Author Topic: RF Signal Generator w/ Sweep for ham radio projects  (Read 21547 times)

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Offline cio74

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RF Signal Generator w/ Sweep for ham radio projects
« on: June 09, 2016, 04:26:18 pm »
Hello,

I could use some help, I'm looking for a RF signal generator that should help me with hobby HF ham radio related projects (RF filters, mixers, pretty much anything related to building a transceiver).

I have been looking on Ebay over the last week, there are a few I like but some of them have rear connectors, that will be very inconvenient for my setup. In the end I am drawn towards an Anritsu MG3633A found on Ebay that I can get for about £600, front connectors, weighing, eh, 60+ lbs. They seem to be built around 2001-2003, question is, are they still good after nearly 15 years and would they still work over the next few years?

Thanks.

Cio
« Last Edit: June 09, 2016, 04:28:30 pm by cio74 »
 

Offline acbern

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #1 on: June 09, 2016, 05:00:50 pm »
Anritsu is good value, everybody wants agilent/keysight, you can get that item even cheaper i would think if you look arround.
Disadvantage: no service manuals with schematics usually and no special repair parts. But on the other hand, these are hard to repair anyway, and the price is low enough to give it a shot.

« Last Edit: June 09, 2016, 05:04:44 pm by acbern »
 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #2 on: June 10, 2016, 08:37:58 am »
Thanks, are they built that good to survive a couple more years, altho not expensive at £600 I would definitely want to use it for at least another 5 years...

 

Offline acbern

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #3 on: June 10, 2016, 05:30:51 pm »
There is no global answer for this. Vice versa, if you spend say 800 for an agilent, you cannot be sure it will work longer. You can sell it easier, thats for sure.
 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #4 on: June 10, 2016, 05:53:03 pm »
Yes, of course, that's all well known.

It is a bit of gambling buying 10+ years old equipment and hope to see it running for few more years. Some would say the price should be low considering there is no warranty of what so ever that the equipment will last for 1 month not 1 year but the reality is different. I think I have seen a few with 1 year warranty but the majority are sold 'as is'


Would I be better off buying some HP instead, perhaps easier to repair or re-sell compared to an Anritsu or Rohde&Schwarz?

 

Offline uncle_bob

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #5 on: June 10, 2016, 06:19:34 pm »
Hi

The biggest drawback of most modern "sweep" generators is the fact that they can sweep amplitude. In most cases this was done with mechanical relay based attenuators. The relays have a rated life of a few million operations. You can easily come up with a sweep pattern that takes the relays past end of life in under a month. I've done this on a couple of generators. Fortunately it was a "test we must do / charge the customer" sort of thing. Hint: Don't do 24 hour a day 7 day a week amplitude sweeps unless somebody is paying you to to it ...

Provided it comes with some sort of warranty, I would not worry about it. Either they work fine when you get it or they don't. If it does not come with a warranty *AND* if Anritsu used the relay approach on this generator, you have some element of risk.

Bob
 

Online PA0PBZ

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #6 on: June 10, 2016, 07:18:10 pm »
Since nobody asked yet: What frequency span are you looking for, what accuracy and what is it you want to sweep, just frequency?
There are still some analog sweeping RF generators out there...
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Offline nctnico

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #7 on: June 10, 2016, 08:17:51 pm »
Would I be better off buying some HP instead, perhaps easier to repair or re-sell compared to an Anritsu or Rohde&Schwarz?
HP easier to repair? I don't think so. Service manuals for more modern HP gear describe at the block diagram level and go no further into details than required to swap a module.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline DimitriP

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #8 on: June 10, 2016, 09:48:31 pm »
You can always go analog and use the extra pounds for extra pints or parts ....

http://www.ebay.co.uk/itm/SIGNAL-GENERATOR-/182161005933?hash=item2a69a45d6d:g:Q~QAAOSwbYZXVTYy
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Offline uncle_bob

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #9 on: June 10, 2016, 09:49:41 pm »
Would I be better off buying some HP instead, perhaps easier to repair or re-sell compared to an Anritsu or Rohde&Schwarz?
HP easier to repair? I don't think so. Service manuals for more modern HP gear describe at the block diagram level and go no further into details than required to swap a module.

