TheRadioBoard

Hi All,
I built a Morgan Regen Receiver according to the following video
http://www.youtube.com/watch?v=PDPZQcU_ ... re=related
with the schematic that appears at time 3:12 except the potentiometer, 10K instead of 5K.
I use 8 x 9V batteries and 2 x 2000 ohms phones.
I noticed that if the pot is connected to plate as shown in the video, the plate voltage is the same at any position of the pot i.e. in my case 54.8V and 74V when the pot is switched off. So I disconnected this wire and I've done a test as it follows: I measured voltage and resistance from off position to max every 45° and I found:
0°-74V-14.6ohms
45°-54.6V-21.6ohms
90°-53.7V-425ohms
135°-52.2V-1070ohms
180°-51.1V-1636ohms
225°-49.7V-2475ohms
270°-50.1V-2190ohms
315°-54.6V-12.5ohms
This seems odd for me, the pot is a Linear Taper 10K w/Switch sold by Surplus-Electronics-Sales.
The receiver works well with 3m wire antenna but the level of sound is very low, antenna?, B supply too low or phones resistance to high?
Best regards.
MichelB

With the morgan schematic you are not controlling the plate voltage with the pot.

THe pot controlls how much of the plate current goes through the tickler coils,

When the wiper is closest to the plate end it presents full resistance and most of the plate current flows through the tickler.

When the wiper is furtherest away from the plate it presents no resistance and the most of the current is shunted around the tickler.

Hope this is slightly clearer than mud.

_________________
Mark

I want to meet the man that put the cat IN the bag!

Is this the circuit you are using?



Rich

_________________
Homebrew Radio ex-Silicon Valley

Yes, the same circuit but with 2 differences, a) Potentiometer 10K instead of 500K b) Capacitor 220 pF instead of 0.0025 µF, phones are 4400 ohms instead of 2000 ohms.
Mikrowave1 in his video uses a 5K potentiometer and connects one side of the potentiometer to the plate. In this case what is the "job" of the potentiometer.
Thank you for your interest of my question.
MichelB
P.S.: Sorry for my poor English.

I think that 10k is a much better choice for that pot. If the pot is set in the
mid position, there is then 125k ohm resistance in series with the plate. This
could cause performance problems.

I like this way of controlling regeneration, but I prefer a slightly different
way of connecting the pot, tickler coil and throttle capacitor. In my hookup,
there is no series resistance to the plate. Here is a circuit of my example.
Ignore the rest of the circuit.



Here is my project page for your reference: http://makearadio.com/tube/hikers1.php

In Rich's post, the schematic, the choke is marked as 2.5uH instead of 2.5mH. Just a typo.

Dave

_________________
Please visit my website at: http://www.makearadio.com

I "borrowed" that circuit image from Big Nick's Alfred Morgan site.

I am a "throttle capacitor" enthusiast and use regen pots with pentodes.

Rich

_________________
Homebrew Radio ex-Silicon Valley

Hi Dave,
what is the part "27 mH", is it a choke?

Yes, that is a choke. For MW it is good to use at least a 10mH choke (for
shortwave 2.5mH is popular). I use a lot of 27mH chokes in my projects as
I have a lot of them and they work well. The value isn't critical for this
application.

Dave

_________________
Please visit my website at: http://www.makearadio.com

Thank you Dave. I'll go to your site to buy one or two 27 mH Chokes.
Best regards.
MichelB

The "job" of the pot is what I explained in my first post to you. It controls how much of the plate current flows through the tickler coil.

_________________
Mark

I want to meet the man that put the cat IN the bag!

Hi Mark, I tested variation of tickler voltage, you are right. But if it does not work when on side of the potentiometer is connected to the plate as shown in the Mikrowave1 video.
Thank you and best regards.
MichelB