On Fri, Jul 12, 2024 at 04:11 PM, Joshua KJ7LVZ wrote:

What is the drive from the HL2 without the onboard PA activated? I know it is a very low level output but I don't remember if it is adjustable. You may not need a t attenuator if the output is sufficient.

Hi Joshua

When the HL2 onboard PA is not enabled, there is NO RF output on the ANT output connector, the ANT connector becomes a RX input connector, and the RF1 connector is the only RF output, 17dBm, from the HL2. RF1 is OUTPUT only so I would still need relay(s) to switch the antenna between RF1 for transmit and ANT for receive, and I'm not sure that RF1 is variable RF level (or indeed low pass filtered).




Thank you Joshua for taking the time to try and help me, really appreciated.

73

Peter - GM8JCf

Can anyone recommend one in the U.S.?
--
Wayne S.
KF7RCM

What is the drive from the HL2 without the onboard PA activated? I know it is a very low level output but I don't remember if it is adjustable. You may not need a t attenuator if the output is sufficient.

Joshua

Thanks Ludwig,

I actually found my dummy load.

I believe it is the coax or possibly even the antenna that is causing my a problem. What was confusing was that the SWR and the Return Loss on the VNA for that same antenna was well within acceptable ranges using the setup I had including the converters I was using to test both QMX and nanoVNA.

The dummy load test as I expect it should so that is a relief. Later I will try an antenna that I know is tuned and works on my other rigs.

Thanks for the suggestions on what to looks for.

73
Sean

Thanks Steve,

I think you may be right.

I found my dummy load (hooray). ?I measured it with my VNA and got 1.07. ?I then put that into my QMX and at first got a set reading if 10 but disconnected everything and tried again and now I am constantly getting a swr of 1.15 on my dummy load.

I am really happy about that.

So it seems that the antenna I have or indeed the coax is causing me issues. ?I will setup another one later that I know for a fact works with both my ICOM 7600 and my Yaesu FT857D and I will test with that.

Thanks again at least I have hope again that I will be able to activate some SOTA and some POTA here in Italy.

On Fri, Jul 12, 2024 at 11:12 PM, Dan Reynolds wrote:

If I unplug the 2x4 pin board there is an open and when I plug the board back in - it's a dead short.

Dan, so it looks like a problem related to this SMPS board.

On the VDD rail with the burnt power board installed there is a dead short on VDD.

Maybe the short comes from something burnt?

Her is a document from the QRP Labs Wiki how to test the SMPS boards off line. The Wiki contains also documents about the internal power supply and the start up process.

I pushed the power encoder and a transistor on the 2x4 pin board lit up - literally and burnt. It was near the far end of the board by the big cap.?

I think it's Q108, the switching transistor to produce VCC. But this should not affect VDD. But there was also something with the VDD board (see No 4 in your post). So please check the two subboards off line first. I think both are not ok. In the moment I have no real idea how this would happen. Maybe you have unwanted connections related to the pin headers of the two SMPS subboards?

73, Ludwig

On Fri, Jul 12, 2024 at 02:13 PM, Bruce Akhurst wrote:

?On Fri, Jul 12, 2024 at 02:13 PM, Bruce Akhurst wrote:

First: I thought it was called 350 and output 300W peak on a very good day but I may be wrong

You say 5W in 130w out

and 10w in 400w out Again - I thought it was called 350 and output 300W but I may be wrong

Otherwise Are you sure its a Linear amplifier ? Are you sure you have 5W from the rig ? What does the RM input SWR look like ? Is this flat across all bands ?

Hi Bruce

Thank you for your comments, as far as I understand it, the BLA-350 is specified in RMS terms, eg the front panel power out meter is in RMS - Page 10 user manual "Analogue Power Meter (b) Displays the output power in Watts RMS.", (I didn't think that Watts RMS was a valid thing, but that's what the user manual says !), and the curves on page 12 of the user manual agree with what I see on the BLA-350 power meter, eg my Hansen FS-500H SWR & Peak reading Power Meter will show 100W when I set the HL2 for around 3W, but the BLA-350 power meter shows about 60~70W (on 60m) which is 100/1.4142 ~= 70.7, so if the curves on Page 12 are correct, then the BLA-350 can develop ~300W "RMS" ~= 400W PEP which is what other users of the BLA-350 have reported - eg = anyway, having warned me, I'll now set up some very carefully controlled tests, eg RF sampler, Oscilloscope, with my dummy load to find out the reality :-)

Your proposal does allow you to treat the 10w linear as a module but it has way more gain than needed and it is possible you could remove the first (BS170) stage and make or adapt the final stage input transformer for 50 ohm input. Nicer but optional Otherwise yes

I am by no stretch of the imagination an analogue engineer never mind an RF analogue engineer, so the idea of me messing/adjusting about with Hans' design is only going to end up with lots of smoke, disappointment and non-functionality. I can put 3 resistors together in a T/Pi pad but it's been way too long (+40 years ago) since I did any serious analogue electronic engineering. Also, I want/need to keep the QRPLabs 10W amplifier to it's standard build so that, a) I can ask for help, and people can help me because my version is not "special", b) if I need another one I can just get another standard QRPLabs 10W linear amp module c) I can easily adjust the attenuator to get the results I need, d) from what I've read on this forum front-ending the QRPLabs 10W linear amp with a resistive attenuator is a good thing to ensure better convergence towards 50ohm input impedance.

