Re: voltage reading for DSB 20 meter version


Carl Weiberg
 

I did get a reply on CQ but lost contact so it’s working. 

QRP is great fun. I have a couple QRP rigs. I  no am putting up a Mosley beam this summer and looking forward to seeing how that works with QRP. The antenna I use for QRP today is an inverted L cut for 80 and 20. On 40 it needs my tuner. 

WSPR is fun for experimenting. I have had spots in the middle of lower Atlantic by Polar Explorer ship. 

My regular station I run barefoot Drake Twins and an Ft-991. Interesting how I gravitate to QRP though. Probably because it’s so easy at 40 or more watts but under 5 a contact is exciting as decades ago when I was a novice and all I had was 5 watts and an indoor dipole.

73’s

iPhone Aloha

On Feb 28, 2021, at 4:40 PM, Nigel Young <multilec@...> wrote:


That's great news Carl well done, I did get into the Jamaica's on 40 with mine, that's not a bad haul from NZ. The antenna is just a simple dipole 15 ft off the ground.
I have also taken it out with an end fed portable, a lot of fun.

Nigel ZL1NAY

Kia Kaha

On Mon., 1 Mar. 2021, 10:30 am Carl Weiberg via groups.io, <carlweiberg=aol.com@groups.io> wrote:
I have had some success!

I installed an NOS Phillips 139, then pulled the transformer verified that was ok, installed both. No replies to CQ, but PSKreporter shows my signals are getting out and amazingly far.

I will continue efforts, but I am thinking the 139 was the issue. 

All you guys are great! What a wonderful group of technical hams jumping in to help. I am still planning to measure the output of the 40 and 20 meter D4D’s with hopefully a little accuracy. 

Frustration is now low, seeing results makes a big difference.

73’s
Carl

iPhone Aloha

On Feb 26, 2021, at 1:44 AM, Nigel Young <multilec@...> wrote:


No worries Carl, take your time and get it fixed. I just got back from work so apologies, I did the tests last night at 2 am our time, if you follow along with my email you should result in a culprit 
Nigel ZL1NAY

Kia Kaha

On Fri., 26 Feb. 2021, 5:10 pm Carl Weiberg via groups.io, <carlweiberg=aol.com@groups.io> wrote:
Hi Nigel,
I had an email issue, and just got it corrected. Ok I will be spending the weekend working on the issue. Will check all voltages.
73’s



iPhone Aloha

On Feb 25, 2021, at 6:37 AM, Nigel Young <multilec@...> wrote:


Ok Carl,

Below is Adams picture with voltage readings in TX mode on my kit. We already established it works on receive.

Now, I am assuming that your kit goes into TX, the relay clicks and the TX light comes on? You can keep it in TX using the APP, don't forget to set Boost in the settings. Use your cable to connect your phone to the audio in jack, use a dummy load and squirt 1khz into the rig.
The rig should go into TX mode and stay on so you can do your checks.

Test Q8 first, this enables the xtal to resonate in TX mode, it basically shorts to ground to give your crystal a ground.
If this checks out we can assume your rig is oscillating at your crystal frequency, you can check also with a short wave receiver.

Next move on to the buffer amp Q2, this buffers the pre driver from the mixer and presents an impedance the mixer is happy with, you should be getting 5v on the collector which is fed from the little regulator on the board. If you have a scope you can follow this signal path through and hopefully watch it grow.

Now move to Q3, this is the start of the business end and boosts your AM signal to a level capable of driving the PA final transistor. Again the collector should be near the value of your power supply after dropping a little via R7.

Next you can check Q4 which again should be at your supply voltage on the collector. Check you mounted it so you can see the writing on the front. Check you have continuity through L1 if no volts present, sometimes you need to scrape the enamel off the wire pretty hard.
If all that checks out we have to look at T1, its a simple coil but 3 ways to get wrong, again check the enamel is cleaned off properly for a nice clean joint.

After all the above and assuming all your resistors are in the correct locations we have no choice but to think something is smoked. The Final transistor is the most likely target since for a strange reason when you power up the rig the TX comes on for a second. This can catch you out if you haven't got a proper load connected. PUFF.
By far the best way is to clip it out, this way you are only unsoldering one leg clipping at a time and preserving the traces on the board. From here you can test the transistor with a multimeter or tester to determine if it was smoked or not and replace with another after checking that one before fitting.

