In this thread, we hack Heathkit's -104 lineup

[N8YX]

I got hold of a couple SB614s which are going to be repackaged into Drake 7-line cabinets for use with my TR7/R7, and as I was contemplating the outcome I wondered what others have done with the SB/HW-104 and related components:


Converted a -104 to the WARC bands?
Built a full featured receiver from a transceiver?
Added QRM-fighting features to the rig?

There will be a number of dual knobs and a couple cases left over from these efforts. Inspire me to do something cool with the leftovers, along with a transceiver or receiver (HR-1661).

[NQ6U]

Inspire me to do something cool with the leftovers

Build a laser death ray, man. Everybody wants a laser death ray.

[KG4CGC]

Cool cool coooool!
In for popcorn!

[wa6mhz]

I know I rebuilt the piss poor power supply Heath came up with. They had some MFCsomething ICS driving transistors for the +11 and +5V. I tore all that out and installed LM350Ks in the pass transistor sockets. The MFCs were blown any way. and with the LM350Ks they are bullet proof!

[kd6vm]

I know I rebuilt the piss poor power supply Heath came up with. They had some MFCsomething ICS driving transistors for the +11 and +5V. I tore all that out and installed LM350Ks in the pass transistor sockets. The MFCs were blown any way. and with the LM350Ks they are bullet proof!

That's good to know. I ended up with an HW-104 with P/S and have yet to get into it.

[N8YX]

That's good to know. I ended up with an HW-104 with P/S and have yet to get into it.
If you wish to sell, I wish to buy.

[kd6vm]

If you wish to sell, I wish to buy.

I have a day off tomorrow. I will pull it out the closet and check it out. See what works and what doesn't.

[W3WN]

I'm curious about how you would do the WARC mods. Drop other bands, or is there a way to shoe-horn in the extra circuitry?

12 meters might not be too bad, if you were willing to sacrifice part of 10 meters. 30 & 17 would be more of a problem.

I see a couple on eBeast right now, both in the $300 neighborhood with PS's. One in need of TLC, and one that (allegedly) belongs(ed) to the seller's father-in-law & was last in use a year ago.

[N8YX]

Saw those, Ron.

What I'm going to do with 1ea HW-104 and SB-104A:

80-40-20-15-WWV-10A-10B-10C-10D become 80-40-30-20-17-15-12-10A. Who needs the top three 10M segments, considering that most of the operating I do occurs in the lowest 500KHz segment?

What I'm going to do with 2x HR-1680:

80-40-20-15-10A-10B become 80-40-20-15-12-10A and 60-30-17-12-11A-11B (or 11A-10B, etc). These will be slaved to a modified HW-104 and can run in transceive mode a la TS-820S/R-820 or TR-7/R-7.

I'm thinking about converting all of the rigs to an 8.9875 or 9MHz IF. HFO crystals for the various bands will be much easier to obtain than those which are employed in Heathkit's 3.395MHz IF premix scheme and filters of various bandwidths are a little more common as well.

Plans are to incorporate 2.1/2.4KHz (wide SSB RX; SSB TX), 1.8KHz (SSB Narrow), 500HZ (CW Wide) and 250HZ (CW Narrow) onto a redesigned Filter/BFO Board. I think SMT will be used to free up space for the extra filters.

Also looking into front-end redesign and a digital version of the SB-644.

ETA: And the creation of an "SB-624". Envision one of those, if you will...

[N8YX]

Got hold of an HFO board, IF/AF board and a bunch of miscellanii for the SB project. An HR1680 is sitting on my shack floor and an HW-104/PSU (courtesy of Ralph) is inbound.

Need the following crystals in either HC/18-U or HC/6-U form factor if anyone has them; all frequencies in MHz:

13.895
18.895
26.895
33.395
35.395
35.895
36.395

Also received four display conversion boards from The Heathkit Shop, a local outfit run by Mike, WB8VGE. These ought to address the noisy display issue which the SB-104 often exhibits.

I'm in search of an SB-604 speaker; condition doesn't matter - and as long as the two black trim strips on its front panel are in good shape, the rest is immaterial. This unit will ultimately be turned into a synthesized remote VFO.

[N8YX]

Paddle knobs - Heathkit's answer to the controls needed to implement a ganged pot or a pot-switch combination.

Lowest I see these go for on FleaBay is around $5 and most average $10.

Yesterday, some RAT BASTARD bid two of them up to $68! :shock: You can get a junker SB-401 or HW-101 donor rig for less.

