181
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182
Home Brew And Tech Forum / CB to 10 meter
« on: October 19, 2015, 02:21:43 PM »
I started this thread over at the AMPhone forum.
http://amfone.net/Amforum/index.php/topic,40838.new.html#new
Looking for another project. been wanting to do some AM phone.
After looking at what the stuff goes for I decided to mod a CB radio for 10 meters.
But not just any radio. I wanted a radio that is known for quality audio.
So I chose the Tram D201.
The reaso other than good AM audio is that there is a VFO in this radio that will cover transmit and receive over the 23 channels. When these were new the VFO was only for receive. This radio uses a 16 MHz and 4 MHz mixing shceme. Should be fairly easy to convert.
http://amfone.net/Amforum/index.php/topic,40838.new.html#new
Looking for another project. been wanting to do some AM phone.
After looking at what the stuff goes for I decided to mod a CB radio for 10 meters.
But not just any radio. I wanted a radio that is known for quality audio.
So I chose the Tram D201.
The reaso other than good AM audio is that there is a VFO in this radio that will cover transmit and receive over the 23 channels. When these were new the VFO was only for receive. This radio uses a 16 MHz and 4 MHz mixing shceme. Should be fairly easy to convert.
183
Electronic Video Blog / Collins KWM-2 damaged Part 2
« on: October 10, 2015, 07:59:32 PM »
A quick look at problems with the damaged KWM-2
184
Electronic Video Blog / Collins KWM-2 damaged in shpping
« on: October 07, 2015, 08:46:47 PM »
In this video we look at a Collins transceiver that was poorly packed and damaged through shipping.
The VFO knob was pushed through the front plastic bezel, this broke the bezel in about 12 pieces.
The VFO knob was pushed through the front plastic bezel, this broke the bezel in about 12 pieces.
185
Electronic Video Blog / A video tour around my old time shop and ham shack
« on: September 26, 2015, 09:45:56 PM »
In this video we have a quick look around my shop and ham shack. Most of my equipment is old and bough in non-working state. I like buying stuff and repairing it to use for myself. Don’t expect to see a lot of flashy new gear here. Hope you enjoy this cluttered mess I call my playground. I spend many hours in the shop and enjoy working on gear of all types. The old computers in the one room are using for programming Eproms like the 27C128 and 27C64 chips. These were used in some older radios.
https://www.youtube.com/watch?v=2LPcLAkhdFE
https://www.youtube.com/watch?v=2LPcLAkhdFE
186
Home Brew And Tech Forum / Alinco DR-570 no tx or rx on UHF
« on: September 22, 2015, 10:05:05 AM »
I have a dr-570 tht has no tx or rx on UHF. Vhf works fine. I started by loocing in the service manual.
The manual says to adjust TC1 for 1.8 volts while monitoring TP3.
Then adjust TC2 for 3.8 volts tx.
The voltage on TP3 is .600 mv. Either adjustments does not affect the reading at TP3.
I have to trace down the schematic and figure out the voltage supplies.
The manual says to adjust TC1 for 1.8 volts while monitoring TP3.
Then adjust TC2 for 3.8 volts tx.
The voltage on TP3 is .600 mv. Either adjustments does not affect the reading at TP3.
I have to trace down the schematic and figure out the voltage supplies.
187
Electronic Video Blog / #009 Com Ser Labs BR1000A overview
« on: September 20, 2015, 08:00:06 PM »
Com Ser Labs communication test set
188
Electronic Video Blog / Heathkit IG-1271 trouble shoot and repair video
« on: September 16, 2015, 05:16:26 PM »
In this video I use a 1.5 volt AA battery as a constant voltage source to track down a shorted capacitor.
189
Basic beginner Electronics / Are non-polarized caps polarized?
« on: July 02, 2015, 04:51:10 PM »
Capacitors.
The other day I worked on a tube audio amp that was very noisy. The amp was just rebuilt and the guy did a fantastic job. But he could not figure out was the noise was coming from so he brought it to me.
TECH TIME…..
We all know that when we install electrolytic capacitors in a circuit we have a polarity to follow. You defiantly do not want to install them backwards or the magic smoke will escape.
So how about non-polarized capacitors? Surly it does not matter which way we install them.
Or does it?
As we know most capacitors are nothing more than two plates with some type of dielectric separating the plates. Sometimes these are rolled up or sandwiched together. When looking at old tube radios you will find a lot of wax type capacitors. Some have a mark on one end but are non-polarized. Most of the time they marked the caps to show a band on the ground end. Other times the caps were switched around and the printing was put on the wrong side. So you cannot always go by the banded end of caps.
INSERT CAP PICTURE HERE
In the tube circuit below we can see several capacitors that are used. We have caps going from low impedance to high impedance circuits. We also have DC blocking. All caps block DC…
Now look at it this way. These caps are non-polarized cylinder type caps. One lead is connected to the outer foil while the other lead is connected to the inner foil. If the caps are installed the wrong way in this low to high Z circuit several things can happen.