Hi

Easier to repair because you *may* be able to find a board to swap out. Good luck finding a source of "donor parts" for some of the other brands.

Bob
 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #10 on: June 10, 2016, 09:54:26 pm »
Since nobody asked yet: What frequency span are you looking for, what accuracy and what is it you want to sweep, just frequency?
There are still some analog sweeping RF generators out there...

0.5-100MHz is more than enough, looking to get an unit I trust, in my view the biggest issue if you don't know if your signal is bad or the measurement is bad, therefore looking for an accurate generator. And yes, frequency sweep is what I have in mind to use. You have a ham radio callsign, think of an instrument useful to help you build various ham related projects, inject signal for pre-amps, mixers, IF alignment, bandpass filters response and so on.

I do like that Anritsu just a little worried since it comes with zero warranty. actually they will replace it if it's defective so no DOA but that's pretty much all warranty I get.
 

Offline Wuerstchenhund

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #11 on: June 10, 2016, 10:55:45 pm »
I have been looking on Ebay over the last week, there are a few I like but some of them have rear connectors, that will be very inconvenient for my setup. In the end I am drawn towards an Anritsu MG3633A found on Ebay that I can get for about £600, front connectors, weighing, eh, 60+ lbs. They seem to be built around 2001-2003, question is, are they still good after nearly 15 years and would they still work over the next few years?

Yes, assuming they have been treated well. But don't forget that Anritu's main customers are cell phone companies, who use such generators for automatic test systems, which will affect the remaining life of the mechanical RF attenuators (which have a limited service life). Newer generators often have the option of an electronic attenuator, which is more durable.

Also, the MG3633A is closer the 1996 - 2000 era, and I'd check the condition of the device very thoroughly before buying. Anritsu gear is generally very robust, and the build quality is very high, but getting parts can be very difficult (don't bother contacting Anritsu as individual, they're pretty much only responsive to businesses, and even a business dealing with Anritsu can be a challenge).
 

Offline acbern

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #12 on: June 11, 2016, 06:00:37 am »
Cio74, i dont know how it is in the uk, but in germany if you buy used gear as an end user (not company) from a company, they have to give you a warranty. Insane imo, but thats how it is.
 

Offline HighVoltage

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #13 on: June 11, 2016, 08:58:42 am »
I have both, an R&S SML-1  and an HP RF sweep generator. Both were bought dead and repaired by me. I was lucky because the repair was not too complicated. I would highly recommend one of these brands, because there are lots of people here on eevblog that can help with them and you can get reasonable prices if you have a little time and watch the market.
My HP generator is the 8648C similar to the one Shahriar repaired in this video episode
http://thesignalpath.com/blogs/2012/10/07/teardown-and-repair-of-an-hp-8648c-synthesized-signal-generator/




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Offline HighVoltage

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #14 on: June 11, 2016, 11:57:21 am »
There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #15 on: June 11, 2016, 07:48:58 pm »
Thanks, it does not have sweep function.

I'll keep an eye on Ebay maybe something good pops up.
 

Offline uncle_bob

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #16 on: June 11, 2016, 07:53:22 pm »
Thanks, it does not have sweep function.

I'll keep an eye on Ebay maybe something good pops up.

Hi

It does have a GPIB interface, so getting it to sweep is pretty easy.

Bob
 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #17 on: June 11, 2016, 08:53:35 pm »
Thanks, it does not have sweep function.

I'll keep an eye on Ebay maybe something good pops up.

Hi

It does have a GPIB interface, so getting it to sweep is pretty easy.

Bob

Thanks for the tip, I'm not familiar with that communication interface, I assume to sweep I will need a PC to send commands. That's doable, I shall read more about how to do that.
 

Offline uncle_bob

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #18 on: June 11, 2016, 09:04:51 pm »


Thanks for the tip, I'm not familiar with that communication interface, I assume to sweep I will need a PC to send commands. That's doable, I shall read more about how to do that.

Hi

Quick run down:

GPIB (also known as HPIB on HP gear) is a standard way to run test gear. A lot of instruments have the magic connector on the back. A variety of people make adapters that either plug into a PC or a USB port. There are a few Ethernet based and serial based devices as well. The USB version is probably your best bet.

