Re: Should I start with uBITX, sBITX or zBITX?
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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.
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
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
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