I noticed two things of interest while playing around with an AM radio tonight (the AM radio in my 1964 Astor G10L phono). The first was the extent of RFI generated by the LED/CFL lighting in our house! When the main lights are on (LED 240v GU10 downlights and E22 CFLs in the ceiling fans), the AM band is non-existent on my radios. All I can pick up is a horrible roaring/pulsing sound when the lights are on. I noticed that when they are off, I can actually pick up tons of AM stations! I almost fell over when I discovered that I was suddenly able to pick up over 100 AM stations (most faint but audible, with a few very clear) all over the dial! I couldn't believe how many were crammed in once I eliminated the RFI.

The other thing I noticed that I was able to pick up a faint station using the callsign "2CA" (2CA Canberra - my favourite station in Canberra, and my dad's favourite I believe). I know AM can transmit a long distance, but I was amazed I could pick up a Canberra station from eight hours North!

Am I right in thinking that 2CA Canberra should be on the exact same place on the dial, no matter whether I'm here or in Canberra? Is there anyway to shield my radio from the horrible RFI generated by our lighting (aside from ripping out the ****** things)?

Chris

Back in the old days of 10kHz spacing, 2CA was on a frequency of 1050kHz and with the introduction of 9kHz spacing, moved to 1053, just a dial pointer width away.
Your location will not change the frequency being received, except in the case of a repeater transmitter which may be on a different frequency. I'm sure this is not the case with 2CA.
Harold

Now you can see how far the enforcement of RFI standards have gone toward non existent.

Whilst atmospherics contribute; 2CH Sydney (519 Km) has little problem here on a decent antenna (evening).

However, on atmospherics 2AY 71Km, is OK all day but late in the afternoon, when the atmosphere changes and distant stations start coming in, it starts fading in and out.

Chris, if the radio is in good nick and you have a nice high antenna there is no reason why you shouldn't be able to get quite a few stations coming in.

Back when I first started collecting I used to bring in 2CH, 2WS, 2UE, 2KO, 3DB, 3MP, 5DN, 6PM, 2TM, 2MO, 2DU, 4BH, 4BC, 4WK and 2XL all on a HMV radiogram in Tamworth. The antenna was about six foot long. What I found at the time was if I made the antenna longer I was getting dozens of stations drowning each other out. The length of antenna will depend on your location and surrounding geography. Naturally, all this was happening at night. The sun's radiation blocks long distance throughout the day.

If you are getting interference from lighting, turn them off and light your room with a desklamp fitted with a fancy round incandescent lamp.

I found that even the circular fluros in my radio room radiate crud. As Chris discovered chalk and cheese as far as reception goes when they are turned off.

The best I have done here (Tamworth) is 2WEB (Bourke)
A NZ station and the BBC. Antenna would be about 15 metres horizontal, plus the lead-in to the room.

You can buy reproduction squirrel cage bulbs on ebay. They really suit the mood when listening to valve sets.

Not all of that crud comes in via the antenna. With sets with an external antenna only, disconnect & just listen. If there is a reasonable amount of "hissy noise", it's coming in via the mains.

Some sets do not have a cap from 0.05 to 0.25mfd on B+ decoupling RF. Not helpful if the set has Electrolytic Filter caps, as they do not pass RF well.

You may find some relief there by making a capacitive mains filter. I also put MOV's in them.

I have a sheet here from RCA Victor showing long wire antenna performance from around 3- 22 Megacycles vs feet in length (not printed yesterday). It clearly shows that there is such a thing as the wrong length and big is not necessarily beautiful: Most sets here were made for 25 feet ant.

Someone had a lot of time to to play with DX listening.

Marcc, I can only get good reception here at night time. During the day, there is very little that reaches here.

Brad, the two AM radios I currently use (both tube types) are a 1964 Astor G10L and 1967 Kriesler 11-99 - both unrestored (shame on me!), but fully working. I run them using the internal ferrite-core antenna.

The lighting in my room isn't an issue, as the "Viribright" LEDs in my ceiling fan seem to generate very little RFI, and all my other lamps run incandescents. I find that my computer generates a fair bit of RFI, though nowhere near as much as the LED and CFL lighting in the kitchen/dining room.

Redxm, I've seen a few of those squirrel-cage lamps about - the trendy city cafes seem to love using them, though they are almost non-existant in a small town like Wauchope. I find that they are generally best for ambient lighting, as the light isn't very practical. I'm not sure what wattages they come in though.

Chris

Think I mentioned this before somewhere, recently a electrician installed a new double tube fluro light in my shed.

A discussion arose and he told me this fitting had new style solid state starters.

The brute completely blots out any AM radio plugged into the same circuit and would not be surprised anywhere else in the house.

If I want to listen to AM at night in the shed use other lights.

Glad I kept a supply of incandescent bulbs handy.

Normal is best radio reception at night.

I am rural so I have better control on things that would dare cause RFI; L.o.n.g wire antennas are not an issue as long as you make provision for lightning Electric fence insulators are cheap and handle around 10KV and fencing wire makes strong antennas.

Marc

Solid state starters aren't a new thing. They've been around for at least 20 years. It sounds like the fitting you have has electronic ballasts which are starterless.

If the tubes light up immediately without flickering or warm up to a full light for about a second with half of each tube shimmering during that initial moment then this will confirm the presence of electronic ballasts.

Fittings with electronic ballasts use about 1/3 of the electricity that is consumed by a fitting with the same tubes running starters and iron core ballasts. The extra power consumed by the latter is given off as heat by the ballasts.

Since it's a console radio, you might have some excess
length in the speaker wire to wrap a few turns around a ferrite rod
at the end closest to the radio chassis,
since at that point you don't mind blocking RF, and passing audio frequencies.

I have noticed on several sets that RF can creep into the audio. A lot due to poor shielding & decoupling, which a CRO can see.

The idea is to get rid of it before it gets to the AF amplifiers, most audio valves can amplify RF. I have in a couple of amps (not confined to valve) added an RFC to stop it being amplified.

Interesting thing I noticed, it's possible to introduce audio to
the AM radio by winding a coupling around the ferrite rod,
and passing pulse width modulated audio through it.
This is an old circuit I had, and it's output for sound is a
DC square wave.
I don't know what's going on there, but now will have to see what happens if I try to inject a proper AC audio signal the same way.

I don't know what's going on there,

It doesn't surprise me. AM receivers will detect all sorts of noise, harmonics, etc. Try listening to AM short wave at night.

I've used an AM transistor portable tuned off station to trace underground wiring for an irrigation system, with a sig gen attached to one end of the cable. Works great.

I'm not really surprised either
A lot of switching sounds end up in the radio audio,
and a pwm circuit would just look like a lot of turning on & off.
So a MOSFET speed controller in a portable drill should be bad news for AM radio also.

I think the audio circuits in early sample playing greeting cards were also a 1 bit digital pwm signal, and just make the
piezo speaker click at the right times.