Re: Ecoflex 15?


John Fell
 

For > 432MHz I have used Andrew Heliax 1/2" Superflexible ,foam dielectric cable for turning loops and LDF450 A for straight runs .

LDF450 will survive without loss increase upto the point where the outer solid copper shield starts to crack - this material is substantial and NOT any kind of thin film construction.

Amateur uses tend to put cables into areas that are not specified as suitable by the original manufacturers .This includes contesting - I used to operate with G4RFR and our various reels of 450 were stored in 5Ft rolls , used approximately 8 times a year over a 15 year period .Failure was low and by far the largest failure seen was due to miss handling during setup,strip down .In some cases it survived where a bend had caused the outer shield to flatten and was reformed (not good practice ! ).

People get put off using it , I think , because it is stiffer than UR67 and terminations are "expensive" .

This issue can be solved by using a bored out backnot and turning up a small brass impeadance transformer for the inner solid copper (or plated Alum) conductor .
Design in most UK Microwave Amateur books .I have on occasion formed one using a 1/2" pillar drill and a flat hand file .
The assemblies can be fully soldered and if this is taken through the Hex backnut will stop suck outs to well above 10GHz .

It is not good value to spend a long time building low noise kit and deploying shonky cables that act as resistive pads or actual noise sources .

At least the current crop of handheld VNAs can tell you where it's all gone Pete Tong 

This topic will be repeated ad nauseum ......

73
John
G0API 


On Thu, 18 Feb 2021 at 00:01, Robin Szemeti - G1YFG <robin@...> wrote:
I tend to use flexible heliax, FSJ4-50B is my tool of choice.

On Wed, 17 Feb 2021 at 23:04, Neil Smith G4DBN <neil@...> wrote:
I have a 25 m run of Ecoflex 15 plus that has never been moved and it is
as good now as when it was installed.  However, the runs that I had on
the pump-up, which were coiled carefully into a 1m diameter heap and
raised/lowered once a day on average, started to get suck-outs and
lossiness at 23cm and 13cm after six months. Might have happened sooner,
but I noticed things were getting slightly worse over time. Same with
some patch leads that Tony brought round.  Some that were 2m long had
3dB loss at 13cm and 1.5dB at 23cm, and the loss changed as you moved
the cables. After slicing off the insulation, we found that the copper
foil was split into sections a couple of inches long, with only the
scanty outer braid carrying the current between the sections. It is a
bit of a swine to terminate reliably as well. Flexy heliax is hugely
more practical.

Neil G4DBN








--
Robin Szemeti - G1YFG

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