Comments

  • SLAC Microwave history
    Hi, Pamela, we do have some readers who speak French - could you send us an image and we will pass it along? Email to
  • In a search for a specific article
    Hi, Oz,

    We have a vague memory that "Microwaves" magazine is now "Microwaves & RF", you might want to check with them. Sorry for the delay in answering this!
  • Anti Air Microwave Weapon
    Henderson replied the topic: Anti Air Microwave Weapon

    Thank you Dave.

    With the plasma channel, it depends if microwaves are as efficient as other lasers

    https://www.youtube.com/watch?time_continue=7&v=Kld3TuqsMkE

    https://youtu.be/9tJF3qBWyUk

    If masers can't produce this effect, I won't be able to use them for this.
  • Anti Air Microwave Weapon
    Dave replied the topic: Anti Air Microwave Weapon

    Hi,

    On frequencies: for most power at the given range, you'll be at the lowest frequency. That's due to atmospheric propagation losses, which increase with frequency, and the difficulty of generating high power as the frequency increases.

    There are different levels of vulnerability:
    First, your receiver is vulnerable to interference. Even a relatively low signal at close range can introduce errors in a digital receiver. And if you've ever listened to AM radio during a thunderstorm, the shot of static every time lightning strikes is another example of interference. It doesn't damage anything, but information is not getting through.

    Moving up a little, higher level signals can overwhelm your receiver input. A good receiver will have some protection against that, so that the outcome is similar to the first scenario - nothing's damaged, but information's not flowing. At a certain level though, the components will be damaged. This won't cause the aircraft to fall out of the sky necessarily, but they might lose a critical capability. When you talk about changing frequencies, this is one area where it makes sense - you might have your antagonists tune their emitters to the right frequencies to black out the protagonist's entire communications system.

    The next step up is the big one. At this level, you're not entering the system through the radio front end, but through any and every crack and crevice in the vehicle skin. A couple of loose screws is enough to let these signals through and cause untold damage. Because once they're through the skin, you're talking about voltages that far exceed the breakdown voltage of the components on the board. All of a sudden the board is fried. And because we're no longer limited to entering through an antenna, it could be any board, like an engine management computer or a flight control computer. Now you're talking about the aircraft falling out of the sky.

    Of course to do that, you need to hit the aircraft with a whole lot of broadband energy, like the electromagnetic pulse from a high altitude nuclear detonation. I would guess that the Chinese system you referred to is probably doing a smaller-scale version of that. As you've noted, aircraft are designed to withstand that sort of thing in the form of lightning strikes. But this is the region you'd need to be in for your story.

    My guess (and it's just a guess) is that to create a plasma channel you'd be up at gigawatt power levels. So if your aliens have mastered lightweight, controlled, compact, fusion reactors, it's plausible.

    Happy writing :)
  • Anti Air Microwave Weapon
    Henderson replied the topic: Anti Air Microwave Weapon

    Yes, the thread has a lot of great data, thank you. With the mention of microwave frequency, I figure the aliens can range-find the target then use the frequency which gives them the most power at the given range (possibly adjusting the frequency as the target moves closer/farther).


    My main question if I may, is how vulnerable aircraft would be to microwaves. China's defence system is said to be effective against missiles and tanks, but we can only guess at its capabilities. For my story's purposes, it doesn't matter if the aliens can't fry military aircraft circuitry with their masers (that's what the electro part of the electro-maser is for).

    I'm afraid I don't properly understand how microwaves cause shorts in electronics, I had thought they built up charge. Originally the plan was that the microwaves would build up charge on the plane's skin, then the electricity would hit the plane with the opposite charge and react. According to the person I spoke to, microwaves don't build up charge, and they can't build up charge in the plane's skin, so I'm wondering if this system will work, or if it would require an impossible amount of power.


    Thank you. sorry for my ignorance.
  • Anti Air Microwave Weapon
    Dave replied the topic: Anti Air Microwave Weapon

    Hi,

    Your question is strikingly similar to a thread from 6 months ago

    I think that'll answer your initial questions; have a look and let us know if it raises any more.
  • Storing expensive coax adapters?
    tc replied the topic: Storing expensive coax adapters?

    I think that Desert Sage is correct. Most male connectors are protected to first order by the coupling nut and most female connectors are protected by a threaded sleeve - so a simple dust, water and debris bag or connector cap is sufficient to protect. APC and GR connectors are the exception since the inner conductor is exposed.
  • Storing expensive coax adapters?
    madengr replied the topic: Storing expensive coax adapters?

    Good advice. I had loads of APC7 and APC14/GR900 parts that were left for years in the wooden boxes. The foam turned to this sticky black paste that gummed up the flower-petals center contacts, and teeth in the GR900. Fortunately I have a spray booth with isopropyl and I was able to save them all. Threw out loads and loads of nice wooden boxes with rotten foam.
  • Storing expensive coax adapters?
    Desert Sage replied the topic: Storing expensive coax adapters?

    You just need to keep them dry, clean and dust free. It is not all that critical. The only exception I know is for APC7 connectors, you probably want to leave the threaded portion lowered to protect the flat gold plated surfaces (inner and outer conductors). Also, you should gage them once in awhile. Maury makes good gages. Gages are expensive, but so is the equipment the connectors connect to.
  • Storing expensive coax adapters?
    madengr replied the topic: Storing expensive coax adapters?

