Hot Indoor Loft antenna Question!

[essexRXer]

This is probably a silly question.

I have now purchased a CB and a power pack- In a vain attempt to save some money, I want to build an indoor homebrew antenna.

Two lengths of Cooker wire cut to 108" each, connected to 50 ohm rg58 clipped to my loft rafters in an inverted 'v' would be a neat solution, however I am worried that I could cause a fire from RF?.

Am I right to be concerned - Should I buy instead?

-Carlos

[scanhermit]

In my youth I had all sorts of homemade dipoles in the loft but never burned the house down. I can only think there would be a danger if you were using a power amp and trying to shove 500watts through a thin copper wire ant.

One other thing - did you buy a SWR meter? You won't transmit very far if your dipole isn't at the right length.

[essexRXer]

In my youth I had all sorts of homemade dipoles in the loft but never burned the house down. I can only think there would be a danger if you were using a power amp and trying to shove 500watts through a thin copper wire ant.

One other thing - did you buy a SWR meter? You won't transmit very far if your dipole isn't at the right length.

Thanks for the reply scanhermit.

I will be running a standard 13.8v bench pack at 3Amps with no boots so you answer is very reassuring. I have not purchased a swr meter as yet, I guess there if it has to be done properly I will need to.

[m0lsx]

I throw 100 watts through various wire antennas in my loft with no issues at all.
If you ever use an artificial earth then tape the end of the wire as I have heard of several people setting fire to bits with the end of an artificial earth which can have very high voltages in it.
Also very inefficient antennas that need massive loading coils on Low Frequency, where they use maybe a kilowatt to produce one watt or less of ERP are known to have created a fire of three.
But if your antenna is efficient it should be fine. Just keep the radiator, especially the ends clear of everything you can.

[essexRXer]

Thanks for the replies, I have now set my wire antenna up in the loft with an inverted V

I have the swr at 1.1 on UK CH1 and a tad under 1.5 on CH 40

No contact made with anyone yet though, its all very quiet

[scanhermit]

Is your rig the old UK40? If you've got the newer allocation and SSB you might hear someone.

[essexRXer]

Well one week in and I have made some contacts!

However with my inverted V in the loft, interesting things are afoot.

I made contact with a mobile who was about 1 mile away and I was not getting out very well, nor was he to me.
However I made contact with someone else who read me at 5 and 9 who was at least 5 miles away.
Both contacts were hard to read for me. So people hear me, I don't copy them well- can anyone explain why. I suspect its the V performs better over longer distances but unsure why.

[m0lsx]

An inverted V is a V & thus neither horizontal nor vertical, it makes a great NVIS antenna, or at height a great DX antenna, where due to the way the ionosphere works any antenna is subject to polarisation rotation. But it is a poor ground wave antenna. So anything via the ionosphere is fine, but it's not a good ground wave antenna.

[essexRXer]

Since my last post I had invested in a new mag-mount 5/8 antenna, I acquired a sheet of metal 1.1m x 1.1m and SWR'd it up in my loft, I managed 1:5 as my highest reading.

I compared the two build that I had and still found that the V was better, so I moved the Magmount setup to my Conservatory roof and SWR'd again.

Still it was no better

I have adjusted the V into a subtle W and now it reads 1:1 across all 40 channels. Today I got some very good signal reports from other stations, they were nearby, however I still find them hard to read them. The solution is to put a real antenna up against the house, but because of the performance of a Magmount; I am reluctant to do so.

If they read me at 9+, there must be something I am not doing!

Yet again I have purchased something that performs no better than a homebrew that I knocked up myself, when will I learn. I am beginning to become quite dissonant about radio and scanning.

[m0lsx]

A VSWR of 1.5:1 is good, with a power loss of just 3%. Of course other factors could mean the loss is much much higher, but SWR is the one that can damage your radio.