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Old 23rd Apr 2022, 12:24 pm   #21
Philips210
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Default Re: Is there an 'industry standard' for a receiver?

Hi.

A design which works very well for a reflex receiver is the "FET Reflex Receiver" by A.W. Whittington, Radio Constructor, August 1971. It is based on the successful G.W. Short's designs. I remember how sensitive the receiver is and the number of stations which could be received. Selectivity is also good for a reflex receiver. The circuit is intended to be used with high impedance headphones which aren't generally available these days. A useful dodge is to use a small low voltage mains transformer to help match lower Z phones to the circuit. Please see attached circuit diagram.

I've also built many of the Sir Douglas Hall's circuits which are certainly interesting but not conventional for say a beginner. My favourite SDH design is the "DRC 3 Bandspread Short Wave Receiver" from RC, June 1972. It has permeability tuning using two ferrite rod aerials.

Regards,
Symon
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Old 26th Apr 2022, 8:03 pm   #22
G6Tanuki
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Default Re: Is there an 'industry standard' for a receiver?

I still think the direct-conversion RX is the way ahead; quite a few of the current cheap-and-cheerful receivers you buy in the likes of Tesco/Lidl use this technique to get I- and Q-elements and then the rest is software... they even give-away such receivers at some sporting events!

As to the 'success' of DC receivers, I think it was Ten-Tec in the US who sold a 20-metre-band QRP CW transceiver that used a DC RX - the "Power Mite" series - it's a great way since you already have a VFO running on the frequency for the transmitter...

I built a DC RX for 2 Metres! A Pye transmit-oscillator/driver strip was modified to be a VXO on 4MHz followed by the multiplier chain to get 100 Milliwatts of shiftable-carrier on 144MHz; this then went into one side of one of the little packaged double-balanced-diode mixer packages.

The antenna was fed into the other port of the mixer-package, after first having been put through a bandpass-filter and a U310 JFET grounded-gate RF amp.

It could easily hear 0.1 Microvolt of SSB, and the VXO gave about 80KHz shift before it became drifty.

So don't say DC receivers don't work!
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Old 26th Apr 2022, 10:04 pm   #23
Sideband
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Default Re: Is there an 'industry standard' for a receiver?

Quote:
Originally Posted by Andrew2 View Post
I'd avoid reflex designs as they are a bit convoluted as Paul says. Also difficult for the beginner to get his/her head around. It's an unnecessary complication these days, as they only came about in order to save on the cost of another transistor/valve. Transistors are so cheap now that it's easier to just shove an extra stage in.
I don't entirely agree with that but everyone has his/her own opinions. Yes I started off with a crystal set but soon got fed up with it....We were about 4 miles from the Croydon 405 mast at the time and BBC would tend to come crashing in instead of normal radio. I did manage to get the Light (now R2) and Home (now R4) by using a different coil but BBC was always hovering in the background.

I then picked up my brother's copy of Practical Wireless (I think September 1965) which had a beginners reflex radio featured. Having mastered soldering and reading simple circuit diagrams (I was 12 at the time) my brother helped me source all the parts and I set to work with a piece of hardboard for the chassis and built the featured radio which included winding the aerial and reaction coils.

It was one of the most successful beginner radio's I ever built. The normal MW stations came romping in (including pirates Caroline and London) and it was so loud, I even got it to drive a small loudspeaker. Not bad for two transistors (OC44 and OC71).
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Old 26th Apr 2022, 10:17 pm   #24
commie1
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Default Re: Is there an 'industry standard' for a receiver?

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Originally Posted by Sideband View Post
I then picked up my brother's copy of Practical Wireless (I think September 1965) which had a beginners reflex radio featured.
It was one of the most successful beginner radio's I ever built.
Yes, okay, but is that the end of the story?, what comes next? How about a 1935 HRO single superhetrodyne receiver.
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Old 27th Apr 2022, 6:19 pm   #25
commie1
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Default Re: Is there an 'industry standard' for a receiver?

Quote:
Originally Posted by Andrew2 View Post
I'd avoid reflex designs as they are a bit convoluted as Paul says. Also difficult for the beginner to get his/her head around. It's an unnecessary complication these days, as they only came about in order to save on the cost of another transistor/valve. Transistors are so cheap now that it's easier to just shove an extra stage in.
Hi Andrew,

I am in full agreement with you. Reflex, just another single tank glorified crystal set.
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