Welcome!

Here is the "whole house" TVSS I built. I have been warned that if the house

burns down, my insurance company may frown on this device. It is, however,

protected by 2 15 amp fuses in the breaker panel. This is a must. MOV's have

been known to short and catch fire if not fuse protected. The TVSS is mounted

on the wall just above the breaker panel. It will fit inside the breaker panel but I

mounted mine outside the panel so I can monitor the 2 green neon lights mounted

in the box. If one or both of the neon lights are out, the TVSS has done it's job and

one or both of the breaker panel 15 amp fuses have blown. Be sure to keep the

wires from the breaker panel to the TVSS box as short as possible (under 30 inches)

and twist the wires together once in the panel. Select 2 breakers that are side-by-side

so you catch both 120v legs feeding the house. This device is not fool proof but it is

better than nothing and cheap to build and install. Wire size is not critical and I used

14-2 with ground Romax. Increasing wire size does not increase efficiency. Most store

bought TVSS's use #14 stranded. The 4"x4" plastic electrical box was purchased from

Lowes. I made a stand-off insulator from some scrap plexiglass and the screws are

brass from Lowes. The rest of the parts came from Mouser. Be sure to buy spare

MOV's and GDT's! You are working with 120 VAC and 240 VAC and an open

breaker panel so KNOW WHAT YOU ARE DOING!!!
73,
Gary, AI4JA


Mouser (and other) parts list

2 - 576-V20E130P  130Vrms 10kA Metal Oxide Varistor (MOV) (order 2 spares)
2 - 576-SL1011A600A  600V Gas Discharge Tube (GDT) (order 2 spares)
2 - Radio Shack 272-0708 120Vac Green Neon Lamp Assembly 2 per bag

(try finding cheap neon lights these days!
2 - Spare 15 amp breakers in you home load panel



Why did I use a MOV and GDT? GDT's are quick acting but cannot handle high current. MOV's are slower acting but carry higher current. The GDT starts clamping

current while the MOV catches up. Both of these devices work by clamping over voltage/current to ground. If the surge is not short but long, as in a high voltage line

falling on another, both devices usually fail in a short mode causing the breaker to trip. Sometimes they fail in an open mode. They do not protect from "brown-outs".

MAKING A J-POLE FROM 450 OHM LADDER LINE

Paul  K3LLH

I needed a two-meter antenna for a project and it also had to work on 440 MHz and it had to be quick, easy and cheap.  The solution is out there on multiple web sites and so I tried the 450 ohm ladder line since I had some lying around.  Here's how it's done.

Take a piece of 450 ohm line (I buy mine from The RF Connection - www.therfc.com) about 5 feet long and strip off about 1/2 inch of insulation from one end.  Take those two ends and solder them together to short out the stub.  Clean off the insulation on both sides from 1 inch to 1 1/2 inches above the shorted part. (Fig. 1).

Measure up one side 18 1/4 inches and cut one wire.  Then (here's the hardest part) trim off the center insulation next to the other wire out to the end; it's easy to nick the insulation or your fingers doing this.  In the first case just paint on some liquid electrical tape; in the second try some liquid Band-Aid (superglue works just as well).  Cut off the longer wire at 38 1/4 inches above the cut short wire. On the top of the long wire, strip it and hook it through an eye terminal.  Keep in mind that the dimension of the long wire INCLUDES THE EYE TERMINAL.

 You'll wind up with this (Fig. 2); bear in mind that these are my final dimensions and you may want to start with slightly longer conductors on both sides.  If you do that, trim carefully as you check the SWR, say 1/2 inch off the long wire and only 1/8 inch off the stub: the frequency changes pretty fast.

Then solder your coax (I use RG-8X) shield to the short side and the center conductor to the long side at 1 1/4 inches above the short on the bottom; tie down the coax with a wire tie.  (Fig 3)

Hang the antenna up and try it out.  If the frequency is too high, trim the long piece as I've noted; if it's too high, you'll have to add some bits or start again.  Once you have a dip in frequency, it is tuned to resonance;  if the SWR is still too high, you can move the coax connection point ever so slightly up or down to see how you can change the SWR. The one described above has a pretty good response on 2 meters. (Fig 4)  The antenna also works well on 440 with an SWR <1.5:1 from 445 to 450 MHz.

To weather proof it, coat the terminals with liquid tape; for a super job, you can use silicone sealer and put on a piece of heat-shrink tubing over the bottom connections,  squeezing out the silicone sealer as it shrinks.  The length of the coax is dependent upon your needs.