Speaking of RBs: Pat ('MHZ), how much has the SB-644 been fetching on average? I know you were chasing them for a while.

[N8YX]

Earlier in the thread, I stated a plan for using crystals to get the extra band segments I'm after.

But how about this approach?

http://midnightdesignsolutions.com/dds60/

One could use a PIC, Arduino, BASIC Stamp or similar embedded micro controller in conjunction with the DDS-60 to generate any HFO signal frequency desired. I have two of them here...perhaps a redesign of the HFO/Premix Board is in order?

[NQ6U]

Looks good, and most of the SMD stuff isn't too tough to solder. But I have to ask: how will it effect the construction of the laser death ray?

[N8YX]

Looks good, and most of the SMD stuff isn't too tough to solder. But I have to ask: how will it effect the construction of the laser death ray?
Hopefully it won't be full of spurs. :lol:

That's always a gotcha when using a derived signal source. But the benefits might outweigh the drawbacks. One thing I can do is incorporate a "sub band up-down" function where the HFO would increment or decrement in 500KHz steps. In the case of a Stamp, incorporating this scheme takes 11 of its 16 I/O pins: 8 inputs for band information, 2 for up/down stepping and 1 for serial output of the control QWORD plus housekeeping byte.

There are 5 I/O pins left over. One could use them to output band information to a readout, an automatic antenna tuner, whatever. The synthesizer data is easy to configure - just precalculate each desired HFO frequency, convert to hex and store as a tagged variable. Then poll the band switch, evaluate which line is active and send the appropriate control string to the DDS by calling said variable. The up-down function merely steps through variable names and doesn't need to calculate anything.

[K7SGJ]

Hopefully it won't be full of spurs. :lol:

That's always a gotcha when using a derived signal source. But the benefits might outweigh the drawbacks. One thing I can do is incorporate a "sub band up-down" function where the HFO would increment or decrement in 500KHz steps. In the case of a Stamp, incorporating this scheme takes 11 of its 16 I/O pins: 8 inputs for band information, 2 for up/down stepping and 1 for serial output of the control QWORD plus housekeeping byte.

There are 5 I/O pins left over. One could use them to output band information to a readout, an automatic antenna tuner, whatever. The synthesizer data is easy to configure - just precalculate each desired HFO frequency, convert to hex and store as a tagged variable. Then poll the band switch, evaluate which line is active and send the appropriate control string to the DDS by calling said variable. The up-down function merely steps through variable names and doesn't need to calculate anything.

Spurs are no big deal. I had them in both elbows, and had them removed. Do you want the name of the quack that did the work?

[N8YX]

Spurs are no big deal. I had them in both elbows, and had them removed. Do you want the name of the quack that did the work?
Dr. Chebyshev, by chance?

[K7SGJ]

Dr. Chebyshev, by chance?

I have no idea what kind of car he drives. Cheby or Ford, maybe a Yugo.

[N8YX]

The next piece of the project puzzle was just sourced off eBay - another HR-1680. I got this one for half of what I paid for the first.

Additionally, Ralph's (vm) HW-104 contribution is unpacked and in the pile. I have a spare HFO/premix board and that rig shall be the first to get a revamp. Since it and the -1680s use analog dials I'm going to add VFO Stabilizers to each of them, whereas the SB portions of this project will get a complete DDS VFO replacement - courtesy of N4YG.

[wa6mhz]

Paddle knobs - Heathkit's answer to the controls needed to implement a ganged pot or a pot-switch combination.

Lowest I see these go for on FleaBay is around $5 and most average $10.

Yesterday, some RAT BASTARD bid two of them up to $68! :shock: You can get a junker SB-401 or HW-101 donor rig for less.

Speaking of RBs: Pat ('MHZ), how much has the SB-644 been fetching on average? I know you were chasing them for a while.

There's one on right now
http://www.ebay.com/itm/VINTAGE-HEATHKIT-SB-644A-REMOTE-VFO-/141400371246?pt=LH_DefaultDomain_0&hash=item20ec1e702e
Up to $107 with 4 days to go!!! YIKES!!!
I got mine alot cheaper cuz it was really butchered. I fixed it and then redesigned the VFO switching circuit in it that didnt work. Somewhere on QRZed I detailed the mod. It used some mini-relays and logic circuits.

Here it is:
http://forums.qrz.com/showthread.php?252095-Fix-your-flaky-Heathkit-SB-644&highlight=sb-644

[N8YX]

Pat, do you know off the top of your head where Heathkit sourced the aluminum trim which was used on the front panels of the SB-104 and its various accessories? Perhaps a modern-day supplier for the stuff?

