Question about mounting aeriels.

Dark Angel has brought this to us :

That method would seriously degrade the reception. You can either mount them on two completely separate masts, or use a U shaped pole adaptor so they mount on one mast but side by side.

If I may enquire, how will that effect reception? All I'm doing is using the bottom bracket as a stand off mast?

If I understand what you're proposing - you'll have the mounting bracket for the lower aerial in the same plane as the actual elements of the aerial.

Harry's right, in that this will detune the aerial and cause you all sorts of problems.

You probably know about this (apologies if I'm teaching granny to suck eggs) but it's not quite as simple as just wiring the two aerials together. If you're trying to get a stronger signal than you need to combine the signal from the two aerials properly, and the spacing between the two aerials is also important....

Regards Adrian

No it's not that, the 2 aeriels are for receiving 2 seperate regions, Yorks and Central (I'm going to use a filtered combiner before you ask).

Obviously I want to avoid the pole from poking between the elements on the second aeriel, which is why I was proposing using the bottom bracket on the side instead of underneath to stand it away from the pole.

The elements won't be between the pole, and by adjusting the U-bolt accordingly the aerial will still be the right polarity.

OK - you saw which way I was thinking

On an aerial like this you don't really want anything metallic in the same plane as the elements - so, in a way, mounting the thing 'normally' so that the aerial mast is at right angles to the elements is better than doing what you propose.

Ideally you'd want _no_ extra metal within the aerial - but having it at 90-degrees to the elements would be better than your plan.

What you say is true - but it'll still be wrong

Best solution is some way to put them both on top of the mast, but separated horizontally (a piece of tubing like a very shallow 'u'-shape - don't know what they're called ) you want to get the two aerials as far apart as possible...

Hope this helps...

Adrian

See

A wideband aerial is not always the best choice - particularly if you are short of signal.

On the Triax aerials, to overcome that problem, you can remove the clamp and re-install it on the stub behind the reflector.

The spec of that aerial concerns me..... No mention of a balun and a gain of

In article , Andy Luckman (AJL Electronics) writes

Much better grade of aerial that.. and available from

That looks like a maxcack?...

And don't for get the CT100 for the aerial downlead;!....

And us! It is our mainstay for installations.

I couldn't quite identify it from the picture. Claims to be branded Labgear. However, they don't exist any more. Nearest I can think of is a Blake, but the connector box is more like a cheap copy of the Triax.

WF100 please!

In article , Andy Luckman (AJL Electronics) writes

Good:)

Reckon Andy Wade could comment on that!..

Yep tho I didn't want to complicate the issue. Is WF100 as widely available as CT100 then?....

Well Philex do sell Labgear branded product, trading as their "Labgear Division." They bought back the trade mark and some other assets after Labgear Ltd. went into administration in 2004. I can't comment on the aerial in question, although the chances are that it's imported.

Actually they're being unusually honest in quoting the gain spread across the band. The gain of all so-called 'wideband yagi' types is quite low at ch. 21 - these aerials really work as yagis at the HF end of the band and as corner reflectors at the LF end, hence the need for the large reflector. It's quite instructive to look at the gain requirements for the various 'benchmark' standards of the CAI/DTG aerial benchmarking scheme, which you can find in

- std. 1 >10 dBd (only one product approved in this category) - std. 2 >7 dBd - std. 3 >5 dBd - std. 4 >7 dBd (log-periodics)

So all the std. 3 benchmarked products (including the Unix 32W) will only just exceed 5 dBd in the lower Group A channels. Most manufacturers only publish the gain at the top end of the band, which of course looks much better :-). If you don't need the extra gain at the HF end then the std. 4 log-periodics are a good bet - much smaller and less windage, and the gain is not drastically lower in the way some people seem to assume.

Quite agree.

It's certainly readily available. E.g. there's always a few reels in stock at a certain establishment on Mitcham's Corner...

I'm sure he could quite well with an online outlet but the last time I was in there the power-that-is prohibited the use of credit cards..

So olde world;!.....