Why does Huber+Suhner report their RG400 cable as having max frequency of 6GHz? - Page 1
Forum section: electronics / testgear

author: matthuszagh
author_rank: Frequent Contributor
timestamp: December 09, 2023, 05:30:52 am
content: Huber+Suhner reports the max frequency of their RG-400 cable as 6 GHz (https://www.mouser.com/datasheet/2/829/HUBER_2bSUHNER_RG_400_U_DataSheet-1489640.pdf). The typical max frequency given for RG-400 cable is 12.4 GHz. I also compared the construction with Pasternack's RG-400 (https://www.pasternack.com/images/ProductPDF/RG400-U.pdf) and it appears to be identical. Any idea why HS would report such a low max frequency? Are they simply being conservative?Clearly, no one is using the cutoff frequency, which is 33.6 GHz for RG-400.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: December 09, 2023, 06:09:48 am
content: That H&S, being among the industries' leaders, is applying conservative measures is certainly one half of the explanation. Looking at their connector specs does support this.Another possible explanation would be that they would like to sell you a Sucoflex variant instead.

author: Gerhard_dk4xp
author_rank: Frequent Contributor
timestamp: December 09, 2023, 06:34:21 am
content: Yes, and RG-XYZ is not a standard. It has been withdrawn > maybe 30 years ago .

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: December 09, 2023, 05:29:50 pm
content: Quote from: Gerhard_dk4xp on December 09, 2023, 06:34:21 amAnd yet, when you open the applicable MIL-C-17 typesheet (MIL-DTL-17/128C in this case, which is active), the designator appears again.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: December 09, 2023, 05:33:20 pm
content: BTW, while 6 GHz is a bit low, I would not consider it beyond 8 GHz.

author: jonpaul
author_rank: Super Contributor
timestamp: December 09, 2023, 05:34:49 pm
content: Belden has 12..22 GHz coax and connectors.Look for 4K SDI UHD for broadcasthttps://www.belden.com/products/cable/broadcast-cable/sdi-video-coax-cable/12g-sdi#sort=%40catalogitemwebdisplaypriority%20ascending&numberOfResults=25Jon

author: coppice
author_rank: Super Contributor
timestamp: December 09, 2023, 05:37:27 pm
content: Quote from: matthuszagh on December 09, 2023, 05:30:52 amThe Huber+Suhner data sheet shows a frequency related loss of 1.51dB at 6GHz. The Pasternack just vaguely says the maximum operating frequency is 12.4GHz. My guess would be that means its 3dB or 6dB point. These two things look quite compatible.

author: matthuszagh
author_rank: Frequent Contributor
timestamp: December 09, 2023, 05:50:16 pm
content: Quote from: Neomys Sapiens on December 09, 2023, 05:33:20 pmWhy's that? Shielding effectiveness? Something else?

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: December 10, 2023, 12:33:37 am
content: Quote from: matthuszagh on December 09, 2023, 05:50:16 pm1.) see above post. I personally would not refer to a 3dB point as being 'within the usable BW' when I could get better.2.) shielding indeed.3.) At those frequencies, most signals occupy significant bandwith. Too much dispersion.

author: tooki
author_rank: Super Contributor
timestamp: December 10, 2023, 12:40:37 pm
content: And here is what the aforementioned military spec says:https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=1019(Pro tip: that is the official US government website for military standards. No need to pay for them on other websites.)

author: matthuszagh
author_rank: Frequent Contributor
timestamp: December 10, 2023, 04:52:38 pm
content: Quote from: Neomys Sapiens on December 10, 2023, 12:33:37 amDo you actually mean dispersion? The variation of permittivity of PTFE as a function of frequency (and therefore phase velocity) at 8 GHz is very small. Are you instead referring to attenuation as a function of frequency? If that's the case, do you stick to lower loss dielectrics like polyethylene foam at 8 GHz?

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: December 14, 2023, 07:00:03 pm
content: Quote from: matthuszagh on December 10, 2023, 04:52:38 pmTo say it more precisely, I was thinking about group delay variation. But you seem to be right here. Regarding the polyethylene foam dielectrics: they help, but they do not make the complete cable automatically better. I have to admit that I'm working in areas spared from the usual monetary pressure. So I get the best cable that fits the budget and has (optimally) lots of margin in every parameter. This has carried over into my own lab. When you have ever handled (for example) the heavy duty Sucoflex variant with a PU mantle, which flexes and bends almost like an oversize test lead, it is hard to go back.