[N8YX]

Revisiting the thread:

I started taking a look at signal paths through an FT-901DM, with a thought to converting the HR-1680/HW-104 IF scheme to the 8.9875MHz of the `901 series...allowing the use of a bunch of its readily obtainable filters. To do so means a lot of unnecessary circuit duplication. I think the better way to go is to stick with Heathkit's 3.395MHz IF then modify the Yaesu IF Shift/Rejection Tuning scheme to use a common Kenwood SSB filter (8.83 MHz) in the passband tuning circuit. The first and second roofing filters will be made from elements of the -1680 SSB filter - each configured in a half lattice arrangement.

This requires a redesign of all three boards in the receiver but I knew that much going in. Benefits of leaving the IF alone means I'll truly be able to track the transceiver via the receiver and direct VFO/HFO injection - no need for an RX Offset Adjust as used on the FL/FR-101.

If I can only find all the needed parts...

[N8YX]

Conundrums.

Heathkit only made two bandwidths of filters for these rigs: 2.1KHz (SSB) and 400Hz (CW). I would like to have an additional narrow filter option for each mode. Inrad used to offer a 1.8KHz and a 250Hz filter for the 104 line (3395KHz IF) but they're showing Out of Stock on the narrower of the pair.

What shall we do? Beg them to make 6 of each at $140 a pop, or convert the rig's IF frequency to something that is much more widely supported? 9 MHz (early Yaesu and Ten Tec), 8.9875 MHz (later Yaesu), 8.83 MHz (Kenwood), 5.645 MHz (Drake), ?

I can get a bunch of BFO crystals for everything but the Drake IF and since I'm going to use a DDS to generate the HFO premix signals I can make said IF anything I want.

Thoughts, especially from a birdie perspective?

[WØTKX]

9 Mhz kind of sucks for 17 meters, usually.

[N8YX]

9 Mhz kind of sucks for 17 meters, usually.
So 8.83MHz, then?

Single conversion like a TS820 or shall I also figure out how to shoehorn a 455KHz IF in there for the three receivers I'm building out of that pile?

[WØTKX]

I think the math works better, yea. I have an Omni D Series C that works on 17, but it's a bit flaky.

Works great on the other bands.

[N8YX]

That or 8.9875 - the FT90x/980 IF.

I have a bunch of filters for those rigs...and BFO crystals...NB/PBT/CAR boards which could be stripped of parts...

[WØTKX]

Doesn't take much of a frequency nudge from 9Mhz to stay out of trouble on 18 Mhz.

[N8YX]

8.9875 it is.

Next, an AD8951 controlled by a BASIC Stamp for HFO (band) and Mode selection. Hmmm...how to enunciate the ranges and modes in cool Heathkit Red fashion... :chin:

[WØTKX]

Nixie tubes, in Signal One fashion. ;)

[N8YX]

13179

[N8YX]

There's also a red backlight with black text version.

The readout will come in handy for the HR1680/HW-104 portion of this effort. Something that displays

14.0MHz USB 2.4K
|||||||||||||||||||||

Top will be band, mode and filter selection. Bottom will be IF shift or notch position, relative to passband.

[WØTKX]

27.185 BOWLING!!
|||||||||||||||||||||

:evil:

[N8YX]

We can do that. :lol:

The HR-1680 uses a 6-position rotary switch to set its operating band; the switch selects bandpass filters and the HFO oscillator crystal. I'm going to use that Stamp/AD8951 combo to generate HFO frequencies. A "band up" and a "band down" pushbutton is all that's required and a memory-write-at-poweroff function will store the last band selected. Same with mode.

I don't want a 60M position due to the VFO frequency (5MHz) so it looks like the following segments will be covered:

3.5
7.0
10.0
14.0
15.0
18.0
20.0
21.0
24.5
26.0
26.5
27.0
27.5
28.0
28.5
29.0

Filter selection will be via a "B/W" pushbutton with auto-default and storage, and it will be tied to the "Mode" function. I'll need decoded band/mode/bandwidth output lines, 4 input lines for control of such, two output pins for serial control of the DDS and two for data output to the LCD.

Front-end bandpass filters will be relay switched.

Now where did I stash those 74154s?

:chin:

[K7SGJ]

We can do that. :lol:

The HR-1680 uses a 6-position rotary switch to set its operating band; the switch selects bandpass filters and the HFO oscillator crystal. I'm going to use that Stamp/AD8951 combo to generate HFO frequencies. A "band up" and a "band down" pushbutton is all that's required and a memory-write-at-poweroff function will store the last band selected. Same with mode.

