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Author Topic: +40 to +60db spike in RF after I release the PTT  (Read 4336 times)

EI9HAB

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+40 to +60db spike in RF after I release the PTT
« on: February 10, 2018, 02:28:21 AM »

Hi All.

I am at the end of my tether at this stage.

The problem is as follows: When transmitting on power >15W the S-meter registers  +40 to +60db spike in RF after I release the PTT (in phone). This manifest itself as noise with the duration of the effect lasting about 5 – 10 seconds (the higher the power the longer the duration of the effect). The Rig is a Yaesu FT 840.

Receiving stations can hear me just fine and I get great audio reports, however, I am completely washed out by noise for those first 5 to 10 seconds after I release the PTT and therefore miss whatever the other side had said in that time period. It makes QSO’s impossible.

The rig/mic checks out fine; I had it checked out at my local club by a club member with signal generators etc etc. We even hooked up to the club antenna and another member went mobile and QSO’d across various bands and power outputs – no problem at the club.

I have swapped out my ATU at home; getting good SWR on my 300ohm open wire 20m doublet. The rig behaves normally on the dummy load at home. RF Grounding or ungrounded makes no difference – but I re-did those wires anyway. I even put up a new 20m doublet and have messed around with the feed line lengths – all to no avail.

I’m stumped!

Any help or insights would be greatly appreciated.

73

Adrian EI9HAB
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G4LNA

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RE: +40 to +60db spike in RF after I release the PTT
« Reply #1 on: February 10, 2018, 05:14:49 AM »

With that sort of signal level it must be something really close to you.

First you need to check out your own house is in order, any chance you can use or borrow a battery and run the rig off that and switch off your mains supply and see if the same thing happens, if it clears itself then you know it must be something in your house.

That duration of noise sounds remarkably like an LED PIR light in the area, try keying at night and see if you see it come on.
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WB4SPT

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RE: +40 to +60db spike in RF after I release the PTT
« Reply #2 on: February 11, 2018, 07:37:55 AM »



The problem is as follows: When transmitting on power >15W the S-meter registers  +40 to +60db spike in RF after I release the PTT (in phone). This manifest itself as noise with the duration of the effect lasting about 5 – 10 seconds (the higher the power the longer the duration of the effect). The Rig is a Yaesu FT 840.
............ The rig behaves normally on the dummy load at home.




This does read like a self induced RFI effect.   Can you measure the 12V power supply current during this episode?   That may lead to the troubled circuit (Tx or Rx). 
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EI9HAB

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RE: +40 to +60db spike in RF after I release the PTT
« Reply #3 on: February 13, 2018, 06:16:26 AM »



The problem is as follows: When transmitting on power >15W the S-meter registers  +40 to +60db spike in RF after I release the PTT (in phone). This manifest itself as noise with the duration of the effect lasting about 5 – 10 seconds (the higher the power the longer the duration of the effect). The Rig is a Yaesu FT 840.
............ The rig behaves normally on the dummy load at home.




This does read like a self induced RFI effect.   Can you measure the 12V power supply current during this episode?   That may lead to the troubled circuit (Tx or Rx). 

Thanks very much for your advice, much appreciated.
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EI9HAB

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RE: +40 to +60db spike in RF after I release the PTT
« Reply #4 on: February 13, 2018, 06:21:01 AM »

With that sort of signal level it must be something really close to you.

First you need to check out your own house is in order, any chance you can use or borrow a battery and run the rig off that and switch off your mains supply and see if the same thing happens, if it clears itself then you know it must be something in your house.

That duration of noise sounds remarkably like an LED PIR light in the area, try keying at night and see if you see it come on.

Paul, your're a legend! That's exactly what it was. We recently had the walls dashed on the side of the extension, and what ever way I had set the light back up had made it more sensitive. I simply dialed back the setting & bob's your uncle. I'm very much obliged.

73
Adrian
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