That seems to be about what mine puts out, but it made a perfectly fine AM contact with it the other day with it. Remember, that’s less than 3 dB down from the advertised level and it doesn’t make that much difference in your transmitted signal. The receiver doesn’t seem to be wildly sensitive, but I think if it were I think it would overload. I set my modulation by the LED activity, with it flashing only on peaks. WTWW (5085) sounds great, as does the net that meets on 3885. I don’t think I will mess with mine. The enemy of good is better!

73,

Charles - NK8O

--

Hello,

I just received and built a QRPometer. It is a 1st class kit. It is not my first kit, but I have not built many. The board is one of the best I have seen and everything fits as it should.  The SWR readings are perfect the power readings on several QRP rigs give a good comparison between the rigs, but I am not sure if they are correct, and if I assembled something incorrectly. Here are my readings:
Cricket 40 @9v - reading 0.13, @11.5v - reading 0.20
Pixie 2 @9v - reading 0.09, @11.5v - reading 0.15
ATS-3B @9v - reading 0.23, @10v - reading 0.35, @11.5v - reading 0.40
I also tested an Elecraft K2 and IC-7300 with power from 0 to about 12 - the readings went up then down, but did not seem close to what the radio meters were showing

I did re-solder the pads on the Velleman meter, but perhaps this is not correct.

Thanks

George VY1GP

Dave:

I know I can't see all that well.?? I also know I don't know everything.?? I also know that I haven't been getting the memos especially since I have been older.?? However, I have worked hard, studied extensively and have a basic understanding of how this stuff works.?? I guess this type of thing comes from the plug and play mentality and a lack of undestanding of how all the basic stuff works.

I just couldn't shut up afte reading your latest email.

Lee, W9HIF

Brian-

The Nouveau-75 conveys information (your voice) by Amplitude Modulating its carrier signal.?? PSK, by contrast, is expecting a steady signal- a tone with phase reversals to signal 1s and 0s. A setup listening for PSK signals from an AM rig won't decode anything intelligible.

There's also the matter of the bandwidth it uses.?? Your transmitted AM signal has both upper and lower sidebands present at equal power levels.?? It may well cause QRM to other operators up to 5-6 kHz away, and that's less-than- ideal practice in the digital portion of the band.

73- (The Other) Dave- K1SWL

On Sat, Nov 2, 2019 at 2:59 PM Brian Crittendon via Groups.Io <aaa5mi=yahoo.com@groups.io> wrote:

Is there any reason we couldn't use this radio with PSK?

-- 
Lee, W9HIF
The station of the Scary Ghost Stories and Tales of the Glories of Ham Radio long, long ago.

Now that I've got my modulator settled down I'm wondering what others are seeing for RF power output?

With a 13.5VDC supply I get 2.8 watts resting carrier and right at 11 watts PEP on voice peaks with 100% modulation.   That was good enough to be heard around the midwest this morning on the Midwest Classic Radio Net, but it's about half of what the Nouveau 75 specification says it should be.

Some comparisons will help determine whether my modulator is still not working right, thanks.

73, Bob W9RAN

You might consider joining the "CalQRP" group on Groups.io. Ken WA4MNT announced the product on that list, and I think some of the QRP Guys are all on that list. You might post to that list with the issue you're having, and see if anyone there can make suggestions.

--
Jeff N0̷MII

Dave,

I've got a band-aid that seems to prevent the thermal runaway from happening but I'm hoping you can provide some insight into "why" and perhaps a better solution.

I found some nasty looking oscillations when scoping the gate of Q11 to see why it was turning on - several volts of unstable crud in the 600-800 kHz range.  A 1nF cap to ground reduced the amplitude and shifted the frequency to the 225 kHz range, so I tried higher values.   As much as 10uF reduces the oscillation without noticeable impact as now for the first time I have positive peaks and 100% modulation (even though I see some spiky things on the carrier which I suspect is the same oscillation).

The problem apparently is an instability in the modulator circuit that I'm just minimizing so the circuit can work but and hopefully this will enable you to get a handle on what's really going on. Meanwhile I think I'll try the radio on the air tomorrow morning!

73, Bob W9RAN

On 11/1/2019 1:30 PM, nm0s_qrp via Groups.Io wrote:

voltages measured for Q3 and Q11 swapped

Ah, no, but I read "IRF-510" and forgot there were two of them, and I was measuring Q1 instead of Q12.   Thus my argument about 0 volts on the drain and resting carrier, etc.

Let me try again with new measured values:

           G        D       S

Q3    9       10.3      12.6    FQP7P06

Q11  7.5    3.5*     12.4    FQP7P06

Q12  5.6    3.5*     2.4       IRF510 (NOT the PA one!)