I don't want a 60M position due to the VFO frequency (5MHz) so it looks like the following segments will be covered:

3.5
7.0
10.0
14.0
15.0
18.0
20.0
21.0
24.5
26.0
26.5
27.0
27.5
28.0
28.5
29.0

Filter selection will be via a "B/W" pushbutton with auto-default and storage, and it will be tied to the "Mode" function. I'll need decoded band/mode/bandwidth output lines, 4 input lines for control of such, two output pins for serial control of the DDS and two for data output to the LCD.

Front-end bandpass filters will be relay switched.

Now where did I stash those 74154s?

:chin:

74154s? Bah. A real ham would go analog. Something like this for all the switching functions.

13183

Who cares if the front panel is the size of '66 Econoline van.

[KG4NEL]

I'm partial to the whole Nike missile vibe.

https://c1.staticflickr.com/1/31/49075278_32818b1855.jpg

[X-Rated]

Dr. Chebyshev, by chance?

Naw. Mrs. Butterworth. Dr. Chebychev knew she was really smooth and tried wooing Mrs. Butterworth with a fruity ripple. She refused to lift her skirts. He so badly wanted to at least go down 69dB but I don't think she was into his kind of transfer function. He knew he had a complex pole and he finally moved on to find a complex conjugate.

[X-Rated]

Earlier in the thread, I stated a plan for using crystals to get the extra band segments I'm after.

But how about this approach?

http://midnightdesignsolutions.com/dds60/

One could use a PIC, Arduino, BASIC Stamp or similar embedded micro controller in conjunction with the DDS-60 to generate any HFO signal frequency desired. I have two of them here...perhaps a redesign of the HFO/Premix Board is in order?

This would be a great way to go. I would assure that my RF is attenuated and shielded as much as possible on its way to the required circuits. Is this output going to a crystal socket?

[N8YX]

This would be a great way to go. I would assure that my RF is attenuated and shielded as much as possible on its way to the required circuits. Is this output going to a crystal socket?
No - the SB/HW-104's HFO/Premix Board has all the crystal oscillators and a couple of mixer circuits attached. The HR-1680 is similar in that it has the HFO and Cal Oscillator circuits on one board.

Thoughts are to mount the Stamp under the chassis in its own enclosure then use two serial lines into a new HFO Board to control the AD8951, which will be mounted on the HFO Board. That part of the assembly will be well shielded from the balance of the circuits. I'll also use output lines from the Stamp to drive 3-to-8 decoders which will control BFO crystal selection and IF filter selection. In the HR-1680s, a 4-to-16 decoder will control relays which select bandpass filters on new Front End Boards. The HW/SB-104s will retain their rotary bandswitches for this function, albeit with a few added tuned circuits for the new 30-17-12M bands.

[X-Rated]

No - the SB/HW-104's HFO/Premix Board has all the crystal oscillators and a couple of mixer circuits attached. The HR-1680 is similar in that it has the HFO and Cal Oscillator circuits on one board.

Thoughts are to mount the Stamp under the chassis in its own enclosure then use two serial lines into a new HFO Board to control the AD8951, which will be mounted on the HFO Board. That part of the assembly will be well shielded from the balance of the circuits. I'll also use output lines from the Stamp to drive 3-to-8 decoders which will control BFO crystal selection and IF filter selection. In the HR-1680s, a 4-to-16 decoder will control relays which select bandpass filters on new Front End Boards. The HW/SB-104s will retain their rotary bandswitches for this function, albeit with a few added tuned circuits for the new 30-17-12M bands.

Sounds like a plan. I would replace the 51 ohm resistor R5 with a 47 ohm resistor due to the fact that the impedance will range from 1 ohm to 6 ohms over 3-30MHz from that AD8008 IC. Couple that with assuring your termination point looks like 50 ohms assuming you are running a coax from these points. Also you may consider a lower frequency cutoff from the LPF on your board. You may have to try playing with control line bypass points to lessen the transmission of signals as well. Maybe this is all overkill. I don't know. Depends on whether you get it together and are pleased or not.

