On Jan 28, 1:43*am, (Scott Dorsey) wrote:
VK3XAO wrote:
I'd like to build a simple tube-type FM broadcast tuner. So far it
looks like a 6BA7 is the best bet for oscillator/mixer but I need a
circuit to avoid the pitfalls and/or reinvention of the wheel.

Look in the back of the RCA Receiving Tube Handbook. *There are some
nice designs in there that are pretty bulletproof.

Your problem is going to be finding good IF transformers, more than
anything else.
--scott
--
"C'est un Nagra. *C'est suisse, et tres, tres precis."

Thanks Scott,

The IF transformers was the easy bit, to be scavenged from a piece of
unused tube-type mobile radio gear that got overtaken by technology.
I've looked at the RCA Receiving Tube Handbook (RC35 in my case) but
would prefer a circuit that used more generally available (in
Australia) tubes. There *must* be some commercial FM broadcast
receivers that used a 6BA7 or a triode-pentode converter stage -
Zenith used a 12AT7 twin triode that works well.

All circuit source suggestions appreciated.

John

"VK3XAO" wrote in message
...
On Jan 28, 1:43 am, (Scott Dorsey) wrote:
VK3XAO wrote:
I'd like to build a simple tube-type FM broadcast tuner.
So far it
looks like a 6BA7 is the best bet for oscillator/mixer
but I need a
circuit to avoid the pitfalls and/or reinvention of the
wheel.

Look in the back of the RCA Receiving Tube Handbook. There
are some
nice designs in there that are pretty bulletproof.

Your problem is going to be finding good IF transformers,
more than
anything else.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Thanks Scott,

The IF transformers was the easy bit, to be scavenged from a
piece of
unused tube-type mobile radio gear that got overtaken by
technology.
I've looked at the RCA Receiving Tube Handbook (RC35 in my
case) but
would prefer a circuit that used more generally available
(in
Australia) tubes. There *must* be some commercial FM
broadcast
receivers that used a 6BA7 or a triode-pentode converter
stage -
Zenith used a 12AT7 twin triode that works well.

All circuit source suggestions appreciated.

John


There are lots of schematics of consumer radios at:
http://techpreservation.dyndns.org/schematics/

You will have to explore around if you don't have specific
model numbers.
For design data there are several good books at Pete
Milette's DIY audio site at:
http://www.pmillett.com/

The Radiotron Designer's Handbook, 4th edition, is sort
of a standard and covers the relative merits of several
mixer and converter circuits.
The 6BE6 seems to be more common in commercial
receivers than the 6BA7, both should be used with external
oscillators. There are better converters for the VHF range.
I am not sure how tubes were numbered in Oz land but,
if British types are more common you should check an
equivalent tube chart. Many US and British types were
interchangable even though they had different numbers.
Scott Dorsey's suggestion to look in the RCA tube
manuals is a good one. Many receiver circuits are nearly
generic and those in the RCA books are generally reliable,
at least as starting points and as aids in understanding how
they are constructed.
There are other editions of the RCA books on line, some
are at the Pete Milett site above.
I would also not discount the American Radio Relay
League _Radio Amateur's Hanbook_ and the various editions of
the VHF handbooks. These will have a lot of practical
information on layout and the pitfalls of working at VHF and
with high IF frequencies.


--

--
Richard Knoppow
Los Angeles
WB6KBL