Look at the circuit below. I have labeled the caps 1 2 3. Cap 1 is an input. Imagine the ground side of the cap is on the left. This means the left side shields the whole cap and no voltage of signals from the grid of the tube are exposed on the capacitor. Other than the lead from the cap to the grid which we would keep as short as possible, this also keeps the voltage of the grid from traveling all the way to the other side of the cap.
Same with cap 2. The trick here is to keep noise off the circuit. Plus we would not want voltage traveling that close to ground. If the cap has a hole in the outer jacket you can get a nasty burn.
In cap 3 we are taking a low Z and feeding it into a high Z. Again proper placement of the capacitor helps to get the noise out.
INSERT PICK HERE OF TUBE CIRCUIT
So how do we determine the correct polarity of our capacitors when they are not marked from the factory?
It is really quite simple. We will use a scope set on the lowest setting and use a 1:1 probe and our body….
The pic below shows how to connect the probe and how to hold the capacitor. We are using our fingers as a signal source to couple into the cap.
INSERT HOLDING CAP HERE
We will now look at the signal on the scope. Notice the wave form. The scope is set to 2ms per division and we are taking 2 divisions.
INSERT CAPTEST1
Now we switch the leads on the capacitor. Notice when we look at the scope that we see a very small reading. This is because the scope center probe is shielded from the signal out fingers produce. So the scope shows a very small waveform.
INSERT CAPTEST2
So looking at the way the scope probe is connected we would mark the ground end of the cap so we can remember the correct way to install it.
INSERT MARKED CAP HERE
This works with all type of capacitors. Regardless of what type of circuit it is. It was just easier to show you this using a tube circuit. This is especially helpful when building transistor amplifiers. Even silver dip caps need to be installed correctly.
I know there are not many folks here to teach but perhaps someone did not know this….
The other day I worked on a tube audio amp that was very noisy. The amp was just rebuilt and the guy did a fantastic job. But he could not figure out was the noise was coming from so he brought it to me.
TECH TIME…..
We all know that when we install electrolytic capacitors in a circuit we have a polarity to follow. You defiantly do not want to install them backwards or the magic smoke will escape.
So how about non-polarized capacitors? Surly it does not matter which way we install them.
Or does it?
As we know most capacitors are nothing more than two plates with some type of dielectric separating the plates. Sometimes these are rolled up or sandwiched together. When looking at old tube radios you will find a lot of wax type capacitors. Some have a mark on one end but are non-polarized. Most of the time they marked the caps to show a band on the ground end. Other times the caps were switched around and the printing was put on the wrong side. So you cannot always go by the banded end of caps.
INSERT CAP PICTURE HERE
In the tube circuit below we can see several capacitors that are used. We have caps going from low impedance to high impedance circuits. We also have DC blocking. All caps block DC…
Now look at it this way. These caps are non-polarized cylinder type caps. One lead is connected to the outer foil while the other lead is connected to the inner foil. If the caps are installed the wrong way in this low to high Z circuit several things can happen.
Look at the circuit below. I have labeled the caps 1 2 3. Cap 1 is an input. Imagine the ground side of the cap is on the left. This means the left side shields the whole cap and no voltage of signals from the grid of the tube are exposed on the capacitor. Other than the lead from the cap to the grid which we would keep as short as possible, this also keeps the voltage of the grid from traveling all the way to the other side of the cap.
Same with cap 2. The trick here is to keep noise off the circuit. Plus we would not want voltage traveling that close to ground. If the cap has a hole in the outer jacket you can get a nasty burn.
In cap 3 we are taking a low Z and feeding it into a high Z. Again proper placement of the capacitor helps to get the noise out.
INSERT PICK HERE OF TUBE CIRCUIT
So how do we determine the correct polarity of our capacitors when they are not marked from the factory?
It is really quite simple. We will use a scope set on the lowest setting and use a 1:1 probe and our body….
The pic below shows how to connect the probe and how to hold the capacitor. We are using our fingers as a signal source to couple into the cap.
INSERT HOLDING CAP HERE
We will now look at the signal on the scope. Notice the wave form. The scope is set to 2ms per division and we are taking 2 divisions.
INSERT CAPTEST1
Now we switch the leads on the capacitor. Notice when we look at the scope that we see a very small reading. This is because the scope center probe is shielded from the signal out fingers produce. So the scope shows a very small waveform.
INSERT CAPTEST2
So looking at the way the scope probe is connected we would mark the ground end of the cap so we can remember the correct way to install it.
INSERT MARKED CAP HERE
This works with all type of capacitors. Regardless of what type of circuit it is. It was just easier to show you this using a tube circuit. This is especially helpful when building transistor amplifiers. Even silver dip caps need to be installed correctly.
