"Bill N2CQR MOHBR" wrote in message
om...
Dale: I was faced with doing the complex analysis of the individual
crystal
parameters when I was building my first superhet (W1FB's "Barebones"
aka
"Barbados" RX). I just skipped all of the analysis and used the same
capacitor
values that Doug had used in his version. I'm sure my filter's
passband wasn't nearly as pretty as it could have been, but it
definitely produced the
desired "single signal effect." I was happy.

As I mentioned in the earlier post, I have an 80/40 meter tube type RX
(Mate
for the Mighty Midget"). It has a 455 kHz IF. This makes homebrew
filter making difficult! I tried, but crystals were hard to come by
in that freq
range. In the end, I threw in the towel and just used a 455 Khz IF
can
in lieu of the filter. Great for listening to AM! But now I want to
narrow
it down a bit, so I'm thinking about yanking out the IF can and
replacing
it with a commercial 455 kc filter from the junkbox. I need to figure
out
how to handle the impedance matching issues (input and output).

73 Bill M0HBR N2CQR CU2JL

Hi Bill,

I too built the Barbados RX- don't know what happened to it though.
Have you thought of using a Murata ceramic filter in your tube RX?
They make a 4KHz unit for under $3. Not CW selectivity, but I'll bet it will
be an improvment over what you have. Typcial Zin and Zout is around 1K.
Although I have never tried it, I wonder about the possibility of brewing
your own ceramic filter from some of Murata's 455KHz ceramic resonators.
Although not the Q of a quartz crystal, it may be worthwhile. I have some
here and think I'll put one on the network analyzer and see what
characteristics I get.

Dale W4OP

Dale: Wow, another Barbados RX builder. That was my first successful
superhet project. I now have the one I built (still on 20), and this
morning
I got another one (the one built by someone else on a factory-made
board)going on 17 with a VXO. I have a THIRD partially built Barbados
RX board. If this
keeps up, I'll soon have a BBRX museum.

As for the tube RX, I have a Toyo Communications CM filter. Markings
look good:
"445 -- 2.4 -- C" Now I have to figure out how to work this into the
existing
RX circuitry. Time to look through some mid-'60s handbooks and QSTs.

73 Bill M0HBR CU2JL N2CQR
http://planeta.clix.pt/n2cqr





Hi Bill,

I too built the Barbados RX- don't know what happened to it though.
Have you thought of using a Murata ceramic filter in your tube RX?
They make a 4KHz unit for under $3. Not CW selectivity, but I'll bet it will
be an improvment over what you have. Typcial Zin and Zout is around 1K.
Although I have never tried it, I wonder about the possibility of brewing
your own ceramic filter from some of Murata's 455KHz ceramic resonators.
Although not the Q of a quartz crystal, it may be worthwhile. I have some
here and think I'll put one on the network analyzer and see what
characteristics I get.

Dale W4OP

The Murata filters range between 1.5k and 2k.

Pete

"Bill N2CQR MOHBR" wrote in message
om...
Dale: Wow, another Barbados RX builder. That was my first successful
superhet project. I now have the one I built (still on 20), and this
morning
I got another one (the one built by someone else on a factory-made
board)going on 17 with a VXO. I have a THIRD partially built Barbados
RX board. If this
keeps up, I'll soon have a BBRX museum.

As for the tube RX, I have a Toyo Communications CM filter. Markings
look good:
"445 -- 2.4 -- C" Now I have to figure out how to work this into the
existing
RX circuitry. Time to look through some mid-'60s handbooks and QSTs.

73 Bill M0HBR CU2JL N2CQR
http://planeta.clix.pt/n2cqr





Hi Bill,

I too built the Barbados RX- don't know what happened to it though.
Have you thought of using a Murata ceramic filter in your tube RX?
They make a 4KHz unit for under $3. Not CW selectivity, but I'll bet it
will
be an improvment over what you have. Typcial Zin and Zout is around 1K.
Although I have never tried it, I wonder about the possibility of brewing
your own ceramic filter from some of Murata's 455KHz ceramic resonators.
Although not the Q of a quartz crystal, it may be worthwhile. I have some
here and think I'll put one on the network analyzer and see what
characteristics I get.

