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QMX SWR PWR Readings

 

I've been holding off posting - I didn't want to bother anyone.? I can't find what's wrong.? I have a factory assembled QMX.? Firmware is 14 and I just did a factory reset.? It looks like my SWR/Power readings are reversed.? PWR shows less than 1 watt and SWR is through the roof.? I'm using a Hyendfed antenna which gives SWR as 1.3:1 on 20 meters measured with: FTDX-10 at 90 watts, Icom 705 at 5 watts - no tuner, using the rig SWR indicators.? Using an SX-100 meter, the readings are the same (output and swr) as the rigs'.

Same antenna with the QMX and the SWR is full bars and with protection enabled (threshold 3), it shuts down transmission.? I disabled the protection and put the SX-100 meter in line and it reads PWR at 5 watts and SWR 1.3:1, the reverse of the QMX meter.? After the factory reset, the readings are the same but the rig no longer shuts down with protection on.

Has this happened with anyone?? Anyway, sorry to trouble you - my QMX has been on the shelf pretty much since I got it because of this (I don't want to blow the finals) and I'm back to using my SW3B, which I like, but I was keen about the QMX.

Thanks for listening.? 72? Ron
 

Merry Christmas! Your gift is appreciated! Before you think me totally insane, you made it clear I am not the only one with this problem! Now, I must re-read your post to see what you did to get the QMX to transmit again!
--
73
Karl
KI4ZUQ
 

Forgot to mention that my QMX is kit-built....
--
73
Karl
KI4ZUQ
 

How to activate the protection when the ROE is higth in QMX?
Thanks
73, Juan LU9CYV
 

Hello Ron
I am reiewing your post from december. I have new kit built High Band QMX which will connect to my antenna normally, but show high SWR/protection if I place tuner of amplifier in the line. Works fine otherwise. You appear to have had a similar ?issue. Did you find an explaination/solution, l can¡¯t find one on this thread.Thanks for your help.
John, N0JT
 

A few quick thoughts. No fault on your part meant to be implied ...?


1) cabled correctly? QMX to transceiver input port of amplifier? Amp connected to antenna?

2) Amp set to the band you wish to transmit on if it's not one that can automatically sense the incoming frequency? If it can't then you'll like get a High SWR or Power protect condition on the QMX when you key or press 'tune' from DiGi software applications.?

3) can the amp/tuner handle the power coming out of the QMX? Likely in the 4-5 watts range??

4) I believe the QMX needs to be shutdown and restarted if a Power or SWR fault is detected.

Hope this helps

Greg KI4NVX






On Fri, Mar 15, 2024 at 2:31 PM, John Terry (W0JDT)
<Jdterry414@...> wrote:
Hello Ron
I am reiewing your post from december. I have new kit built High Band QMX which will connect to my antenna normally, but show high SWR/protection if I place tuner of amplifier in the line. Works fine otherwise. You appear to have had a similar ?issue. Did you find an explaination/solution, l can¡¯t find one on this thread.Thanks for your help.
John, N0JT

 

Hi Greg

All four problems on your list were checked and ok. ?

Amp is automatic RF sensing Micro PA-50, but the problem also occurs with automatic AT100M tuner, but only when they are powered on. ?

I have both low and high band QMX¡¯s, and turns out problem happens is the same on both.?

I was worried about the new unit because i had just finished the build but after verifying actual SWR is low (<1.4:1) I turned off ¡°swr protection¡± and operation is fine, QMX SWR bar normal.?

This appears to be a transient effect associated with brief detecting brief sensing interval associated with these ¡°automatic RF sensing¡± equipment. No good deed goes unpunished.?

Thanks for your help

John N0JT

On Fri, Mar 15, 2024 at 3:24?PM Greg McCain via <gamccain50=[email protected]> wrote:
A few quick thoughts. No fault on your part meant to be implied ...?


1) cabled correctly? QMX to transceiver input port of amplifier? Amp connected to antenna?

2) Amp set to the band you wish to transmit on if it's not one that can automatically sense the incoming frequency? If it can't then you'll like get a High SWR or Power protect condition on the QMX when you key or press 'tune' from DiGi software applications.?

3) can the amp/tuner handle the power coming out of the QMX? Likely in the 4-5 watts range??

4) I believe the QMX needs to be shutdown and restarted if a Power or SWR fault is detected.

