Hi Don and Ted,
While it has been over a year now since I did the VFO- I too had some
difficulties with the QST values. In talking w/ W7ZOI, Wes indicated that
some errors had worked their way into the design over the years. One was on
the audio amp- values I had caused severe rolloff below about 2KHz- making
SSB very tinny.
The other was on the VFO. Because of the Eddystone dial, I wished to make
the VFO as linear as possible- book values led to a highly non linear scale.
I do not recall exactly what I did- although I played with the math for a
long time- to lienarize it- but I would trust your calcs.
At some point I will open her up again as I want to buffer the VFO and tap
off for a TX VFO- the plan is to build a Drake style reciter for the RX- and
at that time will better document the changes I made.

Dale W4OP

Dale & Don,
I haven't had a chance to lash up the components yet, but I checked my
spreadsheet using Wes's example on page 4.4. The numbers check out;
unfortunately, Wes specifies a value for C3 in the EMRFD example, and
in the Progressive Receiver Article, C3 is the unknown; i.e., how much
additional capacitance you'd have to add in parallel with the coil to
use a specific variable cap in the given configuration.
Now that I can see the "C12v" equation in EMRFD, which is not in the
QST article, but I've modified my spreadsheet to include it I can
check the resonance using the given values for L.

Dale, when I looked at your jpg's again yesterday, I noticed that
you've modified the receiver internals a lot since I first saw the
rig. Since the links I had were to a directory on your commercial
site, I'm not sure if you have another site where you described what
you did.

Early last Spring, I got rid of all my new-fangled ham rigs, like the
FT-817 and the not-so-new, but pristine TS-530s and bought an HW-101
and some equipment to restore. Homebrewing and boatanchors is what
I'm about now. I did the VFO alignment on the HW-101 and was able to
get it within 1kHz, end to end, as indicated on the dial, anyway. That
surprised the heck out of me. I've since acquired an LMO from an
SB-401 that I'm going to put in a project somewhere along the line. I
have a complete set of Heath HFO crystals, and both CW and SSB filters
from another source. I might make myself a broadbanded QRP rig out of
those.

73,
Ted KX4OM


On Sun, 02 Apr 2006 02:20:25 GMT, "Dale Parfitt"
wrote:

Hi Don and Ted,
While it has been over a year now since I did the VFO- I too had some
difficulties with the QST values. In talking w/ W7ZOI, Wes indicated that
some errors had worked their way into the design over the years. One was on
the audio amp- values I had caused severe rolloff below about 2KHz- making
SSB very tinny.
The other was on the VFO. Because of the Eddystone dial, I wished to make
the VFO as linear as possible- book values led to a highly non linear scale.
I do not recall exactly what I did- although I played with the math for a
long time- to lienarize it- but I would trust your calcs.
At some point I will open her up again as I want to buffer the VFO and tap
off for a TX VFO- the plan is to build a Drake style reciter for the RX- and
at that time will better document the changes I made.

Dale W4OP

On 1 Apr 2006 15:55:06 -0800, wrote:

Using those old verniers is risky to me only because finding
replacements if they start to slip or have backlash. I at least try to
find or build something I can replace. But the Eddiestone are just so
nice looking.
Well, maybe this one WILL be nice looking

What I did on the HP VFO was like in fig 7.27 EMRFD. The output of the
IC is a square wave. I was concerned after I looked at the output on my
analyzer. I see why the cmos marker generators are so popular. Strong
harmonics way above 100MHz. The output was significantly cleaner from
the tap. Right around then I decided to go back and finish my SSB
receiver and mount it in the chassis so I didn't have to use so many
clip leads while I was playing with it.
Figure 7.27? I don't quite follow that, unless you're talking about
how you've band-switched it.

I was going to do something similar to the fig 12.25 mixing type LO and
I still may. My original receiver had a 9MHz filter but a relatively
strong birdy from the LO at 7.2MHz. I decided to just change the filter
to 9.216MHz and no birdies. Was hell trying to find closely matched
9.216MHz crystals though. I got 65 ea from Mouser and only got ten
within 5%. Mostly a wide discrepancy in ESR. I guess you can make up
for a lossy filter but after spending as much time as I did on both
filters in measuring crystals I wanted something to show for it.
I'm using that design because I'll need 2 HFO's in two separate rigs
I'm working on. That one is interesting because of the 5 MHz output,
but I won't be using that for the rig itself. I'm using a 74HC4053
switch to mix either of two LOs with the 5 MHz VFO. The transceiver
I'm using EMRFD circuits for is a 15 and 20 meter SSB/CW traansceiver.
I'm using a 9MHz If, with HFO frequencies of 25 and 18 MHz. I'll use
the sums to produce the correct LO frequencies.

