On Aug 17, 6:12*pm, mrhaney wrote:
I am looking for a few (10) diodes 1N270...It is a germanium and used
in Double Balanced mixers in SSB generation..Most suppliers have a $25
to $50 min order and I don`t care for that.. thanks * Harold W4PQW

So after all that, any hints on what the original project was? Even
in the 1970s people were speccing matched silicon diodes (e.g. 1N914)
or hot carrier diodes (e.g. 5082-2800) for mixers.

Laura Halliday VE7LDH "Non sequitur. Your ACKS are
Grid: CN89mg uncoordinated."
ICBM: 49 16.05 N 122 56.92 W - Nomad the Network Engineer

On Aug 23, 3:39*pm, laura halliday wrote:
On Aug 17, 6:12*pm, mrhaney wrote:

I am looking for a few (10) diodes 1N270...It is a germanium and used
in Double Balanced mixers in SSB generation..Most suppliers have a $25
to $50 min order and I don`t care for that.. thanks * Harold W4PQW

So after all that, any hints on what the original project was? Even
in the 1970s people were speccing matched silicon diodes (e.g. 1N914)
or hot carrier diodes (e.g. 5082-2800) for mixers.

At least two volumes of "Single Side Band for the Radio Amateur" and
many ARRL handbooks from the 60's show 1N270's used in balanced
mixers.

It was a jellybean of the time, it's odd that someone would not
realize it and slavishly want to use it rather than something more
readily available (and performance-wise far superior) today. Probably
the same guys who insist on carbon-composition resistors everywhere
today too :-).

There are some things that appear in old construction articles that
are worth finding. For example, the BC-453/454/455's tuning capacitors
and drive mechanism are truly superb and I still keep my eyes open for
them today :-).

Tim.

On Aug 25, 6:14 am, Tim Shoppa wrote:
On Aug 23, 3:39 pm, laura halliday wrote:

On Aug 17, 6:12 pm, mrhaney wrote:

I am looking for a few (10) diodes 1N270...It is a germanium and used
in Double Balanced mixers in SSB generation..Most suppliers have a $25
to $50 min order and I don`t care for that.. thanks Harold W4PQW

So after all that, any hints on what the original project was? Even
in the 1970s people were speccing matched silicon diodes (e.g. 1N914)
or hot carrier diodes (e.g. 5082-2800) for mixers.

At least two volumes of "Single Side Band for the Radio Amateur" and
many ARRL handbooks from the 60's show 1N270's used in balanced
mixers.

It was a jellybean of the time, it's odd that someone would not
realize it and slavishly want to use it rather than something more
readily available (and performance-wise far superior) today. Probably
the same guys who insist on carbon-composition resistors everywhere
today too :-).

There are some things that appear in old construction articles that
are worth finding. For example, the BC-453/454/455's tuning capacitors
and drive mechanism are truly superb and I still keep my eyes open for
them today :-).

Tim.

Indeed. I have several old ARRL and RSGB Handbooks and a
number of older references (including Single Sideband for the
Radio Amateur).

You can see the fashions change. At one time the cool part to
use was the 7360 beam deflection mixer tube; at other times the
challenge was to see how many 40673 MOSFETs you could use
in a single radio. Many of these designs are difficult to reproduce
now.

I'll see your BC-455 tuning capacitor and raise you an Eddystone
dial. :-)

You can make nice radios by applying the right technology to
the problem. My recipe for a stable VFO nowadays is a
postage-stamp size surface mount board mummified in bubble
wrap and stuck to the end of a good, solid air variable capacitor.

Laura Halliday VE7LDH "Non sequitur. Your ACKS are
Grid: CN89mg uncoordinated."
ICBM: 49 16.05 N 122 56.92 W - Nomad the Network Engineer

On Aug 26, 11:30*am, laura halliday wrote:
Indeed. I have several old ARRL and RSGB Handbooks and a
number of older references (including Single Sideband for the
Radio Amateur).