I am confident you can get it chooching at least to save some sanity. The power out will be low, you may struggle even with a QRP meter, a scope is your best tool for measuring here. If its all chooching and you can see yourself on the return beacon you can then plan how you are going to increase the output.

Make a note of all your readings which will help determine how that can be achieved. They may not match mine due to tolerances and your supply voltage but they shouldn't be far out.

On Wed, Feb 24, 2021 at 12:19 PM Carl Weiberg via groups.io <carlweiberg=aol.com@groups.io> wrote:
Hi Nigel,
Yes, I am only chasing an output up to a watt.  I will not becc by able to measure my output with B any degree of accuracy for a couple more days. If it is just a bad 139, that would be great.

Thanks to you and everyone for the help.

iPhone Aloha

On Feb 23, 2021, at 5:15 PM, Nigel Young <multilec@...> wrote:


Carl, I will measure mine at the weekend to give you a ball park. My suggestion is check again your final tortoid and if you need more power out I would use the finals as a driver for a parrallelled pair of BD139s that should get you in the ball park of a Watt out and trust me it's all you need on FT8  
Adam has done a great job at supplying a kit at this price but it's no game changer it was supposed to be an experimental approach to DSB Digital modes. Please don't go down the path of trying to make it any more than what it is. Its cheap and it works and is a lot of fun.
Yes you can improve it but there comes a point where you might as well scratch build something and you are feathering on the edge of that. Let me check the readings at the weekend and get back to you. I have one here set up for multi and on 4 different bands.

Nigel ZL1NAY

Kia Kaha

On Wed., 24 Feb. 2021, 4:02 am Carl Weiberg via groups.io, <carlweiberg=aol.com@groups.io> wrote:
Hi TE Fid,
All excellent. I have ordered Phillips BD-139 and will build a dummy load and measure output with both devices. I explored the Toroid site, looks like a lot of interesting projects and a good part source.

I would be happy getting a 1/2 watt out of this little rig. Currently I suspect it is at virtually no output. I tried responding to local stations that signals were strong, but no replies. 

This will be an ongoing project and your suggestions are greatly appreciated. Do you have any voltage test points referenced on this rig? 

Thanks,
Carl

iPhone Aloha

On Feb 23, 2021, at 1:40 AM, Timothy Fidler <engstr@...> wrote:



https://www.mouser.com/datasheet/2/268/2N4427-1593496.pdf 

Carl , this device is also avail frm the chap I mentioned to you.  

This has a guaranteed power gain of 10 dB at 175 Mhz which is of no interest to you but that suggests Gp might be 13 -14 dB easily at HF.

Now there is a power curve given and it shows  2 W out at 135 mW drive remember this is for class C operation and you have to have class A.

Let's say we put two in parallel assuming we can get 270mW out of our downstream power chain - that's quite an ask.  To do this properly we need to have 0.1 R emitter ballast resistors which can only be approx by say five off 1/4 w  1 ohm rs in parallel. Let's say that gives us a -1 dB on max possible power gain from this parallel operation.  so if we treat the Pout possible as  2 x 2 devices W x 0.5 factor for class B from class C  x 0.8  for the -1 dB drop we end up with 1.6 W out.  BUT BUT that should be pretty conservative given you are running at 14 Mhz .. you could easily manage 2.5-3 W out  , class B operation as long as you can keep the 4227s adequately cool with clip on head sinks which I think Diz sells but I am not sure about Dan. 


In order to physically fit these you will need likely have one above the board and one under the PCB which will mean a completely new case I guess.  Old story you can't make a silk purse out of a sow's ear without serious gold being expended.  what's serious.. based on what I see Dan wanting and some postage as long aas you can get cheap heat sinks - perhaps twelve dollars for the full change out .


Previous comments re spurious emissions still apply.

BTW this way to do this properly is with RF mosfets but that requires a complete circuit rebuild.

regards , TE Fidler 





 

 

 


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Best Regards,

Nigel Young
<D4D.jpg>

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