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Low frequency from U-QRSS-kit.

Gérard Vigouroux
 

Belle journ???eHi all !
I just finished assembling my U-QRSS-Kit for 30m.
It seems to work fine at once except the frequency. I couldn't get it higher than 10 139,840 Mhz with adj C8 at minimum.
I replaced C5 (22pF) by 15pF. The freq has up a bit to 10 140,120 Mhz which is still a bit low (for example WSPR is around 10 140,200 +/- 100).
I replaced C4 (22pF) by 15pF. This didn't change anything for the freq ! By the way I don't understand why ?
However 10 140,120 MHz beeing still too low I wonder what is to be done now :
Must I reduce C5 to a lower value (let's say 10pF) ?
Must I reduce C3 ?
I will greatly appreciate your experience and your opinion.
73's to all of you.
Gerard, f6gwb.
Tony Volpe
 

Gerard,

I had the same problem when I started with the kit. I replaced C4 & C5 with 18pf and the frequency went up to about the middle of the wspr band. Replace C5 as well as C4.

Also, I have found that very small changes in circuit voltage will alter the frequency that the circuit oscillates at. In my kit, a change from 4.8v to 5 will move the frequency upward by about 20 or 30htz.?

I run the logic side of the board with the power supplied by a small plug in power supply with an LM 7805 regulator controlling the voltage to the logic chips. The PA is powered directly by the plug in supply at about 6.2 volts. When the PA switches on, the voltage on the logic chips drops by about 0.1volts and the frequency falls a little. This can be seen on ARGO as the line moves down a little. If I run the input voltage on the PA at 9 volts, this does not happen at the logic chips side of the LM7805 and the frequency is more stable.

However - I am sure that if you chage c5 for a lower value, your frequency will rise.

Bonne chance.

de G0BZB - Op Tony
"f6gwb"
 

Hi Tony,

Thanks for your message and hints. I will try reducing C5 value once more.
By the way I saw you spotted me several times in the last 24 hours around 10140.130.
Best 73's.
Gerard.
Tony Volpe
 

Yes Gerard, I spotted you five times last evening and my record shows that you were at about 10.140190. This is well into the WSPR band so do not worry about changing C5. You are already there and working well. My receiver setting may not be perfect, but nonetheless all is well for you and your kit.

Best regards

Tony G0BZB
"f6gwb"
 

OK Tony, I managed to stay inside the WSPR band. However I think to be in the bottom of the lower part but yes it's enough to work. I am a little puzzeled with the freq you announce. I really think to be around 10140.130 and not 10140.190. I checked this morning yet my Rx calibration with the WWV carrier and other BCL stations (which are almost always on a 10kHz boundary) and I think my receiver (Yaesu FT897D) is accurate at +/- 3Hz. So I'm surprised you spotted me on 101403.190. Maybe I'm wrong; maybe your Rx freq is not accurately calibrated.
73's QRO.
Gerard, f6gwb.
Stephen Farthing
 

Hi guys,

As the kit instructions say getting the output frequency in band can be a bit of a challenge. When I did the testing I used a frequency meter which can read down to one hertz which I calibrated against a 10 MHz Rubidium standard. When I get a round tuit I'll modify the counter so it is clocked by the standard so I can be really sure the frequency the meter reads is accurate at all frequencies. .?

I used the standard to check the calibration of my K2, FT817 and TS570 and was surprised to find the receivers were all reading 10.000,00 at zero beat. ?None of them have displays that will show the 0-9 Hz digit. So you really need to resort to using ARGO, or a similar piece of software, to get that information. You need to set it up correctly and make sure your RX is well calibrated.?

When the round tuit arrives I might try to more accurately determine the values of the capacitors Tony says needed to be changed to get into the WSPR band. But IIRR I could easily achieve this with the standard caps when I built the prototype. It's also worth pointing out that later kits in the first batch and all of the kits in the second batch will have a variable capacitor with a wider swing than the one we used to ship. This is because the people we buy from no longer stock it.?

73s Steve G0XAR
Tony Volpe
 

Hi Gerard,

I monitored you on a remote receiver since I like to keep my transmit beacon going too and don't like to overload my home receiver. I control the computer at the remote location with some software across the Internet. The receiver may not be set dead on 10.13870.

But you are not on the bottom of the band or anywhere near it. I just checked your spots and you are being copied by ?a number if stations including some American ones (at around the mid 130s on average, so you are certainly in the band.

I have experimented with c4 and c5 and you can even run without one of them, though if you do this you will raise the frequency a lot. Nevertheless, it can be brought back down with the trimmer. In your case, the way your kit is working, I would leave it alone.

By the way - if you are discouraged by a low number of spots today - I think it is about the conditions. today I have had very few and would say it is the worst for a few weeks.

Best regards


Tony G0BZB
"f6gwb"
 

Hi Tony,

Thanks for your last post.
I think you are wright, I will let C4&C5 as the are now, at least for a while as this seems to work properly.
It also seems that the propagation last night and today was not so generous than yesterday and the night before, as I got only a few local WSPR spots. But wave propagation is so fanciful !
73s QRO.
Gerard, f6gwb.

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