ADF4531 local oscillator to CQ-TV 260 4m upconverter

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M0YDH
Posts: 172
Joined: Sat Dec 31, 2016 5:59 pm

ADF4531 local oscillator to CQ-TV 260 4m upconverter

Post by M0YDH » Wed Oct 02, 2019 7:12 pm

Hello all
I've made a CQ-TV253 PIC controller and programmed it to command a 400 MHz signal from an ADF4351. I want to use this with my receive upconverter that I've finished [except for attenuation for LO signal] . This is a power levels question in relation to the Mike G0MJW's requirement in his article "Measure your LO power and chose suitable values for the LO attenuator so that the mixer sees 7 dBm."
I followed the good instructions in CQ-TV 259
Initially I chose -1 dBm output power. 50Ohms setting and No PAD in use. This resulted in the following trace:-
Programmed with -1dBm output but get -7.5dBm
Programmed with -1dBm output but get -7.5dBm
First output.jpg (40.37 KiB) Viewed 644 times
-1 dBm came out as -7 dBm. I didn't fancy mixing those harmonics either.
Ebay low pass filter added
Ebay low pass filter added
PhotoPictureResizer_190929_120424868-1008x567.jpg (119.21 KiB) Viewed 644 times
I reprogrammed the PIC for +5dBm - its highest value which gave the following result:-
400 MHz and +5dBm produced this.
400 MHz and +5dBm produced this.
20191002_191008-1008x567.jpg (154.85 KiB) Viewed 644 times
Minus 0.5 to 0.7 dBm.

For the upconverter circuit do I put a 0R resistor/link in for the input attenuation?
Will the upconverter work ? What did other constructors do with this project?

regards
David M0YDH

g0mjw
Posts: 981
Joined: Sat Sep 20, 2014 9:15 am

Re: ADF4531 local oscillator to CQ-TV 260 4m upconverter

Post by g0mjw » Wed Oct 02, 2019 8:39 pm

The mixer wants 7 dBm but it will work with less, with less initially you lose dynamic range, then the conversion losses increases until it does not work at all. The opposite with higher power, until the diodes expire. I would think 5 dBm will be fine. You could add an amplifier and an attenuator to get 7dBm but it's not likely to be worth it with 5 dBm. Looking at your unit 5 dBm is not met so a bit of gain may be needed.

Here is the official advice: See the Graph on page 6 and comments on LO drive. It looks like performance of this mixer will start to drop quickly below 4 dBm drive. With 5 dBm the loss is minimal, though it won't handle strong signals quite as well.

https://ww2.minicircuits.com/app/AN00-010.pdf

5. LO DRIVE POWER AVAILABLE.
The LO drive is critical since the function of the LO drive is to switch the mixer diodes fully on and off for lowest distortion. So, for optimum performance, select the mixer level to match the LO drive. Mini-Circuits conveniently identifies its mixer levels by the LO drive requirement; thus a Level 7 mixer refers to a LO drive level of +7 dBm. If there are constraints on the LO power available, select the closest mixer level that is lower than the available LO power. For example, if +12 dBm LO drive is available, select a Level 10 mixer.

Mike

M0YDH
Posts: 172
Joined: Sat Dec 31, 2016 5:59 pm

Re: ADF4531 local oscillator to CQ-TV 260 4m upconverter

Post by M0YDH » Sun Nov 03, 2019 11:52 am

Hello
I put together the chain of modules pictured.
The code asks for 400 MHz at 5dBm. [Analyser levels in brackets].
The ADF4351 outputs today 405MHz and -1.6dBm [Analyser 0 dBm ref at 10dB].
Adding an amp gives 21.4dBm [25dBm ref at 40dB]
Adding 9dB attenuation gives 12.2 dB [same as before]
Adding an EBay low pass filter gives 11.75dBm pictured.
The upconverter has a 6dB attenuation fitted.

Have I understood my analyser correctly i.e. auto attenuation selected and the displayed powers are true? I hope I'm going about this ok. I'll bring the upconverter and LO units to CAT 19 South for the clinic and a tutorial.

73
David
Attachments
Spectrum at 405MHz at the LPF
Spectrum at 405MHz at the LPF
PhotoPictureResizer_191103_111613042-567x1008.jpg (234.68 KiB) Viewed 442 times
ADF4351, club programming board, amp, attenuator and EBay LPF
ADF4351, club programming board, amp, attenuator and EBay LPF
PhotoPictureResizer_191103_111530520-567x1008.jpg (250.29 KiB) Viewed 442 times

G8GKQ
Site Admin
Posts: 1347
Joined: Sun Mar 22, 2009 1:21 pm

Re: ADF4531 local oscillator to CQ-TV 260 4m upconverter

Post by G8GKQ » Sun Nov 03, 2019 2:56 pm

Hi David

All looks sensible to me, although the ADF4351 should be on 400.000 MHz if programmed correctly. Analyser frequency calibration? You could take a look with an RTL-SDR and SDR Sharp.

Dave

M0YDH
Posts: 172
Joined: Sat Dec 31, 2016 5:59 pm

Re: ADF4531 local oscillator to CQ-TV 260 4m upconverter

Post by M0YDH » Sat Nov 23, 2019 9:54 pm

Thank you very much for the test and set up Dave at CAT19 South.
I finished the project and used a pair of Mini-kits coax relays to give bypass or up conversion control.
It worked first time. :D
Long Mynd receiver working at 471 MHz
Long Mynd receiver working at 471 MHz
20191122_120847-567x1008.jpg (260.17 KiB) Viewed 266 times
Upconverter
Upconverter
PhotoPictureResizer_191117_193241032-1008x567.jpg (202.32 KiB) Viewed 266 times
Also works fine with Minitioune .
My video of the new kit in action is https://youtu.be/D9r-Zb_YhsU

73
David M0YDH

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