31-08-2021, 07:37 AM
(This post was last modified: 31-08-2021, 07:39 AM by Murphyv310.)
Hi.
Many thanks for the encouragement and comments.
To be honest prior to becoming a Radio Amateur and being very slightly naughty I used two paralleled 1P24B valves and made an AM transmitter that was fed to a dummy load it would give out anything from 5 Watts up to 30 Watts when the rods would glow a dull red. The valves never failed nor did they tail off in power, the bulb would go over 100c. For a very short period I did connect this to a dipole and using the online SDRs was able to receive it in Ireland, Netherlands, Germany and the Czech Republic. Its been dismantled for nearly a year and was reborn as my experimental line oscillator and output for driving a very small CRT.
I intend to make a QRP AM TX for 40 or 80 meters and use it, as an intermediate licence holder I can construct my own transmitters and of course legally use it.
Back to the current project. I worked on two small changes yesterday with an increase in audio level. The V2 anode load value has been increased to 18k this is now bang on the sweet spot of the 1J42A characteristics and with just a 3k rise the output was significantly increased. The idea of adding a 2.2mh choke in series with the anode load on V1 again made an improvement without altering the reaction operation. In fact just using two valves with no OP valve audio is plenty loud enough on high impedance phones on the stronger stations, it's even audible straight off the detector.
Sunday night from 23.30 to 0.00 I listened to the Memories show on Caroline, comfortable volume and only slow fading, last night the signal was lower with long fading and flutter but on the peaks significantly louder than Sunday. Also I was gobsmacked in the fact I resolved a German amateur station using SSB on top band, remember with no external antenna just the ferrite rod, tuning was very tricky though. The coverage seems to be a wide 170 meters to 650 meters. I received the amateur station nearly at the end of the dial.
One thing for sure I now need to add a volume control!!!
Many thanks for the encouragement and comments.
To be honest prior to becoming a Radio Amateur and being very slightly naughty I used two paralleled 1P24B valves and made an AM transmitter that was fed to a dummy load it would give out anything from 5 Watts up to 30 Watts when the rods would glow a dull red. The valves never failed nor did they tail off in power, the bulb would go over 100c. For a very short period I did connect this to a dipole and using the online SDRs was able to receive it in Ireland, Netherlands, Germany and the Czech Republic. Its been dismantled for nearly a year and was reborn as my experimental line oscillator and output for driving a very small CRT.
I intend to make a QRP AM TX for 40 or 80 meters and use it, as an intermediate licence holder I can construct my own transmitters and of course legally use it.
Back to the current project. I worked on two small changes yesterday with an increase in audio level. The V2 anode load value has been increased to 18k this is now bang on the sweet spot of the 1J42A characteristics and with just a 3k rise the output was significantly increased. The idea of adding a 2.2mh choke in series with the anode load on V1 again made an improvement without altering the reaction operation. In fact just using two valves with no OP valve audio is plenty loud enough on high impedance phones on the stronger stations, it's even audible straight off the detector.
Sunday night from 23.30 to 0.00 I listened to the Memories show on Caroline, comfortable volume and only slow fading, last night the signal was lower with long fading and flutter but on the peaks significantly louder than Sunday. Also I was gobsmacked in the fact I resolved a German amateur station using SSB on top band, remember with no external antenna just the ferrite rod, tuning was very tricky though. The coverage seems to be a wide 170 meters to 650 meters. I received the amateur station nearly at the end of the dial.
One thing for sure I now need to add a volume control!!!
which did you get?
