Weird JT65 problem

[VK4WDM]

My digital setup is: IC-756PRO3, Signalink USB, laptop. The connection between the Signalink and the radio is via the rear accessory socket not the mic socket.

I am getting the following problem when transmitting JT65.

If I bump the table or talk whilst the transmission is in place the power output drops, sometimes as low as 50% depending how loud the noise is. If I disconnect the mic or turn the mic gain right down the problem disappears so it appears that the mic is still picking up sound. The ALC shows no sign over over-driving.

I am not completely sure if this is a new problem or one that has been there since the Signalink was installed and I have just noticed it.

Ideas please?

73

Wayne VK4WDM

[VK2DVZ]

Wayne, have you disabled the inbuilt laptop computer microphone? They often stay activated even though you may be using a separate microphone input for your external equipment.

Worth checking...

[VK5ZD]

Have you selected 'data mode'?

[VK4WDM]

Hi Ross. Thank you for your suggestion. Removing the mic from the rig removes the problem so I don't think it is related to the PC but I will check.

Hi Iain

Changing to "USB -D" solved the transmission problem but creates another on the receive side.

If I use "USB-D" the receive gain on the Signalink and the gain controls on the JT65 program have to be very high for me to see anything at all on the waterfall. This introduces a lot of noise and the number of decodes are a way down on what I get just using "USB."

There is obviously something wrong in the setting up. Suggestings welcome.

73

Wayne VK4WDM

[VK4WDM]

Got it sorted. It seems that the previous owner of the tranceiver had programed a different band pass filter for digi modes than the one recommended. Now getting very good JT65 operation on both sending and receive

73

Wayne VK4WDM

[VK3MIX]

Hi All,

I have been having a good time with JT65 and getting some contacts into the states with only 5 watts on 40m

However I have noticed that a number of JT65 signals show up in the waterfall fairly strong (clearly visible) but never decode. I have tried both with AGC on & off which doesn't seem to make any difference, however I am wondering whether it might be that other stronger signals which are swamping the band 1khz up the waterfall are causing some sort of distortion to other received stations. I am running a Yaesu FT857D via a 1:1 600ohm transformer into the computers audio.

I was watching a demonstration on JT65-HF last night on Youtube and noticed that you can get decodes which are barely visible in the waterfall which makes me think something is not quite right.

Cheers!
Andrew

[VK2MUS]

their clock may be wrong - or yours may be.
John

[VK3DXE]

With strong signals, try turning off your NB and any DSP and/or attenuate it. Otherwise, watch the waterfall to determine if their DT is correct. Up to about 5 seconds shouldn't cause too many problems. It may also be that their end id overdriven and undecodable.

[VK3MIX]

AGC, NB + DSP all off. DT is usually under 1. Being 40m I'm thinking maybe all the noise from poor electronics is messing with the signals too.

[VK7XX]

With strong signals, try turning off your NB and any DSP and/or attenuate it. Otherwise, watch the waterfall to determine if their DT is correct. Up to about 5 seconds shouldn't cause too many problems. It may also be that their end id overdriven and undecodable.

Also, with non decoding strong signals, if you are using JT65-HF (Joe Large variety) try varying the Digital Audio Gain sliders on the left just above the date or, if using WSJT-X the slider on the left bottom. From memory, but this may be inaccurate, the HB9 JT65-HF variety and WSJT do not have these sliders.

<edited to add> and I almost forgot, if you find that adjacent strong signals are killing your weaker decodes, try your manual notch filter ... make sure you select manual, not auto..... I frequently forget all about it, but when I remember, it is amazing.. You can see on the waterfall where it is notching and move it around accordingly.

John
VK7XX