George's Leak Troughline Antenna

Dear Mike,

Thanks for the information!

Of course I cannot have a roof aerial, so this is about the best that I can have. 

ATB from George

I understand George, its good that you can experiment like this & get the best possible in your situation. I am an avid DIY'er in a number of areas, & played around with various full wave loops when I was experimenting some years ago & that led me to go for the G-14; its a big array & not ideal for attic mounting, but fortunately due to my house alignment & roof space it does fit nicely & is only a few degrees off beam to the local TX thats a mere 5km away.

FYI - the Ron Smith circular element is a flat top/bottom circle, not a true circle & measures 107cm x 76cm, they have a max F/B response at 98MHz  - centre of the 88-108MHz band

If you do get the Leaks out, please do post your results on this thread!

ATB from George

and for what it is worth a full wave loop is about 3dBd (IE the gain is 3dB up on a regular half wave dipole).

Of course this means the gain lobes on a full wave loop are slightly more narrow than a dipole, so the full wave loop is marginally more directional than a dipole.

Simon

Love talk of old Brit tuners and how to get the best from them. I have a Quad FM3 in the 'big system' and a Quad FM2 in the workshop system and both sound very good indeed. The FM3 needed a couple of minor mod's to get some proper bass from it but the valve based FM2 is pretty much untouched apart from replacing a couple of dried out ely capacitors. The FM3 gets its signal from a chimney mounted folded dipole and the FM2 is fed from a DIY dipole fixed to a rafter in the workshop loft. Both setups pull in the BBC national and local stations very well, with almost noiseless results.

The workshop dipole: Simply two 75cm lengths of copper microbore pipe fixed to block of wood and with a few turns of the co-ax cable to make a simple balun.

Dear Simon,

I am in the middle of making another larger loop for the window. When I went to the balanced inputs not only the reception of Radio Three got stronger, but the rest of the FM [VHF] range improved so that even near 108 was truly solid. Thus I reckon an experiment with a larger loop - being 3.75 metres and slightly oval - will either be better or not. I looks better as it fits into the casement, so lets hope it works better, but another factor will also be at play with an antenna connecting wires being shortened from 5 metres to 0.5 metres. 

This is my project for the weekend!

ATB from George

Made, tested and rejected the larger oval loop. The circle returns!

The circle is silent on back-ground noise, and oval is rather noisy.

Not a waste of time as no experiment is ...

I adjusted the circle to be visibly more correctly round though I doubt that this makes any significant difference. And included a subtle improvement at the point of connection. Only to make the structure more robust ...

Photos in daylight will follow tomorrow.

ATB from George

Dear Lars,

I am not so far in front of you getting good FM/VHF reception in a marginal place for reception.

I experimented today with a larger oval [balanced] loop and it was both stronger on the signal and noisy.

I have restored the circular loop, with the repositioned tuner for a close coupling with the antenna.

More on the set-up after experiments tomorrow.

Now I want to watch a nice DVD!

Very best wishes from George

George, yes the impedance and the gain of the antenna will be optimum at its resonant frequency... IE the wavelength describing the circumference. Now you more you listen away from the non resonant frequency the more the feeder / antenna impedance mismatch occurs and you start to loose efficiency because of the mis match. The wavelength loop is a low Q antenna, so this increasing mismatch is relatively modest, which means the antenna can work well across the the VHF FM broadcast band.. But set a resonance point well outside of the band .. and the chances are the efficiency will reduce. 

Additionally changing the shape to a more rectangular shape, I seem to remember, reduces the antenna impedance.. Now you can design an antenna where these two things work together to provide an optimum power transfer / impedance match, for a particular non resonant frequency..in fact the options are endless.. 

But I suspect you are best off keeping it simple as you have done for optimum working.

Lars, well I think one of your only practical options would be to use a wire half wave dipole and mount on the edge of your ceiling in a spare / store room. Try and position so the dipole is broadside to the antenna. Try each side of wire dipole being about 2.25 feet.. connect to coax cable, and at the connection loop the coax into a 6 or so 10 " loops ( this makes a balun). The coax is 75 ohms, and the dipole will be approx 50 ohms, which is close enough for a receive antenna.

Sorry correction, a dipole will be approx 60 to 70 ohms..not 50, so an even better match for 75 ohm coax.. But remember the balun loops....

The conclusion of the re-arrangement and the final form of the aerial.

The rejected oval loop..

The finished circular loop.

The repositioned system. The NACA 5 neatly disappears into the cellar. The tuner is very close the antenna, and the volume controls are within reach of my chair!

Altogether quite a satisfactory result, though the tuner really only works completely nicely on Radio Three, but then for speech radio, my preference is for the Tivoli as it burns something like 3 Watts rather than more than ten times that for the big system including the Leak!

Thanks for all the lovely replies.

Best wishes from George

And for something completely different.

