Tuning a vertical beam

I want to install a wide frequency 25-1300mhz vertical beam 300 ohm antenna in the attic.
I am only interested in scanner reception from about 108mhz to 1300 mhz.
It will not fit if i leave the low band elements as they are. Would it be better if i try to fold them inward?
Would folding them affect the reception of the other elements or bands?
Or cut them completely off?

Thanks

73, john

Do you have a link or a model/make for the antenna you are looking at using?

I can see where it would require a lot of headroom if leaving the low band elements intact.

never heard of a vertical beam, explain please.

I am guessing a create log periodic or something similar.

Log periodic
Infamous-grove scanner beam
3 distinct sets of band lengths
Uhf
Vhf high
Vhf low
Im thinking if i alter the vhf low or longest elements, that it will affect the impedence or reception of 100-1300mhz
On the other hand, if i fold them inward, the same result

There's a specific distance between elements and their lenghts that are frequency dependent. If the longest elements wont fit where you plan to have the antenna then remove the elements completly. If you in the future relocate the antenna you have the elements intact and can restore the antenna to its original performance. Keep the removed elements fastened to the mast or coax so they will not be lost.

As with all antennas you will need to keep a distance to other objects that are radiowave sensitive, any metal and anything that collects moist. If some elements don't fit physically in the space then the other elements are probably too close to interfering objects and will screw up the whole antenna. But if that's the only option so go with it, as it will anyhow be better than a single dipole. But then the performance might not be what you would expect from such an expensive antenna.

/Ubbe

You can remove the elements for the lower frequencies but there is an extension of the feed line that has to be accounted for. For a split boom feed its usually an extension of the boom with a short and with a criss-cross feed its usually a hairpiin loop sticking out of feed point for the longest element. This shorted extension is a specific size and length for the lowest frequency the log periodic is tuned for.

It's a match device at the end that are supposed to electrically lenghten the boom to match with the longest element but if the elements are removed it doesn't have any real function for the rest of the antenna. I believe it's only sitting on the 25-1300 LP antenna and not on the 100-1300 version if that antenna are prefered.

/Ubbe

Every LP antenna I've dealt with has the boom extension to the rear and I remember it has to do with a reflection and phase reversal to the last longest element. Most LPs use a feed extension like on split booms or on the Create version they used a coiled wire to achieve the critical length short.

Ubbe said:

It's a match device at the end that are supposed to electrically lenghten the boom to match with the longest element but if the elements are removed it doesn't have any real function for the rest of the antenna. I believe it's only sitting on the 25-1300 LP antenna and not on the 100-1300 version if that antenna are prefered.

/Ubbe

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