Dipole dB Gain

[BaconSarnie]

Alright Necks, I just wanted to know if the max power rating is pre/post gain on something like this: http://www.ebay.co.uk/itm/FM-BROADCASTI ... SwLqFV8X5k

Basically thats 400W but is that the rig can be max 400W or the dipole will only take 400W after gain?

[Spokes]

That would be to take 400w of rf power...but personally I would just build a double myself for less than half the price of that thing! It's not like it's a gamma matched setup or anything special and I really doubt it has the stated gain...

[pjeva]

This is actual gain of about 2.8 db which is ok for stacked dipole. Rated power for antenna is max power of transmitter you can push to that antenna. In this case it is probably 400w because of cables between splitter and dipoles. Each dipole can handle 200w.


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[BaconSarnie]

I would build it myself but I don't have any instructions/schematics, was going to reverse engineer that one. I'm sure someone mentioned on here about uploading tutorial videos for fellow Necks which would be awesome. Thanks for the advice

[pjeva]

I promised video tutorials, and it will be done, but i got baby so don't have enough time to do it. For instructions, you could use google to find formulas and practical examples for antenna calculations. Also, there is a book called "Practical Antenna Design Handbook" or something like that with measures for 144MHz band. You just need to scale dimensions. For example, you divide 144 by 100MHz and you get 1.44 scaling factor. Then, all measures from the handbook you just multiply by 1.44 and you will have measurements for 100MHz


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[sharky]

http://www.apparentlyapparel.com/upload ... n_carr.pdf

[pjeva]

That's the one!


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[shorty]

This is also a good read, it's more of a practical hands on book, you will have to do a bit of maths to adjust measurements from 2m to the fm broadcast band.

http://www.zs6pot.org.za/practical_antenna_design.pdf

[BaconSarnie]

Cheers guys I'll defiantly look into that, what I liked about the pre built one was the fact it was broadband.

[pjeva]

Use 2 inch diameter pipe make it for 98MHz, and your antenna will cover whole fm band. But, do not expect 1:1 swr and maximum gain with broadband antenna...


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[Albert H]

Bacon...

The effort you linked to is made by Paul Hollings - Stephen Moss's ex-business partner. He's totally clueless as an engineer, hopeless as a DJ and was fired by the BBC during his "trial period" for being completely incompetent.

This is the miserable b@st@rd that sued Stephen Moss because Stephen was using his own designs to make products "similar" to the rubbish turned out by Hollings! The Stephen Moss / NRG equipment worked properly and was of high specification.

By comparison, the Hollings rubbish was as much use as an ashtray on a motorbike. he doesn't even understand the circuits and antenna designs he stole, and can't make equipment that works properly.

Don't waste your money on this rubbish. Any competent engineer will tell you that it cannot be "broadband" as Hollings claims.

A properly engineered twin-stack will have a bandwidth of 1 - 2 MHz, and will have the dipoles fed with a proper phasing harness, stubs (or gamma matches) to feed the active elements and will have the distances between dipole centres accurately set and the elements correctly dimensioned for the frequency in use.

Hollings claims "5.6dbi" gain. That's only 2½ dB better than a dipole. My twin gets (measured) 6.8dB, so there's something seriously wrong with "his" design.

As I said.... clueless. Avoid!!