Lets be silly. Take a commercial yagi TV aerial, take a strip of cardboard, and make a full size copy of the layout using bits of 2.5mm T&E cable for the elements, and the cardboard to replace the spine.
How well would it work?
NT
See
In article , snipped-for-privacy@care2.com scribeth thus
It would work .. so would any bit of metal, question is by how much relative to what;!..
The active elements don't have to be "connected" together. The diameter of the 2.5. Elements would have an effect on the bandwidth..
Pleased that you are on this newsgroup. I enjoyed the aerial photos.
Thank you. I've always been here. They haven't found a way to eradicate me. And I'm a cult you know. An absolute cult, that's what some of them on here call me.
Bill
homemade 3 is a stairway to heaven..............
Bill,
For the first time ever I have explored some of the more obscure links on your web site. I'm sad to say I found "Albert's Attic" especially interesting.
I always knew I was a "latent" anorak. Now I know for sure.
David
Tony's right: the good news about yagis is that they "want to work". Anything that is sufficiently yagi-like will tend to be directional and have some forward gain, at some frequency or another.
Making them work *well*, and on the frequency that you want to use, is quite another story.
By removing the metal boom and element clamps, and also changing the diameters of the elements, you have changed two things that affect the resonant frequency of each element. This shifts the frequency response of the whole array. And as for the changes in the driven element, and how they might affect the transfer of signal into the downlead... you have no way to know.
If you are aiming to copy an existing Yagi design, you must copy: * all the element lengths * all the element diameters * the element mounting method. That means: copy EXACTLY. If you change any of these details, you are actually building a new design. The following page isn't specifically about TV yagis, but it gives some idea of what's involved:
Perfectly well on the single frequency it was designed for. The diameter of the elements affects the range of frequencies the antenna will remain effective on so its bandwidth would be less than the commercial equivalent as the wire is thinner than the aluminium tube.
It is ! As a lad I took Dad's decommissioned Band I/III aerial, chopped up its elements and converted it to a Group C/D UHF. I was astounded to discover that simply by pointing out of my ground level bedroom window, I could receive watchable pictures from Mendip (about
90 miles away).Good till it rained.
I built many yagis in my youth, and as long as the main dimensions and connections were right, they all worked. However wood as a boom did tend to dampen the performance....)ouch)
Brian
It's a crossposted thread doncha know.
In 1967(ish), my parents old 3-element Channel 5 (Band 1) aerial got trimmed down for the amateur 4m band (~70MHz). I the furthest contact I made with it was Gibraltar.
Which group?
MBQ
You should try the one in my loft.. I need 24db of attenuation to avoid overloading the Philips set's receiver. Mind you I am only about 6 miles from Sutton and you get a decent digital picture using a screwdriver as an aerial.
I bet that's because it's a Philips screwdriver...........;-)
Chas
Brilliant site Bill! Hmmm... I guess I must qualify for an anorak myself.
Thank you.
Bill
I remember making a horizontal yagi to receive RTÉ in Liverpool on channel 7 back in the sixties.
I'm sure I got the dimensions from Practical Television.
It only worked in the summer the opening season.
That's tropo not pub opening.
Thank you. Anyone who has pictures of particularly interesting/wierd/inexplicable/dodgy aerials please send them in.
Bill
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