Matching and correlating SWR readings is always going to be difficult. Some meters use a Faraday shield around the single turn winding ....the QMX+ does not. Then you have core characteristics, material, etc. "Close" is "good enough" in these situations.

73 Kees K5BCQ

Ian Ill take the QMX 20 - 10 unit please.
GI7FDZ



QMX 20 - 10m ?70 unit please

I had a similar experience, but a factory reset solved the problem, something had become corrupt in the firmware I guess.

Cheers Paul DJOCU

TNX for update. "Let it Go". I like that.
73,
George

Have you tried reducing the the Rise and Fall Thresholds? These control the audio level at which the digi tone is detected. I've got mine set a little lower, 60 and 50 so they work with my phone. If your audio is right on the edge this might explain things. I'd try setting the fall threshold lower to start with.

Chris, G5CTH

George - Just installed FW 20 in my QMX+ but the Message 2 issue persists. I even deleted all of Message 1 and Message 2, thinking that perhaps there was still something in those messages causing the issue. But that did not resolve the issue. Not sure what else to try, but I can live with it.

————————-
Jim?
N7RCS
Palm Bay, FL

Andrew,

The topic is the 10W QRPL amp not some other trash.
Thanks for letting me know what was not news to me years ago.

FYI most of the amps claiming 80W run IRF530 and can do it. Most
are as I've repeatedly called them copies of bad copies of bad designs.
But we aren't talking about those. Seems you are.

First its hard to overdrive as the driver stage will saturate. The load
line makes it hard.

If you read the manual you know my name.

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

开云体育

开云体育

Thanks Ronan really appreciate that and agree. I was just going through the Ops manual and the rate change was there. I guess it was not implemented.

Again, appreciate the info.

Please take care,
Tim

On Mon, Jul 15, 2024 at 05:23 AM, M0WAS wrote:

The burning off of the enamel was the bit of the build which I was always least happy with

Get yourself one of these Knipex 15 11 120 strippers, happiness awaits.

Does anyone else remember Stripex/Strip-X? It was a foul-smalling brownish concoction of phenol etc. which was used to chemically strip enamel.
Dip it in, wait a second and wipe off the enamel cleanly. I am sure they pulled from the shelves for a reason but it worked great.
73, Don N2VGU

On Mon, Jul 15, 2024 at 10:04 AM, toru wrote:

the BS170 gets extremely hot when I do so. At 8V, the current is 1.3A on both 15m and 17m

Hi とる,
for both 17 m and 15 m LPF2 is in use. It looks like something is wrong there.
A high current means a low load impedance towards the BS170.

Looking at your sweep results I guess you was using a dummy load, right?

Afaik for results from LPF scan and SWR scan a bit of rf is enough. This means not all the TX problems are affecting these sweeps significantly. (In such cases sometimes the results are not perfect but also not bad.) So far your sweeps are looking good. (Only the SWR is a bit high for lower frequencies. This could be a result from the real winding of T507. But your T507 should be good enough.)

1. So please inspect the region of LPF2 carefully.
2. The frequency response of your LPF2 seems to be fine. But we don't know the input impedance. So check especially C516 and the region of C516. Has C516 the right value? Is there a bypass with a low resistance, maybe inside C516? These failures would affect the input impedance a lot but not so much the frequency response.
3. If you don't find a problem check the LPF PIN diode switching in RX mode.

73, Ludwig

I remember seeing something in the Operation manual about adjusting the CAT poll time for WSJT-X.

Thank you Steve for your response. I was finally able to get the SWR on the QMX to show between 1.05 and 1.18. I rewound the T507 as outlined here

I do have a couple of follow up questions though:

1.) SWR on 80M (according to the QMX) is still 1.18. That's the worst band. Is that considered acceptable? These were all tested on a dummy load.
2.) My external SWR meter is still showing differently. On the 20M band, the QMX shows 1.05, but my external meter shows 2.1. How do we determine which is the "real" reading?

Thank you for your help so far.

Yes Allison, I do agree at 10W theu are fine, and can handle a poor mismatch. The death of these unit is being over driven, the amp has high overall gain as it is part of another project the SSB transceiver, which may never see the light of day, hugely complicated project.

I have seen other designs running these transistors up to 80W class C, they do get killed off with a mismatch.

I rather like this kit and used it in other projects.

KR

Andrew G8UUG

Okay, resoldered the 6m toroids, got them nice and toasty, the solder flowed nicely. I'm now getting 2.6W output which is broadly in line with everything else. Must have been a bad joint before but they looked okay. 30m and 40m still a concern. I checked the number of toroid turns and they're exactly as the manual says, I shall give the toroids another resolder. They look okay too, but obviously that doesn't necessarily mean anything.

The burning off of the enamel was the bit of the build which I was always least happy with, very little positive feedback that it's been done correctly. I checked continuity after every toroid but who knows.

Anyway, finally got it hooked up to an antenna and got the following results:

CW CQ on RBN


FT8 CQ and QSO on PSKReporter


And little does he know it, but PD5DLB was my first FT8 contact on my QMX+, I was received at +5, and I gave him a +3 report, 500km away.

Interestingly when keying down on CW on 20m I get 2.7W, but when transmitting on FT8 the meter showed 3.2W.

Still working on my CW copy speed so a CW QSO will have to wait a few more weeks/months(/ever?) till I've built up enough confidence.

Both the maps above look quite normal to me, I will have a bit more time towards the end of the week to do a proper test and compare with my QCX+, and QDX (pre-assembled). I also have a Z-Match ATU in transit so I can shift from my attic 20m dipole to my attic G5RV-JR (jury is out on how well that is going to work...) to hopefully get on some different bands (although 40m not looking so promising at the moment).

Hello everyone.

I'm having a problem with the QMX rev4 12V build and can't solve it. I'd appreciate some advice.

I can't transmit on 15m and 17m, and the BS170 gets extremely hot when I do so. At 8V, the current is 1.3A on both 15m and 17m, and about 0.7A on a normal 20m. The SWR value in the Diagostics menu changes randomly from 1.3 to infinity. There doesn't seem to be a problem with the SWR sweep and LPF sweep.

I searched the Groups topics and the wiki, but I couldn't find any articles that could solve the problem.

I'd be grateful if someone could give me some advice. Thank you.
--
JI3VOV_toru