Oh, you were referring to the Simple-X receiver.

The last thing that I did with that project was to laser engrave a front panel, so at least it looks really nice now :-)

I was getting frustrated with the double peaks situation and wasn't making much headway.  Then, I read about the HBR receivers in QST magazine and got the bug to build one of those, so my Simple-X receiver is rear "burner-ed" for the moment.

When I get frustrated with my HBR-11, I'll come back to the Simple-X with vigor renewed and try again :-)

73

--Tom Nickel

Tom,

A "square wave" you say.  I did *not* know that!

But, that's one of the reasons that I enjoy building these projects so much .. all the things that one learns.

Are you referring to the "coupling" between the BFO and mixer?

I'm not that far along yet.

So far, I've fabricated a chassis & front panel, procured most of the parts, punched many holes and mounted components, have the filaments wired & most of the power supply wired.

The BFO was one of the first circuits that I had completed, because it resides in its own little enclosure and needed to be mounted onto the chassis.

I plan to wire the set "backwards", i.e., start with the audio amp & work back towards the front end of the receiver.

So far, I've learned that radios are mostly made of chassis "holes"! :-)

Thanks again,

--Tom Nickel KC9KEP

OK, Jim,

Thank you for the info and prompt reply :-)

I could just imagine how much time & energy I
could have wasted by trying to analyze and
"fix" the circuit to change the tube bias unnecessarily.

73's

--Tom Nickel AKA KC9KEP

Hello Elmers,

I am building an HBR-11 receiver as originally featured in April 1963 QST magazine.

The BFO is a 100 kHz (I believe Hartley) oscillator and uses a tapped coil.

I had to wind my own BFO coil on a used slug-tuned form.

The oscillator is operating and can achieve 100 kHz but .. the bottom of the output sin wave is flattened.  It sort of looks as if the tube isn’t biased in the center of it’s load line.

Can anyone tell me how critical this is?  I would think that this could cause some non-linear distortion in the audio, but the radio is just receiving voice transmission, so perhaps it’s OK to leave it as is?

The BFO signal gets injected into a 6BY6 product detector, should that information be of any significance.

Thanks all!

--Tom Nickel AKA KC9KEP

OK, everyone ..

Thank you for your responses!

73

--Tom Nickel KC9KEP

Hello Elmers!

I've seen several schemes for tube filament wiring in vintage radio receivers:

Twisted pair to each tube, one wire to each filament connection and the other filament lead grounded, and use of shielded cable to run the filament lead.

Do you suppose than any one method has a decided advantage over another?

(Of course, connecting one lead to chassis or using a low value resistor or pot from each filament lead to ground seems to be a common method of reducing hum as well.)

Thank you all and 73!

--Tom Nickel / KC9KEP

I do have some of the transparent type of plug in
coil forms similar to the ones in the QST article.

I'll need to take an inventory of how many I have.

I also have several of the brown Hammarlund coil forms
that accomodate the installation of a trim capacitor.

So, I'll be experimentng with those.

I have collected all the tubes that are required
for the HBR-11 as well as ceramic type tube sockets
for them.

I think that I have some vintage toggle switches
lined up.

I'm sure that I don't have all the "etc." yet :-)

73

--KC9KEP

Thanks for the replies ..

Well, I understand that the 8/11 is not the best,
but I'm having enough trouble locating parts for
this "simple" version of the HBR let alone the 16!

I used to work in an electronics supply store, back
in the early 70's.

All the parts were available back then, but I didn't
have the money to buy anything :-(

I do have nice a Nation ICN dial (lighted) and a
power transformer from Hammond, three 262 kHz I.F.'s
that I understand can be padded to 100 kHz.

I've just purchased a 3-gang 20 pF tuning cap and have
made my own 2 X 7 X 13 chassis.

I've got my fingers crossed!

73!

--KC9KEP

Hello,

I've been inspired to build one of the HBR-8/11 receivers.

