering just the circuit board. I bought that for just over $10 and added my own case and knobs. I found out later that the board I purchased had a binocular core with a 43 mix instead of the BN-73-202 it should have according to the schematic, so I replaced the 43 bino. I also replaced L1 inductor with a 1mh choke for more reactance at the lower freqs. That's the only changes to the circuit I've made so far. I'm contemplating replacing C7 and C8 caps with somewhat more capacitance but I'm not sure what value to use.
Here's my antenna setup: I'm using two verticals spaced around 100 ft. apart. The verticals are each fed with a 25:1 autotransformer at their base made from two stacked BN-73-202 binos. The verticals are not connected to any radials or grounded... they're on insulators. Either antenna can be the "noise antenna". I use which ever one for the noise that works best.
As you mention, I may increase the turns count on the bino in the canceller itself. That may help at the lower freqs.
I found that isolating one or both antenna inputs with an "outboard" 1:1 bino transformer gave the unit the ability to use the canceller at 630m. I've ordered more BN 73's to replace the 43 mix 1:1's I'm using now. I'm hoping that change will be enough to lower the useable freq of the unit to cover the 2200m band. If not, I'll try the mods of the unit itself previously mentioned.
Here's a pic of the canceller doing its magic at 80m.
www.dropbox.com/scl/fi/rw6ji5vxw9a7pbl5bolsm/80m-cancel.jpg?rlkey=ifs2vmkrmxsu7qq2vwsxmixns&dl=0It really did the job for me. A few caveats... it's good to do a "sanity check" on the canceller. Sometimes you can do just as well using your noise blanker in the rig not using the canceller. The only problem with that is if the noise is too intense, you'll create multiple decodes of the station being decoded (such as in wspr reception) when that station is strong, if you push the blanker too hard.
I'm used to using an sdr instead of a box radio. It's much easier to set the canceller up properly if you have a spectrum display to see what your doing. As stated, each change in freq requires a reconfiguration of the antennas/bino's /pot settings, especially at the lower freqs. That's the price to be paid for getting rid of the noise. Ray
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