Since it's a common interface, there are oceans of code out there to deal with it. There are even software empires (LabView) built more or less around it and other common interfaces. If you have modern gear, it is worth investigating.

Bob
 

Offline Howardlong

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #19 on: June 11, 2016, 09:19:20 pm »
Since nobody asked yet: What frequency span are you looking for, what accuracy and what is it you want to sweep, just frequency?
There are still some analog sweeping RF generators out there...

0.5-100MHz is more than enough, looking to get an unit I trust, in my view the biggest issue if you don't know if your signal is bad or the measurement is bad, therefore looking for an accurate generator. And yes, frequency sweep is what I have in mind to use. You have a ham radio callsign, think of an instrument useful to help you build various ham related projects, inject signal for pre-amps, mixers, IF alignment, bandpass filters response and so on.

I do like that Anritsu just a little worried since it comes with zero warranty. actually they will replace it if it's defective so no DOA but that's pretty much all warranty I get.

How about HP/Agilent 8935 E8380A or E6381A? These test sets also include receiver sensitivity tests as well as sweep gen and spec an for sweeping filters if that's what floats your boat. Add an external return loss bridge and it'll do scalar network analysis. General coverage is from 0.4 to 1000MHz, plus a bit of L band for cellular applications. They go for about £500 on eBay.
 

Offline Neganur

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #20 on: June 11, 2016, 09:39:40 pm »
The dwell time (switching time) on the 8648X is pretty limiting when you want to sweep a frequency range in my opinion. It's around 100ms per point.
The R&S one is a bit better with 10ms so I would rather recommend this unit.

of course both will sweep but if you do a 1MHz step on a 1GHz range you can go fetch a coffee. Perhaps taking an VCO IC is a better solution if you want a faster sweep.
 

Offline uncle_bob

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #21 on: June 11, 2016, 09:44:26 pm »
Since nobody asked yet: What frequency span are you looking for, what accuracy and what is it you want to sweep, just frequency?
There are still some analog sweeping RF generators out there...

0.5-100MHz is more than enough, looking to get an unit I trust, in my view the biggest issue if you don't know if your signal is bad or the measurement is bad, therefore looking for an accurate generator. And yes, frequency sweep is what I have in mind to use. You have a ham radio callsign, think of an instrument useful to help you build various ham related projects, inject signal for pre-amps, mixers, IF alignment, bandpass filters response and so on.

I do like that Anritsu just a little worried since it comes with zero warranty. actually they will replace it if it's defective so no DOA but that's pretty much all warranty I get.

How about HP/Agilent 8935 E8380A or E6381A? These test sets also include receiver sensitivity tests as well as sweep gen and spec an for sweeping filters if that's what floats your boat. Add an external return loss bridge and it'll do scalar network analysis. General coverage is from 0.4 to 1000MHz, plus a bit of L band for cellular applications. They go for about £500 on eBay.

Hi

One thing to be careful of on the various "cell phone test sets":

The hardware is broadband in most of them and quite capable of < 1 MHz to >= 1 GHz coverage. They may or may not have been calibrated over that entire range. They may or may not have the full range enabled by default. It's always a good idea to do a bit of research on the specific unit you are bidding on to be sure it has what you are after. Turning a "limited" one into a "full" one apparently is a doable thing. You need a fairly well equipped shop to get the job done. The conversion and calibration is not a quick basement project sort of thing.

All that said, I have one, they do a really good job.

Bob
 

Offline G0HZU

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #22 on: June 11, 2016, 11:03:13 pm »
If you just want a reasonable sig gen for HF use then I'd recommend the little Marconi 2022 if you can find a tidy/healthy one. The phase noise is fairly good on the HF bands but not in the same class as the best generators on the HF bands. But for general ham radio stuff this is a good little sig gen. it isn't going to be much use as a sweeper though. If it has the GPIB option you could sweep it slowly over GPIB with a PC but I don't recommend this as a long term solution for sweeping.

