WA Radio Scanner Users' Group

Hello

I am installing a new 12db base antenna on the side wall of my house, I want to do a proper job and run the coax through the roof and down to a wall plate in my radio room.

I was thinking about making a custom PL259 wall plate. The idea is have the female end in the wall plate and create a custom coax lead (male - male). By doing this, do I lose (noticable) transmission? Has anyone done this before? I have tried searching for the plates but nobody seems to have them.

Please help!

Rusty_Nail wrote:I was thinking about making a custom PL259 wall plate. The idea is have the female end in the wall plate and create a custom coax lead (male - male). By doing this, do I lose (noticable) transmission? Has anyone done this before? I have tried searching for the plates but nobody seems to have them.

I've done much the same as what you're asking, except I used an N-type connector rather than the PL259 type...



That's a normal "blank" wall plate with an N-type socket mounted on there. You could do much the same thing, by getting an SO239 panel mount connector from somewhere like Altronics.



Then, use a PL259 patch lead as you mentioned to connect to that wall plate. Be aware though that in a thunderstorm, your antenna is going to have currents induced into it from the storm, which is going to come right into your "shack" and be present at that wall socket. In an ideal world, you'd have a way of disconnecting your antenna cable before it got into the house, but that's not always possible. Next best thing would be to remove the patch lead from the wall socket whenever there's a thunderstorm forecast.

As for signal loss, the short answer is yes, you will get a loss every time you have plugs and sockets inline with the cable. How much loss really does depend on a number of factors, but again, it's a compromise between what's ideal and what's practicable

If you are more concerned with loss than looks you could run the coax through a blank wall plate with no connector straight into the back of your equipment.

Nice looking wall penetration, no additional connectors, but consider that during lightning you could have a live wire inside the room.

Thanks for that everyone.

I've got a pretty decent antenna on it's way, so signal loss shouldn't be too much of a problem.
I think I'll go for the wall plate option, just so it looks a bit neater if I ever sell the house.
I've been told to use RG213 coax, honestly is there much of a difference between using this and the normal (cheaper) stuff?

Cheers

Rusty_Nail wrote:I've been told to use RG213 coax, honestly is there much of a difference between using this and the normal (cheaper) stuff?

When you say the normal / cheaper stuff, do you mean RG-58 type cable, the sort that's thinner?

If so, then yeah it can make a difference. Take this chart for example - look at the loss per 100ft for RG-58 vs RG-213... At a frequency of around 400MHz (where a lot of the commercial stuff is located), the loss is 11.2dB whereas for RG-213 the loss is only 4.8dB. If you can get your hands on some LMR-400 cable, that'd be even better again, with a loss of only 2.7dB at 450MHz. Of course, the lower the loss, the more dollar notes you have to extract from your wallet

http://www.w4rp.com/ref/coax.html

Ahh huh! I shall use the better stuff then, I don't really want to lose signal
I'm still deciding on whether to solder up a SO239 Female wall plug, or just have the cable running straight into the room (don't cut it). Lightning strikes are a concern, as someone mentioned before, there would be a live wire running into to room if the antenna was hit by lightning.

I did find this on ebay:
http://cgi.ebay.com.au/BLANK-WALL-PLATE ... 20b4629cbb

It's a clipsal wall plate that has a brush like feature keeping out dust etc and making it look a little tidier.
If I ever move house, I simply just pull the antenna's down and pull the cables out.

Thanks

I use a double light switch plate

I chucked the switches and put in bulkhead adaptors (basically a double ended socket with mounting nuts and washers) The cables come down inside the wall and plug into the back of the sockets. There needs to be sufficient room behind the plate of course. I'm using N-type connectors, but the same exists for SO-239 which looks like this

There is some small insertion loss for the connections but the convenience makes up for it.

Otherwise one of these might suit you.

You fit the coax to the back the same way as you would any similar PL-259. http://www.radiospecialists.com.au have them. I haven't seen them in Jaycar or Altronics.

On 10 meters, a full-length 1/4 wave, unloaded antenna is about 96 inches long, but again may be somewhat shorter due to the mast size. Depending on the antenna brand in question, covering 10 and 12 meters will likely require installing a shorter whip. When it doesn't, it means the overall losses are higher than they should be.

Any 160 meter mobile antenna will have very poor efficiency, perhaps as low as .3%. A really good one perhaps 1%. Part of the issue is the requisite inductance of the coil. Even an antenna 13 feet in overall length will require an inductor in the neighborhood of 600 uH. Using the very best of construction techniques, maintaining a Q of even 100 is difficult.