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Weather resistant, covered Litz wire wanted.

 

There¡¯s probably some lore that perpetuates the ¡°RF is black magic¡± thing, and all sorts of myths get accepted into such lore. That¡¯s the thing about disjoint knowledge: people may say ¡°PVC is high loss¡± but they don¡¯t know what are the practical implications of it, they only may have heard it said in relation to an antenna or another ¡°incomprehensible¡± object, and the link from that bit of ¡°fact¡± to everyday life just isn¡¯t there.

There is a very nice Starlink customer terminal tear down video on YouTube (that device is a brilliant bit of engineering BTW) and a good vuunk of the comment section just goes to show that magical thinking is here to stay.

Cheers, Kuba

5 dec. 2020 kl. 9:16 fm skrev Chuck Harris <cfharris@...>:

?Ordinary PVC is very, very low loss through low microwave frequencies, as is
easily demonstrated by putting a piece in your microwave oven.

Do you have a reference I can look at that shows your assertion?

-Chuck Harris

Andy ZL3AG via groups.io wrote:

Depending on the frequency, PVC's loss tangent will ruin your loop Q, so try to use
HDPE or LDPE instead.

Possible source of litz wire can be transformers used in high efficiency SMPS's, but
the ideal litz wire (wire thickness and qty of wires) changes, even across the MW band.

If you want to build a kick-arse receive loop for MW, I highly recommend the late
Graham Maynard's "Sprial loop with Q multiplier" as found in Practical Wireless - the
best loop I've ever used (feeding into a Racal RA17L).
 

Could you just put regular Litz wire in teflon tubing?
 

Bruce : I`m trying to resonate this loop over the HF band, but it may be necessary to switch out turns with a relay etc. I plan to use the loop in its non-resonant mode, then resonate it to produce more output.
Sam : Rainer has Teflon sheathed Litz wire available - nice stuff.
OK on dielectric loss of PVC vs PE. Can anybody comment on how well Teflon weathers?

Virus-free.

On Sun, Dec 6, 2020 at 2:52 PM Sam Reaves <sam.reaves@...> wrote:
Could you just put regular Litz wire in teflon tubing?


Virus-free.

 

A bit like Mary Poppins: Practically perfect in every way.

-Chuck Harris

donald collie wrote:
Can anybody comment on how well Teflon weathers?
 

¿ªÔÆÌåÓý

Am 06.12.2020 um 02:43 schrieb Kuba Ober:
There¡¯s probably some lore that perpetuates the ¡°RF is black magic¡± thing, and all sorts of myths get accepted into such lore. That¡¯s the thing about disjoint knowledge: people may say ¡°PVC is high loss¡± but they don¡¯t know what are the practical implications of it, they only may have heard it said in relation to an antenna or another ¡°incomprehensible¡± object, and the link from that bit of ¡°fact¡± to everyday life just isn¡¯t there.

There is a very nice Starlink customer terminal tear down video on YouTube (that device is a brilliant bit of engineering BTW) and a good vuunk of the comment section just goes to show that magical thinking is here to stay.

Cheers, Kuba



Polyvinylchlorid (PVC-U)
Allgemeine Eigenschaften
Werkstoffnummer
2690
Dielektrischer Verlustfaktor 1 MHz IEC 60250 300
Durchschlagfestigkeit IEC 60243-1 40
Dicke f¨¹r Durchschlagfestigkeit
0,6


Polypropylen Homopolymer (PP-H)
Allgemeine Eigenschaften
Werkstoffnummer
1502
Dielektrischer Verlustfaktor 50 Hz IEC 60250 2,5
Dielektrischer Verlustfaktor 1 MHz IEC 60250 3,5
Durchschlagfestigkeit IEC 60243-1 50


Tabelle 18: Zusammenfassung der Eigenschaften von PTFE, FEP und PFA
Eigenschaften Spezifikationen (ASTM) FEP
Dielektrizit?tskonstante D 150 bei 106 Hz 2,1
Dielektrischer Verlustfaktor D 150 bei 103 Hz 0,0001
Dielektrischer Verlustfaktor D 150 bei 106 Hz 0,0008
Durchschlagsfestigkeit D 149 2000

 

Hi, Lize wire is to compensate for skin effect, and the higher the frequency the shallower the "skin" so more wires equals more skin serface and less losses.

Regarding a loop aerial/antenna for reception, coating dsc or dcc litz wire with transformer varnish sounds reasonable.

You will need to protect it from sunlight, some kind of outer tube round it then flood the whole lot with varnish might work but would need a rigid frame to prevent twisting and cracking the varnish.

best of luck , 73s,
OldBlueBear-G4JHT-Dave

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