If you want to sweep stuff down here then why not build a simple DDS board and drive it with a decent MCU chip? You should be able to sweep it quite fast from LF through the HF bands. If you need to go 'very' fast on the sweep then go for one of the DDS chips that can sweep itself according to your programmed limits.

However, I'm not sure why you want (as in 'need') a sweeper for ham radio stuff. The little Marconi 2015 and 2016 has a sweep/ramp input allowing it to be swept with a function generator within its sub ranges but the sub ranges are fairly limited in range. The primary function of the sweep input is to allow the connection of the synch unit to phase lock it but you can use it as a sweeper with a function generator/ramp waveform.



 

Offline uncle_bob

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #23 on: June 12, 2016, 02:19:18 am »

However, I'm not sure why you want (as in 'need') a sweeper for ham radio stuff.


Hi

I also am a bit puzzled by that. Without some sort of tracking detector, there isn't a lot you can do with a sweeper. To get a good tracking detector, you buy a spectrum analyzer with a tracking generator or a network analyzer instead.

Bob
 

Online vk6zgo

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #24 on: June 12, 2016, 04:17:27 am »

However, I'm not sure why you want (as in 'need') a sweeper for ham radio stuff.


Hi

I also am a bit puzzled by that. Without some sort of tracking detector, there isn't a lot you can do with a sweeper. To get a good tracking detector, you buy a spectrum analyzer with a tracking generator or a network analyzer instead.

Bob
An RF sweeper with a sweep rate sawtooth available to use as a H input on an Oscilloscope,a detector,& you have a device which can show you the amplitude/frequency response of a circuit.
A little more messing around,& you can look at input impedances of circuits,antenna feeders,etc.

It is,in effect a Scalar Network Analyser,
Back in the day,when I worked at a place doing TV Transmitter maintenance,if the Polyskops were all out,we would use a Wavetek  RF sweeper & a detector,instead.

None of this stuff,including a Polyskop,is as good as a VNA,but very useful work can be done with them,nevertheless.
 

Offline HighVoltage

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #25 on: June 12, 2016, 09:27:07 am »
Thanks, it does not have sweep function.

I'll keep an eye on Ebay maybe something good pops up.
Cio
Can you explain to us exactly what you what to do with this sweeping
What frequencies do you want to sweep and how fast ?
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Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #26 on: June 12, 2016, 12:04:27 pm »
The main idea is to use the sweep generator to check filters response and have a visual diagram, one example here

another example with detector 


A spectrum analyser with tracking would probably be better but it's more expensive and not very useful as a stand alone RF signal generator?

In term of frequency, for instance I plan to build a HF transceiver with 2 IF stages, one at 8.2Mhz (because I have a 6KHz bandwidth crystal filter at that frequency from an old Yaesu transceiver) and the second at 455KHz.


« Last Edit: June 12, 2016, 12:08:13 pm by cio74 »
 

Offline uncle_bob

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #27 on: June 12, 2016, 12:11:09 pm »
The main idea is to use the sweep generator to check filters response and have a visual diagram, one example here

another example with detector 


A spectrum analyser with tracking would probably be better but it's more expensive and not very useful as a stand alone RF signal generator?

Hi

Here's the problem with looking at a filter that way:

You do not have enough dynamic range to get a useful plot. With a network analyzer, you can fairly easily look at 120 db of range on a filter. Tracking generators on SA's will get you into the 80 db range with most of them. Without a proper detector, you will be lucky to get 20 db. It's simply not worth doing. The information you get is not good enough to be of use.

Bob
 

Offline Carrington

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #28 on: June 12, 2016, 12:15:56 pm »
A NWT500 maybe? Same 80dB problem, but at least relatively cheap.
My English can be pretty bad, so suggestions are welcome. ;)
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Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #29 on: June 12, 2016, 12:18:54 pm »
Another very useful thing would  be to see frequency response of the band pass filters and image rejection filters. Another one check the mixer response by feeding a fixed frequency from a LO and use the sweep generator on the other entry then see the mixer output.

I have one oscilloscope that can display spectrum analyse, the OP here wants the same thing I want https://www.eevblog.com/forum/beginners/testing-a-low-pass-filter-with-a-spectrum-analyzer-with-no-tracking-generator/
 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #30 on: June 12, 2016, 12:22:56 pm »

...The information you get is not good enough to be of use.

