Budget antenna for my attic, rural location

Talk about radio and non radio stuff in here, a place for Genral Chit Chat

Re: Budget antenna for my attic, rural location

Postby Southwales » Mon Jan 22, 2018 9:33 pm

Chris P wrote:my loft
Image


with a bicone in the foreground which is a 3d version of the bowtie and a couple of home brew log periodics behind


Hi, is this the correct cable to make this a antenna? https://www.toolstation.com/shop/p58713?table=no Also what is the idea of the shape of the antenna in the above picture, Does it somehow reflect the signal of the bottom cone onto the top receiving cone?
Southwales
 
Posts: 162
Joined: Mon Jan 08, 2018 10:19 pm

Re: Budget antenna for my attic, rural location

Postby Chris P » Wed Jan 24, 2018 8:10 am

Yes that's a suitable cable .

Regarding the reflection bit, No it is a bicone which is a single dipole type of antenna in 3D form and is Omni directional , reflectors are found on directional antennas such as a Yagi or quad which consist of several elements usually a reflector and a driven element plus one or more directors which provide gain in one direction ( TV antennas for example )
Regards Chris aka G8FFF nipper or tazmin88
Chris P
 
Posts: 417
Joined: Sun Nov 02, 2014 12:20 pm
Location: 6.5nM west of 06 threshold marham

Re: Budget antenna for my attic, rural location

Postby Southwales » Wed Jan 24, 2018 10:33 am

Is there much advantage with this 3d bicone over the more simpler made bowtie, I have all the parts arriving today so can have a go at making my first antenna. Any tips on how big I should make each cone any other tips please. A close up pic of the coax connection to the aerial would be a big help, have got an electrical block below to connect with. The plastic centre tube was really cheap from screwfix https://www.screwfix.com/p/floplast-ove ... term=47868

Image
Southwales
 
Posts: 162
Joined: Mon Jan 08, 2018 10:19 pm

Re: Budget antenna for my attic, rural location

Postby G4RMT » Wed Jan 24, 2018 4:58 pm

Bowties, used in vertical polarisation are not properly omnidirectional - they have a null when viewed from the side. The one in the picture is a bowties, repeated through 360 degrees so IS omnidirectional. The chocolate block connector is ideal for making antennas of all kinds. Experiment away!
G4RMT
 
Posts: 1322
Joined: Sat Feb 07, 2015 5:45 pm

Re: Budget antenna for my attic, rural location

Postby Southwales » Wed Jan 24, 2018 9:45 pm

Hi, I had a go at making my first antenna, a bit embarrassing :embarrased: really as none of the wires are straight, did I have the right idea about connecting up the coax with the block. I use an old fan stand and it is now in the loft ready, can not test till tomorrow as my f connectors and bnc adapters never arrived today. Can not decide how long to run coax, my bedroom is downstairs but that is going mean close to 50ft of cable ( pf100 ) is that to long or should i just run it to the spare bedroom about 20 feet. If I do the later just means the scanner will get used less, I guess all this depends if my first antenna effort works.

Image

Image
Southwales
 
Posts: 162
Joined: Mon Jan 08, 2018 10:19 pm

Re: Budget antenna for my attic, rural location

Postby Southwales » Thu Jan 25, 2018 2:09 pm

My adapters arrived today so got to test my home made antenna above, I am very happy with how much more signal I am getting, I have had welshpool airport frequency in my scanner for 2 weeks but heard nothing, but with this new antenna I finally heard a few transmissions on that frequency, plus it was 2 way, Some of the civil air frequencies are now hitting 4 to 5 bars, I Was lucky to get 2 bars in my rural location, aother bonus was I heard my first cb FM signal they were on cb Ch 40, sounded like a farmer talking to lorries or tractors.
Southwales
 
Posts: 162
Joined: Mon Jan 08, 2018 10:19 pm

Re: Budget antenna for my attic, rural location

Postby G4RMT » Thu Jan 25, 2018 8:04 pm

My motto was always stick it up and try it! What can you do better? Twisted connections work for a while, but that bright copper will be dull in a week or two, and eventually, the resistance rises. Next time you have a quid or two spare - buy a soldering iron and solder. It's very simply to then heat up those twists and solder them. Good practice too! Then the antenna will last for virtually ever!

Twisting is great for quickness and experiments. Now you know it works, soldering converts it to permanent.

You can also experiment with lengthening the elements, which makes the antenna work even better at lower frequencies. A good bodge up is one that works well - never the prettiest!

I think you've made a decent stab at this one and I'm pleased you're hearing things you couldn't hear before.
G4RMT
 
Posts: 1322
Joined: Sat Feb 07, 2015 5:45 pm

Re: Budget antenna for my attic, rural location

Postby Southwales » Thu Jan 25, 2018 8:27 pm

G4RMT wrote:My motto was always stick it up and try it! What can you do better? Twisted connections work for a while, but that bright copper will be dull in a week or two, and eventually, the resistance rises. Next time you have a quid or two spare - buy a soldering iron and solder. It's very simply to then heat up those twists and solder them. Good practice too! Then the antenna will last for virtually ever!