A video taken a few minutes ago of the Coda of the Tchaikovsky Violin Concerto live on Radio Three using the Trough Line:

https://www.youtube.com/watch?v=aDDyaptAsq0

This give no clue about the decent quality of the violin tone, but does also give the lie to the notion that the ESLs are bass light! And this is only one of them of course! 

Just a laugh really!

ATB from George

Hi George,

Just watched the link really enjoyed it.Glad your getting alot of pleasure from the Troughline

I got a similar buzz from my A@R Cambridge T21.Just because things are now vintage doesn't mean they are bad products.It also makes me question how much better new product are.

What a nice thread this one has been on the forum.

Wishing you a good week.Enjoy the Indian summer !

Cheers Ian.

Thanks George, a reason for re- listen it also here this evening as full recording.

Dear Maurizio,

It is lovely piece of music, and incredibly difficult as well, but worth the work for the performers.

Thanks for your post.

Dear Ian,

Really we have Simon in Suffolk to thank for his help last week that really brought the antenna project to life by causing me to adopt the balanced input on the Leak. Balanced aerials and balanced inputs have been in popular use long before hifi was dreamt off! They ceased, I suppose to be popular because of the near universal adoption of Co-ax cable, and a fashion on more recent tuners to offer nothing other than an unbalanced input. On the evidence of my own experience with this, the move to unbalanced antenna inputs is not a positive thing at least on a suitably designed tuner.

Thanks for your kind comment above.

ATB from George

PS: I have always had my doubts about cable dressing to the nearest millimetre [gross errors should be avoided though], but now the aerial is so fine on Radio Three, I have been fiddling with the height, which is controlled by the draw-string at the top, and the precise verticalness [controlled by the two corks on either side] and it seems that millimetres can make very nice improvements at least with respect to aerials! Radio four has become solid as well. 

Dear Simon,

It is complete luck the direction of the window, because it points to Ridge Hill [Much Marcle] rather than the obvious choice of Sutton Coldfield. Sutton Coldfield does not work here as it is completely shielded by Rainbow Hill behind my street. 

ATB from George

Hi George, has the Troughline come back from the repairers yet?

Fortunately Ridge Hill is a 10KW sender for FM/VHF and as such solid if not quite Sutton-power or the other biggest transmitters. It is also immensely high. over 500 feet at the base of the assembly, and little short of 1200 feet at the top. This clears the southern end of Malvern Hills [near Ledbury] nicely for a direct beam into Worcester. When I lived at Evesbatch [Cradley Herefordshire - west of the Malvern Hills] the recommendation was for Sutton, but we could see the aircraft warning lights on Ridge Hill about twelve miles away at night!

Mind you the house was at 550 feet above sea level, so rather prone to cold in the winter.

ATB from George

Dear Simon,

It has foxed them. No output, and yet apparently healthy [including the magic light] so it will be worked on next weekend. Nothing that cannot be fixed with a bit of detective work!

They have a perfect one for sale, so if all else fails!

I just want a nice radio ready for Cenotaph Service, the Kings Christmas Carols and the New Years Day Concert. 

No doubt that I’ll soon be fixed up!

ATB from George

Hmm, if no audio is coming out of the discriminator, I suspect the oscillator ain't oscillating.. I bet a tuned circuit capacitor has gone open or short circuit.. assuming all valves functioning..

Dear Simon,

It was so nice that I’ll definitely get something sorted out!

And I have to find employment for my aerial as well!

I have to say that your help getting the balanced antenna inputs in play revolutionised what it did!

I am not letting go of these things easily. Okay that FM/VHF may end one day, but in the meantime I intend to enjoy what is possible!

Very best wishes from George

Hi George,

Hope they can get the Troughline working again,but as you say there is one for sale if they can't.

Are you still considering getting a Leak Classic 20 poweramp ; or borrowing one for an extended trail ? .It should be a interesting combination the V1 into classic 20 into a mono 57.

Also that lovely valve glow on the dark winter evenings very cosy.

Hope all is good with you.

Cheers Ian

Dear Ian,

I’ll certainly end up with a working Trough Line soon, be it mine or the one they have for sale. 

As for a set of vintage valve amplification, I am sure that something of the sort will come in the next year, or even sooner perhaps. Not that I would easily part with the NAP 100 for all that. It is the twin of the V1 and it would be a shame to separate them. Though the V1 would no doubt be a very good source for a valve amp set onto the ESL.

To some extent it is a case of being careful of getting a good unmodified set. I found one in completely original state, working, but the timing was wrong on the finances. I have to sell my double bass bow as a start to prime the valve amp fund! Maybe even one of the ESLs. 

I expect that some people think that I am abandoning the Naim ship. That is completely untrue. I have always had my favourite Naim pieces, including the CDS3, Nait 5i, NAPs 100, 200 and 300, I like the SL2s very much in the right room with the right electronics. I also think that the S400 Orator is lovely, but just too big for me now. 

Most certainly the DAC V1 is something I cannot see ever leaving till it will not work anymore! I have heard no DAC that I preferred, including some that are more expensive!

Best wishes from George