HL2, Thetis and Pure Signal

[Ezio Insinna]

Hello,

I'm trying to implement Pure Signal with Thetis on my HL2.

The Rf sampler is shown in the attached picture. With a resistor value of 2.2 KOhm for Rx I get a signal with 2dBm or 0.8Vpp with aro. 200W output from the PA.

The PS pane shows that correction is being made on the signal when I switch the Two Tone test.

Picture 2 shows that the signal is linear and the green field is lighted up. However the PS field below the spectrum window never lights up when I test my LSB transmission.

I can see that the feedback level field in the PS pane stays dark, however if I lower the Rx value to 1KOhm and get over 1,6Vpp  (8 dBm), Thetis displays "ADC1 overload" on the spectrum window.

Are there in Thetis other set-ups in the main menu that I'm not aware of ? Is the Linearity pane the only one or should I activate something else in order to have PS working during transmission ?

As an aside, reports on my modulation are excellent and I do not seem to have any distortion even without PS working.

Many thanks in advance to those who might help me in this matter.

73

Ezio K3EK / F5MWA

73

 

["Christoph v. Wüllen"]

I cannot talk for Thetis, but the feedback level should be about -15 dBm in normal cases.
The HL2 has a preamp/attenuator that goes from -12dB (preamp) to +48 dB (attenuation),
where the "nominal zero" is at about +14dB. Starting therefrom, there should be
enough head-room (34 dB!) for accomodating at +2dBm (or even + 8dBm) feedback signal,
if the PS feedback loop sets the preamp value accordingly.

In your case, it works with two-tone and does not work with LSB? Then almost certainly
the mic preamp is too weak. For PS to set in, you must go to "full drive", that means
the ALC should peak at 0 dB. I therefore suggest to increase the mic level and try again.

Yours, Christoph

> Am 16.01.2023 um 12:27 schrieb Ezio Insinna <k3e...@gmail.com>:
>
> Hello,I'm trying to implement Pure Signal with Thetis on my HL2.The Rf sampler is shown in the attached picture. With a resistor value of 2.2 KOhm for Rx I get a signal with 2dBm or 0.8Vpp with aro. 200W output from the PA.

> --
> You received this message because you are subscribed to the Google Groups "Hermes-Lite" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to hermes-lite...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/6d823ae5-6cb1-4888-8570-93abc82dd200n%40googlegroups.com.
> <Screenshot (14).png><IMG_20230116_110747_086.png><Screenshot (12).png>

[Ezio Insinna]

Hello Christoph,

Many thanks for your answer, however there are many things I do not understand.

When you mention the attenuator, which one is it ? 

The A-Att on the main display is the receiver att.  When I switch to send it goes back to a fixed value of 5 whatever value I set before transmitting. 

This occurs even if I do not check the auto setting in the HL step attenuator pane. 

This value (5 dB) seems to be set somewhere else. 

Your suggestion about the ALC does not work. The ALC peaks well at 0 dB when modulating, so the problem is elsewhere.

As a newbie I can understand that attenuation is necessary when transmitting for the feedback signal, so this att. is used (switched in) when Pure Signal is in use but reverts to the ADC1 input when receiving. But I might be wrong. 

I need here some advice from someone who has Thetis and some explanation about how Pure Signal really works.

The value you mention is really too low (-15 dBm) and does not work for me. Does this value depend on the attenuation Thetis is using ? May be Power SDR (with ANAN) uses a different way to implement Pure Signal ?

Anyway, thanks for your effort.

73

Ezio - K3EK / F5MWA

    

[Ezio Insinna]

Hello Christoph (and eventually others),

I've gathered some more info on the subject.

Now, when activating the two tone button, I get some values as per attached picture. 

The fact that the att. value goes to 5 is due to my checking the auto-attenuate in the Pure Signal pane. But I do not understand the displayed figures. Is the feedback ok ?

can somebody explain to me the values in order to get PS working ?

Is the spectrum shown in the picture ok or not ?

Many thanks

Ezio - K3EK / F5MWA

[Duncan Clark]

In message
<CAD-gBQFdM_q7KbXfD0X2e6rGTUH=AW6wO7ytgGt...@mail.gmail.com>,
Ezio Insinna writes

>can somebody explain to me the values in order to get PS working ?
>Is the spectrum shown in the picture ok or not ?

I would say not simply because you do not have the PS-A button switched
on.

You are showing only -15dBc on IMD3. It should be way better than that.

I am nowhere near my Thetis and HL2 but that PS-A button should be on
IMHO.

IMD3 should be at least 20dB lower if not 30-40dB lower.

I can't remember how much leeway there is in the setPk but I would put
in 0.233 etc.

I run mine such that the Auto attenuator is >10dB, the more the better.
Using a Hermes, (not HL2 cos haven't tried that), I can get >-70dBC IMD3
when using a 10W ClassA PA (MRF300 @ 2A bias) and PureSignal.

Duncan


--
Duncan Clark
G4ELJ

[Ezio Insinna]

Hello Duncan and Christoph,

Many thanks to both of you for your help. 

I've got it working now (see picture). 

The green field below the spectrum pane says "155" and "Correct" so I should be close to good values. 

If I'm not wrong 3rd order are 50dB down.

I guess I will need a few days to get accustomed to this new technology and make the most of it.

Again many thanks

73 to all of you

ezio - K3EK / F5MWA

--
You received this message because you are subscribed to the Google Groups "Hermes-Lite" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hermes-lite...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/hermes-lite/j4Yjq0AjTZxjFwJY%40ntlworld.com.