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Old 15th May 2020, 10:37 am   #1
Sparks
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Default Tandy/Realistic FM wireless intercoms

Does anyone have any experience of these devices, whether good, bad or indifferent ? I remember seeing them in the Tandy catalogues for years in the 1980s with the seemingly bold claim that all you had to do was plug in to the mains, switch on and you were in business, so to speak. If I've got it right, the technology was something like an FM transmission superimposed on the mains cabling, however that worked. I particularly remember that it was possible to use the sets not only within your own house or office, but also with your next door neighbour, provided there was some degree of electricity supply commonality.

I've neither seen nor used any such device and I don't know if the likes of Eagle and Sterdy make them. Obviously, Tandy disappeared years ago.

Many thanks.
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Old 15th May 2020, 11:06 am   #2
SiriusHardware
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Default Re: Tandy/Realistic FM wireless intercoms

Yes, we had some Tandy ones for a while. There are so many other signals superimposed on the mains now - powerline networking adaptors, etc - that I'm not sure such simple 'analogue' devices would be able to function any more.

They did depend on both, or all stations, being on the same mains phase.
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Old 15th May 2020, 11:31 am   #3
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Default Re: Tandy/Realistic FM wireless intercoms

Thankyou Sirius. I thought I remembered something about being on the same mains phase.
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Old 15th May 2020, 8:07 pm   #4
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Default Re: Tandy/Realistic FM wireless intercoms

I have an Altai branded one, probably much the same internally as the Tandy ones. It uses low frequency RF transmission. I think mine can be switched to 150KHz or 250KHz to avoid interference or conflict with your neighbours. Both of these frequencies are in the long-wave band. I can pick up the intercom on a normal domestic LW radio in the same room, even though ithe radio is AM and the intercom is supposed to be FM.

Other than the above reception test, I haven't actually used it as an intercom, since I only have the one base unit. A pair is required. I'm guessing that these intercoms should still work despite much more mains-borne noise these days. FM is supposed to be quite good at rejecting interference.
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Old 15th May 2020, 8:40 pm   #5
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Default Re: Tandy/Realistic FM wireless intercoms

I had one. They didn't like ring circuits (distorted sound to the point of uselessness) but would work fine on an extension lead.

That was in the days of rewireable fuses. With MCBs and RCDs in circuits there might be more obstruction to the signal.

As well as the speaker versions there were one or two handset-style ones available.
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Old 15th May 2020, 9:12 pm   #6
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Default Re: Tandy/Realistic FM wireless intercoms

It was probably quite a good idea, at least initially, to use the mains wiring for something other than moving electricity around and at no added cost. Not unlike the early American telephone networks that used the barbed wire fences around the farms and ranches as transmission cables. Certainly not ideal but better than nothing.
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Old 15th May 2020, 11:03 pm   #7
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Default Re: Tandy/Realistic FM wireless intercoms

I believe that electricity consumer meters are or were opaque at around 150kHz. This means you are isolated from your neighbour's mains intercom
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Old 16th May 2020, 12:56 am   #8
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Default Re: Tandy/Realistic FM wireless intercoms

I've still got 2 pair of them and used them from house to shed until a few years ago.

They had to be used on the same phase and wouldn't work across different phases of a three phase system so it was possible to work the house next door, depending on which phase they were connected to.

Modern equipment, with filters, plugged in around the house does diminish their usefulness to the point of being unusable now.

And yes, they superimposed the audio onto a carrier that was superimposed on the mains.

There were circuits in some of the older mags like Practical Electronics from memory where you could build your own.
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Old 16th May 2020, 8:03 am   #9
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Default Re: Tandy/Realistic FM wireless intercoms

It would be a nuisance if you'd bought a set for something other than in-house communication to find that your individual electricity supplies weren't on the same phase.
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Old 16th May 2020, 8:18 am   #10
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Default Re: Tandy/Realistic FM wireless intercoms

Quote:
Originally Posted by Terry_VK5TM View Post

There were circuits in some of the older mags like Practical Electronics from memory where you could build your own.
I expect it will be a similar idea to my Pye PTC1001 from 1950s/60s. but using semiconductors, not valves.


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Old 16th May 2020, 9:30 pm   #11
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Default Re: Tandy/Realistic FM wireless intercoms

Hi, there is currently a pair of the Tandy/Realistic units that you mention listed on eBay here

I have no association with the seller and have included the link for the purpose of interest only.

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Old 16th May 2020, 9:37 pm   #12
Sparks
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Default Re: Tandy/Realistic FM wireless intercoms

Thanks for the heads up Andi. At that price I believe I'll pass but it would be interesting to see how well they perform these days.
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Old 22nd May 2020, 10:50 pm   #13
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Default Re: Tandy/Realistic FM wireless intercoms

With the same Ebay disclaimer, a pair of the handset style here. Circuit diagram is included - typically for Tandy stuff it will be the USA version in the manual.
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Old 23rd May 2020, 10:11 pm   #14
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Default Re: Tandy/Realistic FM wireless intercoms

I sold mine two years ago for 9.99.
They worked ok in my house and on 25 metre extension to garden shed but we don't have any powerline digital stuff.
The buyer initially claimed they were non-functional although did not return them for testing.
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Old Today, 3:17 pm   #15
ljones0
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Default Re: Tandy/Realistic FM wireless intercoms

Have an old device here as well and strangley it can be received in the long wave band as well(!) - although the radio has to be pretty much next to the device or nothing is received. The device is branded as a national VK233 and I think maybe from the 80s. Unfortunatly mine do not seem to be working all that well - the range is so bad it only works from within the same room (I do have a second device); try plugging in one upstairs and one downstairs and nothing - !

Does anyone know why it should be quite *that* bad? I mean I wouldn't expect mircacles from such an old device, but not doing anything from upstairs to downstairs seems to indicate some sort of fault to me.

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