Indoor AM aerial, advice required

[cws-federal]

I've just finished repairing my first “real” vintage radio, a Murphy A122 which I acquired earlier this week and it now works very well.
When researching aerials online I found a lot of very technical information which has only confused me further.
When on test in my basement it received MW and Radio 4 LW reasonably well using a length of wire about 8 ft long positioned horizontally across a table.
Now that I have moved the set to my lounge I'm using a vertical wire which runs up a door frame from a height of about 2 ft up to the 10ft ceiling. This works very well on MW but on long wave there's an significant increase in electrical interference over the basement setup.
Can anyone suggest an indoor aerial setup which is not too intrusive and will give good reception and reduced interference on both MW and LW?

[G8HQP Dave]

For reduced interference you need to get the antenna away from sources of interference. Unfortunately this means almost any modern electrical appliance apart from an incandescent light bulb!

Originally Posted by cws-federal

Can anyone suggest an indoor aerial setup which is not too intrusive and will give good reception and reduced interference on both MW and LW?

You are asking a lot with todays modern power supplies everywhere. A loop may give slightly better results but I doubt it. For good reception of MW/LW you really need a proper outdoor aerial, it can be made of very thin wire and be invisible.

[Skywave]

Traditionally, indoor aerials for a wireless were often a wire hidden on top of the picture rail that ran around the room - and then another wire from the set to a solid earth connection, which was not the mains supply earth. But even that will still pick up some interference: depends on the received signal and received interference strengths, of course. You obviously have your own reasons for specifying an indoor aerial, but for your purposes, an outdoor aerial was always - and still is - the best choice for clear, interference reception. Failing that, I can only endorse G8HQP's comment.

Al.

[stevehertz]

In a very long thread (or two) on here about six months ago, I went through the same process and came to the conclusion that the only way forwards - for anything approaching good, clear reception - is with a good outdoor aerial that will pick up maximum signal from transmitters, and minimum interference from indoors based SMPs, digital equipment and the like. My outdoor aerial has been 'designed' and wire etc has been purchased, but it has not been erected yet. In the meantime I erected a 'round the room' aerial with a single 90 degree bend that is affixed to a large screw hook at the 'far end', is supported by similar hooks along its length and is kept taught at the set end by a weight as it comes off the final support hook. See photos below. I have found that this 'interim' indoor aerial does perform better than a shorter, 'draped' piece of wire - in my situation. It is simple to construct and it may help you out. But longer term, the only way to go is with an outdoor aerial, away from indoor interference as much as possible. An improved signal to noise ratio; it's as simple as that.

[cws-federal]

Thanks for all your replies. I agree that an outdoor aerial is the best option but unfortunately the rented property where I live doesn't have a suitable space outside to construct one.
The best option is probably the "round the room" setup suggested by stevehertz.

To put it into some perspective. For me to get a good signal with very little noise I have one of these http://www.wellbrook.uk.com/Loop_Antennas/LFL1010-1 at the end of the garden. OK it was expensive, however for the price of a bit of wire and an earth stake you will get a much better signal. Also a fun day can be had putting it all up (and down).

[paulsherwin]

Originally Posted by cws-federal

Thanks for all your replies. I agree that an outdoor aerial is the best option but unfortunately the rented property where I live doesn't have a suitable space outside to construct one.
The best option is probably the "round the room" setup suggested by stevehertz.

Don't be daunted by some of the major aerial installations used by some members. Almost any outdoor aerial is better than nothing. You can run the wire along a garden fence, or replace your clothesline with steel cored line and use that, or you can wind some wire around a plastic drainpipe.

[Synchrodyne]

Where an indoor aerial is unavoidable, then the conventional wisdom is that some form of loop, preferably tuned and/or screened is likely the best option. There was an interesting article in Wireless World 1952 November in which a tuned loop was built to minimize noise on LW and then compared with indoor and outdoor longwire aerials. (See: http://www.americanradiohistory.com/...ld-1952-11.pdf, p.469ff.) In essence, the loop was much better than a wire indoor serial, better than a longwire outdoor aerial with unscreened feeder, and not quite as good as a longwire outdoor aerial with screened feeder.

Basis my own experience, sometimes just a longish single wire, run where it will fit, preferably with some of it vertical, connected in a loop between the aerial and earth sockets will do the job, and indeed there have been some receivers (e.g. the Australian Wright) designed to work with such aerials. However, the available signal level will likely be lowish, and some receivers seem to suffer from input detuning when so connected. What can happen as a result is that one ends up with quite a bit of background hiss, even though the interference (such as from the line timebase of a TV receiver in the same room) has gone.

There have been commercially available indoor loops. In the vintage class I think (from the 1970s) the McKay Dymek DA-3, -5 and -7 were highly regarded, although I have never encountered one. These were orientable, tunable, screened ferrite-based loops, designed for general applications, as well as for use with the McKay Dymek hi-fi AM tuners. Palomar also offered an indoor tuned ferrite loop in the 1980s and 1990s. As I understood at the time, this was a DX’ing device with high Q and quite restricted bandwidth. There were others whose identities escape me now, but those two seemed to be prominent and with good reputations. Both were American, but McKay Dymek did offer a European version (the DA-7) with LW as well as MW, most examples of which one presumes ended up in Europe. I suspect though that they would by now be scarce and not inexpensive, at least when offered by anyone who understood their nature. Whether any similar indoor loops are available these days I do not know.

Cheers,

[bikelectro]

Saw a tune-able one on the web, Tecson AN 200, wonder is it any good?

[Radio Wrangler]

Find a particularly unloved modernish set, maybe a radiogram on its final journey to that lounge in the sky, and rip out the ferrite rod antenna and the tuning capacitor.

