ARCHIVE: Australian Ham Radio Discussion Forum ( AHRDF )

Hi all
I wonder if any of you Aussies can help this poor old POME?
I have just built Drew Diamond VK3XU's "Simple Superhet Receiver for 80 and 40m", and guess what, it don't work. Well, mine doesn't anyway!  
So if anyone is familiar with this rig I would appreciate some help .
As this is my first post, I better introduce myself.  Name is Pete,  oldish (74) with pacemaker (keep away from microwaves!) and a radio therapy shrivelled prostate.  But not old enough yet to consider buying more than one carton of milk too risky!  I spent time as radio operator in the RN, and worked with you guys down there in exercises, and visited Freemantle, HMS Eagle 1960's.
Anyway, back to business.  The above rig is featured in the G-QRP publication Radio Projects for the Radio Amateur vol 4 by Drew Diamond VK3XU.  I have checked my wiring and soldering, positioning of components multiple times, and all seems ok but i don't appear to be receiving any signals, (yes the antenna is connected), only local noise, fridge, heating etc.  Have tried it with battery and still the same.
The input filtering is via 4 x 2mHz xtals, Drew recommends sorting them into two pairs of 1.999mHz and 2.001mHz.  Unfortunately I don't have the equipment to do that, so I just put them in circuit as they came.  Somebody more knowledgeable than me suggested that therein may lie the problem.  I have taken some readings with and without the RF probe and multimeter, (my total test equipment).
I thought maybe one of the IC's may be duff.  The readings are as follows:
IC1 NE602 mixer:  pin 5 4.8v with meter and probe.
IC2 NE602 Prod det. after the xtals both 4.6v with probe and meter.
Hope that may say something to someone,  maybe an alternative input filter may be better?
So, thanks for reading this, if anyone not familiar with this rig I will try and figure out how to send it as an attachment.
73's
Peter

Hi Peter,

I think you can trust Drew's work. Can you hear the VFO and BFO using another receiver? Can you inject a signal into pin 1 on either NE602 and see a corresponding signal at the output?

I don't have notes on the NE602 but are those readings in keeping with expected input for the device?

gDay Peter,

without being familiar with the exact circuitry, my immediate response is the same as Lou's. Check to see if the oscillators are oscillating. It is a good sign that you are hearing broadband noise... at least some RF energy is getting through! If you can detect output voltage from the oscillator using the RF probe and yet still cannot tune in local signals, this implies that the frequency is wrong.

regards

Ian
VK3YCQ

(31-07-2017, 09:09 AM)VK3ALB Wrote: [ -> ]Hi Peter,

I think you can trust Drew's work. Can you hear the VFO and BFO using another receiver? Can you inject a signal into pin 1 on either NE602 and see a corresponding signal at the output?

I don't have notes on the NE602 but are those readings in keeping with expected input for the device?

'morning/evening Lou
ok thanks for that I'll give it a go today.  Don't have a freq gen though, but will try finding bfo and vfo on rx as you suggest.
Peter

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(31-07-2017, 12:20 PM)VK3YCQ Wrote: [ -> ]gDay Peter,

without being familiar with the exact circuitry, my immediate response is the same as Lou's. Check to see if the oscillators are oscillating. It is a good sign that you are hearing broadband noise... at least some RF energy is getting through! If you can detect output voltage from the oscillator using the RF probe and yet still cannot tune in local signals, this implies that the frequency is wrong.

regards

Ian
VK3YCQ

gDay/good evening Ian
Ok thanks for advice will check oscillating today
regards
Peter

Hi Peter,

Once you've found the VFO and/or BFO you should be able to loose couple a signal from a TX (a wire hanging near a dummy load) to the antenna input then search for a signal with your RX at the output of the 1st NE602. Once you have that repeat the process for the remaining stages.

Yes it would be nice to use a sig gen and a 'scope to see what is going on. Is your colleague or a local ham club in a position to assist you?

(31-07-2017, 11:20 PM)VK3ALB Wrote: [ -> ]Hi Peter,

Once you've found the VFO and/or BFO you should be able to loose couple a signal from a TX (a wire hanging near a dummy load) to the antenna input then search for a signal with your RX at the output of the 1st NE602. Once you have that repeat the process for the remaining stages.

Yes it would be nice to use a sig gen and a 'scope to see what is going on. Is your colleague or a local ham club in a position to assist you?

Hi Lou
Thanks advice.  I can't listen for the BFO and VFO on my receiver, as it doesn't cover the frequencies of the oscillators, but according to my RF probe they are oscillating ok.  I connected my main tx/rx to dummy load, wrapped wire around it and connected to ant input of the rx but could not find the signal.  The IC's all seem to be ok, so my next step is to check the toroid link at the ant input by linking the picked up signal from main tx via the dummy load to the other side of the toroid, and see if another rx will pick up signal from there. 
I posted this thread on this site as the rx is an Aussie design, so thought there might be someone there who has built the rig, although it was published some years ago.  Some of the components were difficult to source, like polystyrene capacitors, and the beehive trimmer.  I guess they could have been substituted with something else, but wanted it to be true to Drew's original design. 
It looks to be a good superhet receiver.  I built the 80/40 Tx that goes with it, and it works fine.  I wondered if Drew himself contributed to this site, and might give some advice.  Someone suggested I contacted him myself.  I have his address, but no email so I might drop him a line.  Regarding colleagues, there are a couple of guys at the radio club that might help, as they have alll the test equipment and more knowledge of electronics than me,  but they are busy with other things, and they are into digital stuff, Arduino etc, but I'll give it a shot.  The G-QRP Club that publish the books with Drew's designs in do a service fixing failed homebrew rigs, but I will have to pay.  Pride stops me going there, determined to sort it out myself
Anyway, thanks for all your help, I'll get there in the end.
Hope for a QSO with a VK sometime, but with the way propagation is at the moment not much chance!
Right, back to the drawing board.

73's
Peter