Bob

You want me to break the bank and buy one of those VNA's, do you :)
 

Offline uncle_bob

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #31 on: June 12, 2016, 12:26:16 pm »
Another very useful thing would  be to see frequency response of the band pass filters and image rejection filters. Another one check the mixer response by feeding a fixed frequency from a LO and use the sweep generator on the other entry then see the mixer output.

I have one oscilloscope that can display spectrum analyse, the OP here wants the same thing I want https://www.eevblog.com/forum/beginners/testing-a-low-pass-filter-with-a-spectrum-analyzer-with-no-tracking-generator/

Hi

A good filter will have skirts or notches that are at least 60 db down. You simply can not "see" that far down with a sweeper and an oscilloscope. The "FFT" on your scope is not fast enough to follow the sweeper. The range of the linear display is not enough to show more than about 20 db without driving you a bit nuts.

Bob
 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #32 on: June 12, 2016, 12:36:28 pm »
Thanks for the explanation, if I read it right it seems that

1. I need a RF signal generator that is accurate enough at low signal levels for the usual signal injection into RF pre-amp and other places where a known frequency, modulation and amplitude is required.

2. I need a spectrum analyser with tracking generator to accurate see the frequency response of various filters.

I have a feeling the above are going to be an expensive purchase for a hobby.
 

Offline Nuno_pt

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #33 on: June 12, 2016, 12:56:27 pm »
For filters why not just buy one MiniVNA Tiny or Pro or one DG8SAQ, or N2PK, or one from Array Solutions.

Nuno
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Offline uncle_bob

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #34 on: June 12, 2016, 01:31:03 pm »
Thanks for the explanation, if I read it right it seems that

1. I need a RF signal generator that is accurate enough at low signal levels for the usual signal injection into RF pre-amp and other places where a known frequency, modulation and amplitude is required.

2. I need a spectrum analyser with tracking generator to accurate see the frequency response of various filters.

I have a feeling the above are going to be an expensive purchase for a hobby.

Hi

Yes, a signal generator is mainly used for creating accurate level signals at a fixed frequency with or without modulation.

A spectrum analyzer (by it's self) is used for checking harmonics and spurs (and modulation) out of things like transmitters.

A network analyzer is the proper tool for checking filters and circuit passbands.

A spectrum analyzer plus a tracking generator is a low(er) cost / low(er) performance substitute for a network analyzer.

Back a long time ago (I was in school ...) people rigged up systems with sweep generators and log converters driving CRT displays. Effectively what they did was build a simple scalar network analyzer out of a bunch of different pieces of test gear. That all became a lot less popular in the 1970's when vector network analyzers began to come into the mainstream. 

Bob
 

Offline sanman

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #35 on: June 12, 2016, 06:28:01 pm »
What about one of these from mRS:

http://miniradiosolutions.com/54-2/
 

Offline uncle_bob

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #36 on: June 12, 2016, 06:55:37 pm »
What about one of these from mRS:

http://miniradiosolutions.com/54-2/

Hi

That takes care of the filter stuff. It does not give you the accurate levels or the modulated signals for checking a receiver.

Bob
 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #37 on: June 12, 2016, 07:14:20 pm »
I have been looking long time before at those miniVNA usb based tools for filters. Admittedly, did not know about the other listed by Nuno.

I am currently installing the software and see if I can get an idea of how to operate it, how easy is the UI without actually having a device.

 

Offline Nuno_pt

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #38 on: June 12, 2016, 07:49:06 pm »
The MiniVNA Tiny will be my next buy after the Signal Generator.
Nuno
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Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #39 on: June 13, 2016, 10:19:14 am »
FedEx came first thing in the morning with a very big package that I was not expected.

 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #40 on: June 13, 2016, 10:21:39 am »
Found the Anritsu we've been talking at the beginning of the thread. It came from Finland over the weekend, I have not even paid for it but they have sent it anyway.