You now have a rod with windings for both LW and MW along with the right amount of variable capacitance to tune it.

Add a dozen turns worth of extra winding to feed your vintage set and it should work.

You'll need to retune it every time you change the tuning of the main set, but you should get enough signal and it will be quite selective enough to help a bit with unwanted stuff, and you can wave it around to exploit nulls.

Best of all it's free.

David

[Nickthedentist]

See here, from 2004: https://www.vintage-radio.net/forum/...read.php?t=579

[boxdoctor]

Bang and Olufsen did at one time market an aerial unit in a circular black plastic case about 16 cms. in diameter. This was for use with their models that normally employed a long-wire aerial for AM reception, and replaced the wire aerial. It was aperiodic (untuned), and covered long and medium wavebands. It simply plugged into the aerial and earth sockets on the tuner. I cannot remember whether it was powered or not. I do recall that it contained two large-ish ferrite rods, and worked very well indeed.
Perhaps one of our B&O enthusiasts may have some data on this,(there was a service sheet published,as I remember) as I would think it would be very replicateble, and maybe solve the problem. Tony.

[emeritus]

The booklet (dated July 1985) that came with my Sony ICF-7600D describes an external antenna type AN-1 available as an accessory if the supplied long wire antenna (a long piece of wire with a 3.5mm jack plug on one end, and a plastic croc-type clip on the other) was unsatisfactory. It was said to be usable from LW to SW. It included three coupler leads: a 3.5mm jack plug for Sony radios having an external antenna socket; a telescopic antenna coupler for coupling to the telescopic antenna, and a ferrite bar antenna for coupling to the radio's internal ferrite rod. It used a waterproof whip antenna and mountings for fixing to an external balcony for example, and the illustration shows it connected to the control box via a long cable. I don't know if they were available in the UK. My radio was my late brother-in-law's. His job often took him abroad, and he probably got it in somewhere like Singapore.

[Leon Crampin]

The Philips 141U and a few others from the same maker and period used a single turn heavy gauge loop inside the cabinet. It requires a matching transformer to couple it to the first tuned circuit, but works surprisingly well.

I keep one of these sets as a curiosity - in all other respects, it's a bog standard UCH42 ---- UY41 job. Aligning the set was completely straightforward with the input tuned circuits peaking and tracking correctly.

From the release date, I would guess that it came immediately before the introduction of ferrite rods and I would estimate that its performance is on a par with a similar set using a rod. Interference and modulation hum rejection are somewhat better though.

Leon.

[Synchrodyne]

Re the Sony AN-1, I acquired one of these in the late 1980s for use with the ICF-2010. My recollection is that its performance was hardly startling. It would need to be mounted high enough to be above the interference field, as unlike the loop type, the aerial part had no inherent interference-rejecting properties. My guess, and its only a guess, would be that better results might be had from using a similarly high-mounted vertical rod with a well-executed antistatic screened feeder system, if such could be found today.

Attached is the brochure for the Palomar loop, which I missed adding to my previous posting.

Cheers,

[Phil G4SPZ]

Originally Posted by cws-federal

When on test in my basement it received MW and Radio 4 LW reasonably well using a length of wire about 8 ft long positioned horizontally across a table... Now that I have moved the set to my lounge I'm using a vertical wire which runs up a door frame from a height of about 2 ft up to the 10ft ceiling. This works very well on MW but on long wave there's a significant increase in electrical interference over the basement setup.

I too suffer similarly from electrical interference in my workshop, generally worse on long wave than on medium wave. For what it's worth, my aerial is part indoors and part outdoors. The indoor bit looks very similar to Stevehertz's!

Your original post does contain a major clue, in that the 8 foot short aerial picks up less interference when laid out horizonally than when clipped vertically. Electrical interference is commonly vertically polarised, and radiated strongly within dwellings by the mains power and lighting cables which run vertically up and down walls. Fluorescent lights, CFLs and other lamps seem to give rise to a buzzing/crackling interference, not to mention all sorts of noise from switch mode power supplies, chargers and so on. This noise is stronger at lower frequencies, just where a 'short' vertical aerial wire is at it least efficient at capturing the wanted long wave signal.

A strong signal from the aerial pushes the receiver harder into AGC and the gain reduces, making the reception of interference signals less likely. Hence, any combination of reducing the indoor vertical antenna wire in favour of horizontal, and preferably extended, external wire should repay the effort.

[bikelectro]

Hi again all, I mentioned the Tecsun AN200 earlier in this thread. Well i ordered one online from China and it arrived in good time today.
Well, it is very good. I was using about 2M of vertical wire to the ceiling and just got so much interference from SMPS's etc. 5 live was very poor, with this aerial i just tune the radio and then the aerial and hardly any background noise at all.
I paid £16:00 inc. delivery. It is solid, pretty well made and stylish.
A great solution for those who cannot have an outside aerial

[Junk Box Nick]

Another vote for the Tecsun AN200 here. It is a very neat item and although it can be directly connected to the set, I use it positioned alongside my set(s) and let inductive coupling do the rest. However, it is only a solution for medium wave.

As mentioned, the essence is keeping the set away from interference and in my experience that is away from all electrical equipment and wiring. To hear particular programmes on AM I use a battery portable positioned on a coffee table in the centre of the room with the Tecsun loop alongside. It pulls in stations at a level that is comfortably listenable when they are barely discernible without the loop.

[bikelectro]

I'm in a flat surrounded by stuff fom neighbours and cannot avoid it. I use the lead to connect to the aerial and earth of my '30's AC superhet ( Philips 660a ) It really is to be recommended for those in my situation. I tried it on a transistor with ferrite rod and it also improved matters.