Excellent work, Mike. It's great to actually see some numbers. One thing to keep in mind is that with the power reduced, the pi-net L needs to be increased (and the tune and load C both decreased). With those adjustments the power drop with lower screen voltage may be much less. I double-checked my own numbers with a souped-up 6AV5 (6DQ6 innards), and confirmed that I'm getting close to 11W out with 50V on the screen and about 350V on the plate (40m HC-49 crystal). So try lowering the grid resistance (I assume that will be in Part 4) and also try tweaking the pi-net L value. You are really adding to the knowledge base with your efforts.
I have been chastized to be careful, because not all hams are so happy to hear their sending on CW! Most are thrilled. And Happy Accidents are my trademark on the channel!
Thanks Mike. Glad this didn't turn out to be a horror show featuring exploding HC49s. I did wonder if two or more identical HC49s in parallel would allow for higher power. Quite OK that you ran out of time - we can now look forward to another episode.
Before I managed to get my hands on a couple of Novice Band crystals, I used a couple of old "color burst" crystals(3.58 MHz), salvaged from old TVs, for testing this and earlier transmitters.
Yup me too ! I have a few hundred of those 3.579 xtals. I was designing a qrp xcvr kit for them, till I had some health issues ! Maybe, I'll finish it this year....!
A trick that I learned, when I was just starting out and being on a limited budget(aka, poor), If you dont have a proper socket for an FT-243 xtal, you can also use a socket for an octal base tube :) WA1YKL
Hi Mike, Great show ! While you are on the subject of XTAL's ..... Could you do a video on snubbing, tweaking, ie: grinding xtal's ! There are still a few FT-243 out there but they are not quite on the freq's desired. I know it's a lost art these day's... But considering the main topic of "Novice Transmitters", I'm just pulled back to the times of my Elmers. And the smell of the cooking dust on the tubes, on a cool Autumn morning !
Yes nothing like the smell of dust on hot Valves, I remember years ago as a teen in the 80's listening to shortwave on an old valve set. Well especially in winter when the room was unheated and cold.
I remember at least one local old timer talking about grinding crystals years ago. Struggling to remember but think a sheet of glass and household detergent powder was involved as a grinding paste? Also, that some casualties occurred as it was very easy to break them.
I have seen a practice where two HC-49 crystals are connected in parallel to halve the crystal current. There is at least one person selling HC-49 crystals in FT-243 holders this way. I have had limited success with using these crystals this way. Except for solid state rigs I will stick with the FT-243's, fortunately I have a decent stash of them.
Are the datasheets of the vintage FT-243 crystals published anywhere? I wonder what was the maximum power dissipation declared by the manufacturers of such crystals.
I like CW, thank you for the video! _P.S. I think it would be better (it's just a suggestion) to show the transmitted character simultaneously with its transmission (in Morse code)_
That is a great question. Actually no, but there is enough feedback that a simple coil and capacitor in a separate box connected to the crystal socket, would produce a VFO transmitter!
It's becoming a great cliff hanger series Mike.... I am on the edge of my seat!
Someone is going to have to tool up to make crystals. Great video as always.
I didn't realise just how critical the current was in this context. Modern day crystals are wimps!
Thanks for another informative and educatig video.
Excellent work, Mike. It's great to actually see some numbers. One thing to keep in mind is that with the power reduced, the pi-net L needs to be increased (and the tune and load C both decreased). With those adjustments the power drop with lower screen voltage may be much less. I double-checked my own numbers with a souped-up 6AV5 (6DQ6 innards), and confirmed that I'm getting close to 11W out with 50V on the screen and about 350V on the plate (40m HC-49 crystal). So try lowering the grid resistance (I assume that will be in Part 4) and also try tweaking the pi-net L value. You are really adding to the knowledge base with your efforts.
Very nice and great advice. You are right that the loading has changed.
I always wondered if your contacts knew they were going to be on youtube. Cool that one of them recognized you!
I have been chastized to be careful, because not all hams are so happy to hear their sending on CW! Most are thrilled. And Happy Accidents are my trademark on the channel!
Thanks Mike. Glad this didn't turn out to be a horror show featuring exploding HC49s. I did wonder if two or more identical HC49s in parallel would allow for higher power. Quite OK that you ran out of time - we can now look forward to another episode.
Before I managed to get my hands on a couple of Novice Band crystals, I used a couple of old "color burst" crystals(3.58 MHz), salvaged from old TVs, for testing this and earlier transmitters.
Those crystals out of old TVs were a thing, and QRP nets were built around them.
Yup me too ! I have a few hundred of those 3.579 xtals. I was designing a qrp xcvr kit for them, till I had some health issues ! Maybe, I'll finish it this year....!
A trick that I learned, when I was just starting out and being on a limited budget(aka, poor), If you dont have a proper socket for an FT-243 xtal, you can also use a socket for an octal base tube :) WA1YKL
Old school advice for sure! In fact two FT-243's nest nicely in an octal socket. So just add a switch for QSY.
Hi Mike, Great show ! While you are on the subject of XTAL's ..... Could you do a video on snubbing, tweaking, ie: grinding xtal's ! There are still a few FT-243 out there but they are not quite on the freq's desired. I know it's a lost art these day's... But considering the main topic of "Novice Transmitters", I'm just pulled back to the times of my Elmers. And the smell of the cooking dust on the tubes, on a cool Autumn morning !
Yes nothing like the smell of dust on hot Valves, I remember years ago as a teen in the 80's listening to shortwave on an old valve set. Well especially in winter when the room was unheated and cold.
I remember at least one local old timer talking about grinding crystals years ago. Struggling to remember but think a sheet of glass and household detergent powder was involved as a grinding paste? Also, that some casualties occurred as it was very easy to break them.
I'm thinking the series current limiting resistor is going to be the winner but just a SWAG!
I have seen a practice where two HC-49 crystals are connected in parallel to halve the crystal current. There is at least one person selling HC-49 crystals in FT-243 holders this way. I have had limited success with using these crystals this way. Except for solid state rigs I will stick with the FT-243's, fortunately I have a decent stash of them.
Makes sense! I have also heard of this technique, but for another purpose, increasing the pulling range in a VXO.
Thanks for the video. And yes, you most definitely should cut the power in half! 73s de R2AUK/QRP :)
Spoken like a true QRP man!
Brilliant again mike, My CW sure is rough. But keep working is the best cure for that. just fantastic videos. Fantastic learning videos. VE9MLG
There was a box?
I like that Dow key relay.
No case, but it definitely had a case that was lost, or utilized in a different project. The good old Dow Key.
Are the datasheets of the vintage FT-243 crystals published anywhere? I wonder what was the maximum power dissipation declared by the manufacturers of such crystals.
I like CW, thank you for the video! _P.S. I think it would be better (it's just a suggestion) to show the transmitted character simultaneously with its transmission (in Morse code)_
Yes I just give the gist rather than the actual code, mistakes and abreviations and all.
We'll just need to learn Morse code then, to get the real message. :)
Great video! Does it oscillate even when there is no crystal plugged in? One needs to maximize the gain?
That is a great question. Actually no, but there is enough feedback that a simple coil and capacitor in a separate box connected to the crystal socket, would produce a VFO transmitter!