Tio Pedro wrote:

A lot of folks have reported good results using the 6JH8 in place
of the 7360; with a few reporting better linearity. They appear
to be pretty much the same as far as performance. Have you tried
one?

Yes I have. The results were disappointing compared to the 7360. Perhaps
my values weren't optimised. Maybe I should try again - the 6JH8 is /much/
cheaper!

Bob

"Bob" wrote in message
...
Tio Pedro wrote:

A lot of folks have reported good results using the 6JH8 in place
of the 7360; with a few reporting better linearity. They appear
to be pretty much the same as far as performance. Have you tried
one?

Yes I have. The results were disappointing compared to the 7360. Perhaps
my values weren't optimised. Maybe I should try again - the 6JH8 is
/much/
cheaper!

Bob

Yeah, and I had a shot at a sleeve of them for 60 bucks several months
back Unfortunately, they aren't going to get any less expensive as
time passes.

Pete

Tio Pedro wrote:
"Bob" wrote in message
...
Tio Pedro wrote:

A lot of folks have reported good results using the 6JH8 in place
of the 7360; with a few reporting better linearity. They appear
to be pretty much the same as far as performance. Have you tried
one?
Yes I have. The results were disappointing compared to the 7360. Perhaps
my values weren't optimised. Maybe I should try again - the 6JH8 is
/much/
cheaper!

Bob

Yeah, and I had a shot at a sleeve of them for 60 bucks several months
back Unfortunately, they aren't going to get any less expensive as
time passes.

Pete


There were a few other BD tubes as well.
The 6AR8 and 6ME8 are also listed in the RCA receiving tube
manuals along with the 6JH8. I don't know about current price
and supply on those.

Tio Pedro wrote:
"Bob" wrote in message
...
Tio Pedro wrote:

A lot of folks have reported good results using the 6JH8 in place
of the 7360; with a few reporting better linearity. They appear
to be pretty much the same as far as performance. Have you tried
one?
Yes I have. The results were disappointing compared to the 7360. Perhaps
my values weren't optimised. Maybe I should try again - the 6JH8 is
/much/
cheaper!

Bob

Yeah, and I had a shot at a sleeve of them for 60 bucks several months
back Unfortunately, they aren't going to get any less expensive as
time passes.

Pete


Also check out this link, good info on the 7360 as a mixer.

Seems the 7360 performance is poor with IF's above 1mhz.

"ken scharf" wrote in Also check out
this link, good info on the 7360 as a mixer.

Seems the 7360 performance is poor with IF's above 1mhz.

That poster also claims there is no rejection of either input signal
(grid or deflection plates) offered by the 7360.
Being a balanced modulator, the grid
signal can be cancelled by balancing the plate circuit.
It is used for DSB generation in SSB rigs!

Pete

ken scharf wrote:

Also check out this link, good info on the 7360 as a mixer.

Seems the 7360 performance is poor with IF's above 1mhz.

The writer's an idiot. The 7360 is good to over 50 MHz IF!

Bob

Bob wrote:
ken scharf wrote:

Also check out this link, good info on the 7360 as a mixer.

Seems the 7360 performance is poor with IF's above 1mhz.

The writer's an idiot. The 7360 is good to over 50 MHz IF!

Bob
What he claimed was that the conversion gain dropped to unity above
that frequency. That doesn't mean it isn't a good mixer at 50mhz.
Diode ring mixers have a unity (or LESS!) conversion gain, yet they
are very good mixers.

"ken scharf" wrote in message
. ..
The writer's an idiot. The 7360 is good to over 50 MHz IF!

Bob
What he claimed was that the conversion gain dropped to unity above
that frequency. That doesn't mean it isn't a good mixer at 50mhz.
Diode ring mixers have a unity (or LESS!) conversion gain, yet they
are very good mixers.

I have to wonder if the guy took a broadband, untuned
PD circuit and tried to use it as a broadband mixer?

If that's the case, then the interelectrode c
apacities would definitely limit BW in a high
impedance circuit, unless they were
"tuned" out using a LC resonant circuit. I ran into that
headscratcher trying to figure out how to drive the
deflectors using a broadband balun type arrangement;
like was done in the Squires RX.

Pete

ken scharf wrote:

What he claimed was that the conversion gain dropped to unity above
that frequency. That doesn't mean it isn't a good mixer at 50mhz.
Diode ring mixers have a unity (or LESS!) conversion gain, yet they
are very good mixers.

I get useful conversion gain at higher frequencies (though it's reduced) and
it's easily compensated for by the AGC. I found that I needed fairly
consistent IF signal levels for best performance of my crystal filters.

I appreciate the conversion /loss/ of diode ring mixers, but I find that
amplifying, then attenuating, then amplifying again tends to introduce
additional unwanted noise that can be avoided by use of a sensible gain
distribution. Diode mixers also don't handle very large signal levels very
well, and can produce some very strange results when over driven! I can't
really understand the love that some designers have for them.

My newer design approach is to use a switching ring of FETs, but the results
still can't match up to the 7360.

Bob

Tio Pedro wrote:

I have to wonder if the guy took a broadband, untuned
PD circuit and tried to use it as a broadband mixer?

Almost certainly. He was therefore destined to fail completely!

If that's the case, then the interelectrode
capacities would definitely limit BW in a high
impedance circuit, unless they were
"tuned" out using a LC resonant circuit.

Exactly. "Tuning them out" would make the mixer somewhat less "broadband"!

I ran into that
headscratcher trying to figure out how to drive the
deflectors using a broadband balun type arrangement;
like was done in the Squires RX.

I looked at the Squires design, and it was very clever, but seemed to
require some obscure components that were unobtainable.

Bob