*  the voltage at the drains of Q11 and Q12 measures 3.5V right after the PTT is keyed, but start to rise rapidly, which creates the thermal runaway problem.   The voltage is > 8 volts within 15 seconds or so and when I measured the temp of the Q11 heatsink it quickly rose to > 50 deg.

As with the values your provided, all the above are with PTT keyed but no modulation.

Sorry for the mixup on Q numbers.   Does this suggest anything new?

73, Bob W9RAN

In the receive mode, all three of these MOSFETS should have no drive, i.e. the gate voltages should be close to the source voltage.  Bob, I think you have the voltages measured for Q3 and Q11 swapped, as the drain voltage you report for Q3 is the same as the drain for Q12.
It looks like the gate voltages on Q11 and Q12 are not correct.  I would suspect failure of Q10 or Q13.  These would be the ones I would try replacing.

73 Dave

On 11/1/2019 5:39 AM, W9GY wrote:

Hi Bob, got same issue on mine.  Q11 get real hot real fast in tx.  I'm awaiting some FETs to arrive before additional troubleshooting.  Please keep me in the loop as to what you find. -

Hi Jeff,

You bet.   The only one I've heard was WA8SAJ's and it sounded good thru a linear.

When I first noticed that Q11 was burning up, I saw that the tab of Q12 might have contacted Q11's heatsink.   But while I was waiting for replacement FETs to come I realized the drain of Q11 and Q12 are connected together in the circuit anyway so it wouldn't have mattered if they were touching.

So we both received defective PC boards it seems.   The more I try to understand what's going on with this modulator the more confused I get!    A complete set of voltage measurements from key nodes - each terminal of all active devices at a minimum - would be a big help.

73, Bob W9RAN

Hi Bob, got same issue on mine.  Q11 get real hot real fast in tx.  I'm awaiting some FETs to arrive before additional troubleshooting.  Please keep me in the loop as to what you find.  -73-
Jeff W9GY Calumet, Mi (UP)

On 10/19/2019 8:45 PM, nm0s_qrp via Groups.Io wrote:

I did a quick check of the power transistors on the main PCB, since the SMT parts are too small to probe safely.  With 12.6v supplied, the transmitter keyed, and no modulation:

            G    D    S
Q3    7.9  9.8  11.7    FQP7P06
Q11   12   0    12      FQP7P06
Q12   5.0  0    0       IRF510

A large deviation from these voltages would indicate damage to the board, or defective component.

Hi Dave,

Thanks for that data, but after comparing with my non-working Nouveau 75 I wonder if you could confirm one of those voltages. If  the drain of Q12 is truly at 0 volts with the PTT keyed, there would be zero resting carrier output, and I'm sure that's not right (even controlled carrier rigs have some resting carrier). I measure 10.5 volts on Q12's drain with the PTT keyed, which produces a resting carrier of 3.25 watts and that seems to be in the right ballpark.

The problem I have is that Q11 gets very hot very fast when any modulation is applied and inadequate modulation - something isn't right in the class G modulator.    Here's what those voltages measure on my Nouveau 75:

          G    D    S
Q3   9.6  10.5  13    FQP7P06
Q11   7.5  0  12.7    FQP7P06
Q12   3.8  10.5  .2   IRF510

This modulator never has worked right.  After the first Q11 melted down, I went ahead and replaced all the big FETs, but that did not fix what's wrong.  The BJTs in the modulator have junctions at least, I don't know of a good way to test the small FETs but at least they aren't shorted.

It looks like something is messing up the bias of Q11 -  if the above voltages help you to point me toward the right area of the modulator circuit, I can make additional measurements and do SMT repair.    I just haven't yet had time to build a spice model for that bootstrapped class G modulator to help me understand how it works.

Thanks and 73,

Bob W9RAN

--

I am away from the house this week!   

I have a DX 398 I bought from the shack almost 20 years ago and it is one of the best and most durable radios I have ever owned. It mostly sits in the bedroom proving local FM reception but from time to time I connect it to the HF antenna and do some SWLing. Great radio Bobby!

Someone will be happy with it.

de KB9BVN

I have a Radio Shack DX 398 portable radio for sale. This is the very same radio as the Sangean 909. It is loaded with many features and is in very good condition. It can work on AM,FM,CW AND SSB. The antenna is in good condition. It comes with a carry pouch, manual and wall wart. I am asking $70 shipped to lower US 48. If you are interested or have any questions contact me direct at rolph981@.... Thanks for looking, 73
Bobby Rolph
KB4QNR