WINDOW AERIAL.

[JOHN,YORK]

I have been reading with great interest,the problems that members who live in flats,have in finding a suitable aerial.I have listed 3 aerials below,what I would like to know.Has anyone made one,if so,what were the results.
As these 3 aerials are broadband and could be put in the window,it might solve a lot of problems for people.

1)....T2FD...I know it is meant for HF,but I see no problems for VHF/UHF.The transformer could be a rewired 300:75 one.On HF,it is good for 4-5 octaves,which if the same applies to VHF.One cut for 118mhz,should go up to 470mhz. ????

2)....1/4 whip... cut for 118mhz,but fed with a 9:1 as above.Members have given good reports on HF with this set up with several yards of wire,but on VHF/UHF ????

3)....OCFD...I know this aerial is popular in the USA with scanner enthusiasts,but nothing much is said over here about it.This is fed with a 4:1,(300:75 yet again.).But this aerial only works on harmonics of the design FX.But if several were joined together,like a nest of dipoles, a much wider coverage would be obtained.

I have already made an OCFD,but with just one element,it seems to work ok.
All remarks would be appreciated,as it could solve a lot of problems that members are having with aerials.

Regards,John.

[26CAB40]

All of the above will be sensitive to electrical noise, the TFD not so bad, but that's because it's not very sensitive in general.
An electrically small amplified loop will be your best bet.

[JOHN,YORK]

26CAB40.
Thank you for your quick reply.What I am trying to do,is collate all the information regarding aerials that can be used for scanning,excluding discones.As you will have noticed by reading the topics that crop up,"what is the best aerial for limited space","I want a wide band aerial","help needed for scanner aerial",etc,etc.
So I thought,why don't we try aerials that give good results on HF and make them compact for VHF/UHF.That is why I asked the original question,has anyone made the aforementioned aerials for VHF/UHF,also it will save me making all three of them.
Then,when a member has a query about an aerial,they can come to this post and hopefully find the answer.As you will have noticed,the same questions keep reappearing.

Regards,John.

[26CAB40]

Small wideband antennae would usually be amplified to compensate for loss of efficiency.
This amplifies the noise as well as the wanted signal.
There are many small vertical types with pre-amps, but they are at best patchy performers.

To cover HF and VHF/UHF you would best use two.
The aforementioned amplified loop for MF/HF and a discone for VHF/UHF if only a small antenna can be used.
If indoors, a small directional log-periodic might work well and null out sources of noise etc.

[crusty]

Having built all the above take it from me baluns/ununs are lossy at upper VHFand UHF. I have a nest of 3 OCF dipoles which I use for general scanning. It performs very well but adding a balun of any type results in lower sensitivity (tried several core types and windings), I feed it directly with 75ohm coax (RG59/U) and its at it happiest. The T2FD's design doesn't lend itself well to VHF/UHF as the signal capture is too low (deaf). Multiple verticals work well against a groundplane and are a convenient match to RG59/U.

One other which is worth a mention is the Omniquad. I've been playing with this design on and off, widebanded (works well over 200 MHz bandwidth), and may lend itself to nesting. Not an easy build though.

Just my 2p.

[crusty]

If indoors, a small directional log-periodic might work well and null out sources of noise etc.

If tied to indoors and no attic this too would be my choice. Poked out of a window and make the best of one arc of reception while reducing rearward internal noise. Not too difficult to construct either.

[JOHN,YORK]

CRUSTY.
I can see that we are nearing the thing that I want,good old trial and error advice.I hope that you can appreciate by reading other peoples topics,that some are very restricted to what they can use as an aerial.Also,they are asking if desktop discones are any good,etc,etc.I do not think a 1/2 wave dipole,or nest of them,would be bad advice.But some people fail to realise that something so simple,can sometimes out perform an aerial costing £'s
A bowtie made from bacofoil would make a good wideband aerial,it could be stuck to the window.
The omniquad sounds good,wideband also.Bit tricky to feed and not suitable for a person's windowsill.Regarding the LPA,I can remember there was details of one in a supplement of the SWM.Homemade from copper tape and polystyrene sheet and it covered from 400-1300 mhz.Also in the same supplement,there was a 4 element discone,easy to make,but it's bandwidth was only a 1/4 octave.
I suppose whatever advice people give,in a couple of weeks,someone will be asking about something that has been answered here.It will go on and on.

Regards,John.