cable thickness
 

hi,just noticed new billboards advertising virgins "cable thickness" compared to bt infinity's "cable thinness".pretty pathetic sexual innuendo regarding the images.very Frankie howard.Anyway does the thickness of cable make a difference as virgin are claiming as I would have thought bt would be using comparable quality cable just thinner.Just wondering.

Re: cable thickness
 

May be frankie Howard style but it caught your eye - job done !

Re: cable thickness
 

In electrical wiring, thicker cables have higher bandwidths.

Re: cable thickness
 

The exact opposite of the truth. Thicker cables have lower bandwidths. But they also have lower resistance and thus lower loss.

http://www.microwaves101.com/encyclopedias/coax

---------- Post added at 17:47 ---------- Previous post was at 17:44 ----------

I guess they got bored of yelling "fibre optic" when people wised up to the fact their competitors had just as much if not more "fibre optic".

In respect of broadband, it's the type of cable making the difference, not the thickness. Coaxial and twisted pair are completely different types of cables.

I haven't seen the ad but I suspect it'd fail to mention VM's "thicker" cable gets shared between *cough* hundreds of *cough* users.

Re: cable thickness
 

My electronics and radio telecomms training and experience tends to disbelieve that. Even aerial dipoles are made "thicker" to increase bandwidth. :dozey:

Re: cable thickness
 

But a dipole isn't coax, the increased spacing between centre and shielding will reduce bandwidth but will also reduce attenuation but will increase power handling.

Re: cable thickness
 

As I understand it those who know always rated girth over length to be honest.

Re: cable thickness
 

......and that is why I'm a lesbian ;)

Re: cable thickness
 

Me too.

Re: cable thickness
 

Im just glad they are no longer telling customers we install fibre to the house

Re: cable thickness
 

I'm a lesbian and so is my wife.

Re: cable thickness
 

Your electronics and radio telecoms training seems to have missed out some very basic principles then it seems, like higher order propagation modes.

http://whites.sdsmt.edu/classes/ee48...1Lecture10.pdf

Aerial dipoles are not made thicker to increase bandwidth.

---------- Post added at 10:30 ---------- Previous post was at 10:29 ----------

Exactly this. Thicker cables will carry higher frequencies and more power longer and further as long as those frequencies don't exceed the maximum cut-off frequency (i.e. bandwidth) of the cable .

---------- Post added at 10:31 ---------- Previous post was at 10:30 ----------

Without girth, length would be impossible. But without length, the girth would be useless.

Re: cable thickness
 

I knew I was been misled

Re: cable thickness
 

Thicker elements on a dipole will provide a wider VSWR bandwidth, the technology is used with birdcage dipole elements. Thicker wire in coils for filters will have the opposite effect, having a higher Q than thinner wire produces a narrower bandwidth. Duplex filters or notch filters of the lumped variety etc are often made with microbore plumbing pipe or thick silver coated wire to provide the low losses and high Q required for a sharp cut -off in the case of a duplex filter or narrow bandwidth and low out of band losses for notch filters.

Birdcage antennas often get mistaken for the fan dipole variety, these use thinner cables of slightly different lengths to broaden the resonance.

Re: cable thickness
 

As fascinating as "skin effect" is to whatever Yagi / Moxon / Spider / Delta / Quad etc array we discuss then I still believe the Cable thickness is inversely proportional to the posters IQ... :p
73's and 88's ...

Re: cable thickness
 

I use SSB Aircell 5, as well as LMR400. What does that say about my IQ?

Re: cable thickness
 

Not entirely true, the thickness of a transmission antenna can increase the resonant bandwidth so a thicker dipole might have more bandwidth than a thinner dipole but this bandwidth is in relation to forward and reflected power (otherwise known as SWR measurements).

This is though totally different to bandwidth of a carrier medium like co-axial cable of which he is getting mixed up with.

Re: cable thickness
 

Ah, resonant bandwidth... I was thinking resonant frequency and baseband bandwidth.

Re: cable thickness
 

Practicalities seem to be the biggest problem with thicker elements, it's not much of a problem for VHF or UHF but to make a large increase with for example a top band dipole would be impractical, hence the use of birdcage for HF. I did play around with a prototype VHF 30-90MHz Fractal antenna a few years ago, that had a nice wide bandwidth, reasonably good efficiency and low VSWR across the band, unfortunately the design wasn't mechanically practical for the intended application.


The biggest limitation on bandwidth with coax is generally the absorbing properties of the dielectric as frequency increases. The formula to calculate the loss at a particular frequency when provided with the actual loss at a lower frequency is generally logarithmic until this point is met, then it becomes very unpredictable. The use of a foam dielectric in cables such as LDF4-50a and LDF5-50a (There are more modern types and this shows my age) allows them to be used generally at a higher frequency than the PTFE dielectric types.

Re: cable thickness
 

Ecoflex 15 inparticular which has a gas rich dielectric compound is usable up to 6GHz and there's a more recent plus version which can run up to 8GHz.

I use it on my 2m and 70cm arrays which is probably a bit of overkill but it's mechanically very nice and flexible thus easier to route and work with than hardline :)

Re: cable thickness
 

Aircell 5 is 1/3rd as thick and rated to 10Ghz.

Re: cable thickness
 

Aircell 5 is nice stuff for a short run. A bit lossy for my application as there's a pretty long run up the tower to the pre-amps so the Ecoflex 15 was the compromise between having something approaching heliax for attenuation characteristics but flexible enough to work with easily when doing installation and maintenance.

Re: cable thickness
 

Yeah, it's power handling isn't particularly high either but enough for short runs on 2-6Ghz microwave bands as you say. I have a reel of LMR400 as well. Not as good as Ecoflex but a bit cheaper but both are just too thick to run around a building without anybody noticing :p: (Bloody conservation area/listed buildings...)