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Manhattan Projects: An Update[long]

 

Gang,

Here is photo of my final SolderSmoke DC Receiver challenge project.
I'll do a video sometime in the next few days for proof of life.
The camera is giving me problems again.? Time for a new one.
------------

Manhattan Projects.

1.? The KD1JV all transistor project is on hold.? I have built one
and it has a problem with the high gain in the audio amp causing it
to oscillate when the audio is turned up.? If you want an oscillator,
build an amplifier.? The Hendricks Kits version, called the NADC
(Nearly All Discrete Components) version used an LM386 for the audio
and NE602/NE612s for the mixers.? Maybe I should have payed attention.

2.? The ADC is too complex for starters, so let's do the following.
20 years ago I was going to do the following, but never got round
to it.? Now is the time.? Someone sent me the schematic as a suggestion
that we do this one for the group, but I had
one already from the original web site, which has disappeared and
the WayBack machine has broken links.? So I sent a copy to
VA3IUL to put online.
<>
I have asked him to put JH1PJL's call for the listing, so this link will break shortly and
just replace my call with JH1PJL.? This will save space on the groups file space to
allow for later expansion.? Now you don't have to find a video amp (LT1252) for an arm
and a leg.

I am going for 20m first.? Go to <> and start with
the "Seller's other items" link and look at all the crystals available.? I'm going with
10.000MHz for the VXO and 4.032MHz for the IF.? This will start me out around 14.032MHz
on 20m.

N6KR went with [40m: 4.000 and 11.046MHz], [30m: 4.194 and 14.318MHz] and
[20m: 3.932 and 18.000MHz] for the crystal pairs. 'seattleaccessaries' vendor
does not have 11.046 or 3.932MHz and I haven't found anyone else that does either
on ebay.? I bought all my crystals from <>
for free shipping, but with the trade wars he jacked up shipping to $50 USD and
you and I are not ordering with that in place.

So, I need at least 10 volunteers to build a critter with the band of your choice.
You work out the crystal combos.? 30m will work as is and I have the 20m crystals
worked out.? Just need a combo for 40m and left as an exercise for the student(s).

Q3 will be a 2N3904 and I'm using a 2SC2706 for the PA.? Have to work through
all the L/C combos for each band.? Another exercise.? Change LPF to meet current
FCC specs.

I'm waiting until after this weekend and I'll cave in and order some QRPMe pads.
Rex is busy at FDIM and Dayton this weekend.
Then I plan on copying the AA7EE layout for his SST.? No reason for me or
anyone else to reinvent the wheel and let's go for the chrome ones.
<>
This will be like copying NA5Ns layout for the HP signal generator of old.

I'll be using the KitsAndParts 1W keyer that Diz, W8DIZ<sk>, did.? But, you
can use any 8-pin chip that you have or can find to use or go without the keyer
if you have an old external critter you like.
<> and you can order from Mike and get one for
$5 plus S&H.? I don't know if I still have a K1EL K9 chip laying around.

OK.? That's a first pass outline of the SST Manhattan Project. Clear off the
bench and get out the pen and paper and get to work.? This isn't going to be
too hard, but it should be a challenge to us all.? Not failure, but low aim is crime.

First one across the finish line wins.? Progess reports appreciated.? I'm also
going for a 9cm x 9cm form factor and homebrew enclosure, since I just bought a
shear and brake for the bench.

FYI es tnx,

--
chuck adams, aa7fo
QRP WAS 17m started Apr 2, 2025
WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN
PA,CA,CO,WI,NE,ID,IL,NC,NY,WV
MA,OH,OR,RI,MT,WY,WA,MI
DXCC W,VE,JA,PY,ZL,TX9

p5160005.jpg

 

Chuck and Doug,

The JH1 Doug listed is his (Japanese ham's) homebrewed version of an 40m SST. I have a hardcopy of the schematic that Doug posted from back about 20 years ago.
Another JA ham (don't have his call at hand) made some mods to his VXO on 40m to expand the frequency?coverage; I think I've a hard copy of that somewhere.
?
On my 20m Wilderness SST, I've ?made several mods.?
1. To increase frequency coverage (18 MHx VXO), added 1uH RFC in series with existing?5u6 plus add a small value 1-5 pf capacitor from VXO crystal/RFC junction?to ground, I'm getting 14043-14064 MHz coverage with that.
2. Added a MPF102 IF amp per NA5N's mod, from his QRP Databook, between the crystal IF filter and the '602 product detector. This mod helped the RX NF a bit.
3. Added a second bandpass LC between the TX mixer output and the existing BPF, this cleans up the TX output a bit.?

If ya'll are interested?in the details of these mod's (schematics), I can sketch them out and snailmail them. (My printer/scanner is presently inop.)

Regards,
Walt ?K3ASW

On Fri, May 16, 2025 at 12:18?PM chuck adams via <chuck.adams.phd=[email protected]> wrote:
Gang,

Here is photo of my final SolderSmoke DC Receiver challenge project.
I'll do a video sometime in the next few days for proof of life.
The camera is giving me problems again.? Time for a new one.
------------

Manhattan Projects.

1.? The KD1JV all transistor project is on hold.? I have built one
and it has a problem with the high gain in the audio amp causing it
to oscillate when the audio is turned up.? If you want an oscillator,
build an amplifier.? The Hendricks Kits version, called the NADC
(Nearly All Discrete Components) version used an LM386 for the audio
and NE602/NE612s for the mixers.? Maybe I should have payed attention.

2.? The ADC is too complex for starters, so let's do the following.
20 years ago I was going to do the following, but never got round
to it.? Now is the time.? Someone sent me the schematic as a suggestion
that we do this one for the group, but I had
one already from the original web site, which has disappeared and
the WayBack machine has broken links.? So I sent a copy to
VA3IUL to put online.
<>
I have asked him to put JH1PJL's call for the listing, so this link will
break shortly and
just replace my call with JH1PJL.? This will save space on the groups
file space to
allow for later expansion.? Now you don't have to find a video amp
(LT1252) for an arm
and a leg.

