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black Beauty broad 160-10 Common mode choke
Optimized for best performance across the HF spectrum - best for multi-band antennas
This choke provides outstanding attenuation of common mode current on each of the HF bands, ranging from 48 dB on 40 meters to 35 dB on 10 meters and 40 dB on 160 meters. This balanced broadband performance is perfect for multiband antennas, especially today's popular end feds, EFHW, EFRW, doublets, OCF dipoles, multiband verticals, and fan dipoles.
All of our products are fully characterized
We measure and publish the performance of our chokes. They are fully characterized, like any other important electronic component or subsystem. A spec sheet is included below and performance curves are provided throughout.
Common Mode Rejection Ratio (CMRR)
This choke is designed to provide the most Common Mode Rejection possible with a choke across the entire HF spectrum, 1.8 MHz up through 30MHz. The CMRR plot is shown below.
Insertion Loss
Insertion Loss ranges from .01 dB at 1.9 MHz to 0.06 dB at 30 MHz. This loss is so small that it has no discernable effect on either transmitted or received signals. The Insertion Loss plot is shown below.
Power Handling
This choke will handle up to the full legal limit of 1500 Watts PEP, depending upon frequency and ambient temperature. Check the Power Guideline charts here.
It is not possible to determine precisely the maximum amount of transmitted power that a Common Mode Choke can handle based only on the characteristics of the choke and the amount of power transmitted. This is because the antenna system in which the choke is used determines how much of the applied power comes back to the choke as common mode current.
The components we use can handle 2600 Watts of transmitted power without any problems. However, the temperature of the ferrite core will actually limit the amount of power you can use without damaging the choke. That temperature is a function of the choking impedance of the choke, the magnitude of common mode current generated by the antenna system, the SWR of the antenna, and the location of the choke along the feedline relative to the standing wave current peaks. These are specific to each installation and so cannot be completely determined in advance.
Some portion of the common mode current generated by the user's antenna system is dissipated in the choke due to core loss. The more common mode current that a particular antenna system generates, the greater the power that will be dissipated by the choke. You can think of it as "how hard the choke has to work" to suppress the common mode current.
The amount of power that a Common Mode Choke can handle is almost always limited by how hot it gets. This, in turn, is greatly influenced by how well the enclosure can get rid of heat. This characteristic is called "thermal resistance". It is expressed as the number of degrees that the temperature will rise inside the enclosure for each Watt of power that the choke must dissipate.
For this reason, Watts Engineering chokes are ventilated. This allows air to flow over the ferrite core, cooling it dramatically. This ventilation allows our chokes to dissipate about 80% more power than comparable chokes in sealed enclosures. Notice the 7/8 inch diameter ventilation holes along the bottom of our chokes. Screens keep the bugs out.
How much power can our chokes handle? About 80% more than anybody else's!
The bottom line on power handling is the temperature of the ferrite core in the choke. Measure this temperature by looking up through the ventilation holes on the bottom of the enclosure with an IR temperature measuring device, such as an IR temperature gun or an IR camera. If the temperature inside the choke exceeds 180F, reduce power or make some changes to the antenna system to mitigate common mode current and/or reduce SWR.
We provide some fairly extensive guidance as to the amount of power that one can expect to use with the choke as a function of operating mode and ambient temperature.
Learn more about Power Handling Ability of Common Mode Chokes
Common Mode Rejection (CMRR)
This choke is designed to provide optimal CMRR over the entire HF spectrum, from 1.8 MHz to 30 MHz.
The purpose of a Common Mode Choke is to reduce, or eliminate, common mode current flowing on the shield of coax feedline. It does this by presenting a high impedance to the common mode current, which "encourages" that current to flow into the antenna instead of back along the coax shield. How well it does this is measured as the Common Mode Rejection Ratio (CMRR).
For example, this choke has about 48 dB rejection on 40 meters. This means that only 0.003981% of the common mode current will be allowed through the choke onto the feedline shield. Which is outstanding.
Common mode current flows on the coax shield because the shield is connected directly to one "leg" of the antenna. Placing a Common Mode Choke at the feed point "breaks" that connection and stops the common mode current from flowing on the coax shield. The choke isolates the feedline from the antenna.
