Wonderful vid and series Mike! Boy-oh-boy it takes me back when I see old Bell system parts being used. As a teen (mid 70s) I lived about 2 miles from a Bell Telephone repair truck depot. I visited their dumpster routinely. It was a mysterious, wonderful and generous dumpster! :) Be well and 72 OM! dit dit
Nice video! A minimalistic transmitter from the old days. It remembers me to the early days, when I discovered my passion to RF technology and wireless systems. Many thanks and greetings from Germany.
I like the way you link some theory in with the build. The carbon mic information was fascinating and well explained. Thanks, Mike, I'm waiting for the next episode to see how it all hooks up and starts to oscillate.
Excellent video, Mike ... I really appreciate your work and willingness to share. You are a great 'virtual Elmer' I now find myself going down the rabbit hole of GDOs.... thanks and 73 de AB1DQ/James
Another fine video Mike! I know just enough to be dangerous and would never have thought of damaging the mic much less how to avoid it! Your explanation of the circuit and the role of each component was perfect for me! Your ability to teach without being a "teacher" is a rare and desirable talent.
You have good timing yet again, dealing with microphone issues on the HW-101 I rebuilt. The D-104 I have is a amplified unit and has some issue with it. Getting a Heil kit for it
Just to make sure I'm understanding it right: it seemed like you have antenna switching from receive to transmit, but this is a transmit-only circuit, correct? I don't see any audio output -- so why the antenna switching? To pass through to a separate receiver?
What a lovley 10m-TX you try to build. Can't wait for the next video! "Old Style" - but so beautiful! Should do this too, ... ! 73 de db9pz ; Markus ; JN39FQ
You certainly do not want to have more than 100% modulation as this causes distorsion. Normally, you would aim to have a bit less than 100%. Maybe 80%, to ensure some safety margin and avoid distorsion. The formula is Pt=Pc(1+(m^2)/2). Pt is total power, Pc is carrier power and m is modultion index (where m=1 corresponds to 100% modulation. If you have 10W carrier and m=1, the total power is 15W. The power in each sideband is only 2.5W. So, of your 15W transmit power, only 2.5W is being used at the receive end to copy the signal. The sideband power drops off quite rapidly as you reduce m below 1 (below 100%) due to the m^2 part of the formula. So, that is why you nornally aim to keep modulation index just under 100%. I always remember that for 100% modulation, you have "1+4+1". That is, for 6W total power (1+4+1=6), you have 1W in in each sideband and 4W in the carrier. AM is pretty inefficient! That is why hams switched to SSB.
@@Steve-GM0HUU I was not asking for a detailed technical explanation nor the math behind it. We know the obvious of over 100% modulation, I was wondering can this suppressor grid modulation circuit reach 100% AM modulation!
Wonderful vid and series Mike! Boy-oh-boy it takes me back when I see old Bell system parts being used. As a teen (mid 70s) I lived about 2 miles from a Bell Telephone repair truck depot. I visited their dumpster routinely. It was a mysterious, wonderful and generous dumpster! :) Be well and 72 OM! dit dit
Nice video! A minimalistic transmitter from the old days. It remembers me to the early days, when I discovered my passion to RF technology and wireless systems. Many thanks and greetings from Germany.
I like the way you link some theory in with the build. The carbon mic information was fascinating and well explained. Thanks, Mike, I'm waiting for the next episode to see how it all hooks up and starts to oscillate.
Me too! 😀
Excellent video, Mike ... I really appreciate your work and willingness to share. You are a great 'virtual Elmer' I now find myself going down the rabbit hole of GDOs.... thanks and 73 de AB1DQ/James
Like the microphone in the old AT&T telephones.
I finally got to be your first 'Like' - what a timely project! VK3YE reported Australia to the US and hearing the long path.
Thanks Microwave1
Another fine video Mike! I know just enough to be dangerous and would never have thought of damaging the mic much less how to avoid it! Your explanation of the circuit and the role of each component was perfect for me! Your ability to teach without being a "teacher" is a rare and desirable talent.
Thanks for watching Allen! 10M is open today but I heard no AM stations :( That is going to have to change!
You have good timing yet again, dealing with microphone issues on the HW-101 I rebuilt. The D-104 I have is a amplified unit and has some issue with it. Getting a Heil kit for it
Just to make sure I'm understanding it right: it seemed like you have antenna switching from receive to transmit, but this is a transmit-only circuit, correct? I don't see any audio output -- so why the antenna switching? To pass through to a separate receiver?
Yes to work with a receiver on the same antenna.
What a lovley 10m-TX you try to build. Can't wait for the next video! "Old Style" - but so beautiful! Should do this too, ... !
73 de db9pz ; Markus ; JN39FQ
It is going to take a good antenna and some AM stations to make the big DX contact as promised!
Source of the circuit? Arrl handbook? What year?
Can this transmitter be modulated to 100% or is there a limit below that?
You certainly do not want to have more than 100% modulation as this causes distorsion. Normally, you would aim to have a bit less than 100%. Maybe 80%, to ensure some safety margin and avoid distorsion. The formula is Pt=Pc(1+(m^2)/2). Pt is total power, Pc is carrier power and m is modultion index (where m=1 corresponds to 100% modulation. If you have 10W carrier and m=1, the total power is 15W. The power in each sideband is only 2.5W. So, of your 15W transmit power, only 2.5W is being used at the receive end to copy the signal. The sideband power drops off quite rapidly as you reduce m below 1 (below 100%) due to the m^2 part of the formula. So, that is why you nornally aim to keep modulation index just under 100%.
I always remember that for 100% modulation, you have "1+4+1". That is, for 6W total power (1+4+1=6), you have 1W in in each sideband and 4W in the carrier.
AM is pretty inefficient! That is why hams switched to SSB.
@@Steve-GM0HUU I was not asking for a detailed technical explanation nor the math behind it. We know the obvious of over 100% modulation, I was wondering can this suppressor grid modulation circuit reach 100% AM modulation!
@@JCWise-sf9ww Sorry, my apologies for misunderstanding. Perhaps we shall the answer in the next installment.
ATLEAST YOU SHOULD HAVE SHOWN THE CIRCUIT DIAGRAM PLEASE.