Has anyone on this forum built one of these?

73

--Tom Nickel

Tom, Owen,

In an attempt to not load the circuit, I had tried connecting my scope probe to 3-turns of wire in a 1" loop and just brought it near to the coil.

At that point, I would still see the twin peaks.  They would increase in magnitude as I brought the scope probe coil closer to the tank circuit.

My assumption here was that the scope probe, being a very high impedance, would minimally affect the tank circuit.  I read that the 6U8's input resitance is 5pF and I would assume a very high impedance, but as W8JI has stated, that may not be a constant especially when the tube is oscillating.

I was suprized that a "piece of coax" exhibited better results than the X10 Hi-Z scope probe ..

re: "W8JI: Why don't you just drive down and put it on my network analyzer?"  .. We will be in Ville Platte, Louisiana for Mardi Gras.  How far are you from there :-) ?

73

--Tom Nickel

Hello,

Tom, Tom and Owen have been putting forth some fantastic effort in helping resolve my simple-X input tank issue so I had wanted to post this so that they could see the results that I'm achieving so far ..

By the way, I updated my front panel, see what you think:

http://www.bignick.net/simplex/simplex_front_1.jpg

Tom, Tom and Owen,

See if this makes any sense?

I've bread boarded the circuit with fixed 100 pF capacitors to see if I could replicate W8JI's experiment.

My test setup was still indicating double peaks!

Then, I took the board to where I work and connected it to an HP 8753C network analyzer & 85047A S-Parameter test set and the trace looked perfect! i.e., one sharp peak.

I brought it back home to bench test it again.

If you would, please take a look at these photos that indicate what my root cause appeared to have been caused by .. It actually appears that my scope probe was loading the output tank somehow?

http://my.execpc.com/~bignick/Coil_Experiment.htm

73

--Tom Nickel KC9KEP

Tom, Tom and Owen,

See if this makes any sense?

I've breadboarded the circuit with fixed 100 pF capacitors to see if I could replicate W8JI's experiment.

I test setup was still indicating double peaks!

Then, I took the board to where I work and connected it to an HP 8753C network analyzer & 85047A S-Parameter test set and the trace looked perfect! i.e., one sharp peak.

I brought it back home to bench test it again.

If you would, please take a look at these photos that indicate what my root cause appeared to have been caused by ..

http://my.execpc.com/~bignick/Coil_Experiment.htm

73

--Tom Nickel KC9KEP

How about:

"H"igh frequency "AM"mature?

Just guessing :-)

--KC9KEP

Owen,

Thanks for the advice, I really do appreciate it.

Please understand, I am a HAM neophyte and am learning the best as I know how.

I've never seen this circuit before and didn't even know what it's called, otherwise I would be looking for more information elsewhere.

I am serious about learning and fabricating in order to learn.  Please see my webpage for examples:
http://www.bignick.net/Morgan_Radio/Radio.htm

This Elmers-Forum is described as follows:

"Ask questions, get answers from the experts!"

I thought that was what I was doing.

I have been both an Electronic Technician and design Engineer (NOT RF) for a major corporation for 27 years, as well as an avid hobbyist, having started to build radios in grade school.

However, I am not beyond making occasional stupid mistakes, maybe this is one of them.

But, if my questions are out of line, let me know, and I'm gone.

I run Forums myself and the last thing I want to be is "that guy" who is a problem on the Forum.

73

--KC9KEP

Owen,

Thanks for the info!  

Just a clarification, are you suggesting measuring a coil's inductance independently, then bring the coils into proximity while still measuring, and watch to see when one coil affects the other's inductance?

i.e., determine at what distance the coils are coupling?

(Also note, I had posted some photo's a ways back, showing that the 3-coils are positioned in a mutually orthogonal relationship to minimize coupling, and that I had moved the coils farther from the chassis in an attempt to reduce coupling.)

(Sorry about the narrow formatting .. just habit I guess ..)

--KC9KEP