 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #41 on: June 13, 2016, 10:26:02 am »
Nice warning label :)

 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #42 on: June 13, 2016, 10:29:45 am »
According to the label is had been tested in 2003, would that be the manufacture year? It seems to have some add-on, the W-CDMA transceiver performance test, whatever that is

 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #43 on: June 13, 2016, 10:33:26 am »
And finally the other connectors at the back, may be useful to synchronise with an oscilloscope



I am a little concerned about some previous post made by bob I think who has said they may have been used to sweep the output level and the mechanical attenuator may have been worn out.

Could someone please suggest a good test procedure to make sure everything is  fine, I have an oscilloscope that I can use.

Thanks.
 

Offline msraya

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #44 on: June 13, 2016, 10:49:01 am »

Very nice equipment, Indeed...

For test FM and SSB ham radio receivers for SINAD, for example...
For drive mixer to make experiments..
To make sweeps..

The external modulation input is on the front panel.. nice touch...
You would need it calibrated.. but if you not paid for a calibrated generator and only use it for repair ham radio gear, that is not as important...

I buy one refurbished Stabilock 4032 calibrated, They send me all paper with all measures on different levels and frequencies that are stated in service manual and They test if these measures are into the allowed tolerance level. Happily my equipment pass all the test and they send it to me along with the report...

I can use these references in the report to calibrate (with some tolerances, of course) other of my test gear that I buy second hand and uncalibrated.. This is nice, that I can rely on some test gear in my bench...  :-+

If you have a good friend with calibrated gear, you can send the 18Kg gear to him and take a report of calibrated measures.. or You can send it, at your cost, to a calibration service to get this information.

Manuel
 

Offline uncle_bob

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #45 on: June 13, 2016, 08:18:17 pm »
And finally the other connectors at the back, may be useful to synchronise with an oscilloscope



I am a little concerned about some previous post made by bob I think who has said they may have been used to sweep the output level and the mechanical attenuator may have been worn out.

Could someone please suggest a good test procedure to make sure everything is  fine, I have an oscilloscope that I can use.

Thanks.

Hi

The normal "quick test" is to run the generator into a good spectrum analyzer and make sure the level on the SA agrees with the level on the generator. What you find is a relay that does not close (or open ) on say, the section that takes you from -100 dbm to -120 dbm. You step down the output 3 db on the generator and it  miss tracks on the SA (-120 is -100 or -150). Exactly where the breakpoints are for this or that generator and how many there are is very much a "that depends" sort of thing.

If you don't have an SA, a calibrated receiver can do the job. A scope will let you look at the first section or two of the coarse attenuator.

Bob
 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #46 on: June 13, 2016, 09:10:15 pm »
Thanks Bob, I have done some tests early in the afternoon, it has many relays inside. Each stage has some control with no relay involved but that's small range.

I don't have a good SA, just some oscilloscope with FFT.

I will do more tests tomorrow, I am very pleased after the initial test, everything seems to work just fine, have connected a small wire at the RF output and received modulated AM/FM signal using a ham radio receiver located few yards away.

Have also managed to activate the reverse voltage protection by using low frequency and mismatched output connector.

I can't fault it, it may need to be calibrated and I still have to fully check the attenuator relays.

I may buy another one, to check mixers I'll need two sources :)
 

Offline uncle_bob

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #47 on: June 13, 2016, 10:00:29 pm »
Thanks Bob, I have done some tests early in the afternoon, it has many relays inside. Each stage has some control with no relay involved but that's small range.

I don't have a good SA, just some oscilloscope with FFT.

I will do more tests tomorrow, I am very pleased after the initial test, everything seems to work just fine, have connected a small wire at the RF output and received modulated AM/FM signal using a ham radio receiver located few yards away.

Have also managed to activate the reverse voltage protection by using low frequency and mismatched output connector.

I can't fault it, it may need to be calibrated and I still have to fully check the attenuator relays.

I may buy another one, to check mixers I'll need two sources :)

Hi

Ok, so how about:

Drive one side of a mixer with a handy 10 MHz OCXO.

Set the generator to 10.01 MHz and drive the other side.

Feed the mixer output into a sound card and watch the level change at 10 KHz.