BTW, I'm using 3W metal oxide resistors for the T pad which should easily (famous last words) be able to absorb the 5W or so out fromn the HL2.

Thank you once again for taking the time to share your thoughts with me and trying to help me.

73

Peter - GM8JCF

开云体育

It is a great pity you have misplaced your dummy load, because your antenna appears faultless, and my next step would be to put a decent 50 Ohm load on the QMX and see what it thinks of it.

You're thinking about the right things. I would recommend a bit of testing before building a pyramid

?

First: I thought it was called 350 and output 300W peak on a very good day but I may be wrong

You say 5W in 130w out

and 10w in 400w out Again - I thought it was called 350 and output 300W but I may be wrong

Otherwise Are you sure its a Linear amplifier ? Are you sure you have 5W from the rig ? What does the RM input SWR look like ? Is this flat across all bands ?

?

It's also common for gain reduction (gain compression of the last few dBm of power ) to affect the higher output levels of such amps making the above scenarios even less likely

?

So first decide what power level gives you a signal you're prepared to attach your callsign to and check all the bands .

Then make up a test to see what the Rig output is and what the amp gain at your chosen output level is.

Your proposal does allow you to treat the 10w linear as a module but it has way more gain than needed and it is possible you could remove the first (BS170) stage and make or adapt the final stage input transformer for 50 ohm input. Nicer but optional Otherwise yes - lots of attenuation (amount tbc) but make sure the first stage of attenuation can take the 5W in and see if the attenuation actually needs to vary by band . . .

?

?

1. On my very first startup trying to power on, I got nothing at all. I did the logical thing and reheated a bunch of connections - especially the two push button connection on the encoders.
2. After putting everything back together I tried again and sure enough the "flash drive" showed up on my computer.
3. I got the latest firmware, unzipped it and then put it into the flash drive. That's when trouble started. I guess everything takes off once it has firmware.
4. I noticed a tiny whiff of smoke coving from the 2x3 pin board (3.3 v?)
5. I immediately cut the power. Well actually just unplugged it. I was running a reduced voltage, like 8.5.
6. I checked everything. Both power supply boards seemed warm. I checked it all over again and plugged the power back in.
7. I pushed the power encoder and a transistor on the 2x4 pin board lit up - literally and burnt. It was near the far end of the board by the big cap.
   
8. I remeoved the power and started trying to diagnose it.
9. I don't think I checked resistance on the power rails to ground prior to this.
10. On the VCC rail I get an open. On the VDD rail with the burnt power board installed there is a dead short on VDD.
    (I am measuring resistance between the VCC or VDD rail and ground - open is infinity and dead short is 0)
11. If I unplug the 2x3 pin board there is no change in resistance - it is open with and open without the board installed.
12. If I unplug the 2x4 pin board there is an open and when I plug the board back in - it's a dead short.
13. I have an unfiished QMX (not +) and if I plug in its 2x4 pin board, it is open NOT shorted.
14. Oh, BTW, there is no short to ground on the V+ either.

I have a ticket with Hans, he suggested I poll the group to see what you guys think.

I'm not sure where to go from here. I'm hoping the main board is OK.

But I don't want to incinerate another power board if I can help it.
I was super careful building the kit. I used the recommended precautions/procedures soldering on the main board (6 layers). I have searched the board with a jewler's loupe and have not seen anything odd... I have been building electronic kits starting with an RCA Voltohmyist VTVM when I was young - 5th grade maybe?

I sure hate to think I toasted the thing...

--
Dan Reynolds -- KB9JLO
<><

Thank U Allison, that was very quick off the mark, very much appreciated.

I have used relays for voltage free keying of the BLA-350 and for keying the QRPLabs 10W Linear as the most flexible and blow-up-resistant method,

The HL2 provides an OC keying output, and I currently use that to drive an opto-coupled relay to key the BLA-350, I know that most people just run the EXTTR connection from the HL2 into the PTT input of the BLA-350, but for the sake of approx USD 20 and a little soldering time, I prefer to have a fully isolated connection to protect my precious HL2 !!