[N8YX]

Sounds like a plan. I would replace the 51 ohm resistor R5 with a 47 ohm resistor due to the fact that the impedance will range from 1 ohm to 6 ohms over 3-30MHz from that AD8008 IC. Couple that with assuring your termination point looks like 50 ohms assuming you are running a coax from these points. Also you may consider a lower frequency cutoff from the LPF on your board. You may have to try playing with control line bypass points to lessen the transmission of signals as well. Maybe this is all overkill. I don't know. Depends on whether you get it together and are pleased or not.
I have a built-up NJQRP DDS-60 here, along with a BS24P Stamp and a 2x16 LCD readout. I'm planning to use the Stamp's I2C mode to drive the LCD, an ADC0803 (for IF Shift and Notch readout) and a 24C16 for band/mode/filter stacking memories. May have to buy an I2C compatible LCD but I already have a candidate part lined up from Jameco.

With those parts and some 74HC138/74154s, I'm ready to mock the HFO controller up on a breadboard.

[N8YX]

Late-night eBay surfing netted me an SB-104 with noise blanker and CW filter installed, but no PA assembly or heat sink included.

Perfect for the "HR-104" portion of the project, and I got the thing for about the price of the filter and noise blanker alone.

This is going to be a proof-of-concept experiment where a near-9MHz IF is used with a digital readout rig: The counter unit is preloaded to 6.604MHz when a 3.395MHz (OEM) IF is employed. Obviously, I'll have to change that to get the readout working correctly with a different IF scheme.

Better to find a cheap test bed than a pricey one. :yes:

[kb2vxa]

That's also the difference between a prostitute and a call girl, no comment on the frequency counter.

[N8YX]

A couple days back I got a complete but non-functional SB-104A (including CW filter and noise blanker) for a decent price. One more of those to go along with a couple SB-604s, an SB-230 and perhaps one more junker 104 for cabinet and push buttons then I can begin to build and modify this station.

[N8YX]

Now comes decision time for the IF/HFO/BFO portions of this here project. I want to use an IF frequency which is fairly common (think parts scavenging and filter availability) and which was used in enough HF sets that the odds are good I can snag a bunch of HFO premix crystals (think Yaesu FT90x, 101ZD) for use on the new HFO boards I'll design.

The easiest way to approach this task - bar none - is by the use of a BASIC Stamp and a pair of DDS units to generate all required frequencies. I've heard some not-so-favorable comments regarding the average AD9850's spectral purity when run above 30 MHz...and this rework will require a max HFO frequency of around 43MHz.

Best thing to do here is to get my Stamp debugger up and running then write some test code and put the DDS on my spectrum analyzer to see what's up. I may be able to filter out any spurs that aren't too close in.

The SB104 uses a preloadable counter arrangement to drive its readout. Changing the IF will require changing the preload values in order to properly display the tuned frequency, as it's counting the premix signals. Looks like it's time to order parts needed to build up one of these boards which is DIP switch programmable, then after completion hook a generator running at a calculated frequency to its Input port and see if the higher IF premix frequency can be counted properly.

ETA: This exercise would be a whole lot easier if I could lay my mitts on a bunch of CW filters with 3395.7KHz center frequencies, and in 600/500/400 (tel:600/500/400) and 250Hz bandwidths. Then the entire IF chain wouldn't require redesign. :roll:

[WØTKX]

http://www.google.com/patents/US3938048

Searching that filter frequency of interest, looky what I found. :chin:

[N8YX]

Interesting read, Dave. The Kenwood TS-520/R-599 rigs also used a 3395KHz IF but their CW filter's center frequency is (surprise!) different from that of the SB-104's filter. I'm beginning to consider a change to the earlier generation CW offset of 3395.4 if I keep the IF "stock". Lots more of those filters floating around and it would be relatively easy to modify a 400Hz unit to a narrower bandwidth.

[N8YX]

I got hold of another 104-specific CW filter and a 3395.4KHz crystal today, but the thought of narrower bandwidths - especially on CW - keeps dancing through my head. Next, what if we take that "Tune" position on the Mode switch bank and make it something useful...say, true FSK?

When I construct an "HR-104", the entire right side switch bank will be dedicated to mode selection and power. The left side will have a button to activate the noise blanker and the rest will be used for filter selection. AM, SSB 2.1KHz, SSB 1.8KHz, CW 400 Hz...and possibly something using this:

http://www.google.com/patents/US5051711

If I have enough real estate for extra knobs I'll add a variable bandwidth tuning control to the rig and incorporate some method of electrically shifting the vari-filter's center frequency based on mode. This would also be neat to incorporate in the pending HR-1680 projects and maybe in the SB/HW-104s themselves. A BFO Board redesign will be required in all cases to accommodate the extra filters and offset control signals.

