Log periodic aerial elements length

[DIYspanner]

I bought one of these and looking at it, the elements seem odd in that they don't reduce in length uniformly towards the outer end so I'm wondering is this a properly made aerial?

Opinions welcome.

 

[opps]

Not my area of expertise but I have never seen a Yagi Uda like that before.

I think @Lucid will be able to advise you further.

 

[DIYspanner]

This is full length view of the elements.

 

[Lucid]

I should defer to someone with antenna building experience, but if I had to hazard a guess (and I emphasise a guess) then I would think this relates to the new shorter band for terrestrial now that the 700MHz clearance is complete.

The 'channels' are now 'squashed' into a smaller range, and so the chances of two muxes being just one or two RF channels apart is much higher. This could be to do with avoiding harmonics in the aerial, and so aiding channel separation.

Ericmark might be able to shed more light on this, or Rodders may too. I've kind of moved on to other areas.

 

[DIYspanner]

What intrigues me about the aerial I've bought is the elements near the outer end don't seem to be the correct lengths.

In photos of log periodic aerials I've seen online, the elements form a uniform taper whereas the one I have, they're a bit staggered in length.
Is this acceptable?

A better photo.

 

[endecotp]

I think you should ask them:

Contact

Unispectra

unispectra.com

I can imagine that in principle you might be able to adjust the frequency response in some way by adjusting the lengths - maybe the aim is to impove discrimination from e.g. mobile or something. I've not found anything by searching. It's the sort of thing you might find in a patent search.

Does it work OK?

 

[ericmark]

I tested the aerial on transmit, how much signal was reflected, or voltage standing wave ratio (VSWR), I have found that results are surprising, and I have transmitted and received 2 meter (144-146 Mhz) on a long wire, which in theory should not work.

Basic if it works it is OK, if it does not work it's not.