I know there are not many folks here to teach but perhaps someone did not know this….
190
Shop and Barn talk / Home made sand blast cabinet
« on: May 29, 2015, 06:29:27 PM »
Just started on this
191
The Old Tractor Forum / 1949 Miniapolise oline ZAU restore
« on: May 27, 2015, 05:27:28 PM »
A bit rough but it is doable
192
The Old Tractor Forum / ID and Restore an original MTD 990
« on: April 21, 2015, 07:15:26 AM »
What is it?
I found out what this tractor is.
It is an original MTD 990. Somewhere between 1972 and 1974.
I found out what this tractor is.
It is an original MTD 990. Somewhere between 1972 and 1974.
193
Announcements / Temparary Moderator wanted
« on: April 06, 2015, 12:50:29 PM »
I am currently looking a new moderator for the board.
What I am looking for in a moderator:
Must be very active
Skill level in electronics is not a must be preferred
Willing to help the site grow. That means going out and directing folks here.
Must be a trust worthy person.
This person will be on a 3 month probation. If needs are met then they will become part of the staff.
Disclaimer.
Gokarters.com reserves the right to refuse any person for this posistion
What I am looking for in a moderator:
Must be very active
Skill level in electronics is not a must be preferred
Willing to help the site grow. That means going out and directing folks here.
Must be a trust worthy person.
This person will be on a 3 month probation. If needs are met then they will become part of the staff.
Disclaimer.
Gokarters.com reserves the right to refuse any person for this posistion
194
Design, Project / Another Handy Tool Crystal Oscilator
« on: March 21, 2015, 01:28:36 PM »
Thought I share this quick and easy to build device for testing crystals.
This is build Manhattan style and only take a few minutes to build.
Not only can you test your crystals but you can use it to replace a missing signal from your radio.
Enjoy
This is build Manhattan style and only take a few minutes to build.
Not only can you test your crystals but you can use it to replace a missing signal from your radio.
Enjoy
195
Test Equipment / RF sampler / demodulator for oscilloscope
« on: March 17, 2015, 06:47:42 AM »
So you went out and got you a 0-scope.
Now what can I do with this?
Plenty. One thing is monitor the purity of your carrier and you’re audio. And if you got yourself a multi-channel scope then you can do both at
the same time. Simply run your RF through this simple device between your radio and watt meter. Connect the sample port to channel A and the
DEMOD port to channel B. Select channel A and view your carrier, now select channel B and view your audio that has been picked from the carrier
signal.
While monitoring the carrier you can look at the signal for distortion, also look for bright spots that indicate you are reaching 100%
modulation.
While looking at the demodulated audio you can view the scope to see if your modulation is flat topping or distorted.
Now view both signals at one time. Observe your modulation riding on top of your carrier.
This is a great little tool when working on transmitters. Nothing worse than having a customer come back because folks tell him he sounds
distorted.
This is also great for SSB rigs if your scope has the feature to drive x and y and then you can view the trapezoid waveform on ssb.
Parts list
Small case or 1 inch by 4 inch double sided circuit board
4- BNC chassis mount connectors (if you want you can use 2 SO-239 for RF in and out and 2 BNC for sample and demod)
1- 0.10 uf cap
1 - 10 pf cap
1 – 1000 pf cap
2 – 1N34A geranium diodes (1N60 will work)
1 – 690K resistors
1 - 47K resistors
1 – 1K resistors
Resistors can be ¼ watt since we are only using this to monitor 100 watts and down.
Now what can I do with this?
Plenty. One thing is monitor the purity of your carrier and you’re audio. And if you got yourself a multi-channel scope then you can do both at
the same time. Simply run your RF through this simple device between your radio and watt meter. Connect the sample port to channel A and the
DEMOD port to channel B. Select channel A and view your carrier, now select channel B and view your audio that has been picked from the carrier
signal.
While monitoring the carrier you can look at the signal for distortion, also look for bright spots that indicate you are reaching 100%
modulation.
While looking at the demodulated audio you can view the scope to see if your modulation is flat topping or distorted.
Now view both signals at one time. Observe your modulation riding on top of your carrier.
This is a great little tool when working on transmitters. Nothing worse than having a customer come back because folks tell him he sounds
distorted.
This is also great for SSB rigs if your scope has the feature to drive x and y and then you can view the trapezoid waveform on ssb.
Parts list
Small case or 1 inch by 4 inch double sided circuit board
4- BNC chassis mount connectors (if you want you can use 2 SO-239 for RF in and out and 2 BNC for sample and demod)
1- 0.10 uf cap
1 - 10 pf cap
1 – 1000 pf cap
2 – 1N34A geranium diodes (1N60 will work)
1 – 690K resistors
1 - 47K resistors
1 – 1K resistors
Resistors can be ¼ watt since we are only using this to monitor 100 watts and down.