Uni Project FM TRnasmitter

[Hero999]

That's a cleaver little circuit, it's more of a proof of concept than anything but interesting nonetheless.

I've never tried it but I've heard that a regen can be a great wireless signal booster; have oyu ever tried it?

Obviously it'll be fixed frequency so no good for TV or broadcast radio but it could be handy for a wireless doorbell.

 

[Nigel Goodwin]

Obviously it'll be fixed frequency so no good for TV or broadcast radio but it could be handy for a wireless doorbell.

No, it's tuneable, just as any other LC design is.

 

[Hero999]

That's my point, when you need to change station, you'll also need to retune the booster; you ideally need a wideband amplifier for a radio/TV booster and a regen is narrowband.

 

[marcbarker]

At least a narrowband booster (this example, a tunable preselector) would be more immune from intermodulation distortion due to nearby very strong signals to the frequency of interest. A potential problem with wideband boost is that there needs to be a wide and linear dynamic range in the amplifier, that's why they are often single-chip /hybrid "RFIC"s.

 

[Nigel Goodwin]

At least a narrowband booster (this example, a tunable preselector) would be more immune from intermodulation distortion due to nearby very strong signals to the frequency of interest. A potential problem with wideband boost is that there needs to be a wide and linear dynamic range in the amplifier, that's why they are often single-chip /hybrid "RFIC"s.

You really don't want to use such a device as a booster anyway - the last thing you want to do is cause widespread interference, as a super-regen is likely to do.

 

[marcbarker]

You really don't want to use such a device as a booster anyway - the last thing you want to do is cause widespread interference, as a super-regen is likely to do.

Please clarify what you define as a 'booster' Nigel?

 

[transistor495]

The tuned LC circuit is sensitive enough to catch distant stations without antenna, so I must say it transmits a few short distance limited interference as like any transmitter without antenna do.

All superheterodyne fm receivers has LO working on the same band almost and cause few meters of interference. The JFET receiver without antenna causes same level of interferance I want to say. Does anyone agree or not?

 

[Nigel Goodwin]

Please clarify what you define as a 'booster' Nigel?

The commonly used term 'booster' is what I (and the trade in general) would call an 'aerial amplifier'.

 

[marcbarker]

The commonly used term 'booster' is what I (and the trade in general) would call an 'aerial amplifier'.

OK I thought I'd better check, as the LedZep song says "cos u no sum times wrds hav 2 meanings.."

I agree, using an ultrasonically self-quenched super-regenerative RF amplifier is going to be somewhat risky in a mass-manufactured product. In the very early days of radio receivers, it was not a neighbourly thing to do to advance the 'reaction' control too high and operate your receiver and long antenna wire as the neighbourhood jamming staion!

I thought for a minute that you might had meant 'booster' as boosting the RF output of a transmitter into the antenna.

 

[Nigel Goodwin]

OK I thought I'd better check, as the LedZep song says "cos u no sum times wrds hav 2 meanings.."

I agree, using an ultrasonically self-quenched super-regenerative RF amplifier is going to be somewhat risky in a mass-manufactured product. In the very early days of radio receivers, it was not a neighbourly thing to do to advance the 'reaction' control too high and operate your receiver and long antenna wire as the neighbourhood jamming staion!

Such a device would have a very high chance of wiping reception out over a few miles - a 'booster' needs to be reliable and not cause interferences, above all else.

I thought for a minute that you might had meant 'booster' as boosting the RF output of a transmitter into the antenna.

I'm an old radio ham (G8MMV) - no, no, no!.

 

[Ghosty_Ghoul]

I build a regen when I was a kid, good fun but not as stable as a real radio.

 

[marcbarker]

I'm an old radio ham (G8MMV) - no, no, no!.

Ah pleased to meet you MMV OM, jolly good QSO not much QRN today 73's

 

[moaied]

what about this transmitter but using VCXO?? it is more stable as i think and dose not need any sheilding??

 

[moaied]

and i do think that the varactor is reversd,,
am now bulding a transciver VHF FM,, and i have many designs of transmitters non of them the varactor was forword baised