black Beauty HD Low 160-40
Optimized for 160 and 80 meters
The "HD" in the name refers to the Heavy Duty nature of this choke, while the word "Low" refers to the Low Bands. It incorporates two stacked cores and has been optimized to increase Common Mode Rejection (CMRR) and reduce insertion loss on the 160 and 80 meter bands. It is also highly effective on 40 meters.
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 high a CMRR on the 160 and 80 meters band that exceeds 50 dB, as shown in the CMRR plot below.
Insertion Loss
Also because it has been optimized for 160 and 80, the insertion loss of this choke is extremely low: 0.005 dB, or 0.12%, or less. The insertion loss is still very low on 40 meters at 0.02 dB, or 0.46%.
Power Handling
There is no one number that can correctly describe the power handling capability of a Common Mode Choke. Such claims are often inflated and, as a minimum, they obfuscate reality. This may occur because the makers do not fully understand or measure their products.
In virtually all situations, the power handling ability of a Common Mode Choke is determined by the temperature of the ferrite core, which is heated by insertion loss.
The temperature of the ferrite core is always a function of the transmitted power, the insertion loss of the choke (which is a function of frequency), the duty cycle of the transmissions and the ambient temperature. It can also be affected by residual common mode current that flows through the choke if it is an ineffective choke. The common mode rejection of our chokes is so high that residual common mode current is rarely, if ever, a factor.
Notice the 7/8" diameter ventilation holes along the bottom of the our choke enclosure. This ventilation keeps the ferrite core cooler and allows the choke to handle about 80% more power than a sealed enclosure. There are bug screens to keep critters out.
The maximum PEP power that can be used with this choke on 160 and 80 meters is not limited by internal heating but by the power handling ability of the coax used to the wind the choke (RG400), which is specified as 2500 watts.
Check out how much power you can comfortably run on each band at any given ambient temperature by scrolling down to the Power Limitation curves - down past the datasheet below - or by clicking this button.
Return and Warranty Policy
We accept returns for any reason, or no reason, for 30 days after receipt. Our products are also covered by a full 2 year warranty. Please see our Terms and Conditions.
Common Mode Rejection (CMRR)
This choke is optimized for the 160 and 80 meter bands, where it provided more than 50 dB of CMRR.
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 52 dB CMRR on 80 meters. This means that only 0.000631% 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 reduces received noise - sometimes quite dramatically.
insertion loss
Insertion Loss is a function of frequency. The higher the frequency, the higher the insertion loss.
This specialized choke, Black Beauty HF Low 160-40, is optimized for 160 and 80 meters. The loss on 160 meters is only about 0.002 dB, almost unmeasurable. On 80 meters the loss is about 0.005 dB. On 40 meters the loss is about 0.02 dB, still very low. The Insertion Loss plot above graphically demonstrates insertion loss as a function of frequency. The box highlights the frequencies for which this choke is intended.
The insertion loss of our chokes is very small. Such a small amount of loss does not make any discernable difference in signal strength, either on receive or transmit.
However, this loss can be large enough to cause power to be dissipated by the choke, which causes heating of the ferrite core and the coax used to wind the choke. This heating turns out to be the primary limitation that determines how much power the choke can handle. This is why insertion loss is important.
However, this choke's insertion loss on the frequencies of its intended use are so low that heating is of no real consequence. The power the choke can handle is determined by other factors. Recommended Power Limits are shown on this page Power Limitations of Black Beauty Broad 160-10.
What causes Insertion Loss?
The Insertion Loss of the choke is caused by the coax used to wind the choke. Any loss in the connectors or the core is negligible.
One way to think about this loss is to envision about 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. 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, the insertion loss is negligible.
What makes insertion loss matter is that the coax is wrapped rather tightly around a ferrite core. This concentrates whatever heat is dissipated in the coax into a small space. The temperature of the choke will generally rise more than the temperature of the feedline simply because the feedline is spread out and cooled more efficiently.
Maximum power guidelines for black beauty hd low 160-40
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