I'm stuck ... recently I have purchased a PLL-Local Oscillator module made by HARTWIG Electronics. The module has two preset LO frequencies 2.256 and 1.968 GHz to be used with a 144 or 432 MHz transceiver and the mixer module by HARTWIG. My PLL is set to 2.256GHz and I would like to switch it to 1.968 GHz. HARTWIG supplied a description how to do this but I obviously can't follow and a few attempts led to no change in LO frequency. So, could somebody walk me through the procedure?

73 de Greg DF2IC

I have generated a nice map using the Azimuthal map generator at https://ns6t.net/azimuth/azimuth.html

Center the map at 0°N 26°E and set the radius to 9000km, and if you print the map as a poster on 6-8 A4 sheets you have a nice wall deco

SV1BDS I'm using a design similar to yours, it is sold in DL by DH1ND (see his QRZ.com page)

Another design and an extensive discussion can be found at https://www.helitron.de/dj0abr/index.html "Helix Feed für es'hail-2", (unfortunately in german only but with many pictures )

My combination of Helix-feed and LNB works well, a little bit better than a POTY feed for RX and a little worse than separate TX and RX antennas. By "a little" I mean differences less than 3db in RX, I noticed practically no difference for TX. When transmitting in SSB I sometimes see a "ghost signal" on the waterfall but my receiver is never desensitized.

73 de Greg

pe1hzg

I can confirm the carrier. It has been on the upper beacon since day one. The carrier is not visible/audible on the IS0GRB websdr. That's indeed a bit strange Like DK8KW said this looks like a locally generated carrier. My RX setup is similar to the setup at Goonhilly, we both use the AIRSPY SDR. Another mystery to investigate ....

de Greg DF2IC

PY4ZBZ : Hello Roland,

"S/N and (S+N)/N When measuring signal to noise ratio there are two basic elements to the measurement. One is the noise level and the other is the signal. As a result of the way measurements are made, often the signal measurement also includes noise as well, i.e. it is a signal plus noise measurement. This is not normally too much of a problem because the signal level is assumed to be much larger than the noise. In view of this some receiver manufacturers will specify a slightly different ratio: namely signal plus noise to noise (S+N/N). In practice the difference is not large, but the S+N/N ratio is more correct."

(The above is a quote from https://www.electronics-notes.com ) This quote supports my observation that if you reduce the bandwidth the SNR rises, but at the same time the noise level without any signal present rises too. The ratio "Signal+noise/noise" stays the same. If you want to compare SNR readings you have to ask for the bandwidth too, or for the noise-level without any signal. I don't know if it has to be that way, but at least there seems to be nothing "wrong" with the SNR readings at different bandwidths.

73 de Greg DF2IC & Peace

Quote from DB8TF

.....

The transponder floor already shows a SNR of 6-8dB without any signal.

So the real SNR is around 32-33dB. This was already discussed some time ago in this Forum and should be the correct value.

.....

73s DB8TF

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If you reduce the bandwidth the noise-floor rises too. If I reduce the bandwidth to 10KHz as you did in your screenshot I get an SNR reading of ca. 45, but the noise floor (without any signal present) has increased to ca. 15 which gives me a "real" SNR of ca. 30 which is about the same as with a bandwidth setting of 260 KHz, which is my standard setting.

I finally decided to do what PE1HZG has done and I am very pleased with the result.

Removing the onboard 404 MHz LO resulted in destroying the oscillator, I must improve my de-soldering skills. The new LO was built by DF9NP, 404MHz output at +5dBm with a connector for a 10 MHz external reference, it came ready to use in a nice sheet-metal enclosure. A short pigtail cable was soldered to the oscillator input pad and Resistor R1 on the transverter board was removed. The pigtail connects to the LO via a small hole in the front of the original transverter enclosure. A bigger box is planned for the future.

After this modification I am happy to report that the transverter finally is stable.

Finally the PTC heating elements from China arrived, they are labelled as 12V 50°C

I made a quick setup to see if there is any improvement on stability. After 15 minutes of warmup and a few CQ calls the system seems to have reached a temperature equilibrium that is quite stable. Frequency drift now is reduced to less than 50 Hz during a QSO and the TX is still on spot after long periods of not transmitting. What bothers me now is the accuracy, the TX frequency is 3-4 KHz higher than the RX frequency, so I'm back to sending dots or dashes or a carrier to tune in on frequency. Well, a AD4351 board is ordered and I will try to reproduce what pe1hzg has done

_pe1hzg Thanks a lot for the encouraging info!

PA3FYM I have ordered a small PTC heating element on AliExpress, still waiting. If that route does not give me a significant improvement on stability I will try the other way.

DK8KW

Quote from DK8KW

In the meantime I totally changed my strategy and use the Taiwanese BU-500 up-converter with an IF of 50 MHz.

My Flexradio does cover 50 MHz, so I will keep that strategy in mind.

pe1hzg

Quote from pe1hzg

I've ordered some ADF4351 boards and I'm planning to replace the LO chip with a GPS-locked 404 MHz signal, so everything is GPS-locked.

I'm now waiting for the boards to arrive from the East and will report if I get them to work (PLL should be clean because reference is divided by 5 and VCO would be divided by 202; so the PLL noise should be good, hopefully)

Please keep me updated on the proceedings of your project. Doing something like that is exactly what I was thinking about

om0aao

Viliam, that's interesting. Which type of this transverter do you use? Is it the one with the attenuator board or just the transverter board? My observation is that the less heat is produced in the transverter case the less the frequency drifts. If I reduce the output from the Flex1500 (28 MHz) to about 1 Watt the 432/28 transverter still gives full output but the frequency drift is considerably reduced.

HB9SKA

Of course that would be a solution, and I had already considered buying one. That would obsolete my SG-Lab transverter. How about the purity of the signal on 2,4 GHz when using 28 MHz as input? Would this filter be sufficient?

Newcomer here. Sorry if my post is in the wrong subforum.

My setup: Flex1500 (28 MHz) with ext. GPSDO --> 432/28 transverter from transverters-store.com --> SG-Lab 2400/432 transverter with ext.GPSDO --> Patch antenna in 1m dia. TV dish. (RX: 65cm dia. TV dish + modified LNB with ext. GPSDO --> AirSpy SDR with ext. GPSDO --> SDRConsole)

The setup is basically working fine, but my TX frequency drifts several hundred Hz over the course of a QSO. Nothing serious for CW/SSB operation, just a bit annoying, but not the best for digimodes. The culprit seems to be the 432/28 transverter from transverters-store.com . I have contacted Serge UT5JCW and he wrote:

"It is impossible to improve its stability because it is pll synthesizer and it is
built in chip. Nothing could be done with it. "

1. Does anybody have an idea how to improve the frequency stability of this transverter?

2. Does anybody know of a 432/28 MHz transverter that is more stable and doesn't cost a fortune? (I know of DB6NT, Microwave East, Elecraft, MiniKits)

3. Any idea?

73 de Greg DF2IC