So I thought things were under control with no growlers and other noise carriers walking around.īUT, I was testing a switching supply for transmit purposes, and lo and behold on 160 and 80 meters, all the gremlins started walking around with my on-ground antennas that have a great s/n ratio, making it easier to hear a problem not being masked by noise. How did I discover this? Like many swl / amateurs, I run a linear power supply and not a switching supply.
Wow - I just proved to myself that I needed TWO of the chokes, even *if you can't hear a problem* !! I have a couple of home made versions of the big MyAntennas CMC-230-5K choke using two FT-240-31 cores and two other types so each favors different parts of the band similar to MyAntennas, but I don't have his exact recipe. It would be nice if you could borrow one to test and then purchase only if you see an improvement. You will never know how much it will help until you try one and in some cases there may be no improvement in noise. Otherwise the CMC-130-3K is the most effective commercially made choke for 160 through 10M on this planet, period. I chose the CMC-0510-R because I mostly use the loop for VLF through maybe 20m and it probably has more isolation at 14MHz out of its range than other brands do within their range. Now I use them on everything at multiple locations including a CMC-0510-R on my new W6LPV receive loop. My home made choke was helping but I had no idea the problem was real bad and that another type of choke would make such a big difference. Turns out my coax passed through lots of computer cables inducing noise onto the shield of the coax and carrying it up to the antenna. Going from the home made to the MyAntennas CMC130-3K reduced my noise floor visibly on my Elecraft P3 spectrum display where many birdies and noise humps went away. The first time I used one was an experiment swapping out a home made 1:1 balun of about 10 turns of RG-142 coax around an FT-240-43 core at the coax to ladder line junction of a ZS6BKW dipole. They also have the most isolation or common mode rejection of any brand made at this time including Palomar. I have several MyAntennas common mode chokes because they make a noticeable difference to me. You can use different lenghts of coax to a second antenna to adjust the phase and then use a variable attenuator to balance out the interference, so it can be built by yourself or bought ready made at different costs.Īntenna phasing & noise cancelling- DX Engineering It's a box that changes the phase and adjusts the level to minimise the interference and all boxes should work the same. If the interference are travelling by the mains wiring it works as an antenna and comes from all directions and that's impossible to get rid off using a noise canceller. It only works with one interference at a time but there's often a major one that helps a lot to get rid off. Using the box you can adjust one source of interference to be phased 180 to the original antenna signal and cancel out the interference. It is a telescope antenna connected to your normal one and a box between that can alter the phase. Having the antenna indoors will let it pick up more interferencies than the coax ever can do, so a common mode choke filter will not do anything for you.
Considering I'm using this entire setup indoors, in my office without the advantages of an outdoor, big, high antenna, is this device something that will provide additional quality and clarity to my listening pleasure or is redundant and unnecessary? Things are working quite well without it, but I'm thinking this would help attenuate various electrical noise generated inside my home from just about everything. Now I've stumbled upon a RX Common Mode Filter Choke / Noise Suppressor / RF Isolator.phew that's a mouthful! I'm not wanting to spend more money on more gadgets just for bragging rights but I don't spending money anytime I can improve something. In addition I'm using an MFJ-1886 loop 'receiving' antenna (for low noise) with a built in preamp. As I mentioned in another thread I recently added a Par BCST-HPF high pass AM broadcast filter. It's well designed and has abundance of features to attempt to provide good performance, NB, NR, Twin-PBT, Notch Filters, Roofing Filters etc. I use an ICOM IC-7600 transceiver for my SWL/amature radio monitoring rig.
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