Liveatc EIDW feeder needs better antenna

Mech1

Hi all,
Pat here, I supply the EIDW feed here http://www.liveatc.net/search/?icao=eidw

Now I have a problem, some freq particularly 121.100 is poor on the ground side of the conversation so I want to upgrade my antenna to cure this.

What we have at the moment is a basic discone bought in Maplins a few years ago, its the type without the central "pointing up" element. Its also missing one or two radial elements that fell off a couple of months ago while I was streaming comms to here during the high winds!





My location is approx 10 miles "as the crow flies" from Dublin Airport, just at J12 on the M50.

Coax is rg213 from antenna to scanner on ground floor so maybe 20m or so.

The budget is tight, almost non existant , so I am looking for:

1:someone to donate a antenna that might improve things (I will return if it dosent)

2:someone to diy build a suitable bit of kit

3:recommend a antenna to save up for / try diy myself

I am able to travel to collect any bits if needed.

Many thanks,
Pat.

Mech1

Isnt it great to have a clear blue sky!!!

urajoke

Mech1 wrote: »

Hi all,
Pat here, I supply the EIDW feed here http://www.liveatc.net/search/?icao=eidw

Now I have a problem, some freq particularly 121.500 is poor on the ground side of the conversation so I want to upgrade my antenna to cure this.

What we have at the moment is a basic discone bought in Maplins a few years ago, its the type without the central "pointing up" element. Its also missing one or two radial elements that fell off a couple of months ago while I was streaming comms to here during the high winds!





My location is approx 10 miles "as the crow flies" from Dublin Airport, just at J12 on the M50.

Coax is rg213 from antenna to scanner on ground floor so maybe 20m or so.

The budget is tight, almost non existant , so I am looking for:

1:someone to donate a antenna that might improve things (I will return if it dosent)

2:someone to diy build a suitable bit of kit

3:recommend a antenna to save up for / try diy myself

I am able to travel to collect any bits if needed.

Many thanks,
Pat.

Rarely if ever will you hear the ground side of 121.5, it's rarely used in Dublin. Most of the ground transmissions are done by either Shannon (to high level traffic out beyond 12w or 15w who are not in radio contact) any other ground stuff is Scottish broadcasting SAR ops and giving LAT/LON's for same or London FIS doing practice PAN PAN's with VFR traffic. All these are too far from your aerial and it would need to be the size of RTE's masts to pick up London and Scottish so I wouldn't be too worried about it.

Mech1

Sorry should have been 121.100 Dublin approach. fixed op now.

de biz

Atmospherics might be a factor at present.

Reception may improve when the current high pressure dissipates.Every cloud has a silver lining!

Thanks for your efforts.

martinsvi

I doubt you will get anything decent from a DIY omnidirectional antenna. What you need is an antenna with a gain, such as Yagi! The only thing - 1/2 wave yagis are too big, so I'd go with a quad. I am actually considering to build this - http://www.hamuniverse.com/3el2meterquad.html

this antenna is measured to have the highest gain on 146MHz. What you need to do for 121MHz is add a couple of cm to match the wavelenght. Wavelenght is calculated by dividing a constant of speed of light by frequency. To keep it simple - 300/121 = 2.48m (that's the driven (middle) element)

Even if you leave the size as it is, it will still produce a gain. Just point it at the right direction and it will work like a charm!

martinsvi

de biz wrote: »

Atmospherics might be a factor at present.

Reception may improve when the current high pressure dissipates.Every cloud has a silver lining!

Thanks for your efforts.

Can you explain this in a bit more detail? It is my understanding that current dry weather should be in favour of VHF radio waves. It is water (high humidity, vapour, rain) that attenuates/absorbs radio waves. Have I missed something?