Hope this helps

Greg KI4NVX






On Fri, Mar 15, 2024 at 2:31 PM, John Terry (W0JDT)
Hello Ron
I am reiewing your post from december. I have new kit built High Band QMX which will connect to my antenna normally, but show high SWR/protection if I place tuner of amplifier in the line. Works fine otherwise. You appear to have had a similar ?issue. Did you find an explaination/solution, l can¡¯t find one on this thread.Thanks for your help.
John, N0JT

 

Great trouble shooting!

Good QMX info to know and keep filed away for the future if needed for those who my might run into the same issue.

Can the PA-50 be manually pre set to the band of interest?? And if so, did/does it work without turning the SWR protection off?


Greg KI4NVX.




On Fri, Mar 15, 2024 at 5:35 PM, john terry
<n0jtqsl@...> wrote:
Hi Greg

All four problems on your list were checked and ok. ?

Amp is automatic RF sensing Micro PA-50, but the problem also occurs with automatic AT100M tuner, but only when they are powered on. ?

I have both low and high band QMX¡¯s, and turns out problem happens is the same on both.?

I was worried about the new unit because i had just finished the build but after verifying actual SWR is low (<1.4:1) I turned off ¡°swr protection¡± and operation is fine, QMX SWR bar normal.?

This appears to be a transient effect associated with brief detecting brief sensing interval associated with these ¡°automatic RF sensing¡± equipment. No good deed goes unpunished.?

Thanks for your help

John N0JT

On Fri, Mar 15, 2024 at 3:24?PM Greg McCain via <gamccain50=[email protected]> wrote:
A few quick thoughts. No fault on your part meant to be implied ...?


1) cabled correctly? QMX to transceiver input port of amplifier? Amp connected to antenna?

2) Amp set to the band you wish to transmit on if it's not one that can automatically sense the incoming frequency? If it can't then you'll like get a High SWR or Power protect condition on the QMX when you key or press 'tune' from DiGi software applications.?

3) can the amp/tuner handle the power coming out of the QMX? Likely in the 4-5 watts range??

4) I believe the QMX needs to be shutdown and restarted if a Power or SWR fault is detected.

Hope this helps

Greg KI4NVX






On Fri, Mar 15, 2024 at 2:31 PM, John Terry (W0JDT)
Hello Ron
I am reiewing your post from december. I have new kit built High Band QMX which will connect to my antenna normally, but show high SWR/protection if I place tuner of amplifier in the line. Works fine otherwise. You appear to have had a similar ?issue. Did you find an explaination/solution, l can¡¯t find one on this thread.Thanks for your help.
John, N0JT

 

An RF-sensing amp will always exhibit a transient high VSWR event during TX switchover, as it switches AFTER RF is already applied, as will a switched-element tuner as it does its switching gyrations.

When I am using a tuner I will place my QRP-O-Meter between the transceiver and the tuner.? I put the QRP-O-Meter into the VSWR position which inserts a 6-dB loss VSWR bridge; the loss of the bridge will keep the VSWR under 2:1 under all load VSWRs.? After tuning is done I bypass the bridge.? Of course your tuner must be able to tune with the attenuated TX power level.

When I use an amp I connect a TX line and use that to key the amp; hot-switching avoided.
73, Don N2VGU.
 

Hi Greg

The PA-50 does have manual band selection, but this did not prevent SWR trigger.? There is also ?automatic ?PTT function which would still be active and likely still the problem. There is ?PTT jack but ?includes band selection function which is not part of QMX, and may be a problem. I ?Have been happy with operation when protection is off, but taking a risk. I hate the sinking feeling I get when 10 hours of work goes up in a puff of smoke!

John N0JT
 

Thanks John.
Good info to know. That PA-50 is getting more popular I think.

Greg KI4NVX

Greg


On Sat, Mar 16, 2024 at 10:41 AM, john terry
<n0jtqsl@...> wrote:
Hi Greg

The PA-50 does have manual band selection, but this did not prevent SWR trigger.? There is also ?automatic ?PTT function which would still be active and likely still the problem. There is ?PTT jack but ?includes band selection function which is not part of QMX, and may be a problem. I ?Have been happy with operation when protection is off, but taking a risk. I hate the sinking feeling I get when 10 hours of work goes up in a puff of smoke!

John N0JT

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