Hello
Does anyone know what is the actual cable type used in the SKU: FIT0219 cable?
(e.g RG128, etc)
I would like to know the actual loss (in dB) at various frequencies.
The spec says “DC to 12.5GHz” but says nothing about the actual loss.
Thanks
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Hi Gary.
DF Robot seem pretty reluctant to provide this sort of info. Searching around using 1.13mm as a diameter reveals several suppliers refer to this cable as Mini 1.3 co-ax, including Element 14. One could only guess what the RG number is.The difference here is Element 14 DO provide a Data Sheet obviously supplied by Multicomp. Here is a screen shot.
Note that Multicomp only specify 6GHz.
You don’t specify a frequency range you are interested in but if outside the range of this chart I suggest you draw a graph with these figures and extend the curve to get an approximation. Note this is not linear.
As for length this is linear and has a direct relationship.The chart is for 1 metre so if you want the figure or 0.5 metre halve the attenuation figure and so on.
Cheers Bob
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Hi Gary
Add on to above.
If your frequency of interest is not covered by that chart you may be able to pick a frequency approximately double or half one of the chart frequencies. If double multiply the db figure by √2 (1.4142) or if half multiply by √0.5 (0.7071). This will get you close enough for practical purposes. Decibels are a logarithmic power ratio.
For instance if you are interested it 433MHz this is somewhere near 1/2 of 1GHz so multiply 2.4db by 0.7071 to get 1.697 or in round figures 1.7db. That won’t be far out. 433MHz will be slightly less but the difference will be academic.
Cheers Bob
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Thanks Bob, that’s useful information.
I suspect that the reason it’s so hard to get DFRobot (or any of the other suppliers) to give the actual cable used in this product is that they change it, depending on availability of different cables.
I guess that’s ok, so long as they keep to the minimum specs in the table.
Regards, Gary
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Hi Gary
I strongly suspect the cable assemblies are made outside and Df Robot just re-brand and on sell. At least Core leave the same brand on this sort of thing. The cable seems to be just called “Mini 1.3 Co-ax” by the few suppliers I saw including Element 14. I just googled “1.3mm Co-ax” and got heaps of hits.
I just now found a useful article on this cable here
Gives much the same attenuation figures except quoted per foot. For comparison you would have to convert to Metres. Just multiply the db numbers by the conversion factor foot to metres.
Cheers Bob
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Thanks Bob.
That Data-alliance.net link is very useful.
The problem is that, unlike RG174 or RG178, a cable simply specified by its diameter (e.g. 1.13mm, or 1.37mm) does not have any well defined specification.
If two manufacturers make an RG174 cable, we’re reasonably sure that they’ll have the same specs. But if two manufacturers make a “1.32mm dia” cable, how do we know they’ll be the same?
Having said that, these “1.13, 1.32, 1.37mm” do seem to have some sort of de-facto standard.
Gary
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Hi Gary
Could not agree more. If I were still working this practice seemingly across the whole industry would probably drive me mad. On the other hand the type of work I was involved it included projects where high reliability and traceability were a must so this sort of thing could not be tolerated. Especially traceability where a component had to be traceable right back to the batch number during manufacture.
This is not confined to cable either. Connectors are well into the mix. A classic being the Sub D series where all seem to have the prefix “DB” which is only valid for the 25 pin shell size. The shell second letter here indicates the shell size for the number of “standard” pins. 9 pin = DE, 15 pin = DA, 25 pin = DB, 37 pin = DC and 50 pin = DD. The real confusion comes with 15 pin, they come in DE size (commonly called VGA connector) or “standard” DA size. This convention should be used (although rarely is) as it differentiates between “standard” pin spacing and “high density” spacing. For instance a DE15 is a 15 pin high density in a 9 pin size shell while a DE9 is a “standard” 9 pin connector (sometimes called a “serial” connector. Then you start putting co-ax and high voltage connections into a D shell. Do these all get the “DB” treatment?
Speaking of Co-ax. The connector these days called a “PAL” connector I always knew as a “Belling-Lee” connector and was sometimes used on VHF mobile 2 way radios and some early test equipment, long before “PAL” television. There are a few miniature types to keep track of too.
Multi pin connectors these days seem to sometimes get tagged with whatever device they are mostly used on for a type. I would assume in the background they will each have a “proper” type designation if you can find it. The JST series could be an example here.
I am sometimes glad I no longer work full time and have to deal with this on a daily basis although as mentioned it would have been unlikely if I had being doing the same work.
All too confusing what !!
Cheers Bob
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