You can see the fashions change. At one time the cool part to
use was the 7360 beam deflection mixer tube; at other times the
challenge was to see how many 40673 MOSFETs you could use
in a single radio. Many of these designs are difficult to reproduce
now.

What's amazing is that some of the SSB rigs appearing in the 60's in
the pages of QST use not one, not two, but three 7360's :-).

40673's were also used with wild abandon. If someone wants an honest-
to-goodness 40673 they can pay $15 for a NTE221 in a metal can, but
most experimenters would use a BF998, obviously a different package
but same function.

I'll see your BC-455 tuning capacitor and raise you an Eddystone
dial. :-)

You can make nice radios by applying the right technology to
the problem. My recipe for a stable VFO nowadays is a
postage-stamp size surface mount board mummified in bubble
wrap and stuck to the end of a good, solid air variable capacitor.

The brass-screw-in-a-solenoid is something I just tried in my
reproduction of the MMR-40 and I am very impressed with its stability
and mechanical simplicity as a PTO. A similar but not identical
mechanical design is used in the WA6OTP PTO, I haven't tried it yet.

Tim.

On Aug 26, 10:46 am, Tim Shoppa wrote:
....
The brass-screw-in-a-solenoid is something I just tried in my
reproduction of the MMR-40 and I am very impressed with its stability
and mechanical simplicity as a PTO. A similar but not identical
mechanical design is used in the WA6OTP PTO, I haven't tried it yet.

Tim.

Though not actually PTO if it's a brass screw, right?

Cheers,
Tom

On Aug 26, 2:26*pm, K7ITM wrote:
On Aug 26, 10:46 am, Tim Shoppa wrote:
...

The brass-screw-in-a-solenoid is something I just tried in my
reproduction of the MMR-40 and I am very impressed with its stability
and mechanical simplicity as a PTO. A similar but not identical
mechanical design is used in the WA6OTP PTO, I haven't tried it yet.

Tim.

Though not actually PTO if it's a brass screw, right?

Permeability of brass is slightly less than air, which is why the PTO
goes up in frequency as I screw the brass screw in.

It's not an iron-powder slug (which would go down in frequency as it
enters the solenoid) but it's still a PTO.

If you haven't tried them, I highly encourage you look at the PTO in
the MMR-40 and the WA6OTP PTO. Completely 100% homebrewable and I'm
very happy with the results.

Tim.

On Aug 26, 12:05*pm, Tim Shoppa wrote:
On Aug 26, 2:26*pm, K7ITM wrote:

On Aug 26, 10:46 am, Tim Shoppa wrote:
...

The brass-screw-in-a-solenoid is something I just tried in my
reproduction of the MMR-40 and I am very impressed with its stability
and mechanical simplicity as a PTO. A similar but not identical
mechanical design is used in the WA6OTP PTO, I haven't tried it yet.

Tim.

Though not actually PTO if it's a brass screw, right?

Permeability of brass is slightly less than air, which is why the PTO
goes up in frequency as I screw the brass screw in.

It's not an iron-powder slug (which would go down in frequency as it
enters the solenoid) but it's still a PTO.

If you haven't tried them, I highly encourage you look at the PTO in
the MMR-40 and the WA6OTP PTO. Completely 100% homebrewable and I'm
very happy with the results.

Tim.

Well, I beg to differ with you about the (main) reason the frequency
changes. Consider what happens if you have two coils magnetically
coupled and you monitor the inductance of one while you apply a short
across the other one. Then consider what you'll see on the inductance
meter as you change the coupling between the measured coil and the
shorted one. The references I've been able to find so far suggest the
permeability of brass is slightly higher than that of air, but I
suppose it's a function of the composition of the brass; in any event,
I'd bet that the shorted-turn effect is very much larger than the
permeability effect with respect to changing the inductance of the
oscillator coil.

Cheers,
Tom