Twisting is great for quickness and experiments. Now you know it works, soldering converts it to permanent.

You can also experiment with lengthening the elements, which makes the antenna work even better at lower frequencies. A good bodge up is one that works well - never the prettiest!

I think you've made a decent stab at this one and I'm pleased you're hearing things you couldn't hear before.


Hi, How important would you say it was to solder the joints?, it will be a pain to get back out of the attic as the hatch is quite small. Also If I should make another one and I lengthen the elements is there also any benefit to having more elements or can you have to many?. And By increasing there length will that for example help with picking up cb FM but lower my pmr 446 reception? And if going shorter would increase pmr 446 for example, how do you draw the line before you antenna is to small?

Years ago in the 90s when I had my last scanner I thought it was the bigger and more metal the more distance I could pick up transmissions from, my home made experiment antennas back then were no better than the supplied extending antenna that came with the scanner.
Southwales
 
Posts: 162
Joined: Mon Jan 08, 2018 10:19 pm

Re: Budget antenna for my attic, rural location

Postby Chris P » Thu Feb 01, 2018 1:00 pm

Southwales wrote:
G4RMT wrote:My motto was always stick it up and try it! What can you do better? Twisted connections work for a while, but that bright copper will be dull in a week or two, and eventually, the resistance rises. Next time you have a quid or two spare - buy a soldering iron and solder. It's very simply to then heat up those twists and solder them. Good practice too! Then the antenna will last for virtually ever!

Twisting is great for quickness and experiments. Now you know it works, soldering converts it to permanent.

You can also experiment with lengthening the elements, which makes the antenna work even better at lower frequencies. A good bodge up is one that works well - never the prettiest!

I think you've made a decent stab at this one and I'm pleased you're hearing things you couldn't hear before.


Hi, How important would you say it was to solder the joints?, it will be a pain to get back out of the attic as the hatch is quite small. Also If I should make another one and I lengthen the elements is there also any benefit to having more elements or can you have to many?. And By increasing there length will that for example help with picking up cb FM but lower my pmr 446 reception? And if going shorter would increase pmr 446 for example, how do you draw the line before you antenna is to small?

Years ago in the 90s when I had my last scanner I thought it was the bigger and more metal the more distance I could pick up transmissions from, my home made experiment antennas back then were no better than the supplied extending antenna that came with the scanner.


Soldering the twisted joints will remove the risk of intermittant connections and also make the bicone more physically stable . This sort of antenna is more suited to VHF/UHF frequencies .For CB the length of the elements would probably be too big for loft mounting . Keep experimenting as you can try different antennas on the same feeder (which is the most expensive part of the setup ), PF100 "satellite TV" cable will work fine on any frequency below the 900-1000Mhz it is designed for


The idea of more metal more signal is not always correct, the aim is to have a resonant antenna which matches the receiver input impedance fairly closely for example a simple halfwave dipole will often give better results than a non resonant one of several times the size at the required / interested frequency . However multi element co-linear or phased elements can provide "gain " over a dipole in some circumstances but this type of antenna is not "wideband" like the bicone or bowtie

Reducing the element size may raise the resonant frequency range to the 446 Mhz band but will reduce the response at VHF. Element length of less than one quarter wavelenth (eg 17cm at 450Mhz )will not result in any signal improvement and probably will reduce the signal at the Rx . The important factor in the bowtie or bicone is (according to several publications )the angle between the upper and lower sections which affects the bandwidth it needs to be 130 degrees for optimum performance
Regards Chris aka G8FFF nipper or tazmin88
Chris P
 
Posts: 417
Joined: Sun Nov 02, 2014 12:20 pm
Location: 6.5nM west of 06 threshold marham

Re: Budget antenna for my attic, rural location

Postby m0lsx » Thu Feb 01, 2018 4:10 pm

One point to make soldering slightly easier. If you do not have some Mentholated spirits laying around, then get some cheap alcohol wipes & just give the joints a quick wipe before you solder them. One wipe will cover several joints. And if you do have some Meths around, then just wipe the joint quickly with a slightly moist rag. We leave for want of a better word, grease on the copper as we handle it & giving the joint a quick wipe, removes that & most other unwanted residues & alcohol quickly dissipates under heat.
Cleaning a joint is not essential most of the time, but Solder does not flow as well as on unclean copper & if you have been handling the area, especially if you have been placing finger pressure of the area as you twist the wires together. Then it's certainly not bad practice.
Buy a database from Kimmy JS19 via http://ukscanningdirectory.co.uk/
Or do Google search of this forum via http://www.google.com/cse/home?cx=partner-pub-6291336405621919:2662881632
73 De Alan (M0LSX.)
http://www.qrz.com/db/M0LSX"
User avatar
m0lsx
 
Posts: 5844
Joined: Wed Nov 21, 2012 9:14 pm
Location: Norwich. TG21.

PreviousNext

Return to General Discussion

Who is online

Users browsing this forum: No registered users and 1 guest