    I'd keep caps on the end. Though I never have ordered from the below since I have quite an accumulation of caps (never through them out).

    www.componentforce.com/category/1/caps

    Then use closed foam waffle packs to keep them in. If you have ever seen nasty, rotted wooden cal kit box foam from HP, Maury, etc. its from using open cell foam that rots with moisture absorption. Sometime in the 90's they switched to closed cell foam and no more problems. Maybe some pluckable foam storage cases; i.e. Pelican cases with a desiccant bag (they may be open cell foam but the desiccant should solve that).
  • How to properly torque a right angle SMA connector
    Desert Sage replied the topic: How to properly torque a right angle SMA connector

    Hello. Grey beard here. Here are some thoughts.

    First, I have been making sma connections for a long time. In the lab, I tend to tighten them finger tight unless I am making a phase measurement and then I use a plain old little open end wrench to slightly tighten. If I can't loosen it with my fingers, it is tight enough.

    I don't think the obsession with breaking torque (Ha-ha, microwave parody waiting to happen) is insightful. If it is critical in practice, then stake the connection with epoxy (you don't need a lot).

    The breaking torque is affected by surface finish and cleanliness. A connection made and broken many times will have less breaking torque for the same making torque. If I use a calibrated wrench I click it a few times (I hate break away wrenches).

    It is wise to visually inspect both sides before making connections to look for dirt, damage, even metal particles on the Teflon surface (assuming there is teflon). The metal particles will lower the power handling of the connection and can degrade VSWR. (I worked on space products and we had to gage the connectors, everytime! Pins and dielectric and female holding force.)

    If you see any thing, clean with a DRY q-tip and maybe GENTLE (dry) air clean.
  • How to properly torque a right angle SMA connector
    Dave replied the topic: How to properly torque a right angle SMA connector

    The other variable, even with the right torque wrench, is where you hold it.

    I recall a greybeard once telling me in no uncertain terms that you only ever hold the torque wrench at the end - I've seen some hold it right up near the opening, and if you do that you can apply far more torque than the rated level.
  • How to properly torque a right angle SMA connector
    madengr replied the topic: How to properly torque a right angle SMA connector

    Note that 8 IN-LB are only for steel SMA connectors and 3.5mm connectors. Brass SMA connectors are 5 IN-LB. Which are you using; maybe it is damaging it? I have never measured the breaking torque, but your #1 technique is the proper one to use; not letting the body rotate. This is really critical for the HP style 3.5 mm connectors that have the fingers within the female center socket, as they can be torn out.

    See photos here:

    www.microwaves101.com/encyclopedias/how-...sh-a-calibration-kit

    More torque info here:

    www.microwaves101.com/encyclopedias/connector-torque
  • Short and Open Standard in Calibration Kit
    Unicorn replied the topic: Short and Open Standard in Calibration Kit

    Thank you for your comment.
  • Short and Open Standard in Calibration Kit
    MMWENGR replied the topic: Short and Open Standard in Calibration Kit

    The only clarification I would add is that the VNA knows the polynomial fit coefficients since the cal kit and VNA are a matched pair. If the wrong cal kit is used to calibrate the VNA the accuracy is degraded.

    David
  • Short and Open Standard in Calibration Kit
    madengr replied the topic: Short and Open Standard in Calibration Kit

    No. The SOLT coaxial shorts and opens are offset (i.e. moved from the reference plane) with a delay, and also have a polynomial fit for L and C, respectively. So they are far from ideal, but they are well characterized, thus the VNA can compensate.
  • Straight or 90 degree MMIC input?
    Microwaves101 replied the topic: Straight or 90 degree MMIC input?

    The only times I recall seeing this is when a SPDT switch had both poles exiting on the same side of the chip. If you came out with parallel lines the coupling would kill you, so the 90 degree turn (or just a 45) was the best approach. MMIC switch designers, don't do this ever again please....

    The higher up in frequency (a la mmw), the less likely this will be a good idea.

    Steve
  • Straight or 90 degree MMIC input?
    Desert Sage replied the topic: Straight or 90 degree MMIC input?

    My experience is over 25 years ago. Some of the memories are hazy. The answer to your question is yes I've seen it done and done it.

    However, two caveats come to mind. My experience was the shorter the bond wire the better. But assuming you have a good 50 ohm line close to the pad even at 90 degrees it shouldn't be an issue. We used to laser a hole (for the chip) in alumina to minimize bond lengths. A 50 ohm line running by that hole would be too high impedance due to missing dielectric and would need to be wider. Also, there is a greater chance to EM couple the MMIC to the line that may degrade performance.
  • Rectangular WG transitions - which Z applies?
    UnknownEditor replied the topic: Rectangular WG transitions - which Z applies?

    This is probably not the answer you want, but you can "compute" the mismatch using 3D EM analysis tools....

    Here is my favorite report on waveguide misalignment/tolerance which might be helpful as a way to check the formulas you develop:

    wwwlocal.gb.nrao.edu/electronics/edtn/edtn215.pdf

    Good luck, and please consider "publishing" some of your results on Microwaves101.

    Steve
  • Performance of Limiter with poor match on o/p
    MAH replied the topic: Performance of Limiter with poor match on o/p

    Ok, I will give the NL Capacitor a try.

    Many thanks

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