[TowerTalk] RG402 for Choke/Balun

[Lux, Jim]

On 3/18/21 7:07 AM, Máximo EA1DDO_HK1H wrote:
>
> Jim, I appreciatted your point of view.
>
> Do you think RG402 is good to build chokes at HF on FT240's ?
>
That depends. I don't think the loss is really an issue - it's a short 
length in a choke.


In a choke application, you also have to be concerned about where the 
windings fall - so that your choke isn't bypassed by a parasitic C.


It's more about mechanical things - 141 is really stiff, and it's fairly 
expensive. If I had a big supply of surplus at near free prices (I've 
seen such stuff - old silver plated stuff that is all tarnished, but 
perfectly usable) then the possibility of having to cut it off the core, 
and try again wouldn't be a big deal.


It also depends on how pretty you want it to look.  Once formed, it's 
hard to straighten back out and reform, so if you're recycling or 
rewinding, your turns are going to be lumpy.


I'm used to using it with SMA connectors, crimped on. There are N, and 
probably UHF, connectors available, but it *is* a small diameter cable 
(between RG-174 and RG-58 sized).  I've never used it for "high power" 
(> few watts), but if you do, at least it has well defined thermal behavior.


Can't beat it for shielding, of course - it's basically copper tubing.



One of the choke gurus (Jim K9YC) should weigh in on the "performance" 
aspect.


>
> Thank you
>
> 73, Maximo
>
> ------------------------------------------------------------------------
> *De:* TowerTalk <towertalk-bounces at contesting.com> en nombre de Lux, 
> Jim <jim at luxfamily.com>
> *Enviado:* jueves, 18 de marzo de 2021 14:01
> *Para:* towertalk at contesting.com <towertalk at contesting.com>
> *Asunto:* Re: [TowerTalk] RG402 for Choke/Balun
> On 3/18/21 6:07 AM, john at kk9a.com wrote:
> > I have no experience with RG402.  It appears to be a little smaller
> > and it has a steel conductor.  What RF properties are better?
> >
> > John KK9A
> >
> >
> More commonly known as 0.141" semi rigid (vs 0.085 and 0.047.. there's
> even tinier ones, and a bigger one )
>
> The center conductor is copper clad steel, so the copper is carrying the
> RF, at least in the typical microwave application.
>
> There's also some "formable" coax which is more flexible than semirigid,
> but stiffer than typical flexible coax. The challenge with semirigid is
> that the copper jacket work hardens on bending, so you sort of get one
> chance to bend it to the shape you need.
>
> We use them at work when you worry about leakage (solid shield doesn't
> let much though), and when you want the cable to be "self supporting"
>
>
>
>
> > Máximo EA1DDO wrote:
> >
> > Hi all,
> >
> > I normally use RG400 for chokes on FT240 toroids.
> > Recently I've tryed RG402 semi-rigid coax cable, the "blue one".
> > RF properties are quite similar, in fact RG402 seems to be a bit
> > better than RG400.
> > Because RG402 is semi-rigid, is much easier to make tight turns on the
> > toroids, easier to work with.
> >
> > After some months using it, HF bands legal limit amp, I can't see any
> > issue.
> > Just wondering if I am missing anything, or if someone else have tried
> > the RG402 coax.
> >
> > Thanks
> >
> > 73, Maximo
> >
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