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I've made some successful contacts on FT8 and WSPR using my Raspberry pi and posted a guide on how to do it.

However, monitoring its output on my Icom 7300 I see:

ubitx freq 7074.0,? audio transmitted freq USB 1.708kHz? ?so signal should be at 7075.8 MHz
On the Icom I see
7072.4, 7074.0, 7074.2 big signal, and 7075.8

Any ideas?
Bo W4GHV

Hello Bo,

Have you checked the volume level you are feeding the uBitx? The mic amp isn't expecting more than 40mV.

Also did you have any attenuation turned on the ICOM? The manual says it has settings for 10,20,30 dB attenuation. (I'm terribly curious if that's a hardware attenuator or software based. Looks to be hardware based according to the service manual. 10dB in tuner unit, 20dB in RF unit. Okay.)

I wonder if the spurs will go mostly away with 30dB ATT and checking that the sourdcard feed to the mic amp doesn't exceed 40mV.

The service manual says there is a 20dB voltage controlled attenuator to keep the ADC from getting swamped. Your two radios are so close I'm still sure the 7300 is showing you spurs due to close proximity.

Those are the first 2 things I would check.

73 de Jacob AG7CT

I did make progress by turning the audio down. Power dropped from 7 to 4 watts but the undesired dropped significantly and the desired increased. Then made a 500 mile FT8 contact with the 4 watts.

I just had the RF gain way down to watch the signals.
Anxious to have a nearby ham listen for them.

I plan to put some type meter on the audio input to the rig. It appears to be critical for digital modes at least.

Thanks for input. Bo W4GHV?

Your signal at 7074 is probably the carrier. The ubitx doesn't have the
best carrier suppression in the world. If your receiver is close to the
ubitx it will pick up the carrier being transmitted.

Are you sure the 7072 signal is 7072.4 and not 7072.3? The carrier
frequency of 7074000hz - 1708hz is 7072.292khz.

Could be bad opposite sideband suppression. Are you sure your BFO
frequency is set correctly?

tim ab0wr

On Tue, 22 May 2018 13:51:24 -0700
"Bo Barry" <bobarr@...> wrote:

I've made some successful contacts on FT8 and WSPR using my Raspberry
pi and posted a guide on how to do it.

However, monitoring its output on my Icom 7300 I see:

ubitx freq 7074.0,? audio transmitted freq USB 1.708kHz? ?so signal
should be at 7075.8 MHz On the Icom I see
7072.4, 7074.0, 7074.2 big signal, and 7075.8

Any ideas?
Bo W4GHV

I haven't done any adjustments or calibration yet. ?Been too excited getting it going. I need to Google and get the info to do them.
Thinking an external audio level meter is needed. (my o'scope is too far away)


TNX inputs! Bo

Input levels to any transmitter for any digital modes ARE critical. There are guidances published in various places about how to set up the modulation levels, some give exact instructions for good results and some are more vague and don't give such good results. I ran into difficulties running PSK31 some years ago and learnt the hard way. Now I'm preparing to get going with these new modes and am studying the setting myself so I can't give off the cuff help.

There is one general pointer I can repeat - when you arrive at a suitable level back it off some 5% or even 10%.

Good luck.

A few things I found with my Bitx40 and Ubitx. Turn the drive down in the rig itself for digi modes, also check for any kind of ground looping. When I was 1st running my Bitx40 I ran r136 at half of what is normal after getting reports I was txing in a few spots at once. This was also in combination with a ground loop from my pc, after moving r136 it was reduced and again after using a laptop it was completely gone. I found the audio was over driving the radio even set very low and caused a lot of issues.

?Another thing to make sure is a DC blocking cap on the mic line so as not to mess with the computer or the interface if you use one.

73
--
David

?N8DAH