Here is what I've been working on in London:
40 meter DSB phone HB: UK hams recently got a doubling of their 40
freq allocation and can now go up to 7.2 Mhz. I built a simple 40
transmitter. Solid state. VFO. Built it on a wooden cutting board
a real breadboard. Puts out about 2 watts. I run it into a heavily
Ramsey kit linear. Then to a HB balanced tuner, TV lead up to the
U dipole. Works fine. Lots of fun. I use it with my Drake 2B, but
pressing into service my HB "Mate for the Mighty Midget" RX (see web
(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
I have a Doug DeMaw "Barbados" reciever (someone else put the
a "Circuit Boards Specialists" board. It has a 5Mhz ladder filter that
broadened for pnone. I tried running the VFO at around 13 Mhz with
tuning, but it was unstable, so I'm going VXO. With 2 rocks in the 23
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?
Bill N2CQR M0HBR CU2JL
Thanks for sharing those inspirational pictures.
73 Bill N2CQR M0HBR CU2JL
"William E. Sabin" <w.s...@mchsi.com> wrote in message news:<2HS1e.1208$Vx1.663@attbi_s01>...
As I mentioned in the earlier post, I have an 80/40 meter tube type RX
for the Mighty Midget"). It has a 455 kHz IF. This makes homebrew
filter making difficult! I tried, but crystals were hard to come by
in that freq
range. In the end, I threw in the towel and just used a 455 Khz IF
in lieu of the filter. Great for listening to AM! But now I want to
it down a bit, so I'm thinking about yanking out the IF can and
it with a commercial 455 kc filter from the junkbox. I need to figure
how to handle the impedance matching issues (input and output).
73 Bill M0HBR N2CQR CU2JL
"Dale Parfitt" <p...@parelectronics.com> wrote in message news:<Qx_1e.34384$oa6.2111@trnddc07>...
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.
As for the tube RX, I have a Toyo Communications CM filter. Markings
"445 -- 2.4 -- C" Now I have to figure out how to work this into the
RX circuitry. Time to look through some mid-'60s handbooks and QSTs.
73 Bill M0HBR CU2JL N2CQR
"Bill N2CQR MOHBR" <meara....@virgin.net> wrote in message
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.
"Dale Parfitt" <p...@parelectronics.com> wrote in message news:<0ez2e.30158$191.23924@trnddc02>...
I looked at this approach, along with a method described in QEX last year
for dealing with the center freq shift, but came to the conclusion that I
could design a much better filter if I optimized each BW- even though it
took 3 filters.
One aspect of filters that has long been either ignored or overlooked (
even though W7ZOI details it in EMRFD) is group delay. A friend (N2PK)
recently sent me 2 WAV files of a Yaesu 1000 stock 250Hz filter and his
homebrew 250 Hz filter. The difference was remarkable- his filter was much
cleaner and crisper sounding, no ringing. Great care was taken with group
delay in his design.
"Dale Parfitt" <p...@parelectronics.com> wrote in message news:3Q03e.27300
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
Dale & Bill,
Jim, K8IQY has the Precision VXO and Crystal test rig that uses the
PVXO as a driver for the candidate IF filter crystal under test. I'm
currently building both of those.
Dale, I checked in late on this thread; what is Bill Sabin's site URL?
I've been Googleing to beat the band, but it doesn't turn up.
K8IQY web page for this test rig