The other rig is one I've been working on, off and on, for over a
year. That one is based on G4GXOs Belthorn SSB/IF module. I picked
an IF of 11 MHz for it, because 32 and 25 MHz HFO crystals will allow
me to use a VFO of the toal span of 3.890 4.148 MHz. All of the
crystals are Mouser 39-cent variety.

I didn't realize it, but when I put in my order from Digi-Key last
wee, I stumbled across the ECS 18 MHz crystal, a value I didn't have
in my data base of available frequencies...that allows me to make the
EMRFD rig a 2-bander, adding 20 meters!

I was going to try the control circuit on the tap in my HP VFO. I know
it will work thiough even though I haven't tried it. Its just getting
the correct link and varactor. The fast HP VFO's still amazes me.
I get started on too many things so I went back to my SSB rig.

On the inductor drift I agree. I seem to have luck with slightly lower
L and using the slight neg temp coefficient of the COG caps. I did that
in my tube receiver built with toroids. I ended up using a small silver
mica for temp compensation of all things. Like you I look at other
circuits and copy. I didn't on this VFO because I was copying my own
circuit that worked before from something I am sure I copied. The more
I try other things though the less I copy. Right now I am working on a
25 VDC 6AMP power supply for the transceiver. I am going to try power
mosfets again as I had good luck in the last low power linear I built.
I am only looking for 40W or so. Plenty big for the type of SSB I will
work. I have a 28 VDC 3 A supply I made years ago. Just not sure it is
big enough for the PA I am going to use. Its not that efficient.

Gosh, typo errors in ham publications! Hard to believe! Not!. Good for
you for checking. I have a mess of spreadsheets with most of the common
formulas. I also made some for double and triple tuned BP filters,
feedback amps, my LC meter calculations, a logarithmic power meter and
crystal parameter testing. I check a lot of circuits in books by
plugging in the data to my sheets.

EMRFD is a great book. One thing I have been using in my transceiver LO
now is the hybrid splitter shown in fig 6.75. The vfo in 12.25 shows a
resistive version. I used the hybrid on both my VFO and BFO. That is a
nice technique even if it is a few more parts. I guess Wes must be a
better Numptie than all of us?
I'm not sure I really knew much of anything until I got EMRFD. The
first few weeks, I had a running stream of Q&A emails with Wes, and he
was kind enough to be patient and explain some things. One in
particular was a problem I had in adapting a published L-network to
the actual impedances of my crystal filter in the 30 meter rig I built
for Straight Key Night .

In Fig. 12.25, he's actually using the take-off point from the VFO to
the mixer from the attenuator pad for the 5 MHz output, to get the -10
dBm for 5 MHz for the 20 meter part of the rig.

I bet you will really enjoy experimenting with the fast HP VFO. I
haven't had that much fun with a simple project in a long time. Once
you build a few you start getting alot of ideas on how to use it. Then
it starts adding to your list of projects. You start losing sleep, the
wife keeps asking you to take the trash out, you stop shaving, grow
your hair long and start smoking and drinking too much coffee. Then you
are in Nugatory. Thats ham purgatory. My wife calls it the doghouse.
Sleep? What's that? Fortunately, my wife is busy getting her business
up and running, and I have plenty of time on my hands (I've inherited
the dog and cat-tending responsibilities).

Maybe I will put a picture of my progress on the SSB transceiver on the
tech site soon. I never know what Chuck is willing to accept though. So
I get a little cautious.
I understand completely. However, why not start a folder anyway?
There's only a couple of them there, and it's not like it's stuff that
belongs in the Smithsonian. Now if Dale had his receiver on the site,
that's certainly Smithsonian-quality!

