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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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23rd Apr 2022, 12:24 pm | #21 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
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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 Last edited by Philips210; 23rd Apr 2022 at 12:33 pm. |
26th Apr 2022, 8:03 pm | #22 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
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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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26th Apr 2022, 10:04 pm | #23 | |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
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Re: Is there an 'industry standard' for a receiver?
Quote:
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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26th Apr 2022, 10:17 pm | #24 |
Triode
Join Date: Apr 2018
Location: Buckley, Clwyd, Wales, UK.
Posts: 32
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Re: Is there an 'industry standard' for a receiver?
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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27th Apr 2022, 6:19 pm | #25 | |
Triode
Join Date: Apr 2018
Location: Buckley, Clwyd, Wales, UK.
Posts: 32
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Re: Is there an 'industry standard' for a receiver?
Quote:
I am in full agreement with you. Reflex, just another single tank glorified crystal set. |
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