Thanks a lot Gerry for the clarification. I had started a bit later in the hobby than most of you.

There are a few younger hams in this region still getting hold of 807s and making linear amplifiers for their Radioberry, with excellent on air signals.

Sorry that we have deviated from BITX because of cute nostalgic memories.

Maybe someone may be interested in trying out those tubes as linear amplifiers for BITX.

73

Jon, VU2JO.

On Tue, Apr 15, 2025 at 2:41?AM Gerald Sherman via <ve4gks=[email protected]> wrote:

Jon - the 12 volts is the heater voltage, not the plate!!!? You still need that 750 volts on the plate.

Regarding high voltage - there were tubes made in the early days of transistors that used a plate voltage of 12 volts.? They were used in car radios, where they were used in the RF stages with transistors in the audio stages.? Compared to "conventional" tubes, the difference is that the control and screen grids are "reversed", with the screen being 1st and the control 2nd.? They got rid of the vibrator and power transformer that was used before that to get the 250 volts or so for the tube plates.? Once transistors with respectable frequency capabilities were developed they disappeared.

Gerry

On 2025-04-14 10:15, Jon via wrote:

Gerry,

Thanks a lot for the detailed suggestions, especially as you own all three versions.

I did not know that there is a 12V version of 807! I thought that all vacuum tubes need high voltage. I had wondered how the early car radios worked from batteries.

Regarding the filters and all, getting them here would be tough, though not impossible.

Maybe i will wait till sBITX v4 reviews are out and then decide.

Hope to meet you on air some?time soon.

73

Jon, VU2JO

On Mon, Apr 14, 2025 at 7:04?AM Gerald Sherman via <ve4gks=[email protected]> wrote:

Jon

I would say the uBit is probably the easiest of the lot for a new user to use, although it lacks some of the features of the SDRs.? It's a much less expensive radio than the sBit.? Since you say you won't be operating portable, and you do have a resonant antenna system, you can get away with just an AC power supply and a key to start with.? You might be able to build a suitable power supply, or buy something ready made.? I'm in Canada, so I don't know what it's like to get things locally in India.? It's easy to add a few features later to the radio, after you get familiar with it.? The ones I would suggest are a memory keyer, an audio filter, and an AGC system.? The uBit isn't really designed to handle some of the more modern things like FT8, etc., just plain old CW and SSB.? It may be possible to use these with a sound card and a computer.? I haven't tried this.

With either of the SDRs, you are looking at updates, especially with the zBit, as it is quite new.? You won't have this issue with the uBit.

I have all 3 of these radios, so I do have some experience.

Sotabeams has a good audio filter at a cost of about ?25.00, plus shipping.? Hamcrafters (K1EL) has the K16-EXT keyer, although at the moment his situation is unsettled, as things are uncertain in the USA with some of the president's ideas on international trade.? A lot of his raw materials are imported.? Both of these can be built into the uBit, although the keyer has some practice features that make it very useful on its own.

Your comments about 807 tubes bring back over half a century of memories with 1625s (the 12 volt version of the 807) and WWII surplus equipment.? I used a 1625 in my first transmitter, back in 1970.

Gerry Sherman

On 2025-04-13 23:45, Jon via wrote:

I do not have a BITX yet, but have been closely following the discussions on the group.

My experience in homebrewing was a few decades back, of a VU2VWN QRP with BD 139 final and a 3 x 807 vacuum tube TX running about 120W DC input.

That means I have not meddled with any radio circuit for the past few decades.

Which one should I start with: uBITX, sBITX or zBITX?

As of now, I have no option for portable operations. Only a fan dipole for 40-10m and a dipole for 80m.

Hoping to receive your valuable suggestions.

73

Jon, VU2JO