Bob
 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #48 on: June 14, 2016, 05:42:53 am »
Thanks Bob, I have done some tests early in the afternoon, it has many relays inside. Each stage has some control with no relay involved but that's small range.

I don't have a good SA, just some oscilloscope with FFT.

I will do more tests tomorrow, I am very pleased after the initial test, everything seems to work just fine, have connected a small wire at the RF output and received modulated AM/FM signal using a ham radio receiver located few yards away.

Have also managed to activate the reverse voltage protection by using low frequency and mismatched output connector.

I can't fault it, it may need to be calibrated and I still have to fully check the attenuator relays.

I may buy another one, to check mixers I'll need two sources :)

Hi

Ok, so how about:

Drive one side of a mixer with a handy 10 MHz OCXO.

Set the generator to 10.01 MHz and drive the other side.

Feed the mixer output into a sound card and watch the level change at 10 KHz.

Bob

That could help but the product of mixing is more than just |F1-F2| in the mixer's output. Two RF signal generators and a SA will do a better job.

Speaking of a secondary generator, how good are these new digital generators such as Siglent SDG2042X or Rigol. They do not feature the a very low level output nor their chassis is built with RF shielding in mind so it would be safe to assume they are not suitable for the RF tasks I have explained earlier?
 

Offline uncle_bob

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #49 on: June 14, 2016, 11:42:07 am »
Thanks Bob, I have done some tests early in the afternoon, it has many relays inside. Each stage has some control with no relay involved but that's small range.

I don't have a good SA, just some oscilloscope with FFT.

I will do more tests tomorrow, I am very pleased after the initial test, everything seems to work just fine, have connected a small wire at the RF output and received modulated AM/FM signal using a ham radio receiver located few yards away.

Have also managed to activate the reverse voltage protection by using low frequency and mismatched output connector.

I can't fault it, it may need to be calibrated and I still have to fully check the attenuator relays.

I may buy another one, to check mixers I'll need two sources :)

Hi

Ok, so how about:

Drive one side of a mixer with a handy 10 MHz OCXO.

Set the generator to 10.01 MHz and drive the other side.

Feed the mixer output into a sound card and watch the level change at 10 KHz.

Bob

That could help but the product of mixing is more than just |F1-F2| in the mixer's output. Two RF signal generators and a SA will do a better job.

Speaking of a secondary generator, how good are these new digital generators such as Siglent SDG2042X or Rigol. They do not feature the a very low level output nor their chassis is built with RF shielding in mind so it would be safe to assume they are not suitable for the RF tasks I have explained earlier?

Hi

The output of the mixer would be:

10 KHz from F1 - F2

10 MHz from feedthrough (at least 30 db below the OCXO output)
10.01 MHz from feedthrough (more than 30 db lower than 10 KHz)

20.01 MHz from F1 + F2 (same level as 10 KHz)

The sound card should have input filtering that takes out anything above 40 KHz. That filtering will be pretty effective at >= 10 MHz. If not, put in a simple lowpass filter.

====

The light weight / low cost generators are a great upgrade from a function generator. There are a lot of things they will let you do. One example is driving the mixer in the above setup. They are indeed pretty much useless for receiver sensitivity testing or stuff like IP3.

Bob

 

Offline Nuno_pt

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #50 on: June 14, 2016, 01:24:43 pm »
One generator that I like is the Marconi 2019A or the HP 8467A or HP 8657B, with advantage for the 8647 because of the dial's, and they could be cheap if you wait, I don't know about performance.
My objective is one above 1.5GHz, but still looking for one at affordable price.

Buying from US will be little harder, since here we pay, Invoice + Shipping + 9€ = total value + 23% VAT

Let´s say $400 for the generator, $100 for shipping, 9€ fix amount at customs for opening the package, the you've the price, now add 23% on top of that, and it's the final price that the generator will cost you.

We don't have Tax in lab equipment, measuring, Ham radio, etc... but we do have 23% VAT.
« Last Edit: June 14, 2016, 02:08:03 pm by Nuno_pt »
Nuno
CT2IRY
 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #51 on: June 14, 2016, 02:14:34 pm »
VAT is of no issue but shipping is killing me when looking to buy from the US, those generators are heavy.

