The Improved Neophyte Receiver: Part 2
I searched my archives for a suitable S-Meter circuit and it turns out that I had one in my Project Box. I have a Project Box that I keep kits in for future needs. One of the kits that I had was the Kanga Products "Audio 'S' Meter." The box was down in my basement and I had completely forgotten about it.
According to Kanga Products,
"Most homebrew receivers and transceivers lack any form of 'S' meter. They are not difficult to build but finding a suitable circuit that works is often a problem. This circuit is based loosely upon one from Doug DeMaw W1FB. The circuit samples the audio of the receiver after the detector, but before the audio volume control. The signal is amplified and rectified to give a DC voltage that varies according to the level of audio."
The enclosure style I have chosen for my receiver is to allow me to easily modify my circuitry until I have locked down my choices for performance and usability. I simply used a block of wood and a piece of artist board that has clay in it to build the reciever chassis. As you can see from the front of my receiver the design is constantly evolving. Do you see the 4 holes in a rectangle shape? I was going to mount the S-Meter circuit there but the spacing was a little too tight and it was interfering with the main tuning capacitor. So I decided to mount the main receiver board vertically and then attach the S-Meter board to one corner of the receiver board.
The next modification I want to make to my 40 Meter receiver is to add a digital frequency dial.
Al
N8WQ
Al, nice series on the Improved Neophyte Receiver. I've just finished one myself and am trouble shooting some low audio I'm experiening. I'm curious, what are the specs on the meter you've used for the S-Meter?
ReplyDelete73,
Steve, W1SDR
I am also trying to solve a low audio output from my Improved Neophyte. I tried shorting out R15 in the LM 586 gain circuit which should have increased the audio gain by factor of four. Still have to put speaker up to my ear to hear anything. Did you resolve your problem?
DeleteJim
This comment has been removed by the author.
DeleteHi Steve, thanks for your comments and I will be glad to help you with your receiver if you need anything. The meter supplied with the Kanga S-Meter kit is 200uA. I would like to see a picture of your build if you don't mind sharing it when you are done.
ReplyDeleteBest 73,
Al
Al,
ReplyDeleteThanks for the offer and the S-Meter information, very much appreciated. Work has been keeping my busy lately so I haven't had a chance to do much troubleshooting. I should be back at it in the next week or so and will let you know how it goes.
73,
Steve, W1SDR
This is one of the best DC receivers I ever tried building, I'm listening to the NightWatch net right now on it. Plenty of sensitivity and volume - thanks so much for taking the trouble to publish this.
ReplyDeletePeter
AA1YY
Hi Peter,
ReplyDeleteThanks for stopping by my blog and saying hi.
It is a real joy for me to hear that your receiver is working. Please send me a picture of your receiver if you can.
Best 73
Al
I am also trying to solve a low audio output from my Improved Neophyte. I tried shorting out R15 in the LM 586 gain circuit which should have increased the audio gain by factor of four. Still have to put speaker up to my ear to hear anything. Any suggestions?
DeleteJim
Hi Jim,
ReplyDeleteWhat is a LM586? Is that a audio amplifier? What schematic are you using to build your receiver? R15 on my schematic is AF Gain.
Al,
N8WQ
Wow, my question was full of typos. The resistor I jumped out is R17 (1.5K) in the gain set circuit of the LM 386 (not LM586) audio amp. Furthur testing revealed that the audio is good when I switch the audio filter into the circuit. Guess I need to find what the problem is with the filter switched out. I found the schematic on line when I Googled "Improved Neophyte" but it has no ID.
ReplyDeleteThe schematic is the one you have posted and matches my receiver. I got the receiver in an eBay box deal of QRP equipment.
ReplyDelete