[K7SGJ]

I got hold of another 104-specific CW filter and a 3395.4KHz crystal today, but the thought of narrower bandwidths - especially on CW - keeps dancing through my head. Next, what if we take that "Tune" position on the Mode switch bank and make it something useful...say, true FSK?

When I construct an "HR-104", the entire right side switch bank will be dedicated to mode selection and power. The left side will have a button to activate the noise blanker and the rest will be used for filter selection. AM, SSB 2.1KHz, SSB 1.8KHz, CW 400 Hz...and possibly something using this:

http://www.google.com/patents/US5051711

If I have enough real estate for extra knobs I'll add a variable bandwidth tuning control to the rig and incorporate some method of electrically shifting the vari-filter's center frequency based on mode. This would also be neat to incorporate in the pending HR-1680 projects and maybe in the SB/HW-104s themselves. A BFO Board redesign will be required in all cases to accommodate the extra filters and offset control signals.


The B+, don't forget the B+, and ground it.

This is a great project, Fred. I enjoy following it. I wish I had the time (or more accurately the $$) available to do stuff like this. I guess I should be satisfied with all the building/modifying I did back in the day, while walking uphill in the snow, both ways, rebuilding the filaments in my 6743 and 6146s.

[N8YX]

This is a great project, Fred. I enjoy following it. I wish I had the time (or more accurately the $$) available to do stuff like this. I guess I should be satisfied with all the building/modifying I did back in the day, while walking uphill in the snow, both ways, rebuilding the filaments in my 6743 and 6146s.
The funny thing, Eddie, is that I'm attempting this on the cheap. On Page 1 we started with a $20 SB-614 (with all knobs and circuitry intact, but with a front panel which has most assuredly seen better days). That scope and another like it were destined for the conversion bin, to be made into a pair of "SC-7" units - which is the one piece of equipment Drake never offered for their otherwise comprehensive lineup.

Their soon-to-be-superfluous concentric knobs got me wondering about the type of functionality I could add to an SB/HW-104 or an HR-1680. Then I began to take a look at what Benton Harbor DIDN'T offer in the way of 104-line station accessories. A few came to mind, though at least two of these actually did make it to prototype stage before being killed off:

A synthesized remote VFO with digital frequency readout
A matching antenna tuner (the "SB-670")
A companion receiver, a la the R-820 or R7
A panadapter display, like the SB-620
Whatever else one can dream up with spare full or half-sized cases and matching control knobs, trim, etc

I'm not going to hack "collector quality" accessories here with the exception of one of the SB-614s. It'll become an SB-624. The rest of the stuff? Give me your poor, your downtrodden, your destined-for-the-scrap-heap green boxes and I'll build some useful things from them.

Why? Maybe the odd magazine article of the very late 70s/early 80s which featured the Heathkit series made a lasting impression on a newly minted ham...and said ham was determined to have such a lineup. Some day.

Truth of the matter is, my Omni VI/Opt 3 will slap a "stock" SB-104 into RF oblivion. But I think I can fix that, in part or in whole. ;)

[N8YX]

Some updates - and a reminder that I'm going to have to brush up on my German. First, a few neat links I've found on the subject. I really need to get ahold of the DK4 and do some collaborating:

http://dk4sx.darc.de/sb-104.htm
http://dk4sx.darc.de/sb-104a.htm

I bought four of Mike, WB8VGE's (Heathkit Shop) LED display conversion kits last year. But then I ran across this:

http://www.qsl.net/k/k8lbh//K8LBH/Display.html

The 10MHz digit is controlled by the bandswitch - it isn't counted directly. The 1MHz digit is preloaded to a "6" via hardwired logic in the counter circuit but this can also be changed to other values. And....there's enough space in the readout window for an extra digit.

13593

Using DIP resistor packs instead of discretes saves space and allows me to add one more digit along with control logic. Thus, the 10M A/B band positions (28.0 and 28.5, respectively) become xxx.000.0 or xxx.500.0 - with the hundreds and tens digits controlled by external logic sources. Perfect for the addition of a set of transverters for weak-signal SSB/CW work, and with direct frequency readout to boot.

One or two of the discarded SB-6xx accessory cases will be used to house the transverters and control logic. A call to Down East Microwave ought to net me some data about repackaging their wares and the physical dimensions thereof.

Last week I won a pair of HW-104 junkers on eBay; both come with filters and noise blankers. A working 104A/SB-604/HP-1144A is inbound. First order of business is to replace its questionably-designed +5/+11V regulator circuitry with the LM-350K solution that Pat, 'mhz described a few years back. Then, it's on to modifying the first of the digital rigs. The analog stuff - HW/HR/HX gear - will be done later.

