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Black Beauty Max 80 Common mode choke
Optimized for the 80 meter band
Best for single band 80 meter antennas.
Best for 160 - 80 meter band antennas.
Best for 80-40 meter band antennas.
Best for 160-80-40 meter band antennas.
This choke has been optimized for the highest possible common mode rejection on the 80 meter band. It incorporates two stacked cores, has, 53 dB of common mode attenuation, negligible Inherent Loss, and can be used with full legal limit power of 1500 Watts on all modes, including FT8/4. No compromises here.
All of our products are fully characterized
We measure and publish the performance 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 provides outstanding Common Mode Rejection (CMRR) of 53dB in the 80 meter band. No other choke can match it. This choke provides very high isolation of the antenna and preserves the antenna's radiation pattern and gain. It reduces conducted common mode current on the coax shield by 99.998%.
Inherent Loss
Inherent Loss is also optimized for 80 meters. It is so small that we can't really measure any. Calculations tell us it is about 0.005 dB, or 0.123%. This has no effect on signal levels, whether transmitting or receiving.
Power Handling
This choke is designed to handle full legal limit power of 1500 Watts PEP on the 80 meter band.
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.
Check Power Guidelines for MAX 80
Learn more about Power Handling Ability of Common Mode Chokes
Common Mode Rejection (CMRR)
This choke is optimized for the 80 meter band, providing 53 dB of common mode attenuation.
The purpose of an inline 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 53 dB CMRR on 80 meters. This means that only 0.002% 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.
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 effectively isolates the feedline from the antenna and 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 will also cause RFI. Placing a second 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.
Electrical noise from the local environment is picked up by the coax shield and finds its way to your receiver. Common Mode Chokes placed at the feed point and at the entry to the shack will get rid of that noise. The resultant reduction in noise floor is often dramatic.
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 (EMI) 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 on the coax shield, 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
Inherent Loss is a function of frequency. Low frequency means low Inherent Loss.
Insertion loss includes mismatch loss as well as dissipative loss in the choke itself. Mismatch loss is determined by the feedline and the antenna. It does not directly cause power to be dissipated in the choke. So, it 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.
This specialized choke, Black Beauty MAX 80, is optimized for the 80 meter band, where its Inherent Loss is only about 0.002 dB, virtually unmeasurable. The Insertion Loss plot above tells the story. This loss is so small that it does not have any discernable effect on signal strength, either for transmitting or receiving.
This choke's Inherent Loss on 80 meters is so low that its contribution to heating of the choke is of no real consequence. The power the choke can handle is almost entirely determined by the amount of common mode current generated by the antenna.
Power Guidelines for each band are shown on this page Black Beauty MAX 80.
What causes Inherent Loss?
Inherent Loss in a common mode choke is the loss in the transmission line used to wind the choke. It also includes any loss in the connectors and the core, but these are negligible at these HF frequencies.
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.
power guidelines, black beauty max 80
Run any mode at 1500+ Watts PEP at the choke on 160 or 80 meters
Run any mode other than keydown at 1500+ Watts PEP at the choke on 40