When I was building the SKN Special, I did running updates to the NoGa
list with the latest photos on my web site. Now that it's finished, I
recently went back and reorganized that page to reflect past tense.
One of the highlights was definitely getting the VFO going. On the
scope, the signal has a weird distortion in the sine wave, like the
trailing edge is partially scooped out; I should post that on the
yahoo group site and see if anyone can figure out what it means. But,
since it's feeding an NE602, and they can take square waves, I guess a
little distortion doesn't matter.

Keep me up on your progress.
Tomorrow, I lash up a test capacitance circuit. Then, once I can
finally do the math and figure out which variable I can use, I'll
start building. the Digi-Key prts for the Huff and Puff whould be
here mid-week.

72/73,
Ted KX4OM

"Ted" wrote in message
...
Dale & Don,
I haven't had a chance to lash up the components yet, but I checked my
spreadsheet using Wes's example on page 4.4. The numbers check out;
unfortunately, Wes specifies a value for C3 in the EMRFD example, and
in the Progressive Receiver Article, C3 is the unknown; i.e., how much
additional capacitance you'd have to add in parallel with the coil to
use a specific variable cap in the given configuration.
Now that I can see the "C12v" equation in EMRFD, which is not in the
QST article, but I've modified my spreadsheet to include it I can
check the resonance using the given values for L.

Dale, when I looked at your jpg's again yesterday, I noticed that
you've modified the receiver internals a lot since I first saw the
rig. Since the links I had were to a directory on your commercial
site, I'm not sure if you have another site where you described what
you did.

Early last Spring, I got rid of all my new-fangled ham rigs, like the
FT-817 and the not-so-new, but pristine TS-530s and bought an HW-101
and some equipment to restore. Homebrewing and boatanchors is what
I'm about now. I did the VFO alignment on the HW-101 and was able to
get it within 1kHz, end to end, as indicated on the dial, anyway. That
surprised the heck out of me. I've since acquired an LMO from an
SB-401 that I'm going to put in a project somewhere along the line. I
have a complete set of Heath HFO crystals, and both CW and SSB filters
from another source. I might make myself a broadbanded QRP rig out of
those.

73,
Ted KX4OM

Hi Ted,
I quickly looked at the VFO schematic in my1994 Handbook that had the PR. I
seem to recall in the end I replaced C1 with a short- just eliminating it.
Not 100% positive, but think that was what it came down to in order to get
good linearity out of my VFO.

Dale

On Mon, 03 Apr 2006 01:37:23 GMT, "Dale Parfitt"
wrote:


Hi Ted,
I quickly looked at the VFO schematic in my1994 Handbook that had the PR. I
seem to recall in the end I replaced C1 with a short- just eliminating it.
Not 100% positive, but think that was what it came down to in order to get
good linearity out of my VFO.

Dale

Dale,
I'll check that out. My value for C3 from the spreadsheet came out to
be 319.1 vs the 127.02 in the magazine. I used the spreadsheet on the
example on page 4.4 of EMRFd and it worked out ok. In the QST
example, setting C1 to a very low value actually increases the
discrepancy with C3, though. More mystery!

Tnx,
Ted KX4OM

"Ted" wrote in message
...
On Mon, 03 Apr 2006 01:37:23 GMT, "Dale Parfitt"
wrote:


Hi Ted,
I quickly looked at the VFO schematic in my1994 Handbook that had the PR.
I
seem to recall in the end I replaced C1 with a short- just eliminating it.
Not 100% positive, but think that was what it came down to in order to
get
good linearity out of my VFO.

Dale

Dale,
I'll check that out. My value for C3 from the spreadsheet came out to
be 319.1 vs the 127.02 in the magazine. I used the spreadsheet on the
example on page 4.4 of EMRFd and it worked out ok. In the QST
example, setting C1 to a very low value actually increases the
discrepancy with C3, though. More mystery!

Tnx,
Ted KX4OM
Hi Ted,
No doubt, the VFO could be put on the correct freq range with C3 included-
it was just very nonlinear.

Dale

Doc wrote:
Does anyone in the group have any idea of what an Eddystone dial, Model
898, is worth. I bought a new one, along with the parts for the Ted
Crosby HBR receiver many years ago, but never got around to building
it. The XYL is pushing me to downsize and I need to start somewhere. I
may have an interested party, but can list it on e-Bay if this falls
through. I'd like to get some idea of where to start.
Doc, W4ITJ

Hi Doc:

I bought a good 898 recently for £30 which I guess is around $44.

Regards, Chris M0HMR