Homebrew projects
 

I really enjoyed the message thread sparked by the pictures of
Dale's very FB HB RX. We need more of that kind of discussion...

Here is what I've been working on in London:

40 meter DSB phone HB: UK hams recently got a doubling of their 40
meter
freq allocation and can now go up to 7.2 Mhz. I built a simple 40
meter DSB
transmitter. Solid state. VFO. Built it on a wooden cutting board
(almost
a real breadboard. Puts out about 2 watts. I run it into a heavily
modified
Ramsey kit linear. Then to a HB balanced tuner, TV lead up to the
inverted
U dipole. Works fine. Lots of fun. I use it with my Drake 2B, but
plan on
pressing into service my HB "Mate for the Mighty Midget" RX (see web
site)
(I have a 455 kc filter that I'll install eventually -- right now it
is very broad).

17 SSB phone:
I have a HB 17 meter SSB TX (see my web site). I' also use it with the
2B, but changing bands is a pain. So I'm building a dedicated RX for
17.
I have a Doug DeMaw "Barbados" reciever (someone else put the
components on
a "Circuit Boards Specialists" board. It has a 5Mhz ladder filter that
I've
broadened for pnone. I tried running the VFO at around 13 Mhz with
varactor
tuning, but it was unstable, so I'm going VXO. With 2 rocks in the 23
Mhz
range I shoud cover the phone portion of 17.

More later... Any comments or suggestions? How about following
Dale's lead and posting updates on projects?

73

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

The group may find the picture and very brief discussion of my homebrew gear
on QRZ.COM interesting.

Bill W0IYH


"Bill N2CQR MOHBR" wrote in message
om...
I really enjoyed the message thread sparked by the pictures of
Dale's very FB HB RX. We need more of that kind of discussion...

"Bill N2CQR MOHBR" wrote in message
om...
I really enjoyed the message thread sparked by the pictures of
Dale's very FB HB RX. We need more of that kind of discussion...

Here is what I've been working on in London:

Hi Bill,
I have trouble keeping up with where in the world you are, but visit your
site regularly to see what you are up to.
I would encourage others to brew their own xtal filters. uP xtals are cheap
enough today that you can buy a pile and match up what you need. W7ZOI's
articles on crystal filters takes the mystery out.
Probably the most difficult part is characterizing individual crystals so
you can plug in the numbers. I use an HP network analyzer, but Wes also
shows a test jig for doing this. Alternatively, N2PK's VNA will do an
excellent job. In the end, you can make better filters than you can buy- and
for a heck of a lot less $$.
N2PK recently sent me 2 WAV files- one recorded with the 1000MP stock 250 Hz
filter; the other with a homebrew 250 Hz filter- it took no imagination to
discern which one was cleaner.
Now, I'll go have a look at Bill W0IYH's site.

Dale W4OP

Bill: Very FB! I especially liked the Velvet Vernier in there amidst the
digitial readouts. In my 17 meter SSB TX I used an old Simpson meter that
I had found in a radio club junk box back in 1974.

Thanks for sharing those inspirational pictures.

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



"William E. Sabin" wrote in message news:2HS1e.1208$Vx1.663@attbi_s01...
The group may find the picture and very brief discussion of my homebrew gear
on QRZ.COM interesting.

Bill W0IYH


"Bill N2CQR MOHBR" wrote in message
om...
I really enjoyed the message thread sparked by the pictures of
Dale's very FB HB RX. We need more of that kind of discussion...

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
http://planeta.clix.pt/n2cqr




"Dale Parfitt" wrote in message news:Qx_1e.34384$oa6.2111@trnddc07...
"Bill N2CQR MOHBR" wrote in message
om...
I really enjoyed the message thread sparked by the pictures of
Dale's very FB HB RX. We need more of that kind of discussion...

Here is what I've been working on in London:

Hi Bill,
I have trouble keeping up with where in the world you are, but visit your
site regularly to see what you are up to.
I would encourage others to brew their own xtal filters. uP xtals are cheap
enough today that you can buy a pile and match up what you need. W7ZOI's
articles on crystal filters takes the mystery out.
Probably the most difficult part is characterizing individual crystals so
you can plug in the numbers. I use an HP network analyzer, but Wes also
shows a test jig for doing this. Alternatively, N2PK's VNA will do an
excellent job. In the end, you can make better filters than you can buy- and
for a heck of a lot less $$.
N2PK recently sent me 2 WAV files- one recorded with the 1000MP stock 250 Hz
filter; the other with a homebrew 250 Hz filter- it took no imagination to
discern which one was cleaner.
Now, I'll go have a look at Bill W0IYH's site.

Dale W4OP

Thanks Bill. The Velvet Vernier dial is not only a very good and beautiful
dial, it is excellent nostalgia for an era that has just about disappeared.

Bill W0IYH

"Bill N2CQR MOHBR" wrote in message
om...
Bill: Very FB! I especially liked the Velvet Vernier in there amidst the
digitial readouts. In my 17 meter SSB TX I used an old Simpson meter that
I had found in a radio club junk box back in 1974.

Thanks for sharing those inspirational pictures.

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



"William E. Sabin" wrote in message
news:2HS1e.1208$Vx1.663@attbi_s01...
The group may find the picture and very brief discussion of my homebrew
gear
on QRZ.COM interesting.

Bill W0IYH

"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

Dale - regarding homebrew crystal filters - I wonder if you or any others
here have looked at Elecraft's crystal filter implementation in the K2?
It's built with discrete crystals and the bandwidth is variable over a large
range. Haven't seen that design exploited elsewhere, but don't know why.
It sure works well.

K8AC