Dale W4OP

"Bill N2CQR MOHBR" wrote in message
om...
Dale: Wow, another Barbados RX builder. That was my first successful
superhet project. I now have the one I built (still on 20), and this
morning
I got another one (the one built by someone else on a factory-made
board)going on 17 with a VXO. I have a THIRD partially built Barbados
RX board. If this
keeps up, I'll soon have a BBRX museum.
Hi Bill,
Did I sell you mine years ago? I seem to recall using a temp stabilized
varicap in a shielded enclosure for main tuning. It was done on a factory
board. Or was that a 6M xverter I sold?

Dale

Dale: Wow, small world! Yea I think that is the one I'm working on. I think
you also had a DC-DC converter to bring the voltage to the varicaps up.
Very nice enclosure for the oscillator. I now have it percolating nicely
as a VXO around 23 Mhz (for the 17 meter band). Bill


"Dale Parfitt" wrote in message news:0ez2e.30158$191.23924@trnddc02...
"Bill N2CQR MOHBR" wrote in message
om...
Dale: Wow, another Barbados RX builder. That was my first successful
superhet project. I now have the one I built (still on 20), and this
morning
I got another one (the one built by someone else on a factory-made
board)going on 17 with a VXO. I have a THIRD partially built Barbados
RX board. If this
keeps up, I'll soon have a BBRX museum.
Hi Bill,
Did I sell you mine years ago? I seem to recall using a temp stabilized
varicap in a shielded enclosure for main tuning. It was done on a factory
board. Or was that a 6M xverter I sold?

Dale

"Bill N2CQR MOHBR" wrote in message
om...
Dale: Wow, small world! Yea I think that is the one I'm working on. I
think
you also had a DC-DC converter to bring the voltage to the varicaps up.
Very nice enclosure for the oscillator. I now have it percolating nicely
as a VXO around 23 Mhz (for the 17 meter band). Bill

That's it Bill! Amazing. Hopefully I placed the Dc-DC converter inside that
shielded enclosure. Glad it has a good home.
I believe that board was from A&A Engineering- seem to recall they supplied
for QST back then. That design was a very robust RX. Doug (?) had sent me
the companion TX article before release- but I never got around to building
it.
How many countries has that RX travelled to now?
Dale W4OP
Dale

Dale Parfitt wrote:

"Bill N2CQR MOHBR" wrote in message
om...
Dale: Wow, small world! Yea I think that is the one I'm working on. I
think
you also had a DC-DC converter to bring the voltage to the varicaps up.
Very nice enclosure for the oscillator. I now have it percolating nicely
as a VXO around 23 Mhz (for the 17 meter band). Bill

That's it Bill! Amazing. Hopefully I placed the Dc-DC converter inside that
shielded enclosure. Glad it has a good home.
I believe that board was from A&A Engineering- seem to recall they supplied
for QST back then. That design was a very robust RX. Doug (?) had sent me
the companion TX article before release- but I never got around to building
it.
How many countries has that RX travelled to now?
Dale W4OP
Dale

Dale: I can't remember when it was that I bought it from you. So,
depending on the date, it could have spent time in the Dominican
Republic, Northern Virginia, the Azores Islands of Portugal, and the UK.

BTW, I always admired the neat construction of that RX. The hookup wire
used was very nice. Do you remember what kind of wire you were using.
I'd like to get some of that. Makes a big difference in the appearance
of the final product.

73 Bill N2CQR CU2JL M0HBR
http://planeta.clix.pt/n2cqr

Although I have never tried it, I wonder about the possibility of brewing
your own ceramic filter from some of Murata's 455KHz ceramic resonators.
Although not the Q of a quartz crystal, it may be worthwhile. I have some

I've done this with ceramic filters in tube circuits. You definatly
need to match the impedence to the tubes wich is high both for plate
and grid. What I did for that was to use a transistor IF can, filter,
IF can wired so the high impedence side was to the grids and plates.
Worked very well in a tube RX like the mighty midget.

For transistors the matching for those filters is IF can to get the
high collector impedence down to 1k range then the filter into the
base of the transistor. FETs get treated like tubes.

Allison
KB1GMX