I think I may buy another Anritsu or a Siglent 2000X model, the later may be easy to sell if for whatever reason I don't like it, has 10" screen, font size should be fine:)
 

Offline Nuno_pt

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #52 on: June 14, 2016, 02:24:27 pm »
cio74,

Yes the shipment from US is a killer deal's, but the VAT here for final consumer so no way to get out of 23% over everything.

I remembering one guy ask me $100 to send one Keithley 2000 DMM.

Well I'm divided by 2019A, 8647A or 8657B, specs wise I'm lost here.

Any ideas.
Nuno
CT2IRY
 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #53 on: June 14, 2016, 02:36:01 pm »
cio74,

Yes the shipment from US is a killer deal's, but the VAT here for final consumer so no way to get out of 23% over everything.

I remembering one guy ask me $100 to send one Keithley 2000 DMM.

Well I'm divided by 2019A, 8647A or 8657B, specs wise I'm lost here.

Any ideas.

If you have a  company that is VAT registered and if the company business is related to your purchase you can buy it as company asset and then claim the VAT. When buying within EU but different country you get a better price than the say Ebay listed price, just ask the seller if it's VAT registered and they would be happy to sell for 20% less or whatever the VAT is in their country (you will have to fill some papers for VAT but it's all fine when you fill your VAT return papers, you claim it back). Or maybe you have a friend that can help with a company purchase.

I was looking at all of those, Marconi 2012A, 2022A may do the job but no dial and they look, well, old?

I was about to buy a HP 8647A (8657B also has no dial) but looking at the serial (if talking about the one currently listed on Ebay) it starts with 3414, this means 1960 + 34 = 1994 year of production. The Anritsu is 2003 so I thought it's somehow better.

Now I am seriously considering the Siglent 2042X model, it's low priced and if decent performance I think it would be good to have.

 

Offline Nuno_pt

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #54 on: June 14, 2016, 02:45:14 pm »
No VAT register company here, so no route there.

The 8647A was one offer by a friend in Spain, but it's also on the 3414 range, dam I like those knobs, and also heard that there are no schematics for it.

I agree with you, the 2018, 2019, 2022 from Marconi look very old.

The 8657B also doesn't  have any knobs, but goes over 1.5GHz, and maybe will be better in specs then the others, so could be worth, exchange the knobs for specs.

Or maybe get the 8647A and latter sell it and then buy and Marconi 2024 or one R&S.

I´ll wait for the experts to give there ideas.
Nuno
CT2IRY
 

Offline cio74

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #55 on: June 14, 2016, 05:14:33 pm »
I have set he output level to -143.0 which is the lowest this generator can do and then started to dial up. Every time it goes into a different range there is a 'click' noise, I won't describe it as a relay but more like a mechanical contactor of some sort? Looking at the oscilloscope signal there are no dead 'zones' but sometimes 'glitches' can be seen when changing a range.

-143.0 to -133.0
-132.9 to -132.0
-131.9 to -131.0
.....
-0.9 to 0.0
0.1 to 1.0
1.1 to 2.0
......
6.1 to 23.0

What is that thing exactly, some sort of mechanical attenuator? Or just some noisy relays?

I don't want to open the generator... yet :)
 

Offline uncle_bob

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Re: RF Signal Generator w/ Sweep for ham radio projects
« Reply #56 on: June 14, 2016, 10:52:24 pm »
I have set he output level to -143.0 which is the lowest this generator can do and then started to dial up. Every time it goes into a different range there is a 'click' noise, I won't describe it as a relay but more like a mechanical contactor of some sort? Looking at the oscilloscope signal there are no dead 'zones' but sometimes 'glitches' can be seen when changing a range.

-143.0 to -133.0
-132.9 to -132.0
-131.9 to -131.0
.....
-0.9 to 0.0
0.1 to 1.0
1.1 to 2.0
......
6.1 to 23.0

What is that thing exactly, some sort of mechanical attenuator? Or just some noisy relays?

I don't want to open the generator... yet :)

Hi
 
There are a bunch of different ways to do it. It could be relays. It could be something else. A rotary actuator and a bunch of cams is one way to do it...

Bob
 


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