RadioBanter - View Single Post

April 1st 06, 11:45 PM posted to rec.radio.amateur.homebrew

Don, et al,
Comments in-line:

On 1 Apr 2006 12:29:49 -0800, wrote:

Ted, Dale, Ken,

Ken that is true about the hen's teeth. I think that price is worth it
though. Dales receiver looks like a 2B. The blue backlighting is really
cool.

Dale's receiver looks like it belongs in a hospital, inside the case,
anyway...I'm sure an artificial liver or whatever doesn't have any
more "tubing" connections! That's taking the art of modular
construction to a whole 'nother level! The receiver also looks very
"sanitary", as we used to say back in the '70s, or I guess the word
would be "sick" in today's vernacular. More hospital tie-ins,
yuk-yuk!

I just like making homebrew verniers and dials but am getting lazy and
have been using Jackson Bros.stuff for the last two projects. I tried
what I believe is an Oren Elliot drive but it is so stiff I didn't use
it. One of the last projects used a small CD for the dial. Looks clever
and homebrewish but kinda tacky too. I am dangerous with certain tools
in my hands so I try to use ready made stuff. But the dial on my SSB
transceiver needed a little more work due to the way the dial had to
mounted. I am pleased with my mechanically challenged self. I'll follow
Dales and your advice and create it on my PC. Sharpy usually used here.

I won a door prize at the last NoGa meeting of a National Velvet
vernier. I don't have it handy for the number, but it's a fairly
small one...the dial area is about 3" wide. The cardboard scale has
been humidified somewhere along the way, so I'll need to scan that and
redo it in photoshop. The gears are ok, but a bit stiff. It looks
like it will be perfect for a VFO, maybe my long-wanted heterodyne VFO
for the HT-40.

Ted, on the VFO I roughly calculate the L and C from a few old DeMaw
and Hayward publications. But I generally go for less L more C. I think
those calculations are rough approximations anyways. I think the 2nd
edition of DeMaws QRP Notebook has the rough equations for Colpitts and
Clapp. I haven't seen one for Hartley. I have several old toroids wound
that I use for various things like VFO's. I used a number in the
Huffpuff circuit Hans Summers designed and substituted for
experimentation and optimum performance. I also have a bunch of cut and
try capacitors I use when I am building something like a VFO. I am
afraid to admit I do a lot of empirical construction on VFO's. Just the
opposite on filters and amplifiers. I use my SA when I build LC filters
and I measure all my critical L and C with my homebrew LC meter.
One thing I learned was to use ugly construction on my VFO's. I don't
know the fellow but W7EL mentioned something somewhere that made me try
that method. It simpler at the very least.

From what I understand, all other things being equal, the inductor is
more likely to suffer the effects of temperature-induced drift than
the capacitors, as long as C0G/NP0 and polystyrene caps are used.
Therefore, it makes sense to have a higher C to L ratio, although the
configuration of the VFO circuit will probably impose limits, as in
failure to oscillate at some point. I generally look at somebody
else's design as a prototype, and try to work around the same ratiios.

I went over and over the calculations again, and I'm pretty sure I'm
right, and there's a typo in the "Progressive Receiver" appendix. Then
it suddenly occurred to me, " Why don't you just lash up the
capacitors and the inductor and measure the darn thing?" Duh! I have
a grid dip meter, and I'm still making use of my cheap-but-fairly
accurate Rainbow capacitance meter, the one from the Handbook, until I
get the PIC programmed for the "Everyday Practical Electronics" one
that the Columbus QRP club built. This mystery will soon be solved!

Ted maybe I'll catch you on the other site but did you get the VFO
working? I knew you were working on a Hartley Huff Puff VFO. I tried
link coupling on the output from my Pierce version from the coil and
was suprised at how much cleaner the output was. I was going to try the
control circuit from a link too but had my grandson over the last two
weekends. He is just discovering his feet and rolling over. It is an
important time for grandpas.

One of the Hartley designs I'm looking at for the LO of my EMRFD
transceiver project is the Fig. 6.148 4 MHz one, which I would conver
to 5 MHz. Now that one is tapped, but what you did Don was to not tap
the coil, but to add a coupling winding, as I understand it. In the
Figure I just mentioned, Wes has an MV209 on the tap for fine tuning,
so I guess that's where the Huff and Puff would attach.

The other circuit I've been studying to the point of actually cadding
it, is Figure 12.25 in EMRFD. That one also has the familiar C1 C2 C3
Cvariable issue I've been trying to figure out, as does the Hartley
above. This VFO is a Colpitts, though (I guess; the output is off the
gate alone, and not the source). I suppose I'd either tap onto the
coil or use a coupling winding on that one, similar to what you did.
Conveniently, this one is a 5 MHz VFO already.

I just put in the order to Digi-Key a couple of days ago for the chips
for the fast stabilizer, so no, I haven't built it yet. I decided not
to go ahead with the other 2-chip minimalist one after your suggestion
on the fast one. The crystal oscillator I ordered is 66.66 MHz, so it
should work.

Its spring yardwork weekend here so not much radio going on. BTW, what
is a Nugatory Numptie (see other post)? I could be one. Do we have a
website?

K5UOS

I've got to go back and look at the other post. Don't know how I
missed that!

Ted KX4OM