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VK2ZRG > TECH 01.10.08 11:17l 27 Lines 1196 Bytes #999 (0) @ WW
BID : 2708_VK2ZRG
Read: GUEST
Subj: Re: PL259 losses
Path: IZ3LSV<IK2XDE<F5GOV<VE2PKT<VE2RXY<VK7AX<VK2TGB<VK2IO<VK2AAB<VK2WI
Sent: 081001/0830Z @:VK2WI.#SYD.NSW.AUS.OC #:2978 [Sydney] $:2708_VK2ZRG
From: VK2ZRG@VK2WI.#SYD.NSW.AUS.OC
To : TECH@WW
VK2ZRG/TPK 1.83d Msg #:2708 Date:01-10-08 Time:8:33Z
Hello all technical minded amateurs
John G8MNY wrote in part re PL259 plug losses:-
>Typical plug impedance is 30 ohms for 15mm length. This short impedance
>mismatch means the loss caused is only significant if the mismatch length is
>greater than 1/12 of a wavelength, so this means loss at 70cm is only just
>apparent on a properly made & used plug, & used by a few aerial makers!
>
>Did you know you can get PL259 plugs & SO239 sockets for large low loss LDF550
>coax, for things like 1km VHF radio feeder run on board large ship!
In measuring any losses in these plugs you need to distinguish between
resistive loss and mismatch loss. At 23 cm the VSWR with these plugs is
around 2:1, resulting in a mismatch loss of about 0.5 dB.
One other problem with these plugs is that there're not weather proof.
I wouldn't use them anywhere that they'er likely to get wet especially on
a ship! Sure you can tape them up but that makes it difficult to disconnect
them. My preferred co-ax plugs are type "N", "BNC" and "TNC" for all
frequencies down to DC.
73's de Ralph VK2ZRG @ VK2WI
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