Once again, thank you

Peter - GM8JCF

1. VNA comes with SMA and QMX with BNC. So you use at least one additional adapter. Could you tell how the antenna cable is connected in each case?
2. BNC connectors are reliable. But in rare cases contacts maybe out of shape producing bad connections.
3. I'm not sure about the frequency accuracy of the used VNA. Afaik you could use a VNA as a generator for single frequencies. So you may set the VNA on a frequency in the 20 m band and receive with your QMX. Is there a difference? Please don't connect both! Put each device away from the other. Don't connect an antenna to the QMX. An open BNC should be ok.
4. You should really look for a dummy load.

73, Ludwig

As outlined that is the way to go.

You may consider a low level PTT control for that so the keying voltages
for the amp and driver are compatible. also a way to shut down the
driver amp for a mid power solution.

--
Allison
------------------
Post online only,?
direct email will go to a bit bucket.

Hi

I'm reaching out to the experts for advice, guidance & help please.

The Hermes Lite 2, "HL2", is a DDC/DUC SDR transceiver - - which can output upto 5W PEP RF.

The RM Italy BLA-350 plus, "Linear", is a 400W PEP HF Linear amplifier - with an input drive of upto 10W.

At 5W RF out from the HL2, the BLA-350 puts out about 130W PEP.

So, the problem is how to get the output of the HL2 from 5W to 10W to drive the BLA-350 ?

The solution looks like it might be to use the QRP Labs 10W Linear Amplifier - - “PA”, to generate the 10W required to drive the BLA-350 to full power output.

The first step is to reduce the 5W HL2 output down to 25mW acceptable to the PA, a T attenuator giving about 25~26dB attenuation should reduce 5W to around 25mW. The T attenuator would comprise of 2 x 45 R in series with a tap to ground of 5.6R to yield an attenuation factor of -25.11dB - . The HL2 does have a 17dBm fixed output intended for transverter operations but one would still need to arrange for receive signal switching; the approach I've taken I think permits me to use the drive level in the HL2 to control the output power from the Linear.

During receive, the PA, and attenuator must be bypassed; during transmit, the receive chain needs to be bypassed, relays are used to carry out the required switching operation when PTT is closed /connected to ground by the HL2.

Hopefully the schematic below describes what I think needs doing with sufficient clarity.

I would really appreciate your advice, guidance, help, suggestions for improvements, and of course correct my errors.

Very Many Thanks, 73

Peter - GM8JCF

Hi Francesco,

The green ”COLOUD" speaker that Steve links to is decent and very lightweight. It doesn't have great battery life though, at least my one doesn't.?

The Anker Souncore mini is also decent but it's fairly weighty for its size. Sound-wise, it's a great match for these little radios although theres a very slight latency, even on line input, which could be an issue if you're a speed-machine on the key....

For something really small and lightweight, try one of these (link below). I use it for SOTA etc and it's incredibly small, lightweight and LOUD. It has impressive battery life too. The only downside is that you need a small 3.5mm extension cable due to the location of the audio socket on the QCX/QMX radios. This specific model is no longer in stock but there are many others exactly the same if you look about... Here's the link:

Leadsound Portable Speaker:?


Cheers,
Ronan
MM0IVR?

No problems with a straight key on any of my QCX's. The only time I had a issue was when using a particular amplified Bluetooth speaker. Even though I was plugged into the line input, there was a discernable latency.

I wonder if that's the cause of the OP's issue. A simple check with normal (not Bluetooth etc) headphones plugged directly into the audio out jack should reveal if it is.?

Cheers,?
Ronan
MM0IVR?

I haven't heard of this issue before, but I have experience different audio anomalies with different headphones.? Sometimes it's just the impedance of the headphones, or the connector. I have trouble with those ones that have the four rings. I also had a problem with a pair of Sennheisers that had super long cables. They picked up all kinds of RF and were almost impossible to use.

--
73, Dan - W2DLC

On Fri, Jul 12, 2024 at 06:16 PM, Dave VE3GSO wrote:

Return Loss

Thank you for your suggestion.

So I followed these 2 videos

I calibrated my VNA and set the following parameters:
Freg Range - Start: 13.8Mhz
?????????????????? - End: 14.5 Mhz?

I set 2 markers. One at 14.024 and another at 14.075 750

As you can see from the picture I have a very low SWR. I believe that I also have a Return Loss of -26.77dB at 14.024 MHz and -20.76dB at 14.074 MHz which I think is within the acceptable limits.



I unplugged the antenna from the VNA and plugged it straight into the QMX and as you can see when I run the Hardware Test SWR Sweep I get nearly 5.0 on the 14.074 MHz frequency.



Am I doing something wrong?

Typical pot setting as the IRF transistors start to conduct (yours may vary, increase very slowly )?