Hi,

maybe not exactly home brewed test equipment but it might be useful anyway...
Anyone tested this type of RF signal generator? https://www.ebay.com/itm/LMX2594-10MHz-15GHz-RF-Signal-Generator-Frequency-Source-Sweep/113258615070

Cannot find anyone who have tested it. The closest I get is the Erasynth+ which is 4 times the price.

Cheers
Marcus, SA5PMG

Hi, 

There has been some discussion regarding the March edition of the RF and Microwave Source by AD that notes the ADF4371 which looks really impressive though the chip is about as much as the LMX2594/LMX2595.

http://app.h.analog.com/e/es?s=1548954099&e=230999&elqTrackId=f6a0f1152c78418195f34258393efab9&elq=a218009fe33341338153cde0dfc9de5a&elqaid=8530&elqat=1

 

The ADF4371 will be interesting to see developed onto a more cost effective PCB module and sold more affordably. 

 

If you haven't seen like the ADF4355 or like the LMX2594 you noted already more-so cost effectively modularized yet.  Seems compared to the eval board... there still is potential for a nice profit margin product. 

There is also the following that caught my attention and I commented somewhere in another post:

LMX2595:

https://www.ebay.com/itm/LMX2595-10MHz-19GHz-RF-Signal-Generator-Frequency-Source-Sweep/113682701931

ADF5355:
https://www.ebay.com/itm/NEW-ADF5355-54M-13-6GHz-RF-Source-Generator-Frequency-Source-moudle/122486540575

I haven't read into the performance characteristics yet.  

 

Kindest Regards, 

 

In Christ.

I bought some chinese modules from ebay.
Most had wrong components or bad layout and did not deliver the promised performance
Normally  they copy some sw, copy the hw reference design with some cost reductions and build something.
Example is an adf4351 module.
To get the promised performance you have to use three ultra low noise 3.3v  regulators, one for only the vco. The chinese design uses one normal regulator and some inductor capacitor combination to try to remove crosstalk. That failed and as a result the module has terrible spurs and is not usable.
If you are spending that money better buy known brand from solid seller.

I was thinking the cheap Chinese chips might be counterfeits also and not meeting specifications of the actual AD chips. 

Based on eBay policy... I think these can be refunded and not have to be returned also. 

I was wondering about the board design too and wondering if needed to can in more a stripline or microstrip type enclosed design or technically... if I understand correctly use multilayer PCB designs and similar theory to spec the board more critically... versus just dual layer.

Is there something going on with the black board versus green board designs in general or more a board design performance for each module... I'm probably trying to over generalize?

The below article got me thinking also about not just multilayer PCB design for shielding better with the stripline or microstrip methods thinking... also the layered designs for the traditional components to embed... which isn't that complicated and like double sided boards if using an oven with different melting point solders so highest melting point components soldered first. 

https://hackaday.com/2019/01/18/oreo-construction-hiding-your-components-inside-the-pcb/

Most of the black boards have better RF design than the green one. The
green ones have some part of the PLL loop filter running under the
capacitors that AC couples the output.

A 2 layer design should be sufficient, if done correctly, although a 4
layer design is probably easier to get working. Do pay attention to
the layout and neither should be a problem.

73 de Thomas.

lør. 23. mar. 2019 kl. 23:08 skrev jafinch78 . <jafinch78@...>:

--
With Best regards, Thomas S. Knutsen.

Please avoid sending me Word or PowerPoint attachments.

@Thomas

I did not measure the black boards, only got one of the green boards so far.

Some hints to reduce spurs:
1. Use as high Fcomp as possible.This is done by using as low R
divider as possible. A ADF4351 can use Fcomp on 32MHz, this isn't that
much higher than 10MHz, but any move helps.
2. Use a hard limiter on the Ref input. This is specially important if
you are using a DDS or Si5351 to generate adjustable frequency. A hard
limiter can with some adjustments supress unwanted spurs as much as
20dB. This means also driving the PLL input as hard as the datasheet
allows to reduce spurs.
3. Use a bandpass filter on the Fref input of the module. This way you
reduce the amplitude of the spurs outside the bandwidth of the filter,
should be combined with 2 above.
4. Reduce the loop filter bandwidth as much as you can. The ideal
thing is to optimize this for best PN, but that requires a repeatable
setup to measure PN over a large frequency range, and most people
don't have that.
5. Follow the power supply requirements, and use low noise regulator.
Large capacitors and Capacitance multiplier is a easy way to reduce
noise on the supply lines. This is more to improve phase noise than
spurs, but crosstalk can generate spurs. Having the VCO on a separate
supply rail than the digital stuff helps.

ADF5355 looks like a nice approach to reduce the amount of work in
making a signal generator. A bit expencive, but should be interesting.
There are some chinese boards around, but its probably worth it,
altough more expencive, to make your own. That way you would get the
benefit of knowing that things are done correctly with regards to the
power supplies.

73 de Thomas LA3PNA.



ons. 27. mar. 2019 kl. 12:45 skrev <erik@...>:

--
With Best regards, Thomas S. Knutsen.

Please avoid sending me Word or PowerPoint attachments.