EMRFD Message Archive 4437

Message Date From Subject
4437 2010-03-11 08:12:35 Blanco Hugo Danie... Phasing Receiver.
Hi Friends !!!!

I'm in the early stages of design for a 80 m phasing direct conversion

Probably, I will use a Tayloe detector and, because a low power supply
current is a desired requisite in my list, I chosen to use a polyphase
network at baseband, to minimising the needed operational amplifiers'

Now the question, about to switch from USB to LSB and viceversa :

I know that the output from the polyphase network can be taken from one
or two or four of the that network' outputs.

Well, are there any possibility of sideband switching at this point of
circuit ?

Very Thanks in advance and please forgive me for my Tarzan-like English.


Hugo Daniel Blanco
Buenos Aires

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4438 2010-03-11 08:22:29 Tayloe Dan-P26412 Re: Phasing Receiver.
The difference between picking up one sideband or the other depends on
whether the phasing outputs are added together (one sideband) or
subtracted (the other one).

- Dan, N7VE


4439 2010-03-11 08:42:16 Tayloe Dan-P26412 Re: Phasing Receiver.
The use of a polyphase network introduces a lot of noise and/or loss
which can be compensated for by increasing the gain in front of the
network if you are concerned about maintaining receiver sensitivity,
which in turn would decrease the receiver large signal performance.
However, on 80m, sensitivity should not be an issue and taking the
sensitivity loss is fine.

I guess what I am saying is that the use of a polyphase network at
higher frequencies would tend to hurt receiver performance compared to
an op-amp phasing approach.

You might look at the NC2030 as an example of a very low power phasing
receiver with very high performance which uses op-amp phasing. 12 mA at
12v, 140 dB BDR, 107 dB IP3DR. The receiver was run at 3v and a small
switching supply was used to efficiently convert 12v power down to 3v
power to run the receiver.

- Dan, N7VE


4445 2010-03-12 10:33:28 Blanco Hugo Danie... Re: Phasing Receiver.
Hi Dan and Friends !!!

Very clean answers from You in both e-mails, very thanks.

About the second one, I want to use a LM833 as two differential
amplifier in front of polyphase network, because of noise and loss of

And yes, I know NC2030, very pretty receiver, but I wish to design
something by myself, and with mayority of parts avaliable in my
junk-box, as possible.

Again, thanks to You.

Hugo Daniel Blanco
Buenos Aires

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4464 2010-03-16 05:40:36 hanssummers2000 Re: Phasing Receiver.
Hi Hugo

November 1995 QEX had an article which showed how to choose the resistor and capacitor values so that the polyphase network response is flat across the audio spectrum. You still need the amplification ahead of it to overcome resistor-associated noise, but it helps a lot to flatten the response. On my website I have a reproducti