Re: OT: High Frequency coax?? Copper tubing??

GerryR
 

Thanks Dennis,
After I asked the question I did look up the cable and found out its characteristics. I've spent most of my career (now retired) in industrial electronics / control systems, so some RF stuff still puzzles me. For instance, recently I inquired about a tunnel diode pulser from a person who makes them. He stated that he offered them with SMA connectors; I wanted BNC connectors. He told me that he couldn't get the response with the BNC's that he can get with the SMA's, yet Tektronix offered (at one time) a tunnel diode pulser that had a better response than what he offered, with BNC connectors. Why? Thus, my question as to why the semi-rigid cable is so much better at the higher frequencies? Just curious. Thanks, again; I didn't mean for anyone to do my homework for me.
Best regards,
GerryR
KK4GER

----- Original Message -----
From: "Dennis Tillman W7PF" <@Dennis_Tillman_W7PF>
To: <TekScopes@groups.io>
Sent: Sunday, November 03, 2019 4:54 PM
Subject: Re: [TekScopes] OT: High Frequency coax?? Copper tubing??


Hi Gerry,

Every general class ham should have a coax chart at your fingertips somewhere. Personally I prefer the quickly accessible Wikipedia article on Coaxial Cable at https://en.wikipedia.org/wiki/Coaxial_cable. It contains a very detailed chart listing a very large number of coax types and all of the important parameters anyone would need to compare them all.

It says the insulator / dielectric for RG-402 and RG-405 is PTFE (aka Teflon).

Dennis Tillman W7PF

-----Original Message-----
From: GerryR
Sent: Sunday, November 03, 2019 11:15 AM

I'm not at all familiar with this type of coax. What is the core material, and what makes it so good at the higher frequencies?
GerryR
KK4GER

----- Original Message -----
From: "Dennis Tillman W7PF" <@Dennis_Tillman_W7PF>
Sent: Sunday, November 03, 2019 1:46 PM

These two sizes of Semi-Rigid Copper Coax cable are very common:
RG-402 which is 3.58mm OD (0.141" OD)
RG-405 which is 2.20mm OD (0.0865" OD)

Working with it is very different compared to typical coax we are all used
to. Tools to cut it properly and to bend it properly are expensive. Using
common tools to cut it like a pipe cutter, and to bend it like an
inexpensive bending jig, will almost certainly affect the high frequency
performance of whatever you make.

Dennis Tillman W7PF

-----Original Message-----
From: Reginald Beardsley
Sent: Sunday, November 03, 2019 9:01 AM

Here's a representative link for the information you're looking for:

http://www.sumlocable.com/sub_product/rg401-rg402rg405-semi-rigid-43.html

There's lots more. This was simply the first one google tossed up. It is
great stuff provided you don't want to bend it more than once. Though
rebending used cables is OK. The solder filled braid "RG402" has become my
standard cable for anything above 1 GHz. I've made a couple of H field
probes from a used piece of high grade stuff.

Connector quality on Chinese ebay jumpers is rather variable. I've been
documenting my efforts in this thread:
https://www.eevblog.com/forum/rf-microwave/testing-rf-connectors-and-cables/

I will be supplementing the TDR results with 8753B/85046A testing soon now
that I have an APC-7 cal kit and adapters.
Have Fun!
Reg
--
Dennis Tillman W7PF
TekScopes Moderator




--
Dennis Tillman W7PF
TekScopes Moderator

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