Troubleshooting a NN1G transceiver kit

[Wa1dx]

I am struggling my way through assembling an old model with 2 boards. Even given discrepancies between various published schematics and parts list, and the model I seem to have (Mark II), I have a fair amount of experience, having built more than a dozen kits and a few homebrew projects. I simply cannot get the receiver to work except to pick up strong local AM stations, Even after checking solder joints, bridges, parts, etc.. I am mainly a tube guy and my question is whether I can use my old tube signal generator to inject RF along the receiver chain for troubleshooting, or will this wreck the project?

[ve3lyx]

When doing solid state I use a clip lead and my antenna to inject RF.
No #1 test here when working on RXs is does hooking up the antenna cause a click to be heard in the phones? To much front end gain or too much antenna coupling can cause many Rx problems. So I always look there first. To check any audio amp tube or SS I use the wet finger on grid , gate or base. Very reliable test.  So that's the front and the tail end. Not much left to check now.
donVe3LYX

[Wa1dx]

Many thanks. I'm getting body effect so that I pick up strong AM broadcast stations when I touch ground or the pot before the audio stage.  Is this some recognizable problem--a ground loop perhaps--I'm out of my class when it comes to radio engineering so just guessing

Using the antenna trick you suggest, I get AM stations as I move back in the receiver chain all the way to the output of the mixer (pin 5 of NE 602-labelled U1 on schematic) but I don't know if this is a non-specific effect or just the signal finding its way to ground and overloading the receiver. I take my cue from the many tube receivers I have restored, that things aren't right because the audio does not get louder as I move the antenna connection toward the beginning of the chain, and tuning the various transformers makes no difference.

[Wa1dx]

Guys,
I am hoping someone can help with further advice. I believe this is a fairly standard receiver arrangement (schematic attached) with a NE602A oscillator-mixer followed by four crystals at 10 MHz and then MC1350. I have been able to push a 14 MHz signal through from a signal generator starting at the end of the crystal chain, Y4.I get nothing before the crystal chain at either 10 or 14 MHz and nothing, of course, at the antenna. Also, transformer T4 does not tune anything. I must say, the amplitude of the audio signal is extremely low in comparison to what I am used to injecting RF into a tube receiver.

My idea was to short the crystals one by one to see if I can get a signal through. I looked endlessly for ground shorts that might be pulling the signal often cannot find one.Does it say something that only a 14 MHz signal comes through the chain when the IF is 10 MHz?

Am I all we and do I have to build the back end of the transmitter portion to expect and are signaled to make it through the front-end of the receiver?

There is a schematic in the middle of this article: http://www.zianet.com/dhassall/advmanart.pdf

[n7eku]

Hi,

Some time back I got some mismatched NN1G Far Circuit boards and decided to build them up too.  As their versions were difficult to figure out, I order a new set of boards from Far Circuits, as well as documentation from the ARRL for the original '93 QST article.  It was a complete mess.   The documentation was largely unreadable, the boards had mistakes, and upon research on the transceiver, decided that it was best to write it off.

There were many versions and modifications to this very early project from NN1G.  The Norcal QRP club journal QRPp has some good information it.  Some good readings are here:

http://www.cq.sk/modules.php?name=News&file=print&sid=179

http://www.k7qo.net/nn1g_mark_2.pdf

http://www.w5dor.com/W5DOR-Project-006.html

I think it would be best to use the parts for something else.  There were mistakes on my boards and also there were some design problems too like in the signal routes and also as seen from the numerous changes in the various notes.  As stated in the first link, this was a quick "conception" project with only two days time given to the design.  It eventually evolved into a nice, well-performing, rig.  So one of those later designs would be better to build IMHO.  I think the rig went from NN1G 72  (Mark I, II, III...) -->  40-40  -->  SW40  --> SW40+ at the end.  I think any of the latter three designs would be OK to replicate, but I'm not sure if PCB boards or patterns are available for those.

Anyway, that was just my experience and what I've gleaned from my reading.

73,


Mark

[Wa1dx]

I really appreciate all the help and I am close to writing this off as well. But it was fun trying. I built a solidly functioning SW20+

[n7eku]

Hi,

In case you might be interested, a nice design for which you can still get boards and which uses a similar group of parts, is the NE602-based QRP transceiver by Rick Littlefield, K1BQT, that is in the January '89 issue of Ham Radio magazine.  There is a nice review of it in the Norcal QRP club journal QRPp volume 2 (March '94 p. 54) by Ep Pacyna, W1AAZ.

The boards are $9 from Far Circuits, and also the HR Magazine article has the board patterns, parts layouts, and complete instructions.  It has active filtering, AGC, and RIT.  I haven't built it myself, but it is tempting!

73,


Mark.

[Wa1dx]

Great idea. I think I will pursue. Appreciate everyone's replies