[N8YX]

The "stock" -104A mentioned above is currently tuned to 3843 awaiting the Possums. That the receiver and control circuitry could use some updating is fairly obvious, though it isn't a terrible performer as-is.

Next month I'll get the regulators and update both the +5 and +11v sections. Then on to one of the junker units as a board-test mule.

[KC4TIR]

You might want to try AF4K.com for your crystals.

[N8YX]

You might want to try AF4K.com for your crystals.
If I wanted to spend twice what ICM or the others are charging per rock, yes.

[KC4TIR]

Do you need a downeast 144/28

[N8YX]

Do you need a downeast 144/28
And a 50/28, 222/28 and a 432/28...

[KC4TIR]

Never had a 432/28, sold the 50/28. So where do I send the 144/28. I got the deal of the century on two ssb electronic transverters. 144/28 was last used with a Ren Tec Omni six plus and worked fine. I have some extra mirage amps, however some need repair.

[N8YX]

The prototype SB-644 synthesized VFO is now fixed.

When I bought the thing and first hooked it up, the PLL looked to have some dead-banding issues. That is, even though the synthesizer would lock the output warbled by ~1KHz.

First order of business was to replace all power supply capacitors and all on-board tantalum caps. Luckily, I had a stash of the latter but waited for a week on the former. Once finished, this didn't help stability much. Next, a cleaning of all IC sockets with DeOxIt followed by a re-seating of the devices. No dice. However, I did catch a few chips with marginal pins and replaced them as a preventative measure.

Next was into the loop lifter/error line driver section. This design is a textbook example of a late 70s layout. That is, a timebase serves as a reference input to Pin R of an MC4044 Phase Detector IC. A presettable Divide-by-N counter (whose preload values are defined by the VFO's counter modulus and display circuitry) is used for the V input. Outputs U1 and D1 (run in non-charge-pump mode) feed an LM301A set up as an integrator. Two more '301As serve as an error line amplifier/driver pair. They supply a control voltage to the varactor diode which forms part of an LC tank required by the VCO chip, an MC1648. The output of the VCO feeds a pair of MC12012s: One drives the Divide-by-N counter; the other is used to derive the actual VFO signal.

The loop filter employed a bunch of carbon-comp resistors. All of these were replaced as they drift in value, and if timing is critical then they may not allow for proper loop lock owing to out-of-resonance conditions. All of the polystyrene capacitors in the error amplifier/driver section were also replaced.

What happened next was that - upon powerup - the VFO would slowly drift from 4.0ish MHz up through its capture point of ~5.245MHz...stabilize momentarily...then rapidly proceed to drift to its upper limit. This implied inability of the loop filter to produce a proper output waveform. Inspection of the area revealed...two more overlooked tantalum caps in the +/- input circuits. Order some replacements, wait a week, solder them in...no joy, but upwards drift seemed to occur a bit more rapidly now. So the circuit was integrating the U1/D1 pulses correctly. Hmmm...

A few more back-and-forth component swaps were tried, and ultimately the thing would sit on 4.00xMHz on powerup but refuse to lock. It was as if the Divide-by-N input was absent, but when scoped it was there...albeit with a lot of noise on the line. Puzzling, to say the least - and since I have no schematics or "known good" examples of the device I was unsure of what the waveforms on the pins should look like.

Desparation set in...I began fingering around the board with the VFO powered up. During one of these "touch and feel" sessions the device went into lock perfectly and remained stable. Very interesting. A bit more experimentation showed that if Pin 1 of the PD chip (MC4044) were touched directly the setup would behave.

Capacitance to ground? Resistance to ground? A bit of experimentation led to the tacking of a 22pF ceramic disk capacitor from that pin to a nearby ground connection and the device stabilized nicely. I reset the timebase reference oscillator, threw the covers back on, powered it up and have been running it for 14h straight on the bench. Once thermal stabilization has occurred (likely due to timebase warmup) there is MAYBE a 5Hz random variation noticed on the counter - and I attribute that to circuit noise.

It looks as if Heath's engineers may have missed that one crucial bit about noise on the reference line: If said noise component makes up a significant percentage of the applied signal voltage there's no apparent way to make the loop lock cleanly.

My design will use a DDS setup and the counter/readout board from a junker SB104 but it'll incorporate the same look and feel as the (never produced for sale) Heathkit offering. Meanwhile, I've got to modify the SB-104A so it can output T/R information to the VFO for RIT and split-frequency tracking purposes. Then the prototype goes in-line.

