Hot Indoor Loft antenna Question!

Forum for CB, PMR, Ham, Business users, GMRS, Repeaters and all other TX Chat

Hot Indoor Loft antenna Question!

Postby essexRXer » Mon Jan 16, 2017 11:02 pm

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
User avatar
essexRXer
 
Posts: 170
Joined: Tue Sep 23, 2014 4:04 pm
Location: Essex seaside

Re: Hot Indoor Loft antenna Question!

Postby scanhermit » Mon Jan 16, 2017 11:24 pm

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.
scanhermit
 
Posts: 15
Joined: Sat Nov 14, 2015 10:14 pm

Re: Hot Indoor Loft antenna Question!

Postby essexRXer » Mon Jan 16, 2017 11:31 pm

scanhermit wrote: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. :thumbup: I have not purchased a swr meter as yet, I guess there if it has to be done properly I will need to.
User avatar
essexRXer
 
Posts: 170
Joined: Tue Sep 23, 2014 4:04 pm
Location: Essex seaside

Re: Hot Indoor Loft antenna Question!

Postby m0lsx » Mon Jan 16, 2017 11:52 pm

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.
Buy a database from Kimmy JS19 via http://ukscanningdirectory.co.uk/
Or do Google search of this forum via https://www.google.com/cse/home?cx=partner-pub-6291336405621919:2662881632
73 De Alan (M0LSX.)
http://www.qrz.com/db/M0LSX"
User avatar
m0lsx
 
Posts: 5234
Joined: Wed Nov 21, 2012 9:14 pm
Location: Norwich. TG21.

Re: Hot Indoor Loft antenna Question!

Postby essexRXer » Sun Jan 29, 2017 12:27 pm

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 :thumbup:

No contact made with anyone yet though, its all very quiet :radiocall:
User avatar
essexRXer
 
Posts: 170
Joined: Tue Sep 23, 2014 4:04 pm
Location: Essex seaside

Re: Hot Indoor Loft antenna Question!

Postby scanhermit » Tue Jan 31, 2017 8:48 pm

Is your rig the old UK40? If you've got the newer allocation and SSB you might hear someone.
scanhermit
 
Posts: 15
Joined: Sat Nov 14, 2015 10:14 pm

Re: Hot Indoor Loft antenna Question!

Postby essexRXer » Sat Feb 04, 2017 12:15 pm

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.
User avatar
essexRXer
 
Posts: 170
Joined: Tue Sep 23, 2014 4:04 pm
Location: Essex seaside

Re: Hot Indoor Loft antenna Question!

Postby m0lsx » Sat Feb 04, 2017 12:43 pm

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.
Buy a database from Kimmy JS19 via http://ukscanningdirectory.co.uk/
Or do Google search of this forum via https://www.google.com/cse/home?cx=partner-pub-6291336405621919:2662881632
73 De Alan (M0LSX.)
http://www.qrz.com/db/M0LSX"
User avatar
m0lsx
 
Posts: 5234
Joined: Wed Nov 21, 2012 9:14 pm
Location: Norwich. TG21.

Re: Hot Indoor Loft antenna Question!

Postby essexRXer » Sat Feb 11, 2017 3:39 pm

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 :sad:

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. :sneer:
User avatar
essexRXer
 
Posts: 170
Joined: Tue Sep 23, 2014 4:04 pm
Location: Essex seaside

Re: Hot Indoor Loft antenna Question!

Postby m0lsx » Sat Feb 11, 2017 4:28 pm

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.
Buy a database from Kimmy JS19 via http://ukscanningdirectory.co.uk/
Or do Google search of this forum via https://www.google.com/cse/home?cx=partner-pub-6291336405621919:2662881632
73 De Alan (M0LSX.)
http://www.qrz.com/db/M0LSX"
User avatar
m0lsx
 
Posts: 5234
Joined: Wed Nov 21, 2012 9:14 pm
Location: Norwich. TG21.

Next

Return to The TX'ers Forum

Who is online

Users browsing this forum: No registered users and 2 guests