Can Coax Handle 10 GHz RADAR Power?

  • Thread starter Thread starter dnyberg2
  • Start date Start date
  • Tags Tags
    Power Radar
Click For Summary

Discussion Overview

The discussion revolves around the feasibility of using coaxial cable to transmit 10 GHz microwave RADAR energy, as an alternative to traditional waveguide systems. Participants explore the technical specifications, potential drawbacks, and safety considerations associated with this approach, particularly in the context of high power applications from older RADAR systems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant questions whether a short piece of coax can effectively handle 10 GHz RADAR energy, citing the challenges of using waveguide due to cost and complexity.
  • Another participant emphasizes the importance of calculating peak voltage and average power to determine the suitability of coax, suggesting starting with RG-8 and considering specialty coax like Heliax.
  • Concerns are raised about the legality and safety of unlicensed RADAR operation, with a warning about potential hazards to nearby equipment.
  • A participant defends their knowledge of RF emissions and safety, while expressing interest in the practicality of using coax over waveguide.
  • One suggestion is made to use SR-250 coax with N connectors, noting expected power loss and power handling capabilities.
  • Participants highlight the importance of considering the voltage rating of connectors and the potential for voltage standing wave ratio (VSWR) issues.
  • Discussion includes the limitations of N connectors in high-frequency applications, with some suggesting alternatives like 7mm precision connectors for better performance.
  • Another participant notes that waveguides are preferred due to their lower loss compared to coax and mentions the implications of changing from waveguide to coax on equipment type approval.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility and safety of using coax for 10 GHz RADAR applications. While some provide technical insights and suggestions, there is no consensus on the practicality or safety of this approach.

Contextual Notes

Participants discuss various coaxial cable types and their specifications, but there are unresolved questions about the exact power handling capabilities and safety implications of using coax instead of waveguide. The discussion also touches on regulatory aspects related to RADAR operation.

dnyberg2
Messages
125
Reaction score
2
I am under the impression that a person might be able to use a short (10 foot) piece of coax to run 10 GHz microwave RADAR energy down instead of using WR90 waveguide. Is this even remotely possible? Is there any such coax that can handle the RF peak pulse or AVG power form an old RADAR set from the 50's? I realize the purpose and reasons for waveguide, but its expensive and usually difficult to work with unlike coax. I'm just not versed enough to know if such a thing can work even if there are acceptable drawbacks like a little extra loss. The RADAR I speak of is an old 10kW Bendix airborne RADAR. I use these type relics from eBay to study RADAR and experiment with high power microwaves. Any useful wisdom from some of you more senior microwave types would be very valuable to me in this endeavor. Many thanks and please... Stay Tuned!
 
Engineering news on Phys.org
The answer is that you should find out for yourself. There are two numbers you need to worry about--the peak voltage, which governs breakdown, and average power, which determines heating. Calculate the peak voltage in the line and compare it to the maximum voltage handling spec of your coax. You'll see that the V rating depends on the cable type, frequency, and altitude. Do the same with average power. Be sure to also look at the rating for the connectors, since they need to be special high-voltage types. Start with standard old RG-8, then look at specialty coax like Heliax from Andrew Corp.

BTW, hope you aren't radiating when performing your radar experiments. Unlicensed radiation is illegal, and can create hazards to and interference with legitimate equipment that is used for communications, aircraft navigation, weather observation, etc. Really, if you are not versed enough in electronics and microwaves to know about power handling, I propose that you may be putting yourself and others nearby at significant risk by attempting to experiment with this equipment.
 
Last edited:
marcusl said:
The answer is that you should find out for yourself. There are two numbers you need to worry about--the peak voltage, which governs breakdown, and average power, which determines heating. Calculate the peak voltage in the line and compare it to the maximum voltage handling spec of your coax. You'll see that the V rating depends on the cable type, frequency, and altitude. Do the same with average power. Be sure to also look at the rating for the connectors, since they need to be special high-voltage types. Start with standard old RG-8, then look at specialty coax like Heliax from Andrew Corp.

BTW, hope you aren't radiating when performing your radar experiments. Unlicensed radiation is illegal, and can create hazards to and interference with legitimate equipment that is used for aircraft navigation, weather observation, etc. Really, if you are not versed enough in electronics and microwaves to know about power handling, I propose that you may be putting yourself and others nearby at significant risk by attempting to experiment with this equipment.


Thanks for your concern but it's unfounded. I know more about microwaves than that. I have proper dummy loads and antennas and output on that band is nearly unregulated. You're not required to go and get a license to operate a marine or aviation radar. They don't exist. I'm intimately aware of exposure limits of RF emissions. On the other hand, thanks for your ideas on the coax. I thought as much but wondered and still do why you never see coax used for this moderate and low AVG pwr. Heliax I know well. There are these exotic coax types that have many thousands of volts of stand off. These magnetrons run around several KV pulses so I guess that's the number to use. Ultimately, my inspiration is ease of use and low cost as well as great flexibility rather than these miles of heavy waveguide I have been using. Thanks for your reply!
 
Sure you could use a short section of SR-250 with N connectors at X band to connect the antenna but I would expect to see at least a 3 db loss of power at 10 feet and it might be able to handle about 200Watts CW at that frequency.

http://www.rf.megaphase.com/documents/datasheets/rf/Semi_Rigid.pdf
http://www.amphenolrf.com/products/CatalogPages/TypeN.pdf
 
Last edited by a moderator:
Don't forget about the voltage rating of the N connectors and potential VSWR. Sometimes the connector rating is less than the coax.
 
N connector has exposed center conductor and low breakdown voltage.
 
marcusl said:
N connector has exposed center conductor and low breakdown voltage.

Is it the best connector for 10ghz power? No, but they can handle 5kW at HF and several hundred at X-band easily with proper matching.
 
Wave guide is used because it has very low loss compared with coax.
The TR switch is usually integrated into the coupling at the bottom end of the waveguide.
When waveguides arc over, they do not burn like the dielectric in a coaxial cable.
You would need to use “airline” coax to reduce loss. It is more expensive than waveguide.

dnyberg2 said:
I have proper dummy loads and antennas and output on that band is nearly unregulated. You're not required to go and get a license to operate a marine or aviation radar. They don't exist.
“Type approved” equipment does not need individual licensing. The manufacturer has demonstrated to the appropriate authorities that the equipment, as inspected, satisfied the regulations. A type approval certificate was then issued to the manufacturer for that version of the equipment.

Changing from waveguide to coaxial cable will certainly void any type approval on the equipment.
 
marcusl said:
N connector has exposed center conductor and low breakdown voltage.

The 7mm precision connectors work up to 18GHz or so and will take 2500V RMS, I believe. Better than type N in many respects - except for price!
 

Similar threads

Can a relay handle both AC and DC power sources?
  • · Replies 15 ·
Replies
15
Views
14K
Adding 3 new wires to 1 fuse in fuse box in car
  • · Replies 29 ·
Replies
29
Views
20K