band I aerial to band II

Galway

I have an old band I maghera channel B aerial. How much would i have to cut off it to make it suitable for Band II fm? How far apart would the dipole and reflector need to be or could they be left as they are?

watty

Waste of energy.

Everything is too different. A 12" piece of wire will work better than a Band1 aerial even modified.

If in use any length of time it will be corroded (poor reception) and brittle (break easily). Esp, at joints to main beam.

A band III aerial is not expensive.

A Radio Ham (offically Wireless Experimenter) might buy or carry off a Band1 aerial if it is good order (not corroded or brittle).

If it has been on a sooty chimney for more than 5 years use it as canes to tie up plants.

Galway

It was used in loft,was never mounted outside so is in perfect condition. I am looking to use it for Band II (2) not III! So,as it is neither corroded nor sooty,could it be adapted for band 2? Surely there is not as much a difference between BI and BII configuration and between I and III.I have a 10 element band 3 thanks already but as you know it aint easy to get band II aerials in Ireland except those crap neg. gain circular ones.

So is it any use if adapted???

watty

Must be an awfully big loft!

1/2 wave (width of folded dipole tip to tip) is THREE METERS.

(If the tip to tip is much closer to 1.5m then it is already a Band II aerial).

Approx. dimensions not allowing for "end effects"

Band 1 is 53MHz approx.

Band II is 88 to 108 approx.

But it is NOT as simple as halving every dimension.

Why?

Because the rods ALSO would have to be 1/2 diameter for that to work. To scale for a different frequecy it is ratio of frequcenies, true:

But:
Ratio of lenghts
Ratio of rod spacing
Ratio of rod diameter
Ratio of any matching circuit (may be mechanical layout of aerial connector box) which converts the "balanced" dipole (usually not 75 Ohm) to unbalanced 75 Ohm coax feed cable.

If the SAME diameter rods used for a higher frequency, instead of proportionally smaller I do have a complicated correction formula.

The RSGB VHF/UHF handbook has examples and formulas too.

Yes the halo are no use.

You can get a dipole though (seen them in Homebase) and maybe Maplins does something. There are a few other good suppliers.

Ring a few electrical wholesalers, they useually have one or two 2, or 4 element Band II beams for Installers in stock.

Try the aerial as it is. Trying to modify it could make it worse.


Where are you? (Galway perhaps??)


If you can't get a Band II, I can (new) and would swap it for the Band I if it really is a Band I aerial. (You can perhaps guess why...)

Galway

Thanks,

Do you think electrical factors in limerick might have band II?

I am between tuam and galway, nearer to tuam.

Receive cairn hill with triax unix 100 fringe 26 db mast gr B amp on 15 ft pole on chimney = perfect reception.

Also castlebar and largan hill balla deflector system with gr a version and 26 db triax wb amp.

watty

Yes I chat with someone on Radio in Corrofin Tuam Galway.


Electrical Factors *did* have some Band II aerials last time I rooted around (They let me in the store ). Normally you stand at counter and ask. Or Ring.

Cliona 061-412403


i'd imagine you can get something from Brougher Mtn?

Galway

i can pick up very brougher moutain utv ch4 and bbc1. Divis fades.

Doubt i will get any from there ate 150+ miles away. trying for lim95 only available in isolated pockets on car radio

watty

I won't be up past Galway till early Nov. Going to Mayo then.

Mike 1972

Maplin in Dublin (or Belfast) do Band 2 aerials.

If you cant make it to their shop you can mail order through their website

Galway

Aren't maplins selling those MAXVIEW aerials for Band 2.Someone said maxviw are a crap make? Would i be better off with antiference one?

Mike 1972

Maplin do Antiference as well

I wouldnt say Maxview are "crap" theyre perfectly adequete for local (i.e. TG4 in the South or BBC in the North) stuff but when it comes to fringe reception there are better choices

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