I am going for 20m first.? Go to <>
and start with
the "Seller's other items" link and look at all the crystals available.?
I'm going with
10.000MHz for the VXO and 4.032MHz for the IF.? This will start me out
around 14.032MHz
on 20m.

N6KR went with [40m: 4.000 and 11.046MHz], [30m: 4.194 and 14.318MHz] and
[20m: 3.932 and 18.000MHz] for the crystal pairs. 'seattleaccessaries'
vendor
does not have 11.046 or 3.932MHz and I haven't found anyone else that
does either
on ebay.? I bought all my crystals from
<>
for free shipping, but with the trade wars he jacked up shipping to $50
USD and
you and I are not ordering with that in place.

So, I need at least 10 volunteers to build a critter with the band of
your choice.
You work out the crystal combos.? 30m will work as is and I have the 20m
crystals
worked out.? Just need a combo for 40m and left as an exercise for the
student(s).

Q3 will be a 2N3904 and I'm using a 2SC2706 for the PA.? Have to work
through
all the L/C combos for each band.? Another exercise.? Change LPF to meet
current
FCC specs.

I'm waiting until after this weekend and I'll cave in and order some
QRPMe pads.
Rex is busy at FDIM and Dayton this weekend.
Then I plan on copying the AA7EE layout for his SST.? No reason for me or
anyone else to reinvent the wheel and let's go for the chrome ones.
<>
This will be like copying NA5Ns layout for the HP signal generator of old.

I'll be using the KitsAndParts 1W keyer that Diz, W8DIZ<sk>, did.? But, you
can use any 8-pin chip that you have or can find to use or go without
the keyer
if you have an old external critter you like.
<> and you can order from Mike and get
one for
$5 plus S&H.? I don't know if I still have a K1EL K9 chip laying around.

OK.? That's a first pass outline of the SST Manhattan Project. Clear off the
bench and get out the pen and paper and get to work.? This isn't going to be
too hard, but it should be a challenge to us all.? Not failure, but low
aim is crime.

First one across the finish line wins.? Progess reports appreciated.?
I'm also
going for a 9cm x 9cm form factor and homebrew enclosure, since I just
bought a
shear and brake for the bench.

FYI es tnx,

--
chuck adams, aa7fo
QRP WAS 17m started Apr 2, 2025
WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN
? ? ? ? ? ? ? ? PA,CA,CO,WI,NE,ID,IL,NC,NY,WV
? ? ? ? ? ? ? ? MA,OH,OR,RI,MT,WY,WA,MI
DXCC? ? ? ? ? ?W,VE,JA,PY,ZL,TX9
 

I hope that a few folk get on board with building an SST Manhattan-style. I'm looking forward to following along, though I can't commit to anything, as I'm a bit tapped out from just finishing a project. I need to get away from the workbench and into the outside world. A few thoughts that came to mind -?
?
1) It would be worth adding a bit more filtering between the transmit mixer and the driver stage. I just drew the extra filtering that JN3DMJ added to his 40M SST, but then realized I cannot attach it to this message. Not that it matters though, as the web page on his SST is still online, at - and that page includes details on the extra stage of filtering.
?
2) On my SST, I replaced C10 and C24 in the RX and TX oscillators with trimcaps, so that the TX and RX frequencies can be matched more closely. I don't like leaving that sort of thing to chance, and living with a "good enough" result. Not when it comes to transmitting and receiving on the same frequency. I still wan't able to match them up perfectly, but it was reasonably close.
?
3) Per Walt's point about the extra IF amp. I must admit that my SST20 didn't have any problems with sensitivity. I didn't observe poor S/N ratio on mine, though perhaps I'm just not very discerning! I tried to find details of this added IF amp online, with no luck so far. Walt - I just realized that you emailed me about this mod when I built my SST20. You mentioned that when adding the extra IF amp "If one does this mod, a dual JFET keying switch needs to be added between the 602 product detector and the LM386, otherwise the sidetone is way too loud." With that in mind, I wonder whether the extra complexity this mod adds would be considered worth it by builders here? I can see too much extra circuit complexity acting to deter would-be builders. It makes the Simple Superhet Transceiver a bit less Simple. Just my opinion, of course.
?
4) On my SST20, I added an extra 18MHz VXO crystal in parallel with the existing one, grounded both crystal cans, and achieved a tuning range of 14044.5-14066.5. It's stable at the top end but, if memory serves me correctly, is a bit drifty at the bottom. However, it's easily good enough for brief POTA and SOTA-style exchanges. I seem to remember that it settled down a bit after having been on for a few minutes, though I didn't spend much time attempting to quantify the drift; I just liked the 22KHz tuning range!

Does anyone think the lack of RIT is a concern? There is one local feller who insists on calling me way off my frequency; so much so that it is disconcerting. Lack of an RIT hasn't been much of an issue for me otherwise though. I am a little finickety about being able to match the pitch of the other station's note with my sidetone, but I'm training myself to not bother so much. You could say that I'm in recovery :D
?
Dave
AA7EE
 

I just wanted to add that, while the LT1252 is not the cheapest part around, it is still available from Mouser and Digikey. Mouser have the SMT version for $6.94 and the thru-hole one for $6.68. At Digikey, the prices are $8.09 SMT and $7.58 thru-hole. Certainly nowhere near as cheap as a 2N3904 but if you only need one for this project, maybe a justifiable expense?
?
Just thought I'd mention it, in case anyone here is keen to stick with the original design.
?
Dave
AA7EE

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