Connecting the shield directly to one "leg" of the antenna also makes the shield part of the antenna. This affects the impedance, the efficiency, and the pattern of the antenna. A Common Mode Choke placed at the feed point preserves that antenna's "native" characteristics.
In addition, some of your transmitted signal is picked up by the coax shield, inducing common mode current on the feedline between the feed point choke and the rig. This current will make its way to the rig and can also cause RFI. Placing another Common Mode Choke near the rig, perhaps just before the coax enters the radio shack, will block this common mode current and further reduce RFI and received noise.
RFI and Noise
Common mode current on the coax shield is undesirable because it causes RFI - your signal interfering with other electronic devices.
It is also undesirable because local noise picked up by the coax shield becomes common mode current flowing on the shield which, without a choke, is conducted directly onto the antenna. This raises the noise level during reception.
This noise will also be conducted directly to the rig, and some portion of it will show up as received noise. The cure is to place a second Common Mode Choke in the feedline near the rig.
Common Mode Chokes stop RFI and reduce received noise - sometimes quite dramatically.
insertion loss & inherent loss
Insertion Loss is a function of frequency. The higher the frequency, the higher the insertion loss.
Insertion loss speaks to what happens to power that is applied to the choke. It includes dissipative loss, which we usually think of as resistive loss. But it also includes mismatch loss. Mismatch loss is determined by the feedline and the antenna and it does not cause power to be dissipated and heat to be generated in the choke. Mismatch loss is dealt with in the antenna tuning and matching and so is not really material to a discussion of Common Mode Chokes except to the extent that SWR greater than 1:1 can affect power dissipation in the choke.
Inherent Loss is that portion of the Insertion Loss that dissipates power and generates heat. We care a lot about Inherent Loss.
For this broadband choke, Black Beauty "Broad" 160-10, the worst case Inherent Loss is only 0.06 dB at 30 MHz, which is 1.38%. Best case loss for the same choke is on 160 meters where the loss is less than 0.01 dB, or 0.23%. The Insertion Loss plot above only includes Inherent Loss and tells the whole story.
The Inherent Loss of our chokes is very small. It is so small that it does not have any discernable effect on signal strength, either for receive or transmit.
However, this loss can be large enough to cause power to be dissipated by the choke, which causes heating of the coax used to wind the choke. This contributes to the heating that limits the power handling ability of the choke. This is why Inherent Loss is important.
Click the button below and to the right to examine the The Power Limitation curves, or click here.
What causes Inherent Loss?
The Inherent Loss of the choke is caused by the coax used to wind the choke. It also includes any loss in the connectors and the core, but these are negligible.
One way to think about this loss is to envision three or four feet of coax added on to the coax feedline. If the feedline is 100 feet long, adding the choke is roughly equivalent to adding four more feet of coax to the feedline - from a loss perspective. The coax used in the choke is very low loss, almost certainly lower loss than the feedline itself. So, from the standpoint of its effect on your signal, Inherent Loss is negligible.
What makes Inherent Loss matter is that the coax in the choke is wrapped rather tightly around a ferrite core. This concentrates whatever heat is dissipated in that section of coax into a small space. The temperature of that coax section will rise more than would a comparable length of straight coax out in the open - simply because the straight piece is spread out and cooled more efficiently.
black beauty "broad 160-10 Max power by band and duty cycle
Run 1500+ Watts PEP at the choke on any HF band as long as the ambient temperature is <120F.
Limit PEP power at the choke to 1400 watts on 10 meters on a 130F day
black beauty "broad 160-10 Max power by band and duty cycle
Run full power on 160 and 80, and also on 40 as long as the ambient is <100F
Limit use of 1500 Watts PEP at the choke to cool days or the lower bands
black beauty "broad 160-10 Max power by band and duty cycle
Run full power on 160 and 80. Also on 40 as long as the ambient is <80F
Limit PEP power at the choke on the other bands based on ambient temperature, as shown
black beauty "broad 160-10 Max power by band and duty cycle
Run 1500 Watts PEP at the choke on 160. Also on 80 as long as the ambient is <95F
Limit PEP power at the choke on the other bands based on ambient temperature, as shown