EMRFD Message Archive 4584

Message	Date	From	Subject
4584	2010-04-26 19:03:35	Phil Sittner	14mhz Receiver
I'm finishing up a copy of Wes' 14mhz receiver and have a question regarding the product detector (Fig 6.76, 1st printing). Would there be any advantage to replacing the 6dB pad shown on the audio output with a diplexer similar to that shown in fig 6.72? I would think the diplexer would present a good termination. Does anyone have thoughts about this? regards, Phil kd6rm [Non-text portions of this message have been removed]
4585	2010-04-26 20:29:51	w7zoi	Re: 14mhz Receiver
Hi Phil and gang, I suspect that you would be better off with the pad, for the audio system of Fig 6.78 just uses an op-amp in a circuit that has a 1K input R. If you put a diplexer in, change the audio input circuitry accordingly. For that matter, if you were to change to a diplexer, you may as well do a good one. Some of the stuff in Chapter's 8 and 9 is more refined. The diode ring is a good product detector for the IMD is low. Signal levels are high, so there is no problem with the loss of a pad, and that will certainly provide the needed wide band termination for the ring. Have fun. 73, Wes w7zoi
4588	2010-04-27 07:43:45	Tim	Re: 14mhz Receiver
I can't see how termination-wise it makes any difference. But my experience with the audio qualities: I liked the post-mixer diplexer in my R2Pro so much (the smooth audio rolloff in particular) that I retrofitted it into my homebrew 8-pole crystal filter superhet's product detector. I was expecting some of the "smoothness" to somehow rub off
4590	2010-04-27 16:55:07	Phil Sittner	Re: 14mhz Receiver
Tim- You've confirmed what Wes mentioned in his response. I'll finish things up in the manner shown in EMRFD and give her a go. Thanks for the input. Phil ----- Original Message -----
4591	2010-04-27 17:05:59	Phil Sittner	Re: 14mhz Receiver
Wes- Thanks for the prompt response. Tim gave a similar view of the idea so I'm sticking with the original as published. I can't wait to see what this rig sounds like. Phil, kd6rm ----- Original Message -----