Not a bad design, and there's at least one other version of the setup floating around. Mine has a big Molex connector mounted to the rear bulkhead and this looks to be used for interfacing a logic analyzer to the tuning modulus section.

[N8YX]

It's not every day that you run across the "spark plug" which ignited your desire to become a ham. While searching an archive for a radio-related construction article I happened to remember something I once read...punched in a few keywords...and voila:

http://www.americanradiohistory.com/hd2/IDX-Consumer/Archive-Elementary-Electronics-IDX/IDX/70s/Elementary-Electronics-1979-07-08-OCR-Page-0047.pdf

http://www.americanradiohistory.com/hd2/IDX-Consumer/Archive-Elementary-Electronics-IDX/IDX/70s/Elementary-Electronics-1979-07-08-OCR-Page-0048.pdf

Those of you who have been following this thread will likely pick up on the fact that the one thing Heathkit didn't offer in the way of a 104-line accessory is an antenna tuner, though at least one prototype "SB-670" is known to exist. When I saw that Heathkit lineup many years ago I knew I wanted to build their stuff...and to get my ticket.

And there you have it...why I love the '104. And why I ended up here, of all places. :mrgreen:

[N8YX]

Dancing back around to the transceiver, I thought I had an "oops!" moment when I was only seeing 25-50w out of the thing on 40 and 20M, a bit less on 75 and 15...and 10M appears to be plagued with a spurious PA problem. Running the rig on its HP-1144A supply instead of via the shack's RigRunner/RS-50M seemed to verify good PA health on 40 and 20M with ~100w out - but the other bands need some help. Methinks I've got some cooked toroids in the low-pass filter assembly, which leads to absorption and loss of filter efficiency. Fortunately I've got several more of the assemblies which can be swapped into the unit.

I lost the receiver section earlier in the week. In the process of fixing things I made the S-meter and AGC mods as detailed here:

http://www.nostalgickitscentral.com/heath/73-index/articles/Upgrades%20for%20SB-104-8-98.pdf

The "roofing filter" will be added to each of these rigs as I acquire parts. The converted receivers will use a dual roofing filter scheme - ~4KHz B/W for AM mode and the other a regular Heathkit SSB filter. A couple weeks ago I managed to grab 6 Trio YG-3395S SSB filters (~2.4KHz B/W) and these will be used in the transmitter signal chain. Not quite ESSB but a bit richer sounding than the stock Heathkit parts allow.

[K7SGJ]

<snip>
I lost the receiver section earlier in the week.

Did you look under the bed?

[N8YX]

Did you look under the bed?
It was in a bad 500uF, 15v axial electrolytic on the Detector/AF Board...and also in a tuned circuit on the Front End Board.

The AGC changes really made the receiver come alive. Just 5 more boards to convert! :lol:

[N8YX]

It will be interesting to see what this thing ends up going for:

http://www.ebay.com/itm/Heathkit-SB-670-2KW-Antenna-Tuner-Ultra-RARE-Collectors-check-this-out-/171748349410?pt=LH_DefaultDomain_0&hash=item27fcffd5e2

I'm going to carefully disassemble mine and scan the front panel into a JPG image with the idea of making a silk screen mask. From there I can reproduce the panels - along with an internally metered "674" version - at will. The guts are plain ol' SA-2040.

[N8YX]

It will be interesting to see what this thing ends up going for:

http://www.ebay.com/itm/Heathkit-SB-670-2KW-Antenna-Tuner-Ultra-RARE-Collectors-check-this-out-/171748349410?pt=LH_DefaultDomain_0&hash=item27fcffd5e2

Hold onto your socks, guys and gals: $1045! :shock:

[KG4CGC]

Someone out there wanted it more than some other person.
- Captain Obvious.

[N8YX]

Someone out there wanted it more than some other person.
- Captain Obvious.
I paid the princely sum of $250 for mine. I don't think that all four prototype pieces I bought set me back that much in total!

[NQ6U]

Was beeg mistake, tovarisch. For one-third cost, he could have this (http://www.ebay.com/itm/Antenna-tuner-box-1-5-to-30-MHz-Russian-Soviet-radiostation-R140-R-140-SALE/281640890226?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%2 6asc%3D30003%26meid%3D239b15ee81cf46feb46d64131580 bd94%26pid%3D100011%26rk%3D4%26rkt%3D9%26sd%3D1717 48349410).

[